The Hill Reaction and Light Wattage

Wabash College| The Effects of Light Wattage on the Rate of the Hill Reaction| | | Mark Stoops| 11/29/2012| | Introduction: In the Hill Reaction lab we will be measuring the rate of photosynthesis in light dependent reactions. The goal is to measure the change of absorbance of 2,6-dichlorophenolindophenol (DCIP) and examine the rate of the photosynthetic reactions using this data. The Hill Reaction can be used to study photosynthesis because we can directly measure the rate of the reaction of photosynthesis using DCIP.The Hill Reaction is defined as the photo reduction of an electron acceptor by the hydrogen ions from water, which then produce oxygen. In naturally occurring reactions NADP+ is the final electron acceptor. In the Hill Reaction we will be using 2,6-dichlorophenolindophenol (DCIP) as an electron acceptor instead of NADP+. DCIP is blue in its oxidized state and is colorless in its reduced form. This change in color can be utilized. As the photosynthetic reaction proceeds the DCIP will become increasing transparent. This reduction in blue color leads to change in absorbance and can be measured by the spectrophotometer in lab.Using the Hill Reaction, we hypothesized that the amount of light,(change in wattage) affects the rate of change of absorbance of DCIP in solution. In order to test our hypothesis we set up the experiment with three different strengths of light (15W, 60W, 120W), as well as a light free, negative control. Each run was conducted for ten minutes under similar conditions with a difference in wattage being the only variable. The negative control was conducted with no light to see how the reaction would proceed with no external influences. Having a control allows us to have a baseline of comparison for our three lighted runs.Due to the fact that light dependent reactions use light, we can predict that an increase in the amount of light will increase the rate of reaction of photosynthesis, thus lowering the absorbance. We can also predi ct that our control will have no change in absorption after a ten minute period without light. Method: To begin the Hill Reaction we first isolated the chloroplasts. This was done by placing the pieces of leaves into a mortar with 15ml of ice cold NaCl-buffer. The mixture was then ground for two minutes. After grinding the leaves we filtered the solution through 8 layers of cheesecloth.The juice was rung out and the solution put into a 15ml centrifuge tube. The solution was than centrifuged for one minute at 400xg. Then we decanted the supernatant into another clean, chilled centrifuge tube and spun it at 1000xg for 5 minutes. After the centrifuge process, we decanted the supernatant and suspended the pellet in 7ml of ice cold Nacl. This solution was kept on ice the entire time of experiment. To begin our runs we made a warm water bath for our solutions, then prepared the solutions shown in Figure 1 below. | NaCl buffer| DCIP| DI H2O| Chloroplats (on ice)| Blank| 3. 5 ml| -| 1. 0ml| 0. 5 ml|Control | 3. 5 ml| 0. 5ml| 0. 5ml| 0. 5 ml| Reaction 15W| 3. 5 ml| 0. 5ml| 0. 5ml| 0. 5 ml| Reaction 60W| 3. 5 ml| 0. 5ml| 0. 5ml| 0. 5 ml| Reaction 120W| 3. 5 ml| 0. 5ml| 0. 5ml| 0. 5 ml| Figure 1. Experimental solutions to be prepared in lab. The blank solution was used to zero our spectrophotometer. To zero our spectrophotometer, we used the instructions provided at the spectrophotometer. To prepare the control, we added all solutions shown above and then wrapped it in two layers of aluminum foil to completely block any sources of light. After 10 minutes the control absorbance was tested to provide a negative control.We prepared the 15W, 60W, and 120W reaction tubes immediately before each respective run to avoid light pollution. The procedure we used to test each solution was to prepare the tube and place it 25cm from the source of light. Then, turn on the light and leave it on for a minute. Then at the minute mark the light was turned off and the clock stopped. The tub e was placed in the spectrophotometer and a reading was taken. Then the tube was returned to the water bath, the light turned on, and the clock started. We followed this procedure for ten times for a total of 10 minutes for each solution.The only difference between runs was the changing of bulb wattage. Results: How does the amount of light affect the rate of reaction of photosynthesis and therefore absorbance of the DCIP solution? The data shown in Figure 2 is the results of three reaction runs and a negative control run. The time in minutes is shown on the left and the percent absorbance of the 15W, 60W, 120W, and negative control run are provided in the subsequent columns. Time (minutes)| 15W %A| 60W %A| 120W %A| Negative control| 0| 1. 1| 0. 99| 0. 89| | 1| 1. 09| 0. 945| 0. 716| | 2| 1. 08| 0. 9| 0. 55| | 3| 1. 8| 0. 815| 0. 422| | 4| 1. 07| 0. 772| 0. 322| | 5| 1. 06| 0. 702| 0. 237| | 6| 1. 07| 0. 638| 0. 176| | 7| 1. 055| 0. 578| 0. 125| | 8| 1. 05| 0. 53| 0. 088| | 9| 1. 03 5| 0. 464| 0. 064| | 10| 1. 025| 0. 408| 0. 032| 1. 11| Figure 2. Data values for absorbance of DCIP solutions on a one minute basis. Also shown is the negative control with absorbance taken at 10 minutes. Figure 3 shows us a visual of the data in Figure 2. Figure 3. Time in minutes versus % absorbance of 15W, 60W, 120W, and negative control runs. Figure 4. The effect of bulb wattage on rate of absorbance. Discussion:Our results for our data runs show a common theme which is, the amount of light does have an effect on the rate of photosynthetic reaction. We can see by looking at the data in Figure 2 and depicted in Figure 3 that the amount of light has a direct influence on the rate of absorbance. The 15W run has a very small decline ending with a change in absorbance of only 7. 5%. The 60W bulb shows a change in absorbance of 58. 2%, and the 120W shows a change of 85. 8%, with a final absorption of almost 0. As shown in Figure 4, the rates of change of the 15W, 60W, and 120W runs a re 0. 75%, 5. 8%, and 13. 06 % absorbance/minute respectively.These results show that the higher the wattage, the faster DCIP turns clear, and the faster photosynthesis proceeds. Although the total change and rate of change of the 120W bulb are greatest, the reaction slows down towards the end of the run, as shown in Figure 3. This slowing of the reaction means that the amount of DCIP in its reduced state is very high, and can no longer accept electrons. This corresponds to Figure 3 because the absorbance is 3. 2% at the end. Which show a very low level of DCIP in the oxidized state. If the DCIP is no longer oxidized it can’t accept electrons which is a vital step in the light dependent reaction.Therefore we expect to observe a slowing of the reaction, and this is seen in Figure 3. The positive and negative controls give us a reference to compare our results to. In our case the 60W run is our positive control and is used in our data runs as a part of our data. It shows a line ar decline in absorbance providing a solid point of reference for a normally functioning system. The negative control provides a reference to a non-functioning Hill Reaction. The negative control shows a system without light and shows that the system will not react without sunlight. It also provides a base for 100% absorbance for each run.In conclusion our data does support our hypothesis and our prediction. As shown in the results, a change in the amount of light will produce a change in rate of the photosynthetic reaction. We predicted that a higher wattage will increase the rate. This was indeed shown in figure 2, with the 120W bulb showing the highest rate of reaction, and the 15W bulb with the slowest rate of synthetic reaction. Also we predicted that the negative control would show no reaction without light. This was supported as shown in Figure 2 with no change in absorption over the 10 min period.To test if the slowing of the reaction is due to a shortage of oxidized DCIP in solution, and not from high wattage, I would run each experiment again for a longer period of time. By doing this it would allow each run to reach a lower absorption. At this low absorption we would expect the rate to slow down due to the lack of oxidized DCIP. If this were true, each wattage would show the same slowing effect at low absorption. If the slowing of the reaction is not observed, the change would be due to a different reason such as a high wattage reducing DCIP’s functionality over time. References: Biology 111 Lab Manual. 2012

Thai Pantene Ad: You Can Shine

Yesterday, I saw an impressive video posted by my friend on Facebook. It’s a Thai Pantene commercial about a deaf and mute girl who plays the violin. At first, I didn’t know that it was actually a shampoo commercial because it’s quite long (4:30) and looks more like a movie trailer. A lot of people was inspired by the advertisement while a few contradicted it. I, for one was captivated by the video but I have to admit that the advertisement failed in so many levels. Well, for being a shampoo commercial, it failed. The story is unrelated and too deep and dramatic for a shampoo. But if it was a movie trailer, it would have been brilliant. The plot and storyline are beautifully intertwined. It actually ruined the mood when one founds out that it was just for a shampoo. (The â€Å"Pantene. You Can Shine.† part) Though putting the shampoo concept aside, this is still a great idea well executed. Honestly, what I really liked about this ad was the use of the piece, Pachelbel Canon in D Major. Maybe because it is my favorite piece. It’s actually the reason why I wanted to play the piano because every time I hear it, it makes me want to play the piece so I can really feel the music. I agree with the old man in the ad who said that â€Å"Music is a visible thing. Close your eyes and you will see.†

