Health effects of pesticides
Encyclopedia
Health effects of pesticides may be acute or delayed in those who are exposed. A 2007 systematic review
Systematic review
A systematic review is a literature review focused on a research question that tries to identify, appraise, select and synthesize all high quality research evidence relevant to that question. Systematic reviews of high-quality randomized controlled trials are crucial to evidence-based medicine...

 found that "most studies on non-Hodgkin lymphoma and leukemia showed positive associations with pesticide
Pesticide
Pesticides are substances or mixture of substances intended for preventing, destroying, repelling or mitigating any pest.A pesticide may be a chemical unicycle, biological agent , antimicrobial, disinfectant or device used against any pest...

 exposure" and thus concluded that cosmetic use of pesticides should be decreased. Strong evidence also exists for other negative outcomes from pesticide
Pesticide
Pesticides are substances or mixture of substances intended for preventing, destroying, repelling or mitigating any pest.A pesticide may be a chemical unicycle, biological agent , antimicrobial, disinfectant or device used against any pest...

 exposure including neurological, birth defects, fetal death, and neurodevelopmental disorder.

According to The Stockholm Convention on Persistent Organic Pollutants
Stockholm Convention on Persistent Organic Pollutants
Stockholm Convention on Persistent Organic Pollutants is an international environmental treaty, signed in 2001 and effective from May 2004, that aims to eliminate or restrict the production and use of persistent organic pollutants .- History :...

, 10 of the 12 most dangerous and persistent chemicals are pesticides.

Acute effects

Acute health problems may occur in workers that handle pesticides, such as abdominal pain, dizziness, headaches, nausea, vomiting, as well as skin and eye problems. In China, an estimated half million people are poisoned by pesticides each year, 500 of whom die. Pyrethrins, insecticides commonly used in common bug killers, can cause a potentially deadly condition if breathed in.

Cancer

Many studies have examined the effects of pesticide exposure on the risk of cancer. Associations have been found with: leukemia
Leukemia
Leukemia or leukaemia is a type of cancer of the blood or bone marrow characterized by an abnormal increase of immature white blood cells called "blasts". Leukemia is a broad term covering a spectrum of diseases...

, lymphoma
Lymphoma
Lymphoma is a cancer in the lymphatic cells of the immune system. Typically, lymphomas present as a solid tumor of lymphoid cells. Treatment might involve chemotherapy and in some cases radiotherapy and/or bone marrow transplantation, and can be curable depending on the histology, type, and stage...

, brain, kidney
Kidney cancer
Kidney cancer is a type of cancer that starts in the cells in the kidney.The two most common types of kidney cancer are renal cell carcinoma and urothelial cell carcinoma of the renal pelvis...

, breast
Breast cancer
Breast cancer is cancer originating from breast tissue, most commonly from the inner lining of milk ducts or the lobules that supply the ducts with milk. Cancers originating from ducts are known as ductal carcinomas; those originating from lobules are known as lobular carcinomas...

, prostate
Prostate cancer
Prostate cancer is a form of cancer that develops in the prostate, a gland in the male reproductive system. Most prostate cancers are slow growing; however, there are cases of aggressive prostate cancers. The cancer cells may metastasize from the prostate to other parts of the body, particularly...

, pancreas, liver
Liver cancer
Liver tumors or hepatic tumors are tumors or growths on or in the liver . Several distinct types of tumors can develop in the liver because the liver is made up of various cell types. These growths can be benign or malignant...

, lung
Lung cancer
Lung cancer is a disease characterized by uncontrolled cell growth in tissues of the lung. If left untreated, this growth can spread beyond the lung in a process called metastasis into nearby tissue and, eventually, into other parts of the body. Most cancers that start in lung, known as primary...

