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Risk/Benefit Balancing Under FIFRA

Risk/Benefit Balancing Under FIFRA

The Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) governs EPA's regulation of pesticides. FIFRA requires that all pesticides intended for use in the United States be registered (licensed) by EPA to ensure that they do not cause "unreasonable adverse effects on man or the environment". FIFRA defines unreasonable adverse effects as "any unreasonable risk to man or the environment, taking into account the economic, social, and environmental costs and benefits of the use of any pesticide." Pesticides may pose some risk because they are meant to kill or control insects, weeds, rodents, and other pests. But even though pesticide use entails some risk, pesticides provide substantial benefits to society. Hence, FIFRA, unlike other environmental statutes administered by the Agency, requires EPA to balance these risks and benefits in the pesticide decision making process.

In order to be able to balance risks and benefits, EPA conducts complex risk and benefits assessments that employ the best scientific and economic analyses currently available. FIFRA authorizes EPA to conduct such full and public risk/benefit analysis of pesticides through its Special Review process or under circumstances where data show that a pesticide may pose an imminent hazard to human health or the environment. These reviews are initiated on the basis of adverse human or ecological effects data which come to the Agency's attention subsequent to the initial registration of the pesticide. A Special Review may result in cancellation of some or all uses of the pesticide, the imposition of risk reduction measures such as protective clothing, or continued registration with no changes.

This fact sheet describes both risk/benefit analysis, and how it was applied to a recent EPA decision on whether or not to permit the continued use of a problem pesticide.


EPA's basic approach to evaluating pesticide risk is conservative and protective of public health. These are four steps in the risk assessment process: hazard identification, exposure assessment, dose/response assessment, and risk analysis.

Hazard Identification

The objective of hazard identification is to assess the nature of any adverse health effect that may be caused by the pesticide based primarily on the results of laboratory studies conducted with animals. For example, is the chemical an eye irritant, does it cause acute poisoning, does it cause birth defects, does it cause cancer?

Exposure Assessment

Once the type of hazard has been identified, the exposure must be assessed. This involves estimating the level, duration, frequency and route of exposure. For example: Are people who often mix and apply large amounts of a pesticide overexposed? Is there risk to people who consume foods and drink water containing residues of the pesticide? Will use of the pesticide affect the non-target organisms, including endangered animal and plant species?

Dose/Response Assessment and Risk Analysis

The dose/response assessment explores the relationship between the level of exposure and the occurrence of an adverse effect. Since epidemiological studies with reliable quantitative data on exposure are rarely available, the Agency must rely on the results of experimental - animal studies to estimate dose/response relationships. EPA extrapolates from animal studies to potential effects on humans, and from exposures at high doses in those animal studies to the substantially lower doses to which humans are typically exposed. Obviously, this involves uncertainties; EPA is quite conservative in resolving them.

For almost all chemically-related toxic effects (such as birth defects, reproductive, or non-oncogenic chronic effects), the highest dose level at which the effect is not observed in the animal study (No Observable Effect Level or NOEL) is determined and an uncertainty factor (typically 100 or more) is applied to establish a human exposure level that will pose essentially no human risk. For example, an animal study may show that at 1000 milligrams of the substance in the daily diet of a 1 kilogram body weight test animal (1000 mg/kg/day), the animal showed no adverse effects. By applying a 100-fold safety factor, daily exposure of a human to 10 milligrams per kilogram of body weight would be considered to be safe for a human. In conducting pesticide risk assessments, EPA makes a practice of evaluating all potentially toxic effects, but generally focuses its quantitative risk/benefit balancing process on the effect observed at the lowest dosage level.

Where animal studies indicate that the pesticide chemical has induced cancer at relatively high dose levels, EPA ordinarily presumes that there is no dose at which some level of carcinogenic effect would not be observed. (This presumption sometimes could perhaps be overcome by extremely complex and costly studies, but usually overcoming the presumption is practically impossible.) Thus, EPA uses a mathematical model that assumes some effect could be caused by any dose, even one at a very low level. Such a model expresses the worst-case qualitative carcinogenic "potency" of the pesticide, or the worst-case probability that a given low dose will produce a response in the animal species.