In the Modern World, Image Is Everything

It only takes about seven seconds for a stranger to form a first impression of you. Especially in our modern world, the image we project of ourselves is becoming even more crucial since the increasing openness and inter-connectedness of the world makes it much easier for people to do ‘research’ on who you are. An image is paramount to all levels of society from the individual, to the corporate, to the national. Therefore, image does play a pivotal role in our lives in both the public and private domains. Nowadays, it is rare to find someone who does not have a Facebook profile or a Twitter account.Social networking has become a norm in our world today, with so many people putting up their personal lives on the Internet for anyone to see. What we choose to put on the Internet inevitably forms an image of ourselves that we present to others. This image will be able to make or break you regardless of whether you are in the public spotlight. Almost every celebrity has public ists that help him or her manage their public persona. It is often with their reputations that celebrities are able to land the most well paid jobs.Such employers view the celebrity’s good reputation as one that will be able to most effectively sell a product or a movie. Additionally, the way in which a celebrity manages his or her image when hit with a crisis affects his or her future employment prospects. For example, when Kate Moss was hit the scandal of her being photographed snorting cocaine, she did not do anything that would help fan the flame of the scandal. Alternatively, she continued working hard and producing the beautiful shots that her employers wanted. The scandal did not kill her career, as many would have expected.Moss’ career received a boost instead where she signed lucrative contract with Calvin Klein that effectively doubled her income. Additionally, an increasing number of companies are making use of social networking sites to gather background in formation on prospective employees. Countless people have lost out on amazing job opportunities because they posted pictures of them drunk on their Facebook profiles. This then proves that the image that portray of ourselves has a great impact on our lives in that it can help determine your success or failure in your chosen profession.In the corporate world, many businesses are also starting to realize the importance of the image of the company. Image consultants are being paid thousands of dollars to spruce up a company’s profile, where the company hopes that the better the image it presents the more successful it will become. Marketers and advertisers are also making use of prominent public personalities to help sell their products by making them more attractive to the masses. Given a small business, without a company website can be destroyed as a result of any acerbic comment on the Internet.Potential clients upon doing their research and discovering a bad review of the co mpany’s services will decide to patronize the services of another company instead. The significance of a good public profile is seen clearly in the aforementioned example, whereby a company can falter due to the lack of an image that the fails to showcase to the public. Thus, a positive image presented to the masses can prove to be the deciding factor of whether a company succeeds or fails in the event of a public relations problem, proving that image is indeed everything in the corporate world.On a wider scale, image is also critical to the many nations in the world. Small countries very often want to show the world that it is to be underestimated, while developing countries want to show the world that it is growing into its own and is just as capable. The most explicit examples of this are in the countries that vie to host the Olympic Games. Winning the coveted role of hosting the Olympics is often a great source of national pride for a country whereby it can show the world what it is capable of.The prestige that comes with hosting the Olympics is also immensely substantial thus accounting for the many countries wanting to host the Olympics. Even the first Youth Olympic Games was not spared from the competition between countries to host it. Singapore ultimately won this honour and it was widely celebrated by the government and its people. Almost all of Singapore’s youth were involved in the 2010 Youth Olympic Games in one way or another.All were happy to serve their country in any way they could in this grand and prestigious occasion. Another apt example is when China hosted the 2008 Beijing Olympics. China poured billions of dollars into the organization of the Games and spared no expense in ensuring that the Beijing was ready to receive athletes from all around the world. The pride that the Chinese had in the fact that China was hosting the 2008 Olympics was evident in the hundreds of hours of dedicated service that the Chinese selflessly con tributed.Thus, image is of great significance on a national level where countries are able to display what it is made of and can be a source of great national pride. On the other may argue that image is nothing without substance to back it up. Take the example of a customer going to a company for a particular service due to an initial good impression of the company. However, if the company fails to measure up to the image it presents of itself, the customer will be hugely disappointed and will not patronize the services of that company again and might even influence others into avoiding that company.Although one should concede that â€Å"well done is better than well said† as spoken by Benjamin Franklin, the first impression is ultimately one that is more powerful where a good impression often results in good outcomes. Particularly in our modern world where people move so fast that they only have time for first impressions and where the image one presents is one of the most r eliable ways to judge a persons character in such a short time.We have seen in the paragraphs above that image does play a pivotal role in our individual lives, in the corporate world, and on the national level. Despite the fact that actions do speak louder than words and that substance is more important than the image, it cannot be denied that the first impression is often a strong and lasting one. Image is hence essentially everything in our modern world where people are more often than not caught up in flash and superficiality.

Indonesia Environment Essay Example | Topics and Well Written Essays - 1000 words

Indonesia Environment - Essay Example Indonesia is an archipelago in Southeast Asia. This country comprises of 17 000 islands. Of these islands, 6 000 are inhabited. Nonetheless, the name Indonesia originates from the Greek language, and means â€Å"island.† This could therefore, be attributed to the numerous islands that make up the country. The immediate neighbor countries of Indonesia include Malaysia and Papua New Guinea, to the north and east, respectively. The country of Indonesia is known for being part of the â€Å"ring of fire.† This has the largest number of active volcanoes in the world today. In addition, Indonesia is known for its frequent earthquakes, and this is quite related with its active vulcanicity (BBC News Web). According to the BBC News (Web), Indonesia is a highly diverse and multicultural country. It has high ethnic diversity, and is home to more than 300 local languages. Indonesia hosts diverse cultures and indigenous beliefs. The people living in Indonesia, who are of different cu ltures adopt varying lifestyles. These range from the rural hunter-gatherers to the urban elites. The people’s staple food is rice, and side dishes include vegetables and meat. With regard to religion, Indonesia has a population that mainly consists of Muslims. This country is known for having the world’s largest Muslim population. According to Friends of Indonesia (Web), the religious systems found in Indonesia include a wide variety of beliefs, of which 90% claim to be of the Islamic religion. Although Indonesia is known to be the country with the largest Muslim population, the Islamic practices and beliefs of Indonesian Muslims vary slightly from the mainstream Islam. Apart from Islam, Indonesia also hosts other religious groups including Buddhism, Hinduism, Shamatic Animism, Christianity, and Greek Paganism, among others (Friends of Indonesia Web). Nonetheless, because of the dominance of the Islamic religion in Indonesia, other religions have become unpopular, eve n as more people shift from their religions to Islam. Indonesia is located in Southeast Asia. With regard to the economy of Indonesia, the country is known to be the largest economy in Southeast Asia. The nature of the economy of Indonesia is mixed, whereby the government and private sector contributes significantly to the economy. The country engages in exportations, and was in the past years ranked among the top 30 top exporters in the world. Indonesia mainly exports to Japan, the U.S.A., Singapore, and China. In addition, the country also imports goods from China, Singapore, and Japan. Furthermore, natural resources are important to the economy of a country, and contribute to a country’s economy. Indonesia is endowed with a variety of natural resources, which have a significant influence on the country’s economy. These include crude oil, coal, gold, tin, copper, and natural gas (The Economist Web). The country exports some of its natural resources, and imports chemi cals, foodstuffs, machinery, fuels, and equipment, among others. According to The Economist (Web), Indonesia in the past years has shown great economic prowess and sustainability as compared to other countries in Southeast Asia. The booming economy of Indonesia had attracted many investors in the Indonesian market. Additionally, there was a high demand for

The Law as a form of Deterrence for Drinking and Driving Research Paper

The Law as a form of Deterrence for Drinking and Driving - Research Paper Example According to the National Highway Traffic Safety Administration (NHTSA), in the reporting year 2009, alcohol related offenses across the US totaled 15,331 out of 71,048 traffic related offenses, and some studies have placed this estimate at as much as 60 % of all fatalities. Stated in terms of a percentage, this represents over 20 % of all traffic offenses According to the NHTSA, this is a drop overall in the past few decades which coincides with tougher sentencing, greater public awareness and higher conviction rates. However, the numbers continue to be alarming which means that something within the correlation of deterrence and public perception along with convictions and arrests has not been entirely successful. The following will argue that however much deterrence is a factor in the decline of incidents, it is not sufficient to make that much of a significant impact. Toward demonstrating this thesis, the following will look at the legal and social transformations that have taken place, and in turn, examine the nature of deterrence. Before examining the data, existing literature and arguments for and against the relative success of deterrence, a few remarks concerning methodology need to be stated or outlined. In the field of social research, and indeed, any scientific research, there is an important distinction to be made between a correlation and an association that is causal in nature. [Kothari, 2008, p. 138]. There is a common methodological problem with mistaking a correlation as a causal relationship, and this has significant bearing on the following analysis. A simple and absurd example can best illustrate the problem of mistaking a correlation for a causal relation. If we were to say that sea-gulls like eating marine life because they are white, would be a clear mistake of confusing a correlation for a cause. While it is true that sea-gulls eat or diet on seafood to speak, and it is true (mostly true for the sake of an argument) that seagulls have white coloring, it is not true that the color of a bird is going to effect the dietary practices of the bird. The prevalence of the color is being confused for a cause in this instance. While absurd, the example nonetheless highlights an important preliminary methodological consideration. The following will look at the correlations of deterrence as it pertains to lowered amounts of drunk driving offenses and fatalities, but it will do so cautiously. This common problem in social research will be kept in the foreground of the analysis, and concerning ultimate causes of the decline of offenses, this analysis will suspend making an conclusive judgments, and in turn, focus on the 'correlation' of variables that are associated with deterrence and their prevalence. STRATEGIES FOR DETERRENCE. LEGAL STRATEGIES & INTERVENTIONS: Before blood levels became the way in which DUI was determined, arrests used to be done on the basis of the officer acting as a witness and by them administering some basic road-side tests that would evaluate the co-ordina tion and response time of the individual who was suspected of DUI [Chambliss, 2011, p. 63]. Because of the relatively subjective nature of the investigating techniques, and many of the successful challenges to the enforcement of this, the measurement of blood alcohol levels, through blood, breath and urine, became the more accurate standard, and in almost all states the blood alcohol line is .08 % [Chambliss, 2011, p. 64]. Moreover, a more accurate way of measuring blood alcohol levels, impacted the conviction rate for offenders [Chambliss, 2011, p. 65]. However, it did also create a few problems regarding the administration of the test. If a police officer suspects a driver of DUI they can ask them to submit themselves to a

Discuss Jan Gossaerts treatment of the classical nude figure Essay

Discuss Jan Gossaerts treatment of the classical nude figure - Essay Example ddition, in 1508, he visited Rome and returned with visions of bare flesh, erotic vigor and Adam and Eve in the exact transition from naked to almost nude. This pleased his patron Philip of Burgundy who asked him to make portraits of girls for his walls. However, not everybody was pleased with the explicit portraits of Adam and Eve such as the diarist John Evelyn, and they started criticizing Gossaert’s work. Nevertheless, Gossaert continued to make more nude figures despite the criticism and his exhibition has received more than eighty works from all over the world. This paper will discuss John Gossaert’s treatment of classical nude figure in the renaissance art of the period1400-1550. The admiration for Gossaert’s intriguing works of art from Van Mander and Durer make it frustrating that there is quite a few drawings and painting that can be linked to him. He mostly worked alone although is said to have collaborated with a few other landscape painters and other artists such as Gerald David. According to Elkins (2008; p.42), Gossaert excelled particularly in making single panel paintings and portraits, which were about half of his work. Most of his work involved biblical and devotional themes such as those of the Virgin and Child, Adam and Eve, and some episode from the Passion of Christ among others (Grà ¶ssinger, 1997; P. 13). He also introduced mythological themes, which had nude figures with high eroticism. However, his treatment of nude figures was not limited to mythological themes only but was also essential in his devotional and biblical themes such as the drawings and paintings of the Virgin and Child and Adam and Eve. The biblical theme of Adam and Eve of 1520 shows the influence of Rome on Gossaert’s work. The painting gave Gossaert an opportunity to express the male and female nudes at a life size scale in some of his paintings. He impacts a biblical story of the origin of knowledge of sex through the two figures of Adam and Eve entangled in