, and skin cancer
Skin cancer
Skin neoplasms are skin growths with differing causes and varying degrees of malignancy. The three most common malignant skin cancers are basal cell cancer, squamous cell cancer, and melanoma, each of which is named after the type of skin cell from which it arises...

s. This increased risk occurs with both residential and occupational exposures. Increased rates of cancer have been found among farm workers who apply these chemicals. A mother's occupational exposure to pesticides during pregnancy is associated with an increases in her child's risk of leukemia
Leukemia
Leukemia or leukaemia is a type of cancer of the blood or bone marrow characterized by an abnormal increase of immature white blood cells called "blasts". Leukemia is a broad term covering a spectrum of diseases...

, Wilms' tumor
Wilms' tumor
Wilms' tumor or nephroblastoma is cancer of the kidneys that typically occurs in children, rarely in adults.Its common name is an eponym, referring to Dr. Max Wilms, the German surgeon who first described this kind of tumor....

, and brain cancer.

Neurological

Strong evidence links pesticide exposure to worsened neurological outcomes. The risk of developing Parkinson's disease
Parkinson's disease
Parkinson's disease is a degenerative disorder of the central nervous system...

 is 70% greater in those exposed to even low levels of pesticides. People with Parkinson's were 61% more likely to report direct pesticide application
Pesticide application
Pesticide application refers to the practical way in which pesticides, are delivered to their biological targets...

 than were healthy relatives. Both insecticides and herbicides significantly increased the risk of Parkinson's disease. There are also concerns that long term exposures may increase the risk of dementia
Dementia
Dementia is a serious loss of cognitive ability in a previously unimpaired person, beyond what might be expected from normal aging...

.

The United States Environmental Protection Agency‎ finished a 10 year review of the organophosphate pesticides following the 1996 Food Quality Protection Act
Food Quality Protection Act
The Food Quality Protection Act , or H.R.1627, was passed unanimously by Congress in 1996 and was signed into law by former U.S. President Bill Clinton on August 3, 1996...

, but did little to account for developmental neurotoxic effects, drawing strong criticism from within the agency and from outside researchers.

Reproductive effects

Strong evidence links pesticide exposure to birth defects, fetal death and altered fetal growth. In the United States, increase in birth defects is associated with conceiving in the same period of the year when agrochemicals are in elevated concentrations in surface water. Agent orange
Agent Orange
Agent Orange is the code name for one of the herbicides and defoliants used by the U.S. military as part of its herbicidal warfare program, Operation Ranch Hand, during the Vietnam War from 1961 to 1971. Vietnam estimates 400,000 people were killed or maimed, and 500,000 children born with birth...

, a 50:50 mixture of 2,4,5-T and 2,4-D, has been associated with increased birth defects in Vietnam
Vietnam
Vietnam – sometimes spelled Viet Nam , officially the Socialist Republic of Vietnam – is the easternmost country on the Indochina Peninsula in Southeast Asia. It is bordered by China to the north, Laos to the northwest, Cambodia to the southwest, and the South China Sea –...

.

Fertility

A number of pesticides including dibromochlorophane and 2,4-D has been associated with impaired fertility in males.

Other

Some studies have found increased risks of dermatitis
Dermatitis
-Etymology:Dermatitis derives from Greek derma "skin" + -itis "inflammation" and genetic disorder.-Terminology:There are several different types of dermatitis. The different kinds usually have in common an allergic reaction to specific allergens. The term may describe eczema, which is also called...

 in those exposed.

Additionally, studies have indicated that pesticide exposure is associated with long-term health problems such as respiratory problems, memory disorders, depression,. Summaries of peer-reviewed research have examined the link between pesticide exposure and neurologic outcomes and cancer
Cancer
Cancer , known medically as a malignant neoplasm, is a large group of different diseases, all involving unregulated cell growth. In cancer, cells divide and grow uncontrollably, forming malignant tumors, and invade nearby parts of the body. The cancer may also spread to more distant parts of the...

, perhaps the two most significant things resulting in organophosphate-exposed workers.

According to researchers from the National Institutes of Health
National Institutes of Health
The National Institutes of Health are an agency of the United States Department of Health and Human Services and are the primary agency of the United States government responsible for biomedical and health-related research. Its science and engineering counterpart is the National Science Foundation...

