Extension Toxicology Network

Toxicology Information Briefs

A Pesticide Information Project of Cooperative Extension Offices of Cornell University, Oregon State University, the University of Idaho, and the University of California at Davis and the Institute for Environmental Toxicology, Michigan State University. Major support and funding was provided by the USDA/Extension Service/National Agricultural Pesticide Impact Assessment Program.

EXTOXNET primary files maintained and archived at Oregon State University

Revised 9/93.



In the United States, pesticides are regulated by a myriad of laws and agency rules. No less than fourteen different Federal Acts control some aspect of the manufacture, registration, distribution, use, consumption and disposal of pesticides. The bulk of pesticide regulation falls under the Federal Insecticide, Fungicide and Rodenticide Act (FIFRA). This legislation governs the registration, distribution, sale and use of pesticides. The Environmental Protection Agency is responsible for the administration of this Act and for establishing rules and regulations consistent with the Acts intent.

Other acts govern their presence in water and air, the clean up of spills and releases, the concentrations of pesticide residues in raw and processed food, their impact on endangered species, their transportation, working conditions for manufacturers and applicators, and their disposal.

The three broad categories of concern with pesticide regulation focus on (a) the registration of new pesticides and the reregistration of existing pesticides and on (b) the establishing and monitoring of pesticide levels in food products and on (c) the monitoring of pesticide levels in the environment and especially in ground and surface water.


The EPA is responsible under FIFRA for registering new pesticides to ensure that, when used according to label directions, they will not pose unreasonable risks to human health or the environment. FIFRA requires EPA to balance the risks of pesticide exposure to human health and the environment against the benefits of pesticide use to society and the economy. A pesticide registration will be granted if, after a careful consideration of health, economic, social and environmental costs and benefits, the benefits of the pesticides use outweighs the costs of its use.

Pesticide registration decisions are based primarily on EPA's evaluation of data provided by applicants. Depending on the type of pesticide, EPA can require up to 70 different kinds of specific tests. For a major food-use pesticide, testing can cost the manufacturer many millions of dollars.

Testing is needed to determine whether a pesticide has the potential to cause adverse effects on humans, wildlife, fish, and plants. Potential human risks, which are identified by using the results of laboratory tests, include acute toxic reactions, such as poisoning and skin and eye irritation, as well as possible long term effects like cancer, birth defects, and reproductive system disorders. Data on "environmental fate" (how a pesticide behaves in the environment) also are required so that EPA can determine, among other things, whether a pesticide poses a threat to ground or surface water.

EPA may classify a product for restricted use if it warrants special handling due to its toxicity. Restricted use pesticides (RUP) may be used only by or under the supervision of certified applicators trained to handle toxic chemicals and this classification must be shown on product labels. During registration review, the Agency may also require changes in proposed labeling, use locations, and application methods. If the pesticide is being considered for use on a food or feed crop, the applicant must petition EPA for establishment of a food tolerance.

A brand-new active ingredient may need six to nine years to move from development in the laboratory, through full completion of EPA registration requirements, to retail shelves. This time-frame includes at least two or three years to obtain registration approval from EPA.

Since 1978, when EPA began requiring more extensive data on pesticides than in the past, over 130 new active ingredients have been registered; between 10 and 15 new pesticide active ingredients are registered each year.

EPA is required by law to reregister existing pesticides that were originally registered before current scientific and regulatory standards were formally established. The reregistration process ensures that:

(1) Up-to-date data sets are developed for each of these chemicals (or their registrations will be suspended or cancelled).

(2) Modifications are made to registrations, labels, and tolerances as necessary to protect human health and the environment.

(3) Special review or other regulatory actions are initiated to deal with any unreasonable risks.

Reregistration has proved to be a massive undertaking and has proceeded slowly. To date, EPA has issued about 200 "registration standards." A registration standard includes a comprehensive review of all the available data on an existing chemical, a list of additional data needed for full reregistration, and the Agency's current regulatory position on the pesticide. The standards already issued represent about 85 to 90 percent of the total volume of pesticides used in the United States. Under the 1988 FIFRA amendments, EPA must accelerate the reregistration effort so that the entire process is completed by 1997. FIFRA sets out a five-phase schedule to accomplish this task with deadlines applying to both pesticide registrants and EPA. Many pesticides are being withdrawn from manufacture and sale rather than going through the lengthy and expensive reregistration process.