Repealing National Prohibition in the USA Term Paper

Repealing National Prohibition in the USA - Term Paper Example However, this was not the first time that alcohol was under prohibition in America. The state of Maine was the first state in America to prohibit alcohol; this was far back in the 1850s3. The law made it illegal to possess, manufacture, distribute, consume, advertise, give, or remove alcohol or alcohol-based recipes from a residence or business premise4. The main group that facilitated the implementation of the prohibition was the Anti Saloon League (ASL), a powerful organization that had the support of a majority of the members of the Congress5. People who formulated the law thought that the law would help in reducing the vices in the society, which were associated with alcohol; however, the law elicited widespread debate on the subject. Among the people who were actively involved in the debate were the women who formed two opposing groups. One of the groups, women Christian Temperance Union (WCTU), advocated for the prohibition whereas another group, the Women Organization for Nati onal Prohibition Repeal (WONPR), was against the prohibition6. The main reason that led to the formation of organizations, which were against the prohibition, was that prohibition had led to a significant increase in crime. In addition, prohibition turned people who were previously law-abiding citizens to become criminals7. In addition, prohibition threatened to lead to the moral disintegration of the American society as the people who were supposed to enforce the law were under implication several times in corruption scandals8. Apart from the effects, the prohibition had on the crime rates it also negatively affected several sectors of the economy, which used to provide the livelihoods of millions of America either directly or indirectly. One of the sectors under great impact was the wine industry9. Therefore, for the successful implementation, the government should have first tries to build a consensus and evaluate the effects of the prohibition instead of forcing it down on peopl e10. Annotated Bibliography Behr, Edward. Prohibition: thirteen years that changed America. NY: Arcade Publishing, Inc. 1996. The book offers a comprehensive study of the prohibition of alcohol. It tries to devise reasons that may have brought about certain people to advocate for prohibition strongly. Throughout the book, the author uses temperance to explain why a certain group of people, notably, the Anti-Saloon League (ASL), successfully used temperance to show why alcohol should confront prohibition. In the book, the author tries to analyze the propaganda spread by the ASL to impose fines on certain alcohol manufacturers. The ASL sometimes played the racial cards and tried to capture the American’s hatred towards the Germans to help in the advancement of its goals of imposing prohibition. The author develops the story by showing how â€Å"the good creature of God,† (referring to alcohol) has been an integral part of America. The author even states that the founding president of America, George Washington used to spend huge sums of money on alcohol. By considering these various prominent parties, which were involved and affected, the author is able to paint a more vivid picture of this era.

Notice of cafeteria construction Case Study Example | Topics and Well Written Essays - 250 words

Notice of cafeteria construction - Case Study Example After the renovation, the changes will be made as follows: Meanwhile, you will have to eat lunch outside our building for the three days. Our company has made contracts with three restaurants on Lifelong Building, whose location is next to our building. You will not have to use money to get services from the restaurants for the three days shutdown period. The restaurant will allow every individual to have meals that do not exceed twenty dollars per day upon retrieval of their Employees ID as you would do at our cafeteria. To make it clear, you may spend twenty dollars including taxes in each restaurant (up to 60 dollars in total) in three days. The available restaurants include: If you have any queries regarding the closure of the cafeteria, you can get most of answers from our constructors’ website www.restaurantrenovators.ca. The Human Resource Team are also ready to answer any queries regarding the closure of our cafeteria. Sorry, for any inconvenience

Non-Malignanat Palliative Care -Assignment 2 Assignment

Non-Malignanat Palliative Care - 2 - Assignment Example lignant conditions which need palliative care because of the degree of suffering in the end-stage. One such disease is chronic obstructive pulmonary disease (Croft, 2005). Patients with this condition develop many symptoms which cause great discomfort and despair not only to the patient but also their dear ones. According to Deane (2008), "patients with chronic obstructive pulmonary disease follow a slowly-declining disease trajectory, punctuated by acute episodes of ill health, until the acute episode that proves to be the fatal one." â€Å"More often than not, death is sudden and unexpected† (Deane, 2008). The only solace to such patients would be to provide a comprehensive care which takes care of the physical, psychological, emotional, spiritual and religious needs of the patients so that they lead a peaceful life until their death (Croft, 2005). Such a care is known as palliative care. In this project various aspects of palliative care will be discussed which are individu alized and tailor-made to a 85 year old patient by name James with chronic obstructive pulmonary disease in end-of-life situation. Palliative care needs of patients with COPD James is a known patient of chronic obstructive pulmonary disease and suffers from severe breathlessness, distress, despair and discomfort. Chronic obstructive pulmonary disease or COPD is a devastating medical illness which causes a great degree of human suffering (GOLD, 2008). It characterized by non-reversible airway obstruction due to either emphysema or chronic bronchitis or both. It is not only a major health issue but also a significant source of economic and social burden (Fromer and Cooper, 2008). One of the most frightening and debilitating symptom of COPD is breathlessness which is progressive. The most common cause of COPD is cigarette smoking (Silvermann and Speizer, 1996). This condition affects about 15% of cigarette smokers (NICE, 2004). Many patients with COPD do not receive appropriate end-of0 life care because of the unpredictable course of their disease (Deane, 2008). Along with these symptoms, patients with COPD have other co morbidities which need to be managed too (Deane, 2008). Though the clinical course of COPD is not predicable, end-of-life care is yet possible. In the last year of life, patients like James with COPD are likely to suffer from chronic dyspnea, low mood, weakness, easy fatiguibility and pain (Deane, 2008). COPD most commonly presents as acute infection of the lungs or cough that is productive. The disease is progressive and eventually, the patient develops breathlessness which, over the course of the disease because the most predominant and distressing syndrome. The patient also begins to suffer from exercise intolerance and also easy fatiguibility. All these symptoms make the life of the patient miserable and helpless. The main reason for breathlessness is poor oxygenation of the lungs and ventilation perfusion defects.

Fast, global,and entrepreneurial; supply chain management , hong kong Case Study - 1

Fast, global,and entrepreneurial; supply chain management , hong kong style and interview with victor fung - Case Study Example Several changes have been done since its establishment in a bid to conform to the recent demands in the supply chain management field. Globalization has brought about increased interactions among countries in different continents. As such there has been increased focus on eliminating some of the most recurrent challenges faced during conduction of international business such as language barrier. Organizations conducting international businesses have invested deeply in overcoming language barriers among other challenges leading to elimination of intermediaries such as interpreters. During the first years of its establishment, Li Fung ripped heavily from interpretation due to the ability of its founder to speak English. However, such a role in the modern day is seemingly irrelevant hence the need to come up with other strategies to gain competitive advantage. For instance, Li Fung came shifted focus to production of full products from the entire region rather than a single product from one place. This increased relevance of the company in the supply chain since an organization could rely on Li Fung to get all necessa ry materials required at one point. This implies that organizations need to constantly come up with strategies corresponding to market changes in order to prevent elimination. However, production techniques changed once again hence Li Fung was now charged with the responsibility of managing the entire production process for its clients to come with a finished product. However, changes in economic status in Hong Kong triggered yet another shift to employment of dispersed production. This shows that market status is heavily dependent on the economy among other external factors. The changes evident in the life span of Li Fung are a clear indicator of the many changes requiring attention taking effect in the supply chain management sector. This implies that

Information Systems Management in E-Government Essay

Information Systems Management in E-Government - Essay Example For example, the National Health Service (NHS) aims to have â€Å"access to a far wider, and more detailed suite of digital mapping† (The Health and Social Care Information Centre, 2011). Further, according to HM Government and Ordnance Survey (2011), the initiative of Public Sector Mapping Agreement (PMSA) is targeted to create â€Å"a common location data framework for joining up policy and providing services† and achieve â€Å"better planning to meet e-governance targets and initiatives†. Moreover, there are the Local Government Authorities (LGAs) which are to be extensively inter-networked with the help of ICT integration (The Audit Commission, 2002). 2. Can these targets be achieved? The targets cannot be achieved until it is understood that governance in UK is done through different organisations; hence e-governance will call for extensive coordination of various electronic data and processes. 3. What are the types of problems that are being encountered? Th e inability of the local authorities to sufficiently specify their requirements is a serious problem. â€Å"Around one fifth of authorities (are) reporting that they found it difficult or fairly difficult to specify their requirements in e-government contracts.† (Office of the Deputy Prime Minister et al, 2003, p. 30) Lack of understanding of e-governance is another type of problem. Moreover, there are â€Å"a number of accounts of technologies that were delivered late, mis-specified, failed to provide the required functionality and were slow or costly† (Office of the Deputy Prime Minister et al, 2003, p. 16). 4. What are some of the problems involved in private and public IT projects? Wrong selection of technologies is a major problem. In private sector, scarcity of understanding and process education continues to be a debacle (Kelle & Akbulut, 2005; Jankowicz, 2000). Moreover, lack of political will and socio-technical policy framework may lead to serious concerns in public sector IT projects (Bellamy & Taylor, 1998). 5. What is the impact of technology on business? Technology is designed to simplify the business processes and provide decision support. In the business of e-governance, public interactions through advanced technology interfaces would provide greater participation and understanding. (Guo, Fang, & Winston, 2006) 6. What are some of the real world problems of large IT projects? Software programming error or inadequacy can be a major risk for large IT projects. For example, the Department of Communities and Local Government (DCLG) has revealed concerns about creating optimum software for the purpose of digital mapping and related data analysis (The Health and Social Care Information Centre, 2011). Technological integration in the context of â€Å"change management† is another significant problem, as we have seen in the case of Groupware Technologies (Orlikowski & Hofman, 1997, p. 11). Inter-organisational exchange of critical electronic data is another run time problem in large IT projects. (Bigdeli, Kamal, & deCesare, 2011) Section 2: Analysis 1. How can the technologies used in UK E-Government be expanded and developed? The technologies which are being utilized for the purpose of creating a common platform for UK E-Government are organised inside the Electronic Government Interoperability Framework (eGIF) (Cabinet Office, Office of the E-Envoy, 2001). In expanding this system, we need â€Å"a comprehensive framework to examine the factors affecting