 (NIH), licensed pesticide applicators who used chlorinated pesticides on more than 100 days in their lifetime were at greater risk of diabetes. One study found that associations between specific pesticides and incident diabetes ranged from a 20 percent to a 200 percent increase in risk. New cases of diabetes were reported by 3.4 percent of those in the lowest pesticide use category compared with 4.6 percent of those in the highest category. Risks were greater when users of specific pesticides were compared with applicators who never applied that chemical.

Route of exposure

People can be exposed to pesticides by a number of different routes including: occupation, in the home, at school and in their food.

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
Organic food
Organic foods are foods that are produced using methods that do not involve modern synthetic inputs such as synthetic pesticides and chemical fertilizers, do not contain genetically modified organisms, and are not processed using irradiation, industrial solvents, or chemical food additives.For the...

 movement. Many food crops, including fruits and vegetables, contain pesticide residue
Pesticide residue
Pesticide residue refers to the pesticides that may remain on or in food after they are applied to food crops. The levels of these residues in foods is often stipulated by regulatory bodies in many countries...

s after being washed or peeled. Chemicals that are no longer used but that are resistant to breakdown for long periods may remain in soil and water and thus in food.

The United Nations Codex Alimentarius
Codex Alimentarius
The Codex Alimentarius is a collection of internationally recognized standards, codes of practice, guidelines and other recommendations relating to foods, food production and food safety. Its name derives from the Codex Alimentarius Austriacus...

 Commission has recommended international standards for maximum residue limit
Maximum Residue Limit
Pesticide residues on crops are monitored with reference to Maximum Residue Limits and are based on analysis of quantity of a given AI remaining on food product samples...

s (MRLs), for individual pesticides in food.

In the EU, MRLs
Maximum Residue Limit
Pesticide residues on crops are monitored with reference to Maximum Residue Limits and are based on analysis of quantity of a given AI remaining on food product samples...

 are set by DG-SANCO. In the United States, levels of residues that remain on foods are limited to tolerance levels that are established by the U.S. Environmental Protection Agency‎ 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
Pesticide application
Pesticide application refers to the practical way in which pesticides, are delivered to their biological targets...

, and how much of the pesticide (i.e., the residue) remains in or on food by the time it is 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 is 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
United States National Research Council
The National Research Council of the USA is the working arm of the United States National Academies, carrying out most of the studies done in their names.The National Academies include:* National Academy of Sciences...

 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
Organophosphate
An organophosphate is the general name for esters of phosphoric acid. Phosphates are probably the most pervasive organophosphorus compounds. Many of the most important biochemicals are organophosphates, including DNA and RNA as well as many cofactors that are essential for life...

 pesticide exposure in 23 school children before and after replacing their diet with organic food
Organic food
Organic foods are foods that are produced using methods that do not involve modern synthetic inputs such as synthetic pesticides and chemical fertilizers, do not contain genetically modified organisms, and are not processed using irradiation, industrial solvents, or chemical food additives.For the...

 (food grown without synthetic pesticides). In this study it was found that levels of organophosphorus
Organophosphorus
Organophosphorus compounds are degradable organic compounds containing carbon–phosphorus bonds , used primarily in pest control as an alternative to chlorinated hydrocarbons that persist in the environment...

 pesticide exposure dropped dramatically and immediately when the children switched to an organic diet.

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, however, many pesticides are systemic, which means they penetrate into the fruit and vegetable itself and cannot be washed off. Many pesticides are also by design created to be rain-proof.

Strawberries and tomatoes are the two crops with the most intensive use of soil fumigants. They are particularly vulnerable to several type of diseases, insects, mites, and parasitic worms. In 2003, in California alone, 3.7 million pounds (1,700 metric tons) of metam sodium were used on tomatoes. In recent years other farmers have demonstrated that it is possible to produce strawberries and tomatoes without the use of harmful chemicals and in a cost effective way.

Exposure routes other than consuming food that contains residues, in particular pesticide drift, are potentially significant to the general public.