New data on registered products sometimes reveal the existence of a problem or a potential for hazard that was not known at the time of registration. Congress and EPA have developed various mechanisms to reach sound scientific decisions in these situations.

Under the law, if EPA seeks to revoke the registration of a pesticide, the Agency must first announce its reasons and offer the registrant a formal hearing to present opposing evidence. Because the cancellation process can be very time and resource intensive, EPA often will employ a more informal and often more productive process known as Special Review.

Special Review offers opportunities for interested parties on all sides to comment and present evidence on the risks and benefits of a pesticide. In many cases, the Special Review results in an agreement to modify the registration to sufficiently reduce risk so that a formal hearing is no longer necessary.

If the Special Review process fails to resolve the issues, however, or if EPA decides that the problem is severe enough to warrant cancellation, EPA may issue a proposed notice of intent to cancel without holding a Special Review. The Agency also is required by FIFRA to send the proposed notice to the Scientific Advisory Panel and the U.S. Department of Agriculture (USDA), and must evaluate their comments before proceeding with a final Notice of Intent to Cancel

If no hearing is requested within 30 days of the notice, the pesticide's registration is cancelled immediately. If a hearing is requested, it is conducted in a trial-like manner before an EPA Administrative Law Judge, who issues a recommended decision to the EPA Administrator. At the end of the cancellation process, which may take two years or more, the decision may still be challenged in a federal court of appeals. If there is no appeal to a decision to cancel, all pertinent registrations of the pesticide are automatically cancelled, and the products may no longer be sold or distributed in the United States.

During the entire cancellation process, the pesticide remains on the market and no regulatory restrictions are imposed on the pesticide or its use. In some cases EPA may believe that allowing the pesticide to stay on the market-during a Special Review and/or a cancellation hearing-would pose an unacceptably high risk. In such cases, EPA may issue a suspension order that bans sale or use of the pesticide while the ultimate decision on the pesticide's status is under review.

In order to issue a suspension order, EPA must find that use of the pesticide poses an imminent hazard. In most cases, EPA must first offer the registrant an expedited hearing on the suspension issues. However, if EPA finds that an emergency exists (i.e., that even during the time needed for a suspension hearing, use of the pesticide would pose unreasonable adverse effects), the Agency can ban the sale and use of a pesticide effective immediately.

Under current law, even in an emergency suspension, EPA must assess the benefits of the pesticide as well. This provision makes emergency suspension difficult to use, and EPA has been able to make these findings for only three pesticides, ethylene dibromide (EDB), 2,4,5-T (Silvex), and dinoseb.


The food supply of the U.S. is among the safest in the world. Although many of the foods we consume may contain low levels of pesticide residues as a result of their use, numerous safeguards are built into the regulatory process to ensure that the public is protected from unreasonable risks posed by eating pesticide-treated crops and livestock.

EPA regulates the safety of the food supply by setting tolerance levels, or maximum legal limits, for pesticides on food commodities and in animal feed available for sale in the United States. The purpose of the tolerance program is to ensure that consumers are not exposed to unsafe levels of pesticide residues in food.

Pesticides may be registered by the EPA for use on a food or feed crop only if a tolerance (or an exemption from a tolerance) is first granted, under authority of sections 408 and/or 409 of the Federal Food, Drug and Cosmetic Act (FDCA). EPA has approved about 300 pesticides for food uses; about 200 of them are in common use.

Section 408 of the FDCA pertains to setting tolerances for pesticides in raw agricultural commodities before these products leave the farm. The section allows that costs and benefits of the pesticide use be balanced in the setting of the tolerance. A food product that exceeds its tolerance is rendered unavailable for sale. Section 408 tolerances can be set for pesticides that are non-cancer causing and for carcinogens.

Section 409 of the act presents a more complicated scenario for the regulation of pesticides that concentrate in processed food. This section of the act deals with food additives. When pesticide residues found on raw commodities, such as tomatoes, are concentrated in the processing of food (to tomato paste), the pesticide is then considered a food additive and is thus subject to the control of section 409. Section 409 requires that the sponsor of a food additive must prove with reasonable certainty that no harm will result from the use of the additive. There is no weighing of costs and benefits in this situation. A section of the Act also explicitly deals with food additives that may cause cancer. A summary of the tolerance setting process is shown in figure 1.