The Utilitarianism ethics theory Essay Example for Free

The Utilitarianism ethics theory Essay Utilitarianism, virtue theory, and deontological ethics are major approaches to normative ethics. They share differences and similarities and also with ethics and morality. Values, virtues, and moral concepts also share a relationship with each other. The Utilitarianism ethics theory suggest that an action is morally correct when it maximizes the total utility to produce more good than bad, or more happiness than suffering. Utilitarianism does not relate to morality nor ethics because these are actions are taken in order for the most usefulness, no matter the outcome or end result. Also if we do not know the end result of something we cannot determine if it is ethical or not. The Virtue theory of ethics is known to be different from utilitarianism and deontological theories because they use ones desires and inclinations that are applied to morality. Virtue theory focuses on one’s characteristics instead of looking at an action that someone is or has taken. Virtue theory relates to ethics because it looks at one’s personal virtues on how to live a good life as well as it takes reason an emotion into account. The Deontological ethics theory is similar to and relates highly to morality. Both morality and deontological ethics refers to how we make choices morally no matter if they are required permitted, forbidden. This theory is the complete opposite of virtue theory. This theory can relate to ethics only because it determines if an action is right or wrong; however, it does not leave room for questions. Virtue, values, and moral concepts all show a relationship to each other that apply more to the virtue theory of ethics. Virtue means to do what is right; values is do what is right based on another person , group, or set of principles; and moral concepts is the rules of right or wrong, and making good, or bad judgment choices. The Virtue theory shows a bigger relationship because this is based on the morals and ethics of building’s one’s character and the following of rules to build better character and morals to live a better life. I too believe I follow the virtue theory of ethics because my moral decisions are based on my own person values, virtues, and moral concepts that are also a reflection of my religion and how I was brought up. For instance, I was brought up following the Catholic Church, and we were to make moral decisions based on the beliefs of the church and was also told to build our character to make us a better person, and to reflect this on others. Reference: Boylan, M. (2009). Basic Ethics, 2nd Edition, Chapter 6, 10, 11. Prentice Hall.

