Pesticide toxicity | |
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A sign warning about potential pesticide exposure. | |
Specialty | Emergency medicine, toxicology |
Health effects of pesticides may be acute or delayed in those who are exposed. [1] Acute effects can include pesticide poisoning, which may be a medical emergency. [2] Strong evidence exists for other, long-term negative health outcomes from pesticide exposure including birth defects, fetal death, [3] neurodevelopmental disorder, [4] cancer, and neurologic illness including Parkinson's disease. [5] Toxicity of pesticides depend on the type of chemical, route of exposure, dosage, and timing of exposure. [5]
According to The Stockholm Convention on Persistent Organic Pollutants (2001), 9 of the 12 most dangerous and persistent chemicals were pesticides, [6] [7] so many have now been withdrawn from use.
People can be exposed to pesticides, which include insecticides, herbicides, fungicides, by a number of different routes including: occupation, in the home, at school, in the air, water, soil, and in food. Almost all humans are exposed to some level of pesticides. [5] For example, pesticide drift, may be a potentially significant source of exposure to the general public. [8] Exposure can occur via ingestion, inhalation, or contact with skin. [9] Some pesticides can remain in the environment for prolonged periods of time.
There are concerns that pesticides used to control pests on food crops are dangerous to people who consume those foods. Many food crops, including fruits and vegetables, contain pesticide residues even 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. [10] For example, most people in the United States still have detectable levels of dichlorodiphenyltrichloroethane (DDT), an insecticide, despite its ban in the US in 1972. [7] These concerns are one reason for the organic food movement. In California, 92% of farmworkers are Latino [11] and exposure to pesticides in majority-Latino counties of the state to pesticides is 906% higher than counties in which the Latino population is fewer than 24%. This has raised concerns over environmental justice. [12]
Because of the common use of pesticides in agriculture, the United Nations Codex Alimentarius Commission has recommended international standards for maximum residue limits (MRLs), for individual pesticides in food. [13] In the United States, levels of residues permitted to remain on foods are limited based on tolerance levels considered to be safe as established by the U.S. Environmental Protection Agency (EPA). [14] The EPA sets the permitted levels of pesticide residues based on the toxicity of the pesticide, its breakdown products, the amount and frequency of pesticide application, and how much of the pesticide (i.e. the residue) remains in or on food by the time it is marketed and distributed. [15] Tolerance levels are obtained using scientific risk assessments that pesticide manufacturers are required to conduct—assessments include toxicological studies, exposure modeling and residue studies before a particular pesticide can be registered. However, the effects are tested a single pesticide at a time and there is little information on the possible synergistic effects of exposure to multiple pesticide traces in the air, food and water on human health. [16]
While pesticide use is commonly associated with agriculture, pesticides are also used as part of public health interventions to control vector-borne diseases (e.g. malaria and Dengue fever) and unwanted plants in the landscaping of parks and gardens. [5]
Pesticides are designed to kill living organisms and vary in their mechanisms of action, depending on their class. The major classes of pesticides are organochlorines (OCPs) or persistent organic pollutants (POPs), organophosphates, carbamates, phyrethroids, and triazines. While all pesticides have been shown to have effects on human health, OCPs are notable for significant risk for adverse effects as they dissolve in fatty tissues and can, thus, accumulate to harmful levels in these tissues. For example, some OCPs are structurally similar to estrogen and can mimic the effects of endogenous estrogen via binding to the estrogen receptors. [5] These pesticides exhibit their toxic effects by interfering with hormonal homeostasis, resulting in hormonal dysregulation. This promotes abnormal growth and development of reproductive tissues and can lead to cancer or harmful effects on reproductive health. [9] OCPs or POPs, which were used in agricultural practices in the 1950s, have now been banned in most countries. However, their breakdown products are persistent and can still be found in soil. [17]
Pesticides can also exert their adverse effects on human health by acting on cell receptors and ion channels, suppressing key signal pathways in cells, and by affecting DNA methylation and histone modifications, thus resulting in changes in gene expression and cellular function. [17]
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. [18] In China, an estimated half-million people are poisoned by pesticides each year, 500 of whom die. [19] Pyrethrins, insecticides commonly used in common bug killers, can cause a potentially deadly condition if breathed in. [20]
