Everything about Pesticide totally explained
A
pesticide is a substance or mixture of substances used for preventing, controlling, or lessening the damage caused by a
pest.A pesticide may be a
chemical substance, biological agent (such as a virus or bacteria), antimicrobial, disinfectant or device used against any
pest. Pests include
insects, plant
pathogens, weeds,
molluscs,
birds,
mammals,
fish, nematodes (
roundworms) and
microbes that compete with humans for food, destroy property, spread or are a
vector for disease or cause a nuisance. Although there are benefits to the use of pesticides, there are also drawbacks, such as potential toxicity to humans and other animals.
Types of pesticides
There are multiple ways of classifying pesticides.
Pesticides can also be classed as synthetic pesticides or
biological pesticides (biopesticides), although the distinction can sometimes blur.
Broad-spectrum pesticides are those that kill an array of species, while narrow-spectrum, or selective pesticides only kill a small group of species.
A systemic pesticide moves inside a plant following absorption by the plant. With insecticides and most fungicides, this movement is usually upward (through the
xylem) and outward. Increased efficiency may be a result. Systemic insecticides which poison
pollen and
nectar in the
flowers may kill needed
pollinators such as
bees.
Most pesticides work by
poisoning pests.
Uses, benefits and drawbacks
Pesticides are used to control organisms which are considered harmful. For example, they're used to kill
mosquitoes that can transmit potentially deadly diseases like
west nile virus and
malaria. They can also kill
bees,
wasps or
ants that can cause allergic reactions. Insecticides can protect animals from illnesses that can be caused by
parasites such as
fleas. Uncontrolled pests such as termites and mould can damage structures such as houses. One study found that not using pesticides reduced crop yields by about 10%.
DDT, sprayed on the walls of houses, is an organochloride that has been used to fight
malaria since the 1950s. Recent policy statements by the
World Health Organization have given stronger support to this approach.
Dr. Arata Kochi, WHO's malaria chief, said, "One of the best tools we've against malaria is indoor residual house spraying. Of the dozen insecticides WHO has approved as safe for house spraying, the most effective is DDT." Scientists estimate that DDT and other chemicals in the organophosphate class of pesticides have saved 7 million human lives since 1945 by preventing the transmission of diseases such as
malaria,
bubonic plague,
sleeping sickness, and
typhus. A study for the
World Health Organization in 2000 from Vietnam established that non-DDT malaria controls were significantly more effective than DDT use.
In the US, about a quarter of pesticides used are used in houses, yards, parks, golf courses, and swimming pools.
In 1939,
Paul Müller discovered that
DDT was a very effective insecticide. It quickly became the most widely-used pesticide in the world.
In the 1940s manufacturers began to produce large amounts of synthetic pesticides and their use became widespread. Some sources consider the 1940s and 1950s to have been the start of the "pesticide era." Pesticide use has increased 50-fold since 1950 and 2.5 million tons (2.3 million metric tons) of industrial pesticides are now used each year.
Regulation
In most countries, in order to sell or use a pesticide, it must be approved by a government agency. For example, in the
United States, the
Environmental Protection Agency (EPA) does so. Complex and costly studies must be conducted to indicate whether the material is safe to use and effective against the intended pest. During the registration process, a label is created which contains directions for the proper use of the material. Based on acute toxicity, pesticides are assigned to a
Toxicity Class.
Some pesticides are considered too
hazardous for sale to the general public and are designated
restricted use pesticides. Only certified applicators, who have passed an exam, may purchase or supervise the application of restricted use pesticides. The Ontario provincial government promised on September 24, 2007 to also implement a province-wide ban on the cosmetic use of lawn pesticides, for protecting the public. Medical and environmental groups support such a ban. On April 22, 2008, the Provincial Government of Ontario announced that it'll pass legislation that will prohibit, province-wide, the cosmetic use and sale of lawn and garden pesticides.
The Ontario legislation would also echo Massachusetts law requiring pesticide manufacturers to reduce the toxins they use in production. The Province of Prince Edward Island is also considering such legislation.
On April 3, 2008, the Canadian Cancer Society released opinion poll results conducted by Ipsos Reid, which established that a clear majority of residents in the provinces of British Columbia and Saskatchewan want province-wide cosmetic lawn pesticide bans, and that the majority of respondents believe that cosmetic pesticides are a threat to their health.