Gender Differences in Neurotoxicity

Gender Differences in Neurotoxicity Abstract Neurotoxicity is damage to the structure and/or function of the peripheral and central nervous systems. It is a common outcome of exposure to hundreds of environmental chemicals, which act via a wide range of mechanisms. Due to the fundamental importance of the nervous system to a fully functioning body, the neurotoxic effects of many chemicals have been well investigated. There is evidence from a number of studies of a difference in susceptibility to environmental neurotoxins between genders. Males appear to be more vulnerable than females. There may be many reasons for this difference, a key one being the neuroprotective activities of the gonadal (sex) hormones, which differ between males and females. The female hormone, oestrogen, is thought to have greater protective activity, from a wide range of chemicals than the male hormone, testosterone. This report will examine the available evidence of a gender difference in susceptibility to environmental neurotoxins, and look into the actions of hormones within the nervous system as one of the main reasons for this difference. Introduction The nervous system (NS) is a fundamental component of a fully functioning human body. Due to the immense importance of the NS, any damage that occurs to this system will have huge repercussions throughout the whole body. Unfortunately, the NS is extremely vulnerable, and neurons, with their unique shape, and long, thin extensions protruding from their cell bodies, are highly susceptible to degeneration, from ageing and from exogenous substances (1, 2). It has been observed that exposure to a range of different environmental chemicals can have adverse effects on the NS, resulting in degeneration of neurons, and leading to onset of various neurological diseases (2, 3). The developing NS in particular is extremely sensitive to the effects of such chemicals (2, 4). Prenatal, and early postnatal, exposure to environmental chemicals, such as lead and those in tobacco smoke, can affect the developmental process within the Central Nervous System (CNS). This can lead to slowed and incorrect development, and neurological problems in the early years of life (4). From both animal studies, and human case reports of inadvertent exposures, there is also evidence to suggest a difference between males and females in their susceptibilities to neurotoxicity of some environmental chemicals (5). There are a number of reasons why this may be, including differences in amounts and activities of metabolic enzymes, differences in rates of absorption between the sexes, different rates of clearance of exogenous substances from the body, and differences in exposure to neurotoxic chemicals; diet, hobbies, occupations, etc (6). However, a key reason may be the neuroprotection that is conferred by gonadal hormones, and their metabolites, within the NS (5). The aim of this report is to research evidence of sex differences in responses to environmental chemicals, and investigate hormonal influences as one of the reasons for this difference. Neurotoxicity of Environmental Chemicals Neurotoxicity is a term used to describe damage to the structure and/or function of the peripheral NS (PNS) and CNS, brought about by exposure to particular exogenous substances (7, 8), which act via a range of mechanisms to induce cellular changes, and often cell death (7). Neurotoxicity can be seen in all ages of individuals exposed to hazardous chemicals, however, the developing NS is particularly vulnerable to their effects (2, 4, 7). Development of the NS involves a series of very specific steps, over a prolonged time period, each one occurring only when the previous is finished, and disruption to these events leads to incorrect development and neurological problems (4). The blood-brain barrier (BBB), which prevents many substances from passing to the brain, is not fully complete until several months of age, leaving the NS susceptible to damage (7). The entire NS is not fully mature until puberty (4). A great number of the reports published concerning neurotoxic effects of chemi cals have reported observations on child subjects. This is due to the fact that the developing NS is much more vulnerable, and so the neurotoxic effects may be more easily noticed. There are over 200 chemicals that have been confirmed as neurotoxic to humans (and other animals)as a result of exposure to them (3). A number of these chemicals are identified in Panel 1 (3), and can be divided into groups; metals, organic solvents, pesticides, and other neurotoxic chemicals. Panel 1. There are over 200 chemicals known to cause neurotoxicity in humans. This list identifies some common ones. Adapted from (3). Chemicals in bold and red are those identified within this report. Different toxins have distinct mechanisms through which they influence the NS. This depends on dose, route and duration of exposure (9). Those chemicals which are most widespread in the environment, and those which cause the most drastic effects, have been extensively investigated, and many of the mechanisms causing neurotoxicity have been identified (9). Given the knowledge of these effects, it is important to investigate the possible neurotoxic influences of the large number of other chemicals prevalent in the environment. Mechanisms of neurotoxicity The main mechanisms encompassed by the afore-mentioned groups of substances include; induction of oxidative stress, alterations to neurotransmitter synthesis including inhibition of synaptic signalling, accumulation of the substance within mitochondria leading to dysfunction, alterations to the flow of ions across neuronal membranes, activation of second messengers to induce apoptosis or inhibit neurogenesis, disruption of DNA/RNA, affecting the differentiation and functioning of glial cells, to indirectly influence neuronal cells, alterations to membrane fluidity, abnormal expression of neurotrophic factors (7, 10-20). There is a requirement for metals in many body processes, including within the NS, providing an additional mechanism by which exogenous metals can induce neurotoxicity (17). They can compete with essential metals for protein binding sites and influence cellular processes (17). For example, lead competes with zinc, which is known to have binding sites present in many important receptor channels, such as the N-methyl-D-aspartate (NMDA) receptor involved in glutamate signalling at the synapse. Lead can displace zinc, and therefore alter functioning of these channels, and so influence glutamatergic functions in the NS (13, 14, 17). A relatively recently proposed mechanism thought to induce neurotoxicity via environmental chemicals, is endocrine disruption. Endocrine disruption is believed to be a crucial mechanism of most neurotoxicants, including metals, solvents, pesticides, Polychlorinated Biphenyls (PCBs), Diethylstilbesterol (DES), etc (21-25). Endocrine disrupting chemicals act by mimicking, enhancing, or antagonising the effects of endogenous oestrogens and androgens (21, 22). Their actions can result in alterations to hormone synthesis and/or release, altered transport and clearance of hormones, altered binding of hormones to their receptors (by binding themselves, thereby either mimicking hormone response, or blocking hormonal activation (24)), or altering components of pathways following receptor activation (22). An example of an endocrine disrupting mechanism is one used by lead, which lowers blood levels of testosterone, thereby de-masculinising certain areas of the male brain, and PCBs, which both mimic and antagonise various oestrogenic functions, and disturb production of androgens (21). As hormones are known to have a role in the development of the CNS, including sexual differentiation (26), disruption to their activities may result in disruption to the development of some brain areas, and the possibility of feminisation or masculinisation of particular brain areas (21-25). The neuroprotective function of hormones (discussed later) may also be hindered due to the endocrine disrupting actions of certain chemicals, allowing for their other neurotoxic mechanisms to have greater damaging effects. Neurotoxic investigations Carrying out investigations into the effects of neurotoxic chemicals is much more difficult in humans than it is in other animals, due to the greater difficulty in controlling the surrounding environment and its influences, and there are many potential variables that can have an effect on the overall result, in particular exposure to other environmental chemicals, drugs, alcohol, tobacco, education, culture, etc (27-31). All the potential confounding factors must be taken into consideration in order to analyse the neurotoxic effects only of the chemical in question (32). Often, environmental chemicals induce delayed neurotoxicity, whereby a patient does not present with symptoms until well after exposure to the chemical has ended, providing another problem to investigators (4). There are many different symptoms that can present upon neurotoxicity; migraines or headaches, confusion, memory loss, Multiple Sclerosis (MS)-like symptoms, problems with sleep, balance and hearing, attention impairment and trouble concentrating, anxiety and depression (8). Alterations to cognitive function, motor function and behaviour are common outcomes of neurotoxicity, and are a useful assessment of the effects of exposure to chemicals (32, 33). There are a wide range of different tests commonly used to assess neurotoxicity to the PNS and CNS (4, 32, 33). Measurements of functions such as motor reflexes, insensitivity to pinpricks on the skin, or impairment of sensitivity to temperature and vibration, provide evidence of PNS toxicity (4, 32, 33). Other functional tests, including IQ (Intelligence Quotient) tests, memory tests, assessment of mood and personality, and behavioural questionnaires, are used to assess toxicity to the CNS (4, 32, 33). Damage to the Nervous System can also be established by use of various brain imaging techniques (e.g. Computed Tomography, Magnetic Resonance Imaging) (9). These are useful in observing physical alterations to brain size and appearance caused by brain tissue atrophy following neurotoxic exposure (9). It is also possible, using these images, to ascertain which regions of the brain are particularly affected (9, 33-35). Despite the large quantity of literature outlining investigations concerning exposure to different neurotoxic chemicals, there are relatively few publications available that have identified a difference in response between males and females. Differences between susceptibilities of a range of age groups, and groups with varying levels of exposure, have been acknowledged frequently (27, 36-38), however reports are rare in which results for men and women are assessed independently, therefore it is often difficult to determine any differences in susceptibility between the sexes. Many reports record numbers of each sex taking part in the study, and match controls accordingly, then proceed to analyse results as a whole (27, 28, 39-45). Others exclude female subjects altogether, rather than including analysis of female results, but separate from the male (29, 30, 46-51). This is often the case when the number of female subjects is small compared to men. However, the results could still be analysed, and any differences between them could be noted. Some fail to establish which sexes have been used at all (52-54). Nevertheless, there is evidence from a number of reports, of a difference between genders in neurological functioning following exposure to neurotoxic chemicals. An extensive search using MEDLINE and EMBASE, of published studies and case reports into neurotoxicity of environmental chemicals, identified a number of studies which observed differences between males and females. For the purpose of this report, only those chemicals with gender differences have been mentioned. Evidence of Gender Differences in neurological outcomes of exposure to Neurotoxic Chemicals Metals There are roughly 40 different metals that exist in the environment, some of which are essential for life to occur (e.g. copper, zinc, etc), others which arent (e.g. mercury, lead, etc) (9). Exposure to metals in the environment has been known to cause adverse effects to both the adult and child human NS for many years (3). The neurotoxic effects of these metals are particularly well characterised, and have been well investigated. Included in this report are three of the major neurotoxic metals, of which there has been much exposure to in the environment, and of which there has been some indication of a sex difference in susceptibility to neurotoxic effects; mercury, lead and manganese. These three metals have been more extensively investigated than others, and therefore sex differences observed should not be ruled out of others, and may also be noted if they are as well examined. Mercury Mercury can take various different forms, each of which has distinct effects on human systems (18). Methylmercury (e.g. contaminated seafood), ethylmercury (e.g. Thimerosol, a component of some vaccines), elemental Mercury (present in industrial vapours), and inorganic mercury compounds (e.g. skin lightening creams) (18). Of these forms, methylmercury has been acknowledged as having the greatest detrimental effect on the correct functioning of the human NS, and in particular, the developing nervous system of children (18). In adults, methylmercury is thought to damage specific brain regions, such as the visual cortex, and parts of the cerebellum, whereas in children, as the NS is not completely developed, the effects are thought to be more widespread (7). It has been observed in a number of studies that male children show greater impairments in NS functioning following exposure than female children. In certain neurological tests, which have an association with methylmercury exposure, namely those assessing finger tapping, tendon reflexes, and leg coordination ability, males achieve poorer results (8, 36, 37, 55-57). As the majority of studies reporting results individually for male and female subjects are those carried out in children, the main sex differences reported here have been observed in children. However, similar results are noted in those adult investigations where males and females were analysed separately (27). McKeowyn-Eyssen et al. (1983), Cordier et al. (2002), Myers et al. (2003), Grandjean et al. (1998), and Marsh et al. (1987), all carried out numerous different tests on school children exposed to methylmercury at varying concentrations, pre- and post-natally. Each of these groups identified that, for those tests which have been shown to be more affected by increasing methylmercury levels, including finger-tapping, abnormal muscle tone, tendon reflexes, and leg coordination, male children showed poorer results (19, 57-60). McKeowyn-Eyssen et al. (1983) carried out the same tests on adults, and found an indication of a similar sex difference, with men being more likely than women to develop neurological disorders, following increases in methylmercury levels (37). Davidson et al. (2000) found that male, but not female, responses in neurological tests increased with methylmercury exposure, which is the opposite of the expected results, however, numerous unexamined variables were identified, which could have had influences on the results of the tests (31). Holmes et al. (2003) identified a link between mercury exposure and autism in children. Higher mercury levels in the hair were found to be associated with milder autistic symptoms (61). Perhaps because those children with milder symptoms were more able to excrete the mercury through their hair, before too much damage