As an index for regulatory decisions involving carcinogens, EPA's stated policy is that lifetime incremental cancer risks from exposure to a pesticide in the diet generally should not exceed one-in-one million or 0.000001 (1 x 10 to the minus 6) -- meaning one-in-one million risk over and above the background cancer risk of 1 in 4. This is the concept of "negligible" risk applied by EPA and the Food and Drug Administration.

Finally, the risk is analyzed by integrating the above factors. This usually involves extrapolating exposure in animals to humans. It is scientifically, legally, and ethically impracticable in most cases to do experiments to show whether humans would have different responses to chemical exposure than test animals. Thus, EPA ordinarily assumes that human response is similar to that of test animals.

EPA seeks to express a risk qualitatively and, where appropriate, quantitatively, and to give some perspective to the risk by summarizing the strengths and weaknesses of the supporting data and assumptions. Through risk analysis, the Agency is able to determine areas where additional data may be needed or where regulatory action may be warranted.


In deciding whether to cancel a pesticide, EPA conducts benefits assessment. A benefits assessment follows guidelines that take into account both biological and economic factors. Biological factors involve information about target pests on each site or crop. Economic factors involve the effects of various pest control strategies on the various businesses which produce and distribute commodities to the consumer. Economic impacts are dependent on the treated commodity or registered use sights of the chemical in question. So that means that EPA must do a benefits assessment for each registered use sight. One Special Review chemical can therefore lead to dozens or even scores of benefits assessments. Sometimes EPA must tailor its general approach to the particular pesticide and market conditions encountered. A benefits analysis includes:

Biological Analysis

Benefits are specific to each use site -- for example, corn, soybeans, or tomatoes, etc. The estimation of benefits derived from the use of a given pesticide is a multi-step process. The first step in this process is the identification of the pesticide's use (i.e., agricultural, industrial/commercial, or home use), and the principal pest(s) that are controlled through its application (e.g., insects, weeds, rodents).

Next, EPA takes a comprehensive look at the problem by developing a thorough understanding of the pest populations, the effectiveness of chemical and non-chemical alternatives, the geographic distribution of the pest problem, potential crop yield impacts, and alternative use practices which might mitigate the risk. In other words, the process Starts with gathering basic usage and product performance data in order to determine how important the chemical really is to the production of any crop from corn to mint.

These data are obtained through comprehensive literature searches, data bases created and maintained by EPA, and extensive communications with pesticide users. The latter involves requesting information from pesticide applicators, other government agencies (the Departments of Agriculture and Interior), scientists from state land grant universities, and organizations representing various user groups. When little or no empirical data exist, the Agency relies upon the experience and observations of pesticide applicators, scientists directly involved in studying pesticide effectiveness, and, to some extent, independent agricultural consultants. These data are by no means easy to obtain and sometimes require literally scores of telephone calls, etc. But the Agency is committed to obtaining the most comprehensive, accurate, and up-to-date information possible.

Economic Analysis

The next step of a benefits assessment is to express the biological impacts of yield loss, reduced crop quality, and alternative pest control methods in economic terms. The key question here is, will it cost more to produce the crop? EPA normally evaluates several types of economic impacts. The first step is to determine the relative cost of alternative pest control strategies. In some cases, EPA finds that there are relatively minor economic impacts, because cost effective substitutes (chemical and non-chemical) exist and are readily available. However, in other cases equally effective alternatives do not exist. In this scenario users may have to modify their current use practices, changes which often result in higher costs of production for relevant agricultural and non-agricultural goods and services.

An increase in production cost can be passed down to intermediate processors and ultimately to consumers in the form of higher food prices or more costly control of pests in the home. In determining economic impacts, EPA takes into account such influences as agricultural subsidies, quotas, or allotments, supply and demand factors, and international trade issues.