Many studies have examined the effects of pesticide exposure on the risk of cancer. Associations have been found with: leukemia, lymphoma, brain, kidney, breast, prostate, pancreas, liver, lung, stomach, esophageal, and skin cancers. [7] [21] This increased risk occurs with both residential and occupational exposures. [7] Increased rates of cancer have been found among farm workers who apply these chemicals. [22] Studies suggest an association between carbamate exposure and glioma and meningioma, glyphosate exposure and diffuse large B-cell lymphoma, as well as alachlor exposure and laryngeal cancer. [23] A mother's occupational exposure to pesticides during pregnancy is associated with an increases in her child's risk of leukemia, Wilms' tumor, and brain cancer. [7] [24] Exposure to insecticides within the home and herbicides outside is associated with blood cancers in children. [25] A 2007 systematic review found that "most studies on non-Hodgkin lymphoma and leukemia showed positive associations with pesticide exposure" and thus concluded that cosmetic use of pesticides should be decreased. [26]
The suggested molecular mechanism for association of pesticide exposure and cancer development is damage to genetic materials such as chromosomes, DNA, and histone proteins, or damage to cell organelles such as endoplasmic reticulum, mitochondria, endocrine networks, and nuclear receptors. [21]
This article needs to be updated. The reason given is: https://pubmed.ncbi.nlm.nih.gov/36029574/.(February 2024) |
There is accumulating evidence of neurological effects secondary to pesticide exposure. Acute exposure to high levels of pesticides that affect the central nervous system can cause neurotoxicity, including cognitive and motor changes. [27] [3] In-utero and early-childhood exposure to organophosphates can cause neurodevelopmental impairment, [3] [28] [29] in particular because some pesticides and their metabolites cross the placenta and fetal blood-brain-barrier, which has not fully developed in a fetus. [29] In addition, an accumulation of chronic exposure has been associated with an increased risk of developing neurodegenerative disease later in life. [3] [28] [21] There is strong evidence that chronic exposure to pesticides increases risk of developing Parkinson's disease, potentially through direct toxic effects on dopaminergic neurons (which are depleted in Parkinson's disease). [28] In addition, there is increasing evidence that chronic exposure increases risk of Alzheimer's disease. [28] [21] A review of multiple studies that looked at high pesticide exposure, mainly organophosphates, among agricultural workers further suggested neurological consequences for such exposures. [23] High pesticide exposure is associates with neurologic, neuropsychiatric, and neurodegenerative disorders among agricultural workers who apply the pesticides. [23] [21] The reported disorders are: ADHD, depression, anxiety, dizziness, headaches and olfactory impairment (which was used as an early indicator for neurodegenerative disorders). [23]
The United States Environmental Protection Agency 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. [30] [31] Comparable studies have not been done with newer pesticides that are replacing organophosphates. [32]
Many pesticides act as endocrine-disrupting chemicals (EDC) or substances that interfere with normal hormonal activity. [33] As of 2013, 101 pesticides have been listed as proven or possible endocrine disruptors. As such, high levels of and/or long-term exposure to pesticides can impact reproductive health and is associated with decreased fertility, increased rates of miscarriage, and changes in pattern of maturity. Specifically, triazines, organs-chlorine, and carbamate insecticides have anti-androgenic effects impacting males, resulting in the lack of development of male characteristics including decreases in testicular size, sperm production, and androgen production. [21] A number of pesticides including dibromochlorophane and 2,4-D has been associated with impaired fertility in males. [34] Pesticide exposure resulted in reduced fertility in males, genetic alterations in sperm, a reduced number of sperm, damage to germinal epithelium and altered hormone function. [35]
The effects of endocrine disruption is dependent on the timing of pesticide exposure (for example, during embryogenesis in early pregnancy or in infancy) as windows of varying susceptibility dictate disease manifestation. [33] Several studies suggest that higher levels of pesticides in the blood of the mother is associated with longer time to pregnancy and greater infertility rates. For example, in mothers and/or their partners who reported pesticide exposure, there was an increased risk of miscarriage with the strongest association with exposure during the first three weeks of pregnancy. This is perhaps linked to the possible negative impact of pesticides on oocyte development and fertilization. Similarly, studies evaluating the short-term impact of occupational exposure to a variety of pesticides on reproductive health suggest that pesticides can have deleterious effects on sperm—pesticide exposure, associated with decreased sperm motility, defects in sperm morphology and semen volume. However, the long-term impacts of pesticide exposure on spermatogenesis and fertility are unknown. [29]