occurred. There was a greater number of females showing milder autistic symptoms, and a greater number of males showing severe autistic symptoms (61). From the evidence put forward here, there is a definite implication of a greater susceptibility for males than females to the neurotoxic effects of methylmercury exposure. There is an increased risk of neurotoxicity for children of women with increased levels of mercury in the hair (61). Hair mercury levels in subjects themselves, following equal exposure between the sexes, has been observed on numerous occasions as being lower in males than females, when associated with neurological problems (37, 61, 62). It may be that females have a better ability to excrete mercury through the hair than males, so less is present in body tissues. Lead Lead has long been known as a neurotoxicant, and its widespread release into the environment over the years has resulted in many neurological problems, mainly linked to learning difficulties (17), that have been well studied and characterised (3). Lead toxicity is thought to occur mainly in the hippocampus, cerebellum, and prefrontal cerebral cortex and again, it is thought that children, with their NS still developing, are at greatest risk to the neurotoxic insults of lead (7), so the majority of reports found here have been carried out in children. The elimination of lead from many environmental sources, such as motor vehicle petrol, and paints, has seen a decline in the amount of toxic lead exposure (7). However, it is still a problem in many areas, for example those homes where lead paint has been used in decoration (17). There are a number of studies that have reported a difference in cognitive impairments between male and female children. Tests carried out on school children, in South America, the UK and USA (38, 63-66), all identify a larger correlation between lead levels in the blood and poor cognitive ability in males than in females, while Wasserman et al. (1998) state that mothers reported behavioural problems with male children exposed to lead, more often than with exposed female children (67). An assessment of behavioural problems associated with lead exposure in American children (68) and an assessment of intelligence of children following lead exposure in Port Pirie (69), identified no difference between males and females in the results of their tests, while an assessment of the capabilities of children in school, and association with lead exposure (70), along with another investigation of child IQ by Needleman et al. (71), observed results to suggest females were more susceptible to lead neurotoxicity than male subjects, as they appeared to have greater prevalence of learning difficulties associated with lead. So, there appears to be a significant amount of evidence implying a gender difference in neurotoxicity associated with lead exposure. The majority of reports imply an increased susceptibility for males; however it is important for groups to look at sex differences in future studies, in order to ascertain conclusive results. This evidence also provides a need for investigation of sex differences in effects of lead exposure in adults. Manganese Manganese is another commonly used metal that can cause a toxic effect the NS upon exposure (20, 29, 40, 46, 47). There is a risk of manganese toxicity in various professions, in particular, welding (29, 46), but also through drinking or washing in water containing extraordinarily high levels of manganese (20, 40). There are a large number of reports confirming the neurotoxicity of manganese (20). Investigations have shown decreased intellectual ability in children over-exposed to manganese (40), and mood disturbances in men exposed occupationally (e.g. welders, factory workers.) (29, 40, 46, 47). In children, a report into an association between hair manganese levels and prevalence of hyperactivity, found that while there was a higher amount of manganese present in girls than boys, no difference was found between the sexes in assessment of neurological behaviour tests (72). Perhaps female brains are better able to cope with a higher amount of manganese. In adults, Dietz et al. (2001) found that a relationship between levels of manganese exposure and its effect on the Globus Pallidus area of the brain was seen only in men. These investigators give the reason that female workers have lower blood concentrations of manganese, and have a lower cumulative exposure index (73). However, they do not state whether there was a difference in actual exposure between sexes. If the exposure levels were the same, this could be an indication of increased susceptibility to males. In another study, results of neurological tests following manganese exposure were poorer for men than for women (74). As the majority of studies on manganese actually exclude females from results, or do not give separate results for each sex, it is difficult to make any definite assumptions about gender differences in neurotoxicity susceptibility. Implications from the three studies above provide a suggestion of a sex differences in manganese toxicity, with a greater effect within males. However, in future studies, where possible, females should be included, and the results analysed separately, in order to establish conclusive evidence for sex differences in neurotoxicity to manganese. Solvents There is a vast array of solvents that are used in many different industries and work places, meaning daily exposure for many different workers, including hairdressers, laboratory workers, painters, dry cleaners, and carpet layers, among others (33, 75-78). Due to the composition of solvents, they are particularly dangerous to the tissues of the NS. They are lipophillic compounds, and therefore have strong affinity for tissues rich in lipids, including the brain (33, 79). It is thought that psychomotor performance is the most common deficit (51) of solvent exposure, and prolonged exposure can cause permanent damage (15). Other symptoms include anxiety, insomnia, irritability, memory loss, fatigue and seizures (15, 33, 75). Solvent substances most often consist of a mixture of different chemicals, which can affect different regions of the brain. This can result in difficulties determining the toxic effects of a particular chemical (9). There have been many studies published that report clear association between solvent exposure and neurological deficits. Nelson et al. (1994) report that solvent exposure in workers at an automobile assembly plant, correlates with increased neurological disease, and, noticed in particular, an association with increased prevalence of a condition closely resembling MS (52). Cavalleri et al. (1994) obtained results to indicate deterioration of colour vision in factory workers following perchloroethylene exposure, even at low levels (53), and Boor et al. (1977) confirm a damaging effect of toluene on the CNS (54), a chemical that is also known to effect CNS development prenatally (3). Alcohol (Ethanol) is a major environmental solvent, although exposure rarely occurs occupationally, and it is most often taken in voluntarily (3). Hommer et al. (2001) studied the brain volumes of alcoholic and non-alcoholic men and women, and found that alcoholics had a much smaller volume of grey matter than non-alcoholics. This difference was found to be much more significant in females than males, suggesting an increased susceptibility of females to neurotoxic effects of alcoholism (34). In contrast, Pfefferbaum et al. (2001), in the same journal publication, indicated that the results of their study into alcohol effects on brain structure, show larger cortical sulci and lateral and third ventricles found in the alcoholics compared to non-alcoholics, which was a much greater and more significant difference in male subjects than female subjects. They also note that female brains show quicker and more effective recovery than those of males during abstinence (35). Jacobson (1986) ca rried out a study examining the brains of male and female alcoholics compared to non-alcoholic controls. It was noticed that the appearance of the brains on a CT scan was different between alcoholics and controls. Also observed was the fact that females appear more susceptible to structural changes in the brain following chronic alcohol intake, but are much more effective at recovering following cessation of intake, and the recovery occurs much quicker (80). Taking these 3 reports into consideration, there may be a difference in susceptibility of particular brain areas in males and females; however, females consistently recover more quickly from damage than males, indicating perhaps, a decreased susceptibility to long term damage. Neurophysiological deficits have also been reported in numerous studies of children exposed to alcohol pre-natally (81-83). However, few have noted results separately for male and female children. Nanson and Hiscock (1990) observed that female Fetal Alcohol Syndrome (FAS) children appear to have a higher IQ than males with FAS (83). As mentioned above, the majority of studies into other solvents, such as toluene, trichloroethene, n-hexane, chlorinated solvents (84), and solvent mixtures (49, 50, 76, 78, 85) in the workplace, report an obvious detrimental effect on the CNS, PNS, or both, following exposure. However, the majority included only men in the reports, or male and female results were analysed together. Again, it has been observed that the developing NS is especially susceptible to the neurotoxic effects of solvents, due to their high affinities for the brains lipid tissues (33, 79), and the BBB not being fully formed (7). Laslo-Baker et al. (2004) and Till et al. (2001) carried out studies on organic solvent exposure in pregnant women, taken in accidentally from occupational exposure, and the effects on neurodevelopment of their offspring. Both groups confirmed that children exposed pre-natally had poorer cognitive functioning than those not exposed, with lower results in neurological tests (75, 86). Again, no distinction was made between results for female and male children. Considering the obvious effects of solvents, including alcohol and toluene, on the NS, and the observations of sex differences from other neurotoxins, and the implications of sex differences in effects of alcohol mentioned here, it should be suggested that future studies automatically investigate male and female results separately, and allow for observation of any differences in results. Pesticides The term pesticides encompasses a wide range of chemicals, commonly used within a wide range of industries, particularly agriculture (87, 88). Included are the sub-groups; organophosphates, organochlorines, fumigants, and herbicides, all of which act to damage the NS of an organism, either directly, or via alteration of the cellular mechanisms that support it (87). Pesticides cause concern for human health as they are extremely widely used, and so readily released into the environment (88). It has been known for a long time that exposure to certain levels of these chemicals will adversely affect the human NS, as well as those organisms they are designed against (87, 88). Indeed, numerous studies have linked exposure to various pesticides with a number of neurological disorders, including Parkinsons disease (87, 89). In a similar situation to that for metals and solvents, there are many publications from groups investigating the effects of pesticide exposure on the human Nervous System, using an array of cognitive and neurobehavioural tests, with almost every study confirming the presence of some form of Neurotoxicity in subjects exposed to a range of doses. The following reports have identified separate results for neurological effects of pesticide exposure on male and female subjects, and an apparent greater effect on males. A report investigating the influence on the onset of Parkinsons and Alzheimers Diseases in elderly people living in the south of France, where pesticides are used daily in vineyards, noted a significant association between these disorders and pesticide exposure, in males only (90), suggesting a potentially increased susceptibility to males. Stallones et al. (2002) acknowledge males being at increased risk of developing neurological problems related to pesticide exposure than females, in an investigation into farmers, and their families in Colorado, USA (91), with the percentage of illnesses caused by exposure to pesticides almost three times greater in males. An assessment of neurobehavioural activity of Hispanic agricultural workers (92) identified a significant difference between the genders on results for 2 out of 10 tests, with females scoring lower than males. In the remaining tests, no significant differences were found between the sexes, although all exposed subjects faired worse than control, non-exposed (92). Similarly, pesticide-exposed Ecuadorians achieved lower outcomes in neurobehavioural tasks set by Cole et al. than did non-rural, unexposed Ecuadorians, and females were found to respond better in one task, with no significant difference between genders in others (93, 94). Guillette et al. (1998), carried out an assessment of Preschool children in Mexico, exposed to pesticides through living in close proximity of farm land. They identified a significant difference between those exposed and those living further away from the farm lands, with females performing better than males in several of the neurological tests (95). It appears that when there is a gender difference observed in the neurotoxic effects of pesticides, females tend to fair better than males, implying an increased susceptibility of males to the influences of pesticides on the NS. As it is more commonly males that are in the closest proximity to pesticides, within farming industries in particular, this could have some influence on this hypothesis. However, as the differences are also apparent in male and female children, with equal exposure, it does indicate a greater risk for males. The finding that there was only a significant difference in some tests may indicate an increased susceptibility of some brain areas in males over others, which correlates with results of studies of alcohol and tobacco smoke (below). Other Sources of Environmental Neurotoxicity Tobacco Smoke The chemicals contained in tobacco smoke, particularly nicotine, are now known to cause a variety of neurological problems, in addition to their other effects, including behavioural and cognitive problems during development, tremor, and an increased risk of stroke, from both smoking directly, and through passive smoke; inhalation or exposure prenatally (96-100). Various groups investigating toxicity caused by intake of tobacco smoke have described minor sex difference in the neurological outcome. Louis (2007) reports that, when looking into hand tremor as an outcome of tobacco smoking, the difference in score between smokers and non-smokers is greater in women than in men, which would indicate more of a susceptibility to women, rather than men (96). Jacobsen et al. (2007) investigated auditory and visual attention in adolescent smokers and non-smokers, with and without prenatal exposure to tobacco (101). They observed that different areas of the brain are apparently affected differently in male and female subjects exposed to tobacco smoke. In females, both auditory and visual attentions appear equally vulnerable, performing slightly more poorly in visual tests than males, while in males, auditory attention seems significantly more affected than visual attention, and in this auditory test, males performed substantially worse than females (101). The results of this investigation, put together with those from the Louis (2007) report, point towards sex-specific variation