Pesticides are chemicals used to eliminate or control a variety of agricultural pests that can damage crops and livestock and reduce farm productivity. The most commonly applied pesticides are insecticides (to kill insects), herbicides (to kill weeds), rodenticides (to kill rodents), and fungicides (to control fungi, mold, and mildew). The latest US Environmental Protection Agency (EPA) information on US pesticide usage, from 2007, reports that over 1 billion tons of pesticides are used in the US every year. 1 This is 22% of the estimated 5.2 billion pounds of pesticides used worldwide. 1 Agricultural use accounted for 80% of pesticide use in the US. 1 Of the pesticide classes, herbicides are the most widely used in all US sectors. 1
Pesticides are not a modern invention. Elemental sulfur was used by ancient Sumerians to protect their crops from insects. Medieval farmers and scientists experimented with chemicals ranging from arsenic to lead on common crops. Nineteenth century research focused on more natural techniques involving compounds made with the roots of tropical vegetables and chrysanthemums. 2 In 1939, Dichloro-Diphenyl-Trichloroethane, or DDT, was discovered to be extremely effective and rapidly became the most widely used insecticide in the world. Twenty years later, serious concerns about the human safety and biological effects of DDT led 86 countries to ban its use. 2 The consolidation of farms and subsequent rise in industrial growing practices (such as monocropping ) that began in the 1950s kicked off an era of heavy pesticide use. 4 There are over 350,000 current and historic pesticide products registered in the United States, 5 and the pesticide business is a 12.5 billion dollar industry in the US alone. 1
Pesticides are tested and approved for use by the EPA, which establishes “tolerances,” or maximum residue levels, that describe the amount of a given pesticide that can safely remain in or on a food. 6 The US Food and Drug Administration (FDA) is then responsible for monitoring pesticide levels on fruits and vegetables, while the US Department of Agriculture (USDA) is charged with the task of surveying pesticide residues in meat, eggs, and dairy products.
There is some criticism of the EPA’s methods for setting “tolerances” for pesticide exposure in humans. 7 Short-term testing is conducted on laboratory animals exposed to only a single chemical at a time, usually in high doses. 7 However, in real life, humans are often exposed to a number of different chemicals over long periods of time – this type of exposure can cause problems that might not be observed in a short-term study of the effects of a single chemical. 7 The FDA has also been criticized for inadequate monitoring of pesticide levels on fruits and vegetables. 8 Ineffective sampling of food for pesticide residue testing, problems with data analysis, and lack of authority to fine or otherwise punish growers (or importers) who use illegal pesticides are common criticisms. 8
The Environmental Working Group compiles a yearly list of fruits and vegetables with the highest levels of pesticide residues, based on USDA and FDA testing data. 9 The current top 12 are: 9
According to Cornell entomologist David Pimentel, “[i]t has been estimated that only 0.1% of applied pesticides reach the target pests, leaving the bulk of the pesticides (99.9%) to impact the environment. 10 Harmful environmental impacts of pesticide use include:
Pesticides have been linked to a number of health problems, including neurologic and endocrine (hormone) system disorders, birth defects, cancer, and other diseases. 7 17 Although it is widely understood that exposure to pesticides is dangerous to humans, Centers for Disease Control and Prevention (CDC) data show that a high percentage of individuals tested had certain pesticides or the chemical breakdown of those pesticides (metabolites) in their blood and/or urine. 17 18 CDC research also shows that people in the US carry levels of pesticides in their bodies that, for certain pesticides, exceed the EPA’s “acceptable” levels. 17 For example, CDC data show that the average American child between the ages of six and eleven carries unacceptable levels of the organophosphorus pesticides, chlorpyrifos and methyl parathion, both of which are known to have neurotoxic properties. 17 19 It should also be noted that the human health effects of low dose, chronic exposure to many of these pesticides is listed as “unknown” by the CDC. 18
Children are especially susceptible to the harmful effects of pesticide residues due to their lower body mass, rapid development, and higher rates of consumption of affected products. 18 19 In children, exposure to certain pesticides from residues in food can cause delayed development; disruptions to the reproductive, endocrine, and immune systems; certain types of cancer; and damage to other organs. 20 Prenatal exposure to certain pesticides can affect cognitive development and behavior. 19 Several studies have found that pesticide levels in children dropped to low or undetectable levels when test subjects consumed an organic diet. 22 23
Farmworkers are also highly vulnerable to these health threats due to intensive exposure to a variety of pesticides, either from applying these chemicals or from harvesting pesticide-sprayed agricultural products. 24
Approximately 80% of the corn and 22% of the wheat produced in the US every year is used for animal feed, while 30 million tons of US-produced soy meal is consumed annually as livestock feed. 25 This grain is grown by intensive industrial farming operations that use large amounts of pesticides and other inputs, and often rely on genetically engineered (GE ) crop varieties. 10 28 Common genetic modifications include plants that are bred to contain insecticides within their genetic makeup (e.g., Bt corn) or to withstand direct application of herbicides (e.g., glyphosate resistant soybeans).
In addition to causing environmental damage, when grain is grown with pesticides and then fed to livestock, pesticide residues can accumulate in the animals' fatty tissue and milk. 29 Pesticides, such as arsenic compounds, are also included in livestock feed to control intestinal parasites and other pests. 30
Many sustainable farms use Integrated Pest Management (IPM) as an alternative to the heavy use of pesticides. 31 IPM is a growing movement among farms of all sizes that incorporates a variety of techniques to eliminate pests while minimizing environmental damage. 31 For instance, an IPM farm may grow pest-resistant crop varieties, use predatory insects to kill plant-eating pests, employ mechanical pest traps, and eliminate pest nesting areas by plowing under harvested crops. 31 Chemical and natural pesticides are used only as a last resort. 31
Other techniques used by sustainable farms include crop rotation, which involves planting crops in different places each season in order to replenish nutrients removed from the soil by a particular plant, and intercropping, a method of planting crops in close proximity. These practices help to break pest cycles, allow the soil to naturally replenish itself, help reduce weeds, and encourage plant diversity in order to avoid insect and pest infestation.
When you prepare conventional food, you can take several measures to reduce your intake of pesticides. Washing fruits and vegetables helps remove some pesticide residues – but only for certain pesticides (others are not affected by washing). 32 Peeling fruits and vegetables is a more effective method of removing pesticide residue. For meat and dairy products, it is best to consume foods that contain less fat, since pesticides typically accumulate in the fatty tissue of animals. Purchase skim milk or low-fat dairy products and remove the fat from cuts of meat before you cook them. 33
The best way to avoid consuming pesticides along with your food is to eat organic produce, meat, and dairy products. Organic food is grown and processed without being treated with pesticides. Look for the USDA-certified organic label on your foods and visit local farmers' markets or farms, where you can ask the farmer directly about his or her pest control methods. Some sustainable farms aren’t certified organic, but don’t use any pesticides at all. The only way to find out is to ask!