Fact Sheet – Pesticides
Population at risk: 7 million people
Estimated DALYs: 1 million
Pesticides have been used extensively throughout the world to increase agricultural output and protect crops from pests and diseases. They are also used for controlling disease vectors like mosquitoes in malaria areas. Often chemical in form (though heavy metals have also been used), they are used to repel or eliminate species that have an adverse effect on agricultural or horticultural production. Pesticides may be classified according to the organism being targeted, its chemical structure or the potential health hazard it may pose.1 These compounds work by interfering with biological mechanisms, particularly those used for the function of ion channels in the nervous system.2
Pesticides were first used on a large scale starting in the 15th century. Farmers would often use arsenic and lead compounds to eliminate insect species, but it was not until the 17th to 19th centuries that a wider range of pesticides, including nicotine sulfate, pyrethrum, and rotenone were applied to fields. Many of these compounds were extracted from natural products.3 During the Green Revolution, a movement lasting from the 1940s to 1970s, which focused on the promotion of technology development initiatives for agriculture, there was a global promotion and application of synthetic (and was later on understood harmful) agrochemicals. Primarily occurring in India, the programs worked to expand industrial irrigation infrastructure, develop new hybrid seed varieties and foster use of synthetic fertilizers and potentially toxic pesticides. Pesticides have also been used to protect human populations from vector-borne tropical diseases, such as malaria since the 1950s.4
Many pesticides can cause detrimental health effects, including both organophosphate and organochlorine pesticides. These compounds work by disrupting enzymes that regulate specific neurotransmitters. Organochlorines are classified as Persistent Organic Pollutants (POPs), as they may remain the environment for extended periods of time and have global mobility. When introduced into the food chain, they may bioaccumulate with the highest concentrations being found in humans, fish-eating birds and marine mammals. A number of organochlorines, including DDT, chlordane and lindane, have since been largely banned for use in multiple countries as it became clear that their persistence and ability to transport over long distances resulted in severe consequences for wildlife and the environment.5
While not as persistent as organochlorines, organophosphates are considered to be more toxic, and as a result, have had the use restricted or banned. Organophosphate chemicals include chlorpyrifos, methyl parathion, azinphos methyl, and malathion. Other pesticides known or suspected to cause detrimental health effects include glyphosphate, methyl bromide, metadof, duron and novaquat.
A handful of these compounds are so dangerous that some organophosphates were further developed before and during World War II into chemical warfare agents.6 One such compound, Agent Orange, was an equal combination of two herbicides and was used as a defoliant during operations conducted in the Vietnam War era. As manufacture of the herbicides took place at an accelerated pace, it is believed that dioxins were introduced into the defoliant which was then spread onto environments in Vietnam, Laos and Cambodia.7 Obsolete pesticides such as this have been stockpiled around the world, often in poor containment structures that corrode and leak.
The economic costs of acute effects from pesticide exposure are substantial. One study in Nepal found that the average treatment cost from pesticide exposure was around 114 Nepalese Rupees per person, nearly a third of a Nepalese resident’s total health expenditure. Overall, the study found that the health costs for people in Nepal suffering from pesticide-related illnesses were almost eight times higher than for those not directly exposed to pesticides.8
Pure Earth estimates that 7 million people are at risk for exposure to pesticides globally, with an estimated burden of disease of 1 million DALYs. As of 2015, the Toxic Sites Identification Program has identified over 200 sites around the world where exposure to pesticides threatens the health of the population. In view of the global, long-term use of pesticides, this number will very likely increase in the future.
Pathway & Exposure Routes
After application, pesticides are often washed away by rain into bodies of water. Over a million tons of pesticides will experience this fate annually, generally a result of excessive application. Pesticides can also enter the environment through leaching of chemicals from pesticide storage facilities. A number of these compounds are classified as persistent organic pollutants (POPs), which are known to have long life spans and slow deterioration rates. These POPs can bioaccumulate in human and animal tissues and may also increase in concentration throughout the food chain through a process called biomagnification, as many POPs can accumulate in the fats of species and become absorbed by the species’ predators.
Exposure to pesticides most commonly occurs through absorption, inhalation, ingestion and direct dermal contact.9 Dermal exposure may occur during pesticide loading and mixing, application or clean up. Absorption of pesticides through the skin may vary based on the amount of chemical and duration of the exposure event, presence of other foreign substances on the skin, the ambient temperature and humidity, as well as the use of personal protective equipment.20 Pesticides may also enter the body through inhalation during pesticide application or the ingestion of contaminated crops. Multiple cases of food poisoning around the world have also resulted from the ingestion of foodstuffs heavily contaminated with pesticides. For example, between 1993 and 1994, over 600 cases of food poisoning due to pesticides were reported in Vietnam.11 Ingestion of POPs-contaminated foodstuff will also lead to biomagnification in the body fat with related long-term health effects.
