Copper compounds such as copper sulphate are used as fungicides and algaecides, one of the first pesticides ever used was the Bordeaux mixture to control fungal diseases of vines. This fungicide has a history of over a century, and is still used, it is brilliant at withstanding various weather conditions, although the copper can out and pollute streams. It has a high level of corrosiveness and is more phytotoxic than other chemical pesticides.
It has many uses in agriculture such as, control of fungus diseases, correction of copper deficiency in soils, correction of copper deficiency in animals and stimulation of growth for fattening pigs and broiler chickens.
Most pesticides are not persistent and are quickly broken down so it doesn’t get passed along the food chain as to destroy other organisms the pesticide hasn’t been aimed at, so it harmless. However, some pesticides such as DDT are quite harmful. DDT is a colourless substance which is crystalline and was used very widely as an insecticide after 1945 and also wiped out malaria from North America and Europe.
DDT is highly persistent and was seen to accumulate in fatty tissue, when experimented on in America in the early 70’s.
DDT and its metabolic products accumulate through the food chain. In particular, DDT has been cited as a major reason for the decline of the in the and .
DDT is also toxic to aquatic life however was not seen as such a potential threat to humans as it has not been proven to cause cancer however there may be a link to breast cancer and DDT.
By the , in some uses, doses of DDT and other insecticides had to be doubled or tripled as resistant insect strains developed.
DDT was oficially banned from the UK in 1984.
However, many humans contain more DDT than is prmitted by many countried in food.
Many studies however, have been conducted into researching the link between DDT and Cancer but such a link is yet to be proven.
According to Silent Spring by author Rachel Carsons (Published 1962), she accused ‘the chemical industry spreads disinformation and public officials accept industry claims uncritically’.
Silent Spring is credited with the ultimate banning of the in the United States.
In the production and use of herbicides such as Agent Orange, the risk is far higher. Agent Orange (as well as , , and ) contain which have caused serious harm to the health of exposed Vietnamese, South Koreans, Australians, New Zealanders, Canadians and Americans, as well as their children and grandchildren, as this powerful herbicide was used widely in the Vietnam War to uncover enemy base camps.
Agent Orange contains (2,4-D) and (2,4,5-T), which were first manufactured for use in controlling broad-leafed plants. When sprayed on crops such as or , it selectively killed just the broad-leaf plants in a field, the weeds, leaving the crops relatively uneffected.
The herbicide 2,4-D does not contain dioxin, and remains one of the most used herbicides in the world today, but we found out that dioxin, a cancer causing agent is produced as a side effect of the manufacture of 2,4,5-T, and was thus present in any of the herbicides that used it.
Dioxin can cause cancer, various skin disorders and abnormalities in unborn babies even in the tiniest of quantities, however if exposed to in larger quantities, a single gram is sufficient enough to cause the death of 5000 humans.
There are certain pesticides which have relative low human toxicity such as Malathion which is an insecticide of low human toxicity and is commonly used to treat body and head lice and also Scabies. Malathion does however break down into Malaoxon if it enters an indoor environment, proving to be 60 times more toxic then Malathion.
Malathion was sprayed in many cities to combat .. Use of the insecticide has been blamed for large die-off in Long Island.
In , numerous workers in were poisoned by isomalathion, a common impurity in malathion, so the actual level of toxicity has not been evaluated properly.
Warfarin is an example of a rodenticide which does not get passed along the food chain and can also be used to treat thrombosis in humans. When used on rodents, it causes no harm to humans or other organisms as the substances are broken down so there is no risk of it being congested by eg maggots.
Aldrin is also a common insecticide, which breaks down to form dieldrin, a . It is a highly effective alternative to DDT, however is highly persistent as in it is not easily broken down so is easily passed along the food chain into other organisms including humans. It is proven to be more toxic to other organisms than the one it had been targeted at and has therefore been banned throughtout most of the world.
Chemical pest control therefore in ‘good’ to a certain extent.
In personal opinion even though chemical pest control seems to be somewhat effective, there are too many risks associated with it. If a pesticide is unharmful to humans it will be harmful to birds, if it is unharmful to birds it will be harmful to aquatic life, and so on and so forth.
The extent of toxicity could be debated however it would be unethical to test such hypotheses on pregnant women for example, as they would be most susceptible to being harmed.
Pests however are seen detrimental to health and the economy but there should be other means to try and combat it before deciding on chemical methods.
Many pests have only become a problem because of the direct actions of humans. Modifying these actions can often substancially reduce the pest problem.
Alternatives such as biological pest control, selective breeding or just leave crops to be untreated so food can be grown organically.
Biological pest control is seen to be more economically friendly as well as healthier to the environment.
Chemical pollutants toxicate the air and contribute to health hazards. Adults are susceptible to these effects, but children are even more likely to suffer negative effects from pesticide exposure because of their lower body weight, their less developed immune and detoxification systems, and the fact that they're still growing. In and around homes, children spend more time than adults on floors and lawns, where pesticide residues are often found in high concentrations.
BIBLIOGRAPHY
Textbooks
1)
A New Introduction to AS Biology – Bill Indge et al. (Pages 209-212)
2)
Essential AS Biology – Toole and Toole (Pages 376-378)
3)
Journals
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http://www.newscientist.com/channel/health/mg18725174.200
Websites
1)
http://jan.ucc.nau.edu/doetqp/courses/env440/lectures/lec25/lec25.html
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http://www.checnet.org/healthehouse/education/articles-health.asp
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Encyclopaedias
1)
The Encyclopaedia Britannica
2)
Wikipedia Encyclopaedia (various articles)