Because some pesticides and their resulting metabolites can cross the placenta and, therefore, the blood-brain-barrier, they can also impact development of the fetus; strong evidence links pre- and post-natal exposures to pesticides to congenital disorders, including physical and/or mental disabilities, fetal death and altered fetal growth. [3] [29] [21] Perhaps the more widely known health effect of pesticides is the elevated rate of birth defects in areas in Vietnam sprayed with defoliant or Agent Orange, a 50:50 mixture of 2,4,5-T and 2,4-D, which has been associated with bad health and genetic effects in Malaya and Vietnam. [36] [37] [21] It was also found that offspring who were at some point exposed to pesticides had a low birth weight and had developmental defects. [38] Maternal exposure to pesticides has also been linked to higher incidence of hypospadias in the newborn, which is the abnormal opening of the urethra in males. [21]
Some studies have found increased risks of dermatitis in those exposed. [3]
Additionally, studies have indicated that pesticide exposure is associated with long-term respiratory problems. [39] A significant association was found between exposure to pesticides and decreased lung function along with related airway symptoms. [23] Studies have suggested an association between exposure to pesticides and airway symptoms such as wheezing, cough, shortness of breath, runny nose, sore or irritation of throat, and difficulty breathing. [23] [40] Decreased lung function was associated with occupational exposure to pesticides. Studies have suggested a correlation between inhibition of cholinesterase by pesticides like carbamate and organophosphate and reduction or impairment of lung function. [40] In addition, exposure to pesticides was also reported to be linked with obstructive and restrictive lung conditions. Specifically, organophosphate exposure was associated with lung function decline driven by a restrictive process. [40]
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. [41] [42]
There is increasing evidence that possibly suggests increased risk of development of type 2 diabetes with exposure to pesticides and their metabolites. [9]
Pesticides exposure cannot be studied in placebo controlled trials as this would be unethical. [3] A definitive cause effect relationship therefore cannot be established. [3] Consistent evidence can and has been gathered through other study designs. [3] The precautionary principle is thus frequently used in environmental law such that absolute proof is not required before efforts to decrease exposure to potential toxins are enacted. [43]
The American Medical Association recommend limiting exposure to pesticides. [44] They came to this conclusion due to the fact that surveillance systems currently in place are inadequate to determine problems related to exposure. [44] The utility of applicator certification and public notification programs are also of unknown value in their ability to prevent adverse outcomes. [44]
The World Health Organization 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. [45] According to one study, as many as 25 million workers in developing countries may suffer mild pesticide poisoning yearly. [46] Detectable levels of 50 different pesticides were found in the blood of a representative sample of the U.S. population. [7]
Concerns regarding conflict of interests regarding the research base have been raised for some research into toxicity of pesticides. For example, Richard Doll of the Imperial Cancer Research Fund in England was found to have undisclosed ties to industry funding. [47] [48]
A number of pesticides including the neonicotinoids clothianidin, dinotefuran, imidacloprid are toxic to bees. [49] Exposure to pesticides may be one of the contributory factors to colony collapse disorder. [50] A study in North Carolina indicated that more than 30 percent of the quail tested were made sick by one aerial insecticide application. Once sick, wild birds may neglect their young, abandon their nests, and become more susceptible to predators or disease. [51]
Dichlorodiphenyltrichloroethane, commonly known as DDT, is a colorless, tasteless, and almost odorless crystalline chemical compound, an organochloride. Originally developed as an insecticide, it became infamous for its environmental impacts. DDT was first synthesized in 1874 by the Austrian chemist Othmar Zeidler. DDT's insecticidal action was discovered by the Swiss chemist Paul Hermann Müller in 1939. DDT was used in the second half of World War II to limit the spread of the insect-borne diseases malaria and typhus among civilians and troops. Müller was awarded the Nobel Prize in Physiology or Medicine in 1948 "for his discovery of the high efficiency of DDT as a contact poison against several arthropods". The WHO's anti-malaria campaign of the 1950s and 1960s relied heavily on DDT and the results were promising, though there was a resurgence in developing countries afterwards.