Pesticides can be very toxic to the human body. However, some health effects are unique to certain pesticides, as pesticides vary in chemical structure and application. Generally, acute effects from pesticide exposure often include headaches, nausea, dizziness and convulsions. All of these symptoms were reported in a survey of 2,000 agricultural workers in Asia, Africa, and Latin America.12 Unfortunately, acute pesticide poisoning is often underreported and based on inaccurate and inadequate information.13 The World Health Organization (WHO) predicts that nearly 3 million agricultural workers primarily from LMICs suffer from acute pesticide poisoning. Furthermore, they estimate that an additional 20,000 unintentional deaths and 735,000 cases of chronic illness occur as a result of pesticide exposure.14
Multiple studies have indicated that chronic exposure to pesticides may result in neurological, reproductive and dermatological health impacts.15 A variety of health effects have been noted, including chronic head and stomach pains, vision loss, birth defects, damage to the central nervous system, immune system deficiencies, pulmonary diseases, respiratory issues, deformities, DNA damage, hormone system disruption and death. Exposure to pesticides has also been determined to be a risk factor for cancer development. Multiple pesticides have been associated with cancers of the prostate, pancreas, liver and other organs.16 For example, lindane has been associated with breast cancer and fertility problems. Contact with organophosphate residues on fruit and vegetables has also been shown to double a child’s risk for development of attention-deficit/hyperactivity disorder (ADHD) development.17
Exposure to dioxins deriving from such obsolete herbicides such as Agent Orange may result in a number of additional health effects. As dioxin belongs to the class of persistent organic pollutants, it may remain in the environment over long periods of time, contaminating fine soil particle and finding its way into fish, molluscs and fowl. Exposure to dioxin may cause disruption in bodily functioning and reproductive processes. It may additionally affect the skin, as well as the reproductive, immune, cardiovascular, endocrine, gastrointestinal and nervous systems. Pre-natal exposure to dioxin may result in disrupting development of the nervous, reproductive and immune systems.18
1 Anderson SE, Meade BJ. Potential health effects associated with dermal exposure to occupational chemicals. Environmental Health Insights. 2014;8(Suppl 1):51
2 Mostafalou S, Abdollahi M. Pesticides and human chronic diseases: Evidences, mechanisms, and perspectives. Toxicol Appl Pharmacol. 2013;268(2):157-177
3 Miller G, Spoolman S. Living in the environment: Principles, connections, and solutions. Cengage Learning; 2011
4 van den Berg H, Yadav RS, Zaim M. Strengthening public health pesticide management in countries endemic with malaria or other major vector-borne diseases: An evaluation of three strategies. Malar J. 2014;13:368-2875-13-368
5 Van Dyk JS, Pletschke B. Review on the use of enzymes for the detection of organochlorine, organophosphate and carbamate pesticides in the environment. Chemosphere. 2011;82(3):291-307
6 U.S. EPA (U.S. Environmental Protection Agency). Types of pesticides. U.S. EPA Web site. http://www.epa.gov/pesticides/about/types.htm. Published 2014. Updated 2014. Accessed October 2, 2015
7 Bailey CR. Agent orange: History, science, and the politics of uncertainty. by Edwin A. Martini. Pacific Affairs. 2014;87(1):187-189
8 Atreya K. Health costs from short-term exposure to pesticides in Nepal. Soc Sci Med. 2008;67(4):511-519
9 Eddleston M, Bradberry SM, Thompson JP. Pesticides, herbicides, and rodenticides. Oxford Desk Reference: Toxicology. 2014:297
10 Dung NH, Thien TC, Hong N, et al. Impact of agro-chemical use on productivity and health in Vietnam. Economy and environment program for Southeast Asia (EEPSEA); 1999
11 Dung NH, Thien TC, Hong N, et al. Impact of agro-chemical use on productivity and health in Vietnam. Economy and environment program for Southeast Asia (EEPSEA); 1999
12 Pesticide Action Network (PAN) Asia. Communities in Peril: Global report on health impacts of pesticide use in agriculture. Regional reports for PAN International Production Supervision. 2010
13 Litchfield MH. Estimates of acute pesticide poisoning in agricultural workers in less developed countries. Toxicological reviews. 2005;24(4):271-278
14 World Health Organization. Public health impact of pesticides used in agriculture. . 1990
15 Wesseling C, McConnell R, Partanen T, Hogstedt C. Agricultural pesticide use in developing countries: Health effects and research needs. International Journal of Health Services. 1997;27(2):273-308
16 Jaga K, Dharmani C. The epidemiology of pesticide exposure and cancer: A review. Rev Environ Health. 2005;20(1):15-38
17 Bouchard MF, Bellinger DC, Wright RO, Weisskopf MG. Attention-deficit/hyperactivity disorder and urinary metabolites of organophosphate pesticides. Pediatrics. 2010;125(6):e1270-7
18 White SS, Birnbaum LS. An overview of the effects of dioxins and dioxin-like compounds on vertebrates, as documented in human and ecological epidemiology. Journal of Environmental Science and Health, Part C. 2009;27(4):197-211