Agricultural pesticide contamination results from the use and/or misuse of agricultural pesticides, and is manifested as adverse effects on human health and the environment. An agricultural pesticide is any substance or mixture of substances intended for preventing, destroying or mitigating the effects of any pest that may adversely affect the growth and/or productivity of any agricultural product. The term includes defoliants, fruit-thinning substances, substances that are intended to prevent premature fall of fruits, and substances that may be applied (pre- or post-harvest) to prevent deterioration of agricultural products during storage or transportation.
The development and manufacture of agricultural pesticides became widespread after World War II, as wartime scientific knowledge was applied to several technological initiatives including the production of agricultural pesticides. These chemicals were introduced into U. S. agriculture and subsequently to other parts of the world. They were touted as miracle technology that would eradicate hunger in the world. While agricultural pesticides may not have eradicated hunger and famine in the world, these chemicals have lived up to their expectations in boosting agricultural productivity – increased crop yield and reduced post-harvest losses. For example, pesticides were used effectively for the control of insect and fungal pests of potato in the U. S. in the 1940s, the control of insect pests of rice in Japan in the early 1950s and the control of boll weevil in El Salvador in 1953.
Adverse human health and environmental effects
Agricultural pesticides are, however, deliberately manufactured as poisons, albeit to destroy agricultural pests. By the same token, these chemicals may result in extensive damage to human health and the environment. Adverse human health effects or symptoms of agricultural pesticide contamination include headache, body weakness, blurred vision, vomiting, irritability, impaired concentration and abdominal pain. Other effects include the suppression of the human immune system, non-institutional depression, asthma, reduced sperm concentration and vigor, blood and liver diseases, and nerve damage.
Unfortunately, the adverse health effects of some agricultural pesticides may be latent and insidious and may therefore not be traceable to the incriminating pesticide. Also, adverse health effects such as nausea, body weakness and sweating may be confused with flu which has similar symptoms. In addition, the adverse effects of chronic cases – exposure to relatively low levels of pesticides over a long time period – are not well understood as the symptoms are relatively unobservable, and the health consequences may be delayed. Apart from the adverse effects of the active ingredients of agricultural pesticides, the inert ingredients and impurities may pose more serious adverse health effects. For example, dioxins may be present as impurities in agricultural pesticides while carbon tetrachloride and chloroform often used as inactive ingredients pose substantial risks to the liver and the nervous system.
The adverse effects of agricultural pesticide contamination are not limited to human health but extend to the environment. Pesticide residues may enter streams through run-off and pose dangers to fish, birds, wild animals and plants in the aquatic habitat. In addition, persistent pesticides such as DDT pesticide may bioaccumulate, move through the food chain and eventually be ingested by and adversely affect birds, wild animals and domestic livestock. For example, DDT is implicated in the thinning of the egg shell of bald eagle. The effect of the indiscriminate and excessive use of pesticides on the environment was chronicled by Rachel Carson’s book, Silent Spring, considered by many as instrumental in spurring the environmental movement in the U. S. in the 1960s. Methyl bromide which is currently being replaced by phosphine for the fumigation of stored cocoa beans has been identified as an ozone-depleting substance.
Sources of misuse and/or unsafe use of agricultural pesticides
The incidence of agricultural pesticide contamination or poisoning is exacerbated through misuse and/or unsafe use. Factors of agricultural pesticide misuse and/or unsafe use that are especially prevalent in developing countries include the absence of stringent regulations and the lack of enforcement of existing ones, the failure to follow label instructions and guidelines, and the importation of toxic agricultural pesticides that have been banned or whose use are severely restricted in developed and industrialized countries. Others include the use of leaking equipment, the use of domestic utensils for measuring and dispensing pesticides, exposure to pesticide drifts, failure to wear personal protective equipment (PPE) such as gloves, long pants and respirators and “calendar spraying” – inflexible, scheduled application of pesticides irrespective of the level of pest infestation.
Other unsafe practices that are especially common in developing countries include storage of pesticides in family bedrooms and in unlocked cabinets that can easily be accessed by children, improper disposal of empty pesticide containers, the use of empty containers for domestic purposes – e.g., storing foodstuffs and water for both humans and domestic animals. However, the misuse or unsafe use of agricultural pesticides is not limited to developing countries. Toxic agricultural pesticides that are meant for outdoor use are often used indoors even in developed and industrialized nations for the control of household pests. An extensive indoor application of methyl parathion, a restricted-use agricultural pesticide, led to the temporary relocation of more than 250 households in Jackson County, Mississippi, U. S. in 1997.
Sources of human exposure to agricultural pesticides
Human exposure to agricultural pesticides and the subsequent contamination or poisoning may be occupational, nonoccupational, intentional, unintentional, or accidental. Also, exposure may be through ingestion (oral), through the skin (dermal) or through inhalation (respiratory). Occupational contamination or poisoning has been identified as the most serious problem associated with the use of agricultural pesticides, especially in developing countries. Nonetheless, the effect of accidental contamination can be very serious and even fatal. More than 400 people reportedly died in Iraq in 1972 after eating bread that had been prepared from cereals treated with a fungicide. Also, at least 37 people reportedly died of endosulfan poisoning in Republic of Benin during the 1999/2000 cotton growing season. In 1958, all members of the family of a local chief who is a prominent cocoa farmer at Okebode in southwestern Nigeria were hospitalized after eating a leaf vegetable undergrowth of a cocoa farm that was earlier sprayed with lindane. In 2004, carbofuran pesticide residues found on several batches of noodles manufactured in Nigeria may have resulted in 23 reported cases of vomiting and one death.
Strategies for reducing agricultural pesticide contamination
Several strategies that have been suggested to reduce agricultural pesticide contamination and its effects include comprehensive risk communication and education programs, the use of appropriate personal protective clothing, the discontinuation of calendar spraying, selection of disease-resistant hybrids, and the adoption of Integrated Pesticide Management (IPM). IPM emphasizes non-chemical and cultural cultivation pest control strategies such as removal of diseased plant parts, crop rotation that may disrupt the life cycle of pests, and biological control such as the use of insect predators. While the need exists to prevent or reduce agricultural pesticide contamination and its effects world-wide, special attention needs to be paid to developing countries for several reasons. These include the observations that three-fourths of the estimated annual instances of pesticide poisoning and pesticide-related deaths occur in developing countries, and that these countries represent the fastest growing market for agricultural pesticides. Also, the adverse human health effects of pesticide poisoning are particularly high in many of these countries because of the low nutritional status, and the scarcity of heath care facilities especially in the rural areas where most of the agricultural activities occur.
- Ibitayo, O. O. (2006) Reducing agricutural pesticide poisoning in sub-Sahara Africa: Beyond zero-risk. In Edward C. Booking (ed), Trends in Hazardous Materials Research, Nova Publishers: Hauppauge, NY (Forthcoming).