Pesticides are substances that are used to control pests. They include herbicides, insecticides, nematicides, fungicides, and many others. The most common of these are herbicides, which account for approximately 50% of all pesticide use globally. Most pesticides are used as plant protection products, which in general protect plants from weeds, fungi, or insects. In general, a pesticide is a chemical or biological agent that deters, incapacitates, kills, or otherwise discourages pests. Target pests can include insects, plant pathogens, weeds, molluscs, birds, mammals, fish, nematodes (roundworms), and microbes that destroy property, cause nuisance, or spread disease, or are disease vectors. Along with these benefits, pesticides also have drawbacks, such as potential toxicity to humans and other species.
Chlordane, or chlordan, is an organochlorine compound that was used as a pesticide. It is a white solid. In the United States, chlordane was used for termite-treatment of approximately 30 million homes until it was banned in 1988. Chlordane was banned 10 years earlier for food crops like corn and citrus, and on lawns and domestic gardens.
Piperonyl butoxide (PBO) is a pale yellow to light brown liquid organic compound used as an adjuvant component of pesticide formulations for synergy. That is, despite having no pesticidal activity of its own, it enhances the potency of certain pesticides such as carbamates, pyrethrins, pyrethroids, and rotenone. It is a semisynthetic derivative of safrole and is produced from the condensation of the sodium salt of 2-(2-butoxyethoxy) ethanol and the chloromethyl derivative of hydrogenated safrole (dihydrosafrole); or through 1,2-Methylenedioxybenzene.
A pesticide poisoning occurs when pesticides, chemicals intended to control a pest, affect non-target organisms such as humans, wildlife, plants, or bees. There are three types of pesticide poisoning. The first of the three is a single and short-term very high level of exposure which can be experienced by individuals who die by suicide, as well as pesticide formulators. The second type of poisoning is long-term high-level exposure, which can occur in pesticide formulators and manufacturers. The third type of poisoning is a long-term low-level exposure, which individuals are exposed to from sources such as pesticide residues in food as well as contact with pesticide residues in the air, water, soil, sediment, food materials, plants and animals.
Lindane, also known as gamma-hexachlorocyclohexane (γ-HCH), gammaxene, Gammallin and benzene hexachloride (BHC), is an organochlorine chemical and an isomer of hexachlorocyclohexane that has been used both as an agricultural insecticide and as a pharmaceutical treatment for lice and scabies.
Carbofuran is a carbamate pesticide, widely used around the world to control insects on a wide variety of field crops, including potatoes, corn and soybeans. It is a systemic insecticide, which means that the plant absorbs it through the roots, and from there the plant distributes it throughout its organs where insecticidal concentrations are attained. Carbofuran also has contact activity against pests. It is one of the most toxic pesticides still in use.
Malathion is an organophosphate insecticide which acts as an acetylcholinesterase inhibitor. In the USSR, it was known as carbophos, in New Zealand and Australia as maldison and in South Africa as mercaptothion.
Imidacloprid is a systemic insecticide belonging to a class of chemicals called the neonicotinoids which act on the central nervous system of insects. The chemical works by interfering with the transmission of stimuli in the insect nervous system. Specifically, it causes a blockage of the nicotinergic neuronal pathway. By blocking nicotinic acetylcholine receptors, imidacloprid prevents acetylcholine from transmitting impulses between nerves, resulting in the insect's paralysis and eventual death. It is effective on contact and via stomach action. Because imidacloprid binds much more strongly to insect neuron receptors than to mammal neuron receptors, this insecticide is more toxic to insects than to mammals.
Chlorpyrifos (CPS), also known as chlorpyrifos ethyl, is an organophosphate pesticide that has been used on crops, and animals in buildings, and in other settings, to kill several pests, including insects and worms. It acts on the nervous systems of insects by inhibiting the acetylcholinesterase enzyme. Chlorpyrifos was patented in 1966 by Dow Chemical Company.
Persistent organic pollutants (POPs) are organic compounds that are resistant to degradation through chemical, biological, and photolytic processes. They are toxic and adversely affect human health and the environment around the world. Because they can be transported by wind and water, most POPs generated in one country can and do affect people and wildlife far from where they are used and released.
