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EPA ExpoBox

Exposure Assessment Tools by Chemical Classes - Pesticides



A pesticide is any chemical used to prevent, destroy, repel, or mitigate pests. They might be used to control insects, mice and other animals, weeds, or fungi. Pesticides also are used to kill organisms that can cause diseases such as bacteria and viruses, including those in hospital and medical environments. Pesticides products contain both active ingredients and inactive, or inert, ingredients. These chemicals may be harmful to people, animals, or the environment, depending on how they are used.

Pesticides include organic compounds, such as pyrethroids and paradichlorobenzene, as well as metals and other inorganic substances, such as certain tin compounds that have historically been used as antifoulants on the undersides of ships.

Pesticides have widespread applications and may affect human and environmental health in a variety of settings. Exposure to a particular pesticide may occur through multiple exposure routes (oral, dermal, and inhalation) depending on the type and use of the pesticide. Common sources of exposure to pesticides for the general population include residues in food and drinking water.

Children are a highly susceptible population for pesticide exposure in part because of their hand-to-mouth behaviors. Occupational exposure to pesticides is a concern for farm workers and commercial pest control operators. See the Lifestages and Populations Tool Set in EPA ExpoBox for additional information and resources specific to workers and children.

It is not the intent of this tool set to provide detailed information for specific pesticides. Detailed information can be obtained from EPA websites (see below). Instead, this tool set provides a general discussion of types of pesticides and an overview of factors that are relevant to conducting an assessment of pesticide exposure - specifically, exposure routes, exposure media, and potentially exposed populations.

General information about pesticides related to human health and safety issues, environmental effects, pest control, pesticide regulatory activities, and compliance and enforcement information can be found at Pesticides

Resources related to pesticides in food and water are available at: Pest Control and Pesticide Safety for Consumers

Note: The Routes and Media Tool Sets of EPA ExpoBox provide additional information and resources about pesticides.

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EPA currently regulates thousands of pesticide active ingredients used in agricultural, commercial, or consumer products. Pesticides can be grouped according to chemical class, the type of pest they control, the method by which they are derived, or the sites at which they are used (e.g., agricultural, residential).

  • Chemical class - Chemical classes to which pesticides may belong include organophosphates, neonicotinoids, pyrethroids, and many others. Within the general class of pesticides, subcategories are sometimes defined according to a common chemical characteristic or functional group.

    For example, organophosphate pesticides are those that contain an ester of phosphoric acid. Subcategories that are defined by chemical characteristics may well share common qualities that would be useful when conducting an exposure assessment. Organophosphate pesticides tend to degrade relatively rapidly via hydrolysis reactions once released into the environment. 
  • Type of pest - Pesticides are often classified according to the type of pest they control. These groups include insecticides (to control insects and other arthropods), herbicides (to eliminate weeds), fungicides (to kill fungi), rodenticides (to control mice and other rodents), and bactericides (to disinfect or sanitize), among others.

    These pesticides have household, industrial, and agricultural applications; for example, insecticides may target crop-eating insects or a cockroach house infestation.
  • Derivation - Pesticides can also be classified as synthetically-derived (e.g., organophosphate pesticides and organochlorine insecticides) or derived from a natural source or production method (e.g., biopesticides). Many biopesticides are derived from natural materials such as plants (e.g., citrus oil, diatomaceous earth, neem oil); bacteria (e.g., Bacillus thuringiensis toxin); or minerals (e.g., boric acid).
  • Use sites - Pesticides may be registered for different types of use sites. Some are used in agricultural settings on certain types of crops. Others are used in residential settings (e.g., home and garden).

Note: The Consumer Products Tool Set of EPA ExpoBox provides additional information and resources organized by pestcide types.

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Physicochemical Properties

After a pesticide is released to an environmental medium, its transport, dispersion, and transformation may be governed by certain physicochemical properties. Physicochemical property data can help determine a contaminant’s likelihood to remain in that medium, partition to other media, or transform physically, chemically, or biologically after release.