Gender Differences in Neurotoxicity Gender Differences in Neurotoxicity Abstract Neurotoxicity is damage to the structure and/or function of the peripheral and central nervous systems. It is a common outcome of exposure to hundreds of environmental chemicals, which act via a wide range of mechanisms. Due to the fundamental importance of the nervous system to a fully functioning body, the neurotoxic effects of many chemicals have been well investigated. There is evidence from a number of studies of a difference in susceptibility to environmental neurotoxins between genders. Males appear to be more vulnerable than females. There may be many reasons for this difference, a key one being the neuroprotective activities of the gonadal (sex) hormones, which differ between males and females. The female hormone, oestrogen, is thought to have greater protective activity, from a wide range of chemicals than the male hormone, testosterone. This report will examine the available evidence of a gender difference in susceptibility to environmental neurotoxins, and look into the actions of hormones within the nervous system as one of the main reasons for this difference. Introduction The nervous system (NS) is a fundamental component of a fully functioning human body. Due to the immense importance of the NS, any damage that occurs to this system will have huge repercussions throughout the whole body. Unfortunately, the NS is extremely vulnerable, and neurons, with their unique shape, and long, thin extensions protruding from their cell bodies, are highly susceptible to degeneration, from ageing and from exogenous substances (1, 2). It has been observed that exposure to a range of different environmental chemicals can have adverse effects on the NS, resulting in degeneration of neurons, and leading to onset of various neurological diseases (2, 3). The developing NS in particular is extremely sensitive to the effects of such chemicals (2, 4). Prenatal, and early postnatal, exposure to environmental chemicals, such as lead and those in tobacco smoke, can affect the developmental process within the Central Nervous System (CNS). This can lead to slowed and incorrect development, and neurological problems in the early years of life (4). From both animal studies, and human case reports of inadvertent exposures, there is also evidence to suggest a difference between males and females in their susceptibilities to neurotoxicity of some environmental chemicals (5). There are a number of reasons why this may be, including differences in amounts and activities of metabolic enzymes, differences in rates of absorption between the sexes, different rates of clearance of exogenous substances from the body, and differences in exposure to neurotoxic chemicals; diet, hobbies, occupations, etc (6). However, a key reason may be the neuroprotection that is conferred by gonadal hormones, and their metabolites, within the NS (5). The aim of this report is to research evidence of sex differences in responses to environmental chemicals, and investigate hormonal influences as one of the reasons for this difference. Neurotoxicity of Environmental Chemicals Neurotoxicity is a term used to describe damage to the structure and/or function of the peripheral NS (PNS) and CNS, brought about by exposure to particular exogenous substances (7, 8), which act via a range of mechanisms to induce cellular changes, and often cell death (7). Neurotoxicity can be seen in all ages of individuals exposed to hazardous chemicals, however, the developing NS is particularly vulnerable to their effects (2, 4, 7). Development of the NS involves a series of very specific steps, over a prolonged time period, each one occurring only when the previous is finished, and disruption to these events leads to incorrect development and neurological problems (4). The blood-brain barrier (BBB), which prevents many substances from passing to the brain, is not fully complete until several months of age, leaving the NS susceptible to damage (7). The entire NS is not fully mature until puberty (4). A great number of the reports published concerning neurotoxic effects of chemi cals have reported observations on child subjects. This is due to the fact that the developing NS is much more vulnerable, and so the neurotoxic effects may be more easily noticed. There are over 200 chemicals that have been confirmed as neurotoxic to humans (and other animals)as a result of exposure to them (3). A number of these chemicals are identified in Panel 1 (3), and can be divided into groups; metals, organic solvents, pesticides, and other neurotoxic chemicals. Panel 1. There are over 200 chemicals known to cause neurotoxicity in humans. This list identifies some common ones. Adapted from (3). Chemicals in bold and red are those identified within this report. Different toxins have distinct mechanisms through which they influence the NS. This depends on dose, route and duration of exposure (9). Those chemicals which are most widespread in the environment, and those which cause the most drastic effects, have been extensively investigated, and many of the mechanisms causing neurotoxicity have been identified (9). Given the knowledge of these effects, it is important to investigate the possible neurotoxic influences of the large number of other chemicals prevalent in the environment. Mechanisms of neurotoxicity The main mechanisms encompassed by the afore-mentioned groups of substances include; induction of oxidative stress, alterations to neurotransmitter synthesis including inhibition of synaptic signalling, accumulation of the substance within mitochondria leading to dysfunction, alterations to the flow of ions across neuronal membranes, activation of second messengers to induce apoptosis or inhibit neurogenesis, disruption of DNA/RNA, affecting the differentiation and functioning of glial cells, to indirectly influence neuronal cells, alterations to membrane fluidity, abnormal expression of neurotrophic factors (7, 10-20). There is a requirement for metals in many body processes, including within the NS, providing an additional mechanism by which exogenous metals can induce neurotoxicity (17). They can compete with essential metals for protein binding sites and influence cellular processes (17). For example, lead competes with zinc, which is known to have binding sites present in many important receptor channels, such as the N-methyl-D-aspartate (NMDA) receptor involved in glutamate signalling at the synapse. Lead can displace zinc, and therefore alter functioning of these channels, and so influence glutamatergic functions in the NS (13, 14, 17). A relatively recently proposed mechanism thought to induce neurotoxicity via environmental chemicals, is endocrine disruption. Endocrine disruption is believed to be a crucial mechanism of most neurotoxicants, including metals, solvents, pesticides, Polychlorinated Biphenyls (PCBs), Diethylstilbesterol (DES), etc (21-25). Endocrine disrupting chemicals act by mimicking, enhancing, or antagonising the effects of endogenous oestrogens and androgens (21, 22). Their actions can result in alterations to hormone synthesis and/or release, altered transport and clearance of hormones, altered binding of hormones to their receptors (by binding themselves, thereby either mimicking hormone response, or blocking hormonal activation (24)), or altering components of pathways following receptor activation (22). An example of an endocrine disrupting mechanism is one used by lead, which lowers blood levels of testosterone, thereby de-masculinising certain areas of the male brain, and PCBs, which both mimic and antagonise various oestrogenic functions, and disturb production of androgens (21). As hormones are known to have a role in the development of the CNS, including sexual differentiation (26), disruption to their activities may result in disruption to the development of some brain areas, and the possibility of feminisation or masculinisation of particular brain areas (21-25). The neuroprotective function of hormones (discussed later) may also be hindered due to the endocrine disrupting actions of certain chemicals, allowing for their other neurotoxic mechanisms to have greater damaging effects. Neurotoxic investigations Carrying out investigations into the effects of neurotoxic chemicals is much more difficult in humans than it is in other animals, due to the greater difficulty in controlling the surrounding environment and its influences, and there are many potential variables that can have an effect on the overall result, in particular exposure to other environmental chemicals, drugs, alcohol, tobacco, education, culture, etc (27-31). All the potential confounding factors must be taken into consideration in order to analyse the neurotoxic effects only of the chemical in question (32). Often, environmental chemicals induce delayed neurotoxicity, whereby a patient does not present with symptoms until well after exposure to the chemical has ended, providing another problem to investigators (4). There are many different symptoms that can present upon neurotoxicity; migraines or headaches, confusion, memory loss, Multiple Sclerosis (MS)-like symptoms, problems with sleep, balance and hearing, attention impairment and trouble concentrating, anxiety and depression (8). Alterations to cognitive function, motor function and behaviour are common outcomes of neurotoxicity, and are a useful assessment of the effects of exposure to chemicals (32, 33). There are a wide range of different tests commonly used to assess neurotoxicity to the PNS and CNS (4, 32, 33). Measurements of functions such as motor reflexes, insensitivity to pinpricks on the skin, or impairment of sensitivity to temperature and vibration, provide evidence of PNS toxicity (4, 32, 33). Other functional tests, including IQ (Intelligence Quotient) tests, memory tests, assessment of mood and personality, and behavioural questionnaires, are used to assess toxicity to the CNS (4, 32, 33). Damage to the Nervous System can also be established by use of various brain imaging techniques (e.g. Computed Tomography, Magnetic Resonance Imaging) (9). These are useful in observing physical alterations to brain size and appearance caused by brain tissue atrophy following neurotoxic exposure (9). It is also possible, using these images, to ascertain which regions of the brain are particularly affected (9, 33-35). Despite the large quantity of literature outlining investigations concerning exposure to different neurotoxic chemicals, there are relatively few publications available that have identified a difference in response between males and females. Differences between susceptibilities of a range of age groups, and groups with varying levels of exposure, have been acknowledged frequently (27, 36-38), however reports are rare in which results for men and women are assessed independently, therefore it is often difficult to determine any differences in susceptibility between the sexes. Many reports record numbers of each sex taking part in the study, and match controls accordingly, then proceed to analyse results as a whole (27, 28, 39-45). Others exclude female subjects altogether, rather than including analysis of female results, but separate from the male (29, 30, 46-51). This is often the case when the number of female subjects is small compared to men. However, the results could still be analysed, and any differences between them could be noted. Some fail to establish which sexes have been used at all (52-54). Nevertheless, there is evidence from a number of reports, of a difference between genders in neurological functioning following exposure to neurotoxic chemicals. An extensive search using MEDLINE and EMBASE, of published studies and case reports into neurotoxicity of environmental chemicals, identified a number of studies which observed differences between males and females. For the purpose of this report, only those chemicals with gender differences have been mentioned. Evidence of Gender Differences in neurological outcomes of exposure to Neurotoxic Chemicals Metals There are roughly 40 different metals that exist in the environment, some of which are essential for life to occur (e.g. copper, zinc, etc), others which arent (e.g. mercury, lead, etc) (9). Exposure to metals in the environment has been known to cause adverse effects to both the adult and child human NS for many years (3). The neurotoxic effects of these metals are particularly well characterised, and have been well investigated. Included in this report are three of the major neurotoxic metals, of which there has been much exposure to in the environment, and of which there has been some indication of a sex difference in susceptibility to neurotoxic effects; mercury, lead and manganese. These three metals have been more extensively investigated than others, and therefore sex differences observed should not be ruled out of others, and may also be noted if they are as well examined. Mercury Mercury can take various different forms, each of which has distinct effects on human systems (18). Methylmercury (e.g. contaminated seafood), ethylmercury (e.g. Thimerosol, a component of some vaccines), elemental Mercury (present in industrial vapours), and inorganic mercury compounds (e.g. skin lightening creams) (18). Of these forms, methylmercury has been acknowledged as having the greatest detrimental effect on the correct functioning of the human NS, and in particular, the developing nervous system of children (18). In adults, methylmercury is thought to damage specific brain regions, such as the visual cortex, and parts of the cerebellum, whereas in children, as the NS is not completely developed, the effects are thought to be more widespread (7). It has been observed in a number of studies that male children show greater impairments in NS functioning following exposure than female children. In certain neurological tests, which have an association with methylmercury exposure, namely those assessing finger tapping, tendon reflexes, and leg coordination ability, males achieve poorer results (8, 36, 37, 55-57). As the majority of studies reporting results individually for male and female subjects are those carried out in children, the main sex differences reported here have been observed in children. However, similar results are noted in those adult investigations where males and females were analysed separately (27). McKeowyn-Eyssen et al. (1983), Cordier et al. (2002), Myers et al. (2003), Grandjean et al. (1998), and Marsh et al. (1987), all carried out numerous different tests on school children exposed to methylmercury at varying concentrations, pre- and post-natally. Each of these groups identified that, for those tests which have been shown to be more affected by increasing methylmercury levels, including finger-tapping, abnormal muscle tone, tendon reflexes, and leg coordination, male children showed poorer results (19, 57-60). McKeowyn-Eyssen et al. (1983) carried out the same tests on adults, and found an indication of a similar sex difference, with men being more likely than women to develop neurological disorders, following increases in methylmercury levels (37). Davidson et al. (2000) found that male, but not female, responses in neurological tests increased with methylmercury exposure, which is the opposite of the expected results, however, numerous unexamined variables were identified, which could have had influences on the results of the tests (31). Holmes et al. (2003) identified a link between mercury exposure and autism in children. Higher mercury levels in the hair were found to be associated with milder autistic symptoms (61). Perhaps because those children with milder symptoms were more able to excrete the mercury through their hair, before too much damage