Vinclozolin is a common dicarboximide fungicide used to control diseases, such as blights, rots and molds in vineyards, and on fruits and vegetables such as raspberries, lettuce, kiwi, snap beans, and onions. It is also used on turf on golf courses. Two common fungi that vinclozolin is used to protect crops against are Botrytis cinerea and Sclerotinia sclerotiorum. First registered in 1981, vinclozolin is widely used but its overall application has declined. As a pesticide, vinclozolin is regulated by the United States Environmental Protection Agency. In addition to these restrictions within the United States, as of 2006 the use of this pesticide was banned in several countries, including Denmark, Finland, Norway, and Sweden. It has gone through a series of tests and regulations in order to evaluate the risks and hazards to the environment and animals. Among the research, a main finding is that vinclozolin has been shown to be an endocrine disruptor with antiandrogenic effects.
Endosulfan is an off-patent organochlorine insecticide and acaricide that is being phased out globally. It became a highly controversial agrichemical due to its acute toxicity, potential for bioaccumulation, and role as an endocrine disruptor. Because of its threats to human health and the environment, a global ban on the manufacture and use of endosulfan was negotiated under the Stockholm Convention in April 2011. The ban took effect in mid-2012, with certain uses exempted for five additional years. More than 80 countries, including the European Union, Australia, New Zealand, several West African nations, the United States, Brazil, and Canada had already banned it or announced phase-outs by the time the Stockholm Convention ban was agreed upon. It is still used extensively in India and China despite laws against its use. It is also used in a few other countries. It is produced by the Israeli firm Makhteshim Agan and several manufacturers in India and China. On May 13, 2011, the India Supreme Court ordered a ban on the production and sale of endosulfan in India, pending further notice.
Methoxychlor is a synthetic organochloride insecticide, now obsolete. Tradenames for methoxychlor include Chemform, Maralate, Methoxo, Methoxcide, Metox, and Moxie.
Azinphos-methyl (Guthion) is a broad spectrum organophosphate insecticide manufactured by Bayer CropScience, Gowan Co., and Makhteshim Agan. Like other pesticides in this class, it owes its insecticidal properties to the fact that it is an acetylcholinesterase inhibitor. It is classified as an extremely hazardous substance in the United States as defined in Section 302 of the U.S. Emergency Planning and Community Right-to-Know Act, and is subject to strict reporting requirements by facilities which produce, store, or use it in significant quantities.
Dichlorvos is an organophosphate widely used as an insecticide to control household pests, in public health, and protecting stored products from insects. The compound has been commercially available since 1961. It has become controversial because of its prevalence in urban waterways and the fact that its toxicity extends well beyond insects. Since 1988, dichlorvos cannot be used as a plant protection product in the EU.
Organophosphate poisoning is poisoning due to organophosphates (OPs). Organophosphates are used as insecticides, medications, and nerve agents. Symptoms include increased saliva and tear production, diarrhea, vomiting, small pupils, sweating, muscle tremors, and confusion. While onset of symptoms is often within minutes to hours, some symptoms can take weeks to appear. Symptoms can last for days to weeks.
Environmental toxicology is a multidisciplinary field of science concerned with the study of the harmful effects of various chemical, biological and physical agents on living organisms. Ecotoxicology is a subdiscipline of environmental toxicology concerned with studying the harmful effects of toxicants at the population and ecosystem levels.
Fenpropathrin, or fenopropathrin, is a widely used pyrethroid insecticide in agriculture and household. Fenpropathrin is an ingestion and contact synthetic pyrethroid. Its mode of action is similar to other natural (pyrethrum) and synthetic pyrethroids where in they interfere with the kinetics of voltage gated sodium channels causing paralysis and death of the pest. Fenpropathrin was the first of the light-stable synthetic pyrethroids to be synthesized in 1971, but it was not commercialized until 1980. Like other pyrethroids with an α-cyano group, fenpropathrin also belongs to the termed type II pyrethroids. Type II pyrethroids are a more potent toxicant than type I in depolarizing insect nerves. Application rates of fenpropathrin in agriculture according to US environmental protection agency (EPA) varies by crop but is not to exceed 0.4 lb ai/acre.