Setting Pesticide Tolerances on Raw Food

To evaluate the risks posed by pesticides in the diet, EPA follows standard risk assessment guidelines. The agency uses different procedures for cancer risks and non-cancer risks.

For non-cancer effects, EPA determines what the highest level of exposure to a pesticide is at which there are no observed adverse effects in animals (called the no adverse effect level, the NOEL). Then an "uncertainty factor" (usually about 100) is then multiplied to that number in order to estimate the level of daily exposure to the pesticide that is acceptable for humans (that is, that would not cause any adverse effects). This level is called the Reference Dose (RfD). It was once known as the Acceptable Daily Intake (ADI). Keep in mind that the reference dose is based on animal studies over the animals lifetime and extrapolated to human populations by an uncertainty factor.

Next, the EPA estimates the levels of people's exposure to pesticide residues in food, based on pesticide residue studies (how much residue is found on different crops after application) as well as studies of how much food people consume. This calculated value for potential exposure to the pesticide from food is termed the theoretical maximum residue contribution (TMRC). Then, using the information on both the chemical's toxicity to humans (the RfD) and a persons potential exposure (the TMRC), the Agency sets tolerance levels that will not pose significant dietary risks to the consumer. Therefore, certain crops, for which a pesticide is registered, may not exceed the tolerance value for that pesticide. If it does exceed the tolerance value it is rendered unavailable for sale.

EPA usually will deny a registration use if the anticipated exposure to humans from a proposed new use of a pesticide on a food crop, when added to estimated exposure from other food uses of that pesticide, exceeds the pesticide's Reference Dose.

In cases where a food-use pesticide is a carcinogen (cancer causing agent), EPA uses a second approach in addition to the one discussed above. EPA assesses the cancer risk associated with exposure to the pesticide in food over the course of a person's lifetime. EPA then determines whether that cancer risk can be considered "negligible." In general, EPA will grant a tolerance and register any pesticide that poses a negligible or no-cancer risk.

The notion of negligible risk is an attempt to set a standard below which the cancer risk is so small that there is no cause for worry from a regulatory or public health perspective. EPA's pesticide program defines a negligible risk a one-in-a-million or less chance of getting cancer as a direct result of a lifetime of exposure to a particular substance. (By contrast, the overall risk to the U.S. public of getting cancer, from all sources combined, is on the order of one in four or one in five.)

For pesticides that pose a cancer risk greater than negligible (one in a million), there are two different policies, depending on the situation. For pesticide residues in raw agricultural commodities, EPA may register the pesticide if the benefits of its use outweigh its risks.

Pesticide Tolerances on Processed Food

Pesticides that concentrate in processed foods are treated like other food additives. Section 409 provides no balancing of the costs and benefits for the use of food additives. The processor or sponsor must clearly show that the use of that additive is safe and that no harm will come to the users of the product. The procedure for granting tolerances under this section is generally the same as under section 408. If the Theoretical Maximum Residue Contribution (TMRC) is less than the Acceptable Daily Intake for the pesticide, then the tolerance will be granted. Pesticides that do not concentrate appreciably (10% or less) are not required to have a 409 tolerance. The 408 tolerance for the raw food is used. This is termed the "flow through" provision.

Cancer causing pesticides present a very complex scenario known as the Delaney Paradox. The history of the EPA's interpretation of the Delaney Clause is complex and confusing. In a nutshell, in 1958 an amendment was added to section 409 stating that no food additive could be used that had been shown to cause cancer. This ultimately meant that no pesticide could be granted a tolerance for processed food (remember, that pesticides concentrated in processed food are treated like food additives) if it caused cancer in test animals. The current interpretation of this section of the Act comes from a Supreme Court decision in 1992. The EPA must automatically deny any tolerance for a cancer causing pesticide that is found in processed food. The ban is absolute. Following the court case, the EPA prepared a list of 27 pesticides for 48 different foods that would lose their 409 tolerance and thus their registration for those uses (5).

Pesticide tolerances, set by EPA, are enforced by the Food and Drug Administration, which monitors all domestically produced and imported foods traveling in interstate commerce except meat, poultry, and some egg products. FDA conducts a Total Diet Study, also known as a Market Basket Study, which measures the average American consumer's daily intake of pesticide residues from foods that are bought in typical supermarkets and grocery stores, and prepared or cooked as they would be in a household setting. The findings of the ongoing Total Diet Study show that dietary levels of most pesticides are less than one percent of the Reference Dose. Imported foods receive special attention in FDA's monitoring program. Above-tolerance residues in 1987 and 1988 were found in less than one percent of import samples. Even so, FDA has tightened its import policy in the last few years: if a single shipment from a given source is found to violate U.S. tolerance regulations, all shipments from the same source are subject to automatic detention.