Though pesticide regulations differ from country to country, pesticides and products on which they were used are traded across international borders. To deal with inconsistencies in regulations among countries, delegates to a conference of the United Nations
Food and Agriculture Organization adopted an International Code of Conduct on the Distribution and Use of Pesticides in 1985 to create voluntary standards of pesticide regulation for different countries. The FAO claims that the code has raised awareness about pesticide hazards and decreased the number of countries without restrictions on pesticide use.
Two other efforts to improve regulation of international pesticide trade are the
United Nations London Guidelines for the Exchange of Information on Chemicals in International Trade and the
United Nations Codex Alimentarius Commission. The former seeks to implement procedures for ensuring that prior informed consent exists between countries buying and selling pesticides, while the latter seeks to create uniform standards for maximum levels of pesticide residues among participating countries. Both initiatives operate on a voluntary basis.
Environmental effects
Pesticide use raises a number of environmental concerns. Over 98% of sprayed insecticides and 95% of herbicides reach a destination other than their target species, including non-target species, air, water, bottom sediments, and food.
Pesticide drift occurs when pesticides suspended in the air as particles are carried by wind to other areas, potentially contaminating them. Pesticides are one of the causes of
water pollution, and some pesticides are
persistent organic pollutants and contribute to
soil contamination.
Health effects
Pesticides can present danger to consumers, bystanders, or workers during manufacture, transport, or during and after use.
The American Medical Association recommends limiting exposure to pesticides and using safer alternatives:
Particular uncertainty exists regarding the long-term effects of low-dose pesticide exposures. Current surveillance systems are inadequate to characterize potential exposure problems related either to pesticide usage or pesticide-related illnesses…Considering these data gaps, it's prudent…to limit pesticide exposures…and to use the least toxic chemical pesticide or non-chemical alternative.
Farmers and workers
There have been many studies of farmers with the goal of determining the health effects of pesticide exposure.
The World Health Organisation and the UN Environment Programme estimate that each year, 3 million workers in agriculture in the developing world experience severe poisoning from pesticides, about 18,000 of whom die.
Organophosphate pesticides have increased in use, because they're less damaging to the environment and they're less persistent than organochlorine pesticides. These are associated with acute health problems for workers that handle the chemicals, such as abdominal pain, dizziness, headaches, nausea, vomiting, as well as skin and eye problems. Additionally, many studies have indicated that pesticide exposure is associated with long-term health problems such as respiratory problems, memory disorders, dermatologic conditions, cancer, depression, neurological deficits, miscarriages, and birth defects. Summaries of peer-reviewed research have examined the link between pesticide exposure and neurologic outcomes and cancer, perhaps the two most significant things resulting in organophosphate-exposed workers.
Consumers
There are concerns that pesticides used to control pests on food crops are dangerous to people who consume those foods. These concerns are one reason for the organic food movement. Many food crops, including fruits and vegetables, contain pesticide residues after being washed or peeled. Chemicals that are no longer used but which are resistant to breakdown for long periods may remain in soil and water and thus in food.
The United Nations Codex Alimentarius Commission has recommended international standards for Maximum Residue Limits (MRLs), for individual pesticides in food.
In the EU, MRLs are set by DG-SANCO
. In the US, levels of residues that remain on foods are limited to tolerance levels that are established by the US EPA and are considered safe. The EPA sets the tolerances based on the toxicity of the pesticide and its breakdown products, the amount and frequency of pesticide application, and how much of the pesticide (for example, the residue) remains in or on food by the time it's marketed and prepared. Tolerance levels are obtained using scientific risk assessments that pesticide manufacturers are required to produce by conducting toxicological studies, exposure modeling and residue studies before a particular pesticide can be registered, however, the effects are tested for single pesticides, and there's little information on possible synergistic effects of exposure to multiple pesticide traces in the air, food and water.
A study published by the United States National Research Council in 1993 determined that for infants and children, the major source of exposure to pesticides is through diet. A study in 2006 measured the levels of organophosphorus pesticide exposure in 23 school children before and after replacing their diet with organic food (food grown without synthetic pesticides). In this study it was found that levels of organophosphorus pesticide exposure dropped dramatically and immediately when the children switched to an organic diet.