occurred. There was a greater number of females showing milder autistic symptoms, and a greater number of males showing severe autistic symptoms (61). From the evidence put forward here, there is a definite implication of a greater susceptibility for males than females to the neurotoxic effects of methylmercury exposure. There is an increased risk of neurotoxicity for children of women with increased levels of mercury in the hair (61). Hair mercury levels in subjects themselves, following equal exposure between the sexes, has been observed on numerous occasions as being lower in males than females, when associated with neurological problems (37, 61, 62). It may be that females have a better ability to excrete mercury through the hair than males, so less is present in body tissues. Lead Lead has long been known as a neurotoxicant, and its widespread release into the environment over the years has resulted in many neurological problems, mainly linked to learning difficulties (17), that have been well studied and characterised (3). Lead toxicity is thought to occur mainly in the hippocampus, cerebellum, and prefrontal cerebral cortex and again, it is thought that children, with their NS still developing, are at greatest risk to the neurotoxic insults of lead (7), so the majority of reports found here have been carried out in children. The elimination of lead from many environmental sources, such as motor vehicle petrol, and paints, has seen a decline in the amount of toxic lead exposure (7). However, it is still a problem in many areas, for example those homes where lead paint has been used in decoration (17). There are a number of studies that have reported a difference in cognitive impairments between male and female children. Tests carried out on school children, in South America, the UK and USA (38, 63-66), all identify a larger correlation between lead levels in the blood and poor cognitive ability in males than in females, while Wasserman et al. (1998) state that mothers reported behavioural problems with male children exposed to lead, more often than with exposed female children (67). An assessment of behavioural problems associated with lead exposure in American children (68) and an assessment of intelligence of children following lead exposure in Port Pirie (69), identified no difference between males and females in the results of their tests, while an assessment of the capabilities of children in school, and association with lead exposure (70), along with another investigation of child IQ by Needleman et al. (71), observed results to suggest females were more susceptible to lead neurotoxicity than male subjects, as they appeared to have greater prevalence of learning difficulties associated with lead. So, there appears to be a significant amount of evidence implying a gender difference in neurotoxicity associated with lead exposure. The majority of reports imply an increased susceptibility for males; however it is important for groups to look at sex differences in future studies, in order to ascertain conclusive results. This evidence also provides a need for investigation of sex differences in effects of lead exposure in adults. Manganese Manganese is another commonly used metal that can cause a toxic effect the NS upon exposure (20, 29, 40, 46, 47). There is a risk of manganese toxicity in various professions, in particular, welding (29, 46), but also through drinking or washing in water containing extraordinarily high levels of manganese (20, 40). There are a large number of reports confirming the neurotoxicity of manganese (20). Investigations have shown decreased intellectual ability in children over-exposed to manganese (40), and mood disturbances in men exposed occupationally (e.g. welders, factory workers.) (29, 40, 46, 47). In children, a report into an association between hair manganese levels and prevalence of hyperactivity, found that while there was a higher amount of manganese present in girls than boys, no difference was found between the sexes in assessment of neurological behaviour tests (72). Perhaps female brains are better able to cope with a higher amount of manganese. In adults, Dietz et al. (2001) found that a relationship between levels of manganese exposure and its effect on the Globus Pallidus area of the brain was seen only in men. These investigators give the reason that female workers have lower blood concentrations of manganese, and have a lower cumulative exposure index (73). However, they do not state whether there was a difference in actual exposure between sexes. If the exposure levels were the same, this could be an indication of increased susceptibility to males. In another study, results of neurological tests following manganese exposure were poorer for men than for women (74). As the majority of studies on manganese actually exclude females from results, or do not give separate results for each sex, it is difficult to make any definite assumptions about gender differences in neurotoxicity susceptibility. Implications from the three studies above provide a suggestion of a sex differences in manganese toxicity, with a greater effect within males. However, in future studies, where possible, females should be included, and the results analysed separately, in order to establish conclusive evidence for sex differences in neurotoxicity to manganese. Solvents There is a vast array of solvents that are used in many different industries and work places, meaning daily exposure for many different workers, including hairdressers, laboratory workers, painters, dry cleaners, and carpet layers, among others (33, 75-78). Due to the composition of solvents, they are particularly dangerous to the tissues of the NS. They are lipophillic compounds, and therefore have strong affinity for tissues rich in lipids, including the brain (33, 79). It is thought that psychomotor performance is the most common deficit (51) of solvent exposure, and prolonged exposure can cause permanent damage (15). Other symptoms include anxiety, insomnia, irritability, memory loss, fatigue and seizures (15, 33, 75). Solvent substances most often consist of a mixture of different chemicals, which can affect different regions of the brain. This can result in difficulties determining the toxic effects of a particular chemical (9). There have been many studies published that report clear association between solvent exposure and neurological deficits. Nelson et al. (1994) report that solvent exposure in workers at an automobile assembly plant, correlates with increased neurological disease, and, noticed in particular, an association with increased prevalence of a condition closely resembling MS (52). Cavalleri et al. (1994) obtained results to indicate deterioration of colour vision in factory workers following perchloroethylene exposure, even at low levels (53), and Boor et al. (1977) confirm a damaging effect of toluene on the CNS (54), a chemical that is also known to effect CNS development prenatally (3). Alcohol (Ethanol) is a major environmental solvent, although exposure rarely occurs occupationally, and it is most often taken in voluntarily (3). Hommer et al. (2001) studied the brain volumes of alcoholic and non-alcoholic men and women, and found that alcoholics had a much smaller volume of grey matter than non-alcoholics. This difference was found to be much more significant in females than males, suggesting an increased susceptibility of females to neurotoxic effects of alcoholism (34). In contrast, Pfefferbaum et al. (2001), in the same journal publication, indicated that the results of their study into alcohol effects on brain structure, show larger cortical sulci and lateral and third ventricles found in the alcoholics compared to non-alcoholics, which was a much greater and more significant difference in male subjects than female subjects. They also note that female brains show quicker and more effective recovery than those of males during abstinence (35). Jacobson (1986) ca rried out a study examining the brains of male and female alcoholics compared to non-alcoholic controls. It was noticed that the appearance of the brains on a CT scan was different between alcoholics and controls. Also observed was the fact that females appear more susceptible to structural changes in the brain following chronic alcohol intake, but are much more effective at recovering following cessation of intake, and the recovery occurs much quicker (80). Taking these 3 reports into consideration, there may be a difference in susceptibility of particular brain areas in males and females; however, females consistently recover more quickly from damage than males, indicating perhaps, a decreased susceptibility to long term damage. Neurophysiological deficits have also been reported in numerous studies of children exposed to alcohol pre-natally (81-83). However, few have noted results separately for male and female children. Nanson and Hiscock (1990) observed that female Fetal Alcohol Syndrome (FAS) children appear to have a higher IQ than males with FAS (83). As mentioned above, the majority of studies into other solvents, such as toluene, trichloroethene, n-hexane, chlorinated solvents (84), and solvent mixtures (49, 50, 76, 78, 85) in the workplace, report an obvious detrimental effect on the CNS, PNS, or both, following exposure. However, the majority included only men in the reports, or male and female results were analysed together. Again, it has been observed that the developing NS is especially susceptible to the neurotoxic effects of solvents, due to their high affinities for the brains lipid tissues (33, 79), and the BBB not being fully formed (7). Laslo-Baker et al. (2004) and Till et al. (2001) carried out studies on organic solvent exposure in pregnant women, taken in accidentally from occupational exposure, and the effects on neurodevelopment of their offspring. Both groups confirmed that children exposed pre-natally had poorer cognitive functioning than those not exposed, with lower results in neurological tests (75, 86). Again, no distinction was made between results for female and male children. Considering the obvious effects of solvents, including alcohol and toluene, on the NS, and the observations of sex differences from other neurotoxins, and the implications of sex differences in effects of alcohol mentioned here, it should be suggested that future studies automatically investigate male and female results separately, and allow for observation of any differences in results. Pesticides The term pesticides encompasses a wide range of chemicals, commonly used within a wide range of industries, particularly agriculture (87, 88). Included are the sub-groups; organophosphates, organochlorines, fumigants, and herbicides, all of which act to damage the NS of an organism, either directly, or via alteration of the cellular mechanisms that support it (87). Pesticides cause concern for human health as they are extremely widely used, and so readily released into the environment (88). It has been known for a long time that exposure to certain levels of these chemicals will adversely affect the human NS, as well as those organisms they are designed against (87, 88). Indeed, numerous studies have linked exposure to various pesticides with a number of neurological disorders, including Parkinsons disease (87, 89). In a similar situation to that for metals and solvents, there are many publications from groups investigating the effects of pesticide exposure on the human Nervous System, using an array of cognitive and neurobehavioural tests, with almost every study confirming the presence of some form of Neurotoxicity in subjects exposed to a range of doses. The following reports have identified separate results for neurological effects of pesticide exposure on male and female subjects, and an apparent greater effect on males. A report investigating the influence on the onset of Parkinsons and Alzheimers Diseases in elderly people living in the south of France, where pesticides are used daily in vineyards, noted a significant association between these disorders and pesticide exposure, in males only (90), suggesting a potentially increased susceptibility to males. Stallones et al. (2002) acknowledge males being at increased risk of developing neurological problems related to pesticide exposure than females, in an investigation into farmers, and their families in Colorado, USA (91), with the percentage of illnesses caused by exposure to pesticides almost three times greater in males. An assessment of neurobehavioural activity of Hispanic agricultural workers (92) identified a significant difference between the genders on results for 2 out of 10 tests, with females scoring lower than males. In the remaining tests, no significant differences were found between the sexes, although all exposed subjects faired worse than control, non-exposed (92). Similarly, pesticide-exposed Ecuadorians achieved lower outcomes in neurobehavioural tasks set by Cole et al. than did non-rural, unexposed Ecuadorians, and females were found to respond better in one task, with no significant difference between genders in others (93, 94). Guillette et al. (1998), carried out an assessment of Preschool children in Mexico, exposed to pesticides through living in close proximity of farm land. They identified a significant difference between those exposed and those living further away from the farm lands, with females performing better than males in several of the neurological tests (95). It appears that when there is a gender difference observed in the neurotoxic effects of pesticides, females tend to fair better than males, implying an increased susceptibility of males to the influences of pesticides on the NS. As it is more commonly males that are in the closest proximity to pesticides, within farming industries in particular, this could have some influence on this hypothesis. However, as the differences are also apparent in male and female children, with equal exposure, it does indicate a greater risk for males. The finding that there was only a significant difference in some tests may indicate an increased susceptibility of some brain areas in males over others, which correlates with results of studies of alcohol and tobacco smoke (below). Other Sources of Environmental Neurotoxicity Tobacco Smoke The chemicals contained in tobacco smoke, particularly nicotine, are now known to cause a variety of neurological problems, in addition to their other effects, including behavioural and cognitive problems during development, tremor, and an increased risk of stroke, from both smoking directly, and through passive smoke; inhalation or exposure prenatally (96-100). Various groups investigating toxicity caused by intake of tobacco smoke have described minor sex difference in the neurological outcome. Louis (2007) reports that, when looking into hand tremor as an outcome of tobacco smoking, the difference in score between smokers and non-smokers is greater in women than in men, which would indicate more of a susceptibility to women, rather than men (96). Jacobsen et al. (2007) investigated auditory and visual attention in adolescent smokers and non-smokers, with and without prenatal exposure to tobacco (101). They observed that different areas of the brain are apparently affected differently in male and female subjects exposed to tobacco smoke. In females, both auditory and visual attentions appear equally vulnerable, performing slightly more poorly in visual tests than males, while in males, auditory attention seems significantly more affected than visual attention, and in this auditory test, males performed substantially worse than females (101). The results of this investigation, put together with those from the Louis (2007) report, point towards sex-specific variation