Monitoring meat and poultry products is conducted by USDA's Food Safety and Inspection Service (FSIS). Each year, FSIS conducts 10,000 to 20,000 pesticide residue analyses. Currently, fewer than one percent of these tests show illegal residues, and the violation rate has been declining steadily over the last two decades. State regulatory agencies are also involved in monitoring the safety of the food supply; some states have their own pesticide residue regulations for food produced and sold within state boundaries.


Historically, environmental fate and the movement of pesticides have been subject to less regulatory scrutiny than the protection of our food supply and registration and reregistration of pesticides. Registration and regegistration of pesticides requires thorough testing of the fate and movement of pesticides and the effects of pesticide exposure to non-target plant and animal species. However, little regulatory emphasis was placed on the monitoring and establishment of specific levels of pesticides in the environment once a pesticide was registered for use.

Recent efforts by several regulatory agencies have placed a greater emphasis on this area of pesticide control. Mostly, the responsibility lies with the EPA under the requirements of several different federal statutes. Most notably, the requirements for monitoring are found in the protection of rare and endangered species as controlled by the Endangered Species Act, and in the necessity to set discharge limits for manufacturers from point-source dischargers under the Clean Water Act. An additional source of considerable growing importance comes from the Safe Drinking Water Act. This statute requires that specific ceilings be set for concentrations of certain chemicals, including some pesticides. These levels, called Maximum Contaminant Levels (MCLs) are established to protect the public from contaminants in public water supplies, including both surface and ground water sources. As of 1988 the EPA had detected 46 different pesticides in the groundwater in 26 states as a result of normal agricultural use. Maximum Contaminant Levels have been set for seventeen pesticides.

In addition, a major five year effort to determine the extent of pesticides in the drinking water supply was undertaken by the EPA. The National Pesticide Survey was the first study of its kind to be conducted on a national scale. The EPA sampled over 1300 community water systems and rural domestic wells across the country for over 100 different compounds. Results and conclusion from this survey will be available when the agency issues its National Survey of Pesticides in Drinking Water Wells Phase II Report. Additional information may be obtained from the EPAs Safe Drinking Water Hotline (1-800-426-4791).

Figure 1. Regulatory structure for setting tolerances on raw and processed food under the Federal Food, Drug and Cosmetic Act.

Section 408 allows a balancing of costs and benefits in setting tolerances for pesticides on raw commodities. Tolerances reflect a compromise between these interacting factors.

Section 408 allows a balancing of costs and benefits in setting tolerances for pesticides on raw commodities; however, EPA will generally only set a tolerance if the risk of cancer is very low (usually one in a million or lower).
Section 409 treats pesticides as food additives and makes no provision for the balancing of costs and benefits of pesticide use. The sponsor of the pesticide must show that pesticide use is safe for its intended purposes.

Section 409 requires that pesticides that are found in processed food at any level be denied registration based on the Delaney Clause of the the Act.


(1) EPA'S Pesticide Programs. 1991. United States Environmental Protection Agency. Pesticides and Toxic Substances. 21T-1005.

(2) Winter, C.K. 1992. Pesticide Tolerances and Their Relevance as Safety Standards. Regulatory Toxicology and Pharmacology 15:137-150.

(3) National Survey of Pesticides in Drinking Water Wells. 1990. United States Environmental Protection Agency. Office of Water, Office of Pesticides and Toxic Substances. 570/9-90-015.

(4) Regulating Pesticides in Food. The Delaney Paradox. 1987. Committee on Scientific and Regulatory Issues Underlying Pesticide Use Patterns and Agricultural Innovations. Board of Agriculture, National Research Council. National Academy Press. Washington, DC.

(5) Statement on Pesticide Regulation. Environmental News. February 2, 1993. United States Environmental Protection Agency. Communications, Education and Public Affairs. (A-107).

DISCLAIMER: The information in this brief does not in any way replace or supersede the information on the pesticide product label/ing or other regulatory requirements. Please refer to the pesticide product label/ing.