In the US, the National Academy of Sciences estimates that between 4,000 and 20,000 cases of cancer are caused per year by pesticide residues in food in allowable amounts.
For example, on page 30 is comprehensive data on pesticides on fruits. Some example data:
Fresh Fruit and
Vegetables |
Number of
Samples Analyzed |
Samples with
Residues Detected |
Percent of
Samples with
Detections |
Different
Pesticides
Detected |
Different
Residues
Detected |
Total Residue
Detections |
| Apples | 774 |
727 |
98 |
33 |
41 |
2,619
|
| Lettuce | 743 |
657 |
88 |
47 |
57 |
1,985
|
| Pears | 741 |
643 |
87 |
31 |
35 |
1,309
|
| Orange Juice | 186 |
93 |
50 |
3 |
3 |
94
|
They were also able to test for multiple pesticides within a single sample and found that:
» These data indicate that 29.5 percent of all samples tested contained no detectable pesticides [parent
compoundand metabolite(s) combined], 30 percent contained 1 pesticide, and slightly over 40 percent » contained more than 1 pesticide. - page 34.
To reduce the amounts of pesticide residues in food, consumers can wash, peel, and cook their food; trim the fat from meat; and eat a variety of foods to avoid repeat exposure to a pesticide typically used on a given crop.
The public
Exposure routes other than consuming food that contains residues, in particular pesticide drift, are potentially significant to the general public.
The
Bhopal disaster occurred when a pesticide plant released 40
tons of
methyl isocyanate (MIC) gas, intermediate chemical in the production of some pesticides. The disaster immediately killed nearly 3,000 people and ultimately caused at least 15,000 deaths.
In China, an estimated half million people are poisoned by pesticides each year, 500 of whom die.
Children have been found to be especially susceptible to the harmful effects of pesticides. A number of research studies have found higher instances of brain cancer,
leukemia and birth defects in children with early exposure to pesticides, according to the
Natural Resources Defense Council. Often used for ridding school buildings of rodents, insects, pests, etc., pesticides only work temporarily and must be re-applied. The poisons found in pesticides are not selectively harmful to just pests and in everyday school environments children (and faculty) are exposed to high levels of pesticides and cleaning materials. "No testing has ever been done specifically pertaining to threats among children"
Peer-reviewed studies now suggest
neurotoxic effects on developing animals from
organophosphate pesticides at legally-tolerable levels, including fewer
nerve cells, lower
birth weights, and lower
cognitive scores. The
EPA finished a 10 year review of the
organophosphate pesticides following the 1996
Food Quality Protection Act, but did little to account for developmental neurotoxic effects, drawing strong criticism from within the agency and from outside researchers.
Some scientists think that exposure to pesticides in the
uterus may have negative effects on a
fetus that may manifest as problems such as growth and behavioral disorders or reduced resistance to pesticide toxicity later in life.
A new study conducted by the
Harvard School of Public Health in Boston, has discovered a 70% increase in the risk of developing
Parkinson's disease for people exposed to even low levels of pesticides.
A 2008 study from Duke University found that the Parkinson's patients were 61 percent more likely to report direct pesticide application than were healthy relatives. Both insecticides and herbicides significantly increased the risk of Parkinson's disease.
One study found that use of pesticides may be behind the finding that the rate of birth defects such as
missing or
very small eyes is twice as high in rural areas as in urban areas. Another study found no connection between eye abnormalities and pesticides.
Continuing development
Pesticide safety education and pesticide applicator regulation are designed to protect the public from pesticide misuse, but don't eliminate all misuse. Reducing the use of pesticides and choosing less toxic pesticides may reduce risks placed on society and the environment from pesticide use. For example,
potato cyst nematodes emerge from their protective cysts in response to a chemical excreted by potatoes; they feed on the potatoes and damage the crop. and the
gypsy moth. However, this can be a costly, time consuming approach that only works on some types of insects.
Some evidence shows that alternatives to pesticides can be equally effective as the use of chemicals. For example,
Sweden has halved its use of pesticides with hardly any reduction in crops.
In Indonesia, farmers have reduced pesticide use on rice fields by 65% and experienced a 15% crop increase.
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