Questions About Pesticide Exposure

Many people are concerned with pesticides and how they might be exposed. Here are a few frequently asked questions and answers aimed at these concerns:


Pesticides can be found, often in small amounts, almost anywhere worldwide. Where you live and your lifestyle largely determines the potential for exposure to pesticides. Most non-occupational exposure comes from food or home pesticide use. In addition to use in agriculture and forestry, pesticides are used in many public places, including office buildings, restaurants, schools, parks, golf courses, and along roads, railroads and power lines. People are not intentionally exposed to pesticides, except for public health reasons. Instructions on the pesticide label are designed to minimize exposure, both to workers and the general public.

There are three main routes of exposure: oral, dermal, inhalation. Ingestion of food or water containing pesticides is oral exposure. Smoking can also transfer pesticide on the hands to the mouth, resulting in oral exposure. Inhalation exposure can occur by breathing air containing pesticides as vapor, aerosol or on small particles (dust). Dermal exposure occurs when the skin comes in contact with pesticides. Protective eye wear can prevent exposure to the eyes when mixing or applying pesticides.

When applying pesticides follow the directions on the label. This may include wearing long sleeve shirt and pants, rubber boots, gloves, and eye wear. If you are aware of a pesticide application around the home or in a public place, avoid exposure. If you live in a rural area adjacent to agricultural or forest lands where pesticides are applied, contact the land owner and ask to be informed of pesticide applications. Although some pesticides are found in food, the levels are very small and extensive testing is required to assure that levels in food are safe. Although a rare occurrence, drinking water may also contain small amounts of pesticides. Ask your city water board for the results of pesticide testing. If you are not on city water and have a reason to be concerned, consult with your county Extension agent.

The amount of pesticide applied and the area of application are important in determining exposure. Pesticides that are applied infrequently or in small quantities to a limited area in a remote location are less likely to result in significant human exposure, and visa versa. In populated areas, notification of pesticide application should reduce the chance of inadvertent exposure by the general public.

Once a pesticide has be introduced into the environment, its chemical and physical properties determine its fate: where it goes and how long it lasts. Each pesticide has its own unique set of properties. Pesticides that break down quickly do not offer much opportunity for exposure. How quickly a pesticide breaks down depends on the pesticide’s chemistry, as well as environmental factors, such as temperature, rainfall, soil pH. Pesticides are designed to last long enough to do their job -- control pests, then break down to non-toxic substances. However, pesticide persistence is highly variable, from a few hours to days, months or years. Most pesticides used today last from a few days to a few months.

A pesticide’s mobility depends on its water solubility, solubility in fat, adsorption to soil, and its tendency to become a vapor. A pesticide that is adsorbed to or taken up into a plant is less likely to become a vapor, be washed off onto the soil, or be transferred to the skin if the plant is touched. Pesticides that strongly adsorb to soil are not very mobile in water that infiltrates toward groundwater, or water that runs off into surface water, such as a pond, lake or stream. Pesticides strongly adsorbed to soil may still enter surface water if there is soil erosion. Pesticides strongly adsorbed to soil do not volatilize easily.

Risk of adverse health effects is a function of pesticide toxicity and exposure. Exposure to a pesticide determines the dose and the pesticide’s toxicity determines the potency of the dose. For pesticides that do not cause cancer, there is a dose below which there will be no effect. For pesticides that do not cause cancer, a no effect threshold has been determined for each pesticide, which is inversely related to its potency. For pesticides that may cause cancer the probability that exposure will result in cancer is related to dose -- the greater the exposure the greater the probability of cancer. In each case risk is directly related to exposure, as exposure determines dose. If exposure is low enough the risk of adverse health effects is nil.

If your home is sprayed by a commercial applicator, do not stay in the house during application. Do not return to the house until the spray has dried and vapors have dissipated; this may be 2-4 hours. For some broadcast applications where pesticides are applied to the entire floor and other surfaces, and for applications using insecticide canisters that release an aerosol throughout the room, a longer period before reentry may be prudent. If possible open windows and air out before reentry. Keep off lawns and garden areas until the spray has thoroughly dried. Wash off decks, lawn furniture and toys that may have been sprayed. Never leave food items out where they can be sprayed. During the first few days after application, if the lawn becomes wet by dew, fog, light rain or watering, pesticide residues may again be available for transfer to the skin.

Common pets like dogs and cats have similar susceptibility to pesticides as humans. However, they do not wear protective clothing. Pet habits, such a grooming, can also increase the risk of exposure. Pets such as birds, fish or amphibians, may be much more sensitive to certain pesticides. The risk from exposure to the same dose is greater for smaller animals.

Here are some very informative internal and external links that pertain to pesticide exposure:

Extoxnet FAQHome
Extoxnet Pesticides

This Page prepared by the EXTOXNET FAQ Team. , January 1998