Health effects of pesticides

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. Exposure can occur via ingestion, inhalation, or contact with skin. 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. 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. 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. 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). 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. 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. 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. == Mechanism of action ==

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 (OCs) 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. 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. 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. == Acute effects ==

Acute health problems tend to be prevalent in workers who handle pesticides, especially in agricultural activity. Common health issues are abdominal pain, dizziness, headaches, nausea, vomiting, and skin and eye conditions. Dizziness is a common acute problem caused by organophosphates and pyrethroids, due to the inhibition of an enzyme that aids the central nervous system (Potential Health Effects of Pesticides). (). Penn State, 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. ==Long-term effects==

Cancer Pesticide residues on food do not cause cancer. Some medical research has suggested glyphosate exposure may cause cancer, but there is no good evidence of this, even with high-level exposure. Agricultural workers exposed to high levels of synthetic pesiticide have an increased prevalence of some cancers (including lymphoma and prostate cancer), and a decreased prevalence of others. Neurological A review of multiple studies that looked at high pesticide exposure, mainly organophosphates, among agricultural workers suggested an association with various neurological disorders, but the evidence was weak. Comparable studies have not been done with newer pesticides that are replacing organophosphates. In-utero and early-childhood exposure 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. in particular because some pesticides and their metabolites cross the placenta and fetal blood-brain-barrier, which has not fully developed in a fetus. Parkinson's disease and Alzheimer's disease An accumulation of chronic exposure has been associated with an increased risk of developing neurodegenerative disease later in life. 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). Organochlorines specifically have been linked with autism. Reproductive effects Many pesticides act as endocrine-disrupting chemicals (EDC) or substances that interfere with normal hormonal activity. 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. 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. 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. 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. A significant association was found between exposure to pesticides and decreased lung function along with related airway symptoms. 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. 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. Other Some studies have found increased risks of dermatitis in those exposed. There is increasing evidence that possibly suggests increased risk of development of type 2 diabetes with exposure to pesticides and their metabolites. ==Prevention==

Pesticides exposure cannot be studied in placebo controlled trials as this would be unethical. The American Medical Association recommend limiting exposure to pesticides. The utility of applicator certification and public notification programs are also of unknown value in their ability to prevent adverse outcomes. ==Epidemiology==

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. 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 the blood of a representative sample of the U.S. population. ==Other animals==

A number of pesticides including the neonicotinoids clothianidin, dinotefuran, imidacloprid are toxic to bees. Exposure to pesticides may be one of the contributory factors to colony collapse disorder. 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. == See also ==