Some pesticides can remain in the environment for prolonged periods of time for example most people in the United States still have detectable levels of (DDT) in their bodies even though it was banned in the US in 1972.

Prevention

Pesticides exposure cannot be studied in placebo controlled trials as this would be unethical. A definitive cause effect relationship therefore cannot be established. Consistent evidence can and has been gathered through other study designs. The precautionary principle
Precautionary principle
The precautionary principle or precautionary approach states that if an action or policy has a suspected risk of causing harm to the public or to the environment, in the absence of scientific consensus that the action or policy is harmful, the burden of proof that it is not harmful falls on those...

 is thus frequently used in environmental law
Environmental law
Environmental law is a complex and interlocking body of treaties, conventions, statutes, regulations, and common law that operates to regulate the interaction of humanity and the natural environment, toward the purpose of reducing the impacts of human activity...

 such that absolute proof is not required before efforts to decrease exposure to potential toxins are enacted.

The American Medical Association
American Medical Association
The American Medical Association , founded in 1847 and incorporated in 1897, is the largest association of medical doctors and medical students in the United States.-Scope and operations:...

 recommend limiting exposure to pesticides. They came to this conclusion due to the fact that surveillance systems currently in place are inadequate to determine problems related to exposure. The utility of applicator certification and public notification programs are also of unknown value in there ability to prevent adverse outcomes.

Epidemiology

The World Health Organization
World Health Organization
The World Health Organization is a specialized agency of the United Nations that acts as a coordinating authority on international public health. Established on 7 April 1948, with headquarters in Geneva, Switzerland, the agency inherited the mandate and resources of its predecessor, the Health...

 and the UN Environment Programme estimate that each year, 3 million workers in agriculture in the developing world experience severe poisoning from pesticides
Pesticide poisoning
A pesticide poisoning occurs when chemicals intended to control a pest affect non-target organisms such as humans, wildlife, or bees.-Cause:The most common exposure scenarios for pesticide-poisoning cases are accidental or suicidal poisonings, occupational exposure, by-stander exposure to...

, about 18,000 of whom die. According to one study, as many as 25 million workers in developing countries may suffer mild pesticide poisoning yearly. Detectable levels of 50 different pesticides were found in blood samples of a group people in the United States .

Society and culture

Concerns regarding conflict of interests regarding the research base have been raised. A number of researchers involved with pesticides have been found to have undisclosed ties to industry including: Richard Doll
Richard Doll
Sir William Richard Shaboe Doll CH OBE FRS was a British physiologist who became the foremost epidemiologist of the 20th century, turning the subject into a rigorous science. He was a pioneer in research linking smoking to health problems...

 or the Imperial Cancer Research Fund in England and Hans-Olov Adami of the Karolinska Institute in Sweden.

In other animals

A number of pesticides including clothianidin
Clothianidin
Clothianidin is an insecticide developed by Takeda Chemical Industries and Bayer AG. Similar to thiamethoxam and imidacloprid, it is a neonicotinoid. Neonicotinoids are a class of insecticides which act on the central nervous system of insects with lower toxicity to mammals...

, dinotefuran
Dinotefuran
Dinotefuran is an insecticide of the neonicotinoid class developed by Mitsui Chemicals for control of insect pests such as aphids, whiteflies, thrips, leafhoppers, leafminers, sawflies, mole cricket, white grubs, lacebugs, billbugs, beetles, mealybugs, and cockroaches on leafy vegetables, in...

, imidacloprid
Imidacloprid
Imidacloprid is a nicotine-based, systemic insecticide, which acts as a neurotoxin and belongs to a class of chemicals called the neonicotinoids. Although it is now off patent, the primary manufacturer of this chemical is Bayer CropScience,...

 are toxic to bees. Exposure to pesticides may be one of the contributory factors to colony collapse disorder
Colony Collapse Disorder
Colony collapse disorder is a phenomenon in which worker bees from a beehive or European honey bee colony abruptly disappear. While such disappearances have occurred throughout the history of apiculture, the term colony collapse disorder was first applied to a drastic rise in the number of...

.
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