Sources of physicochemical values include the following:

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The relevant pathways of exposure to pesticides are dependent on the type of pesticide and its registered uses. Exposure to pesticides can occur from dermalHelpdermalPertaining to the skin contact, or as a result of unintentional ingestionHelpingestionThe act of swallowing something through eating, drinking, or mouthing objects. A hazardous substance can enter the body this way. or inhalationHelpinhalationThe act of breathing. A hazardous substance can enter the body this way. The table below gives examples to illustrate these pathways:

Route Example(s) for Pesticides
Dermal contact Direct and indirect dermal contact exposure can occur through use of consumer products containing pesticides. Occupational activities can also result in dermal exposures.
  • Direct exposure can occur when receptors come into contact with pesticides in consumer products during use.
  • Direct occupational exposure can occur from mixing, loading, and applying pesticides.
  • Postapplication exposure to pesticide residues can occur when workers or consumers contact treated foliage (e.g., during weeding, harvesting) or surfaces.
  • Indirect exposure could occur when a nonuser comes into contact with pesticide residues on indoor surfaces (e.g., that have been sprayed with disinfectant) or on food that had been sprayed with a pesticide.
  • Indirect exposure could also occur by contacting pesticide-laden dust that has settled on carpets, floors, clothing, counter tops, or other surfaces.
  • The addition of pesticides to food commodities or packaging could result in contamination of fruits, vegetables, grains, and other food products.
  • Exposure to pesticides in consumer products might occur by incidental ingestion (e.g., from hand-to-mouth contact).
  • Occupational or residential exposure to pesticide products during or after application might occur by inhalation of particulates, vapors, or aerosols.

Note: The Routes Tool Set of EPA ExpoBox provides additional information and resources organized by route.

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Pesticides have widespread uses and may affect human and environmental health in a variety of settings. In addition to direct and indirect contact with agricultural pesticide products, people may be exposed to pesticides in consumer products and pesticide residues in exposure media, including food, drinking water, air, and soil. 

Media Sources of Pesticides
  • Contamination of foods may occur as a result of intentional use of pesticides. Pesticides that are applied to agricultural areas or gardens can contaminate food products. Consumers may be exposed to these pesticide residues via consumption of fruits, vegetables, grains, and other agricultural commodities.
  • Pesticides released to abiotic media may end up in the food chain. Some pesticides are resistant to breakdown and biomagnify up through the food chain. Others are lipophilic and tend to concentrate in the fatty tissues of animals such as fish that may be consumed by humans.
Drinking water
  • Pesticides that are applied to farmlands, gardens, and lawns can migrate to ground water or surface water systems. These systems might be used as drinking water supplies.
Consumer products
  • Many household products contain pesticides. The following are examples of household pesticide products: cockroach sprays and baits; insect repellents for personal use; rat and other rodent poisons; flea and tick sprays, powders, pet collars; kitchen, laundry, bath disinfectants; products that kill mold and mildew; some lawn and garden products (e.g., weed killers); and some swimming pool chemicals.
  • Pesticides could be a source of outdoor and indoor air pollution. Examples of household pesticide products used indoors include insecticides and disinfectants.
  • Contaminants from products used on agricultural lands or lawns and gardens outdoors might drift indoors and contaminate indoor air.
  • Anthropogenic sources of soil contamination might include application of pesticides. Agricultural fields, public access ways, or lawns and gardens treated with pesticides can contaminate the surrounding soil.
  • Contaminants in soil from products used on lawns and gardens might be tracked inside the house.

Note: The Media Tool Set of EPA ExpoBox provides additional information and resources organized by media.

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Exposed Populations

Pesticides have widespread uses and may affect both the general population and occupational workers.

The general population may be exposed both indoors and outdoors. Certain populations and lifestages may be at risk for higher exposures than the general population (see below).

  • A developing fetus may be at increased risk to certain pesticides if exposure to the pregnant woman occurs during critical developmental stages.
  • Nursing infants are highly susceptible to pesticide exposure through breastmilk.
  • Toddlers and young children may be susceptible to pesticide exposure because of certain behaviors (e.g. tendency to mouth objects or hands) and activities (e.g., crawling or playing on the floor indoors where dust contaminated with pesticides has settled, playing on the lawn where pesticides are commonly applied) that increase their chances of exposure.

Due to the nature of the work, certain occupations may result in higher exposure levels of pesticides to workers. Protecting occupational workers from the potential effects of pesticides is an important role of EPA's Pesticide Program. Workers may be exposed to pesticides through various activities, including:

  • Preparing pesticides for use–e.g., mixing a concentrate with water, loading a pesticide into application equipment.
  • Applying pesticides, such as in an agricultural or commercial setting. This includes employees on farms, forests, nurseries, greenhouses, and others who work around pesticides.
  • Entering an area where pesticides have been applied to perform specific tasks such as picking crops.

EPA has employed strategies for reducing the potential risk to workers from pesticides by implementing the Worker Protection Standard, which, among other things, requires worker pesticide safety training.

Note: The Lifestages and Populations Tool Set of EPA ExpoBox provides additional resources related to particular population groups and lifestages including workers, children, and women of child-bearing age.

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