The Agency estimates both short- and long-term impacts at the user level. This analysis accounts for the net impacts to producers/suppliers by examining economic effects on users and nonusers of the pesticide under review. Based on this information short- and long-term effects in down-stream markets (i.e., processors, distributors, consumers) can also be estimated. Potential local/regional impacts are also identified as part of this analysis. These local effects may result from movement of economic activity to foreign markets, or to other areas of the country where pest infestation is not a problem (and therefore pesticide availability is relatively unimportant).


To illustrate this highly complex process, consider the case of the herbicide, dinoseb. In October 1986, EPA issued a formal notice of intent to cancel and deny all registrations for pesticide products containing dinoseb. Simultaneously, EPA issued an emergency suspension order to immediately stop dinoseb use during the time to complete the cancellation proceedings. These regulatory actions were based on the risk/benefit balancing scenario described below.

Hazard Identification

In assessing the risks of exposure to dinoseb, the first step involved identifying the hazard, based on the results of animal studies. The hazard evaluation of dinoseb focused on animal test results indicating that it may cause birth defects to females exposed to dinoseb during pregnancy, and may also cause sterility or decreased fertility in males, acute toxic poisoning, and other potential adverse effects on health and the environment.

Exposure Assessment

EPA estimates potential human exposure based on either actual data or surrogate data. Surrogate exposure data is simply data from studies of exposure to other pesticide chemicals (surrogates) that are of similar formulation to, and are applied in the same way as, the pesticide in question. Appropriate adjustments in the calculations are made to reflect differences in the rate of active ingredient applied per area, per hour, etc. In the case of dinoseb, three exposure scenarios were identified:

  • Possible dietary exposure to the public through consumption of food or drinking water containing residues of dinoseb;

  • Occupational exposure to workers who mix, load, and apply dinoseb; and

  • LSecondary or coincidental exposure to bystanders, farmworkers, and others who could be exposed to dinoseb through spray drift, contact with residues in treated fields, or even contact with contaminated clothing or farm equipment immediately after dinoseb application.

Dose/Response and Risk Analysis

In assessing the test animal dose/response for birth defects, EPA used an oral feeding study with rabbits to provisionally set a NOEL at 3 milligrams per kilogram of body weight per day (mg/kg/day) -- meaning that adverse effects in test animal offspring were apparent in all oral exposure levels higher than 3 mg/kg/day, the lowest dose administered.

For dinoseb the main risk of concern was the 3 mg/kg/day NOEL for birth defects in rabbits. EPA compared this NOEL from laboratory studies with expected human exposure levels to obtain numerical margins of safety (MOS). (NOEL divided by exposure equals margin of safety, or MOS).

Even when certain "worst case" assumptions regarding dietary exposure levels were factored into these calculations, the MOS for the risk of birth defects occurring from eating foods from crops treated with dinoseb was found to be ample -- over 2700. Similarly, from consumption of drinking water, the MOS was roughly 2430. However, for workers, in many instances the estimated exposure levels were equal to or greater than the NOEL of 3 mg/kg/day -- leaving essentially no margin of safety against the calculated risk of birth defects in the offspring of pregnant workers handling the pesticide.

The benefits assessment of dinoseb was driven by the risk factors described above. Based on data from the U.S. Department of Agriculture and other sources, EPA conducted an assessment of the benefits of dinoseb by calculating the short-and long-term economic impacts expected to occur if dinoseb were unavailable for certain registered uses. Dinoseb use sites included soybeaneveloping fetuses. There was also convincing evidence that exposure to dinoseb under both exposure scenarios posed additional risks of adverse reproductive effects in males and acute toxic poisoning. EPA considered a range of measures to reduce the risk, which included additional protective clothing, protective farm equipment, lower application rates, and product reformulations. EPA determined that none of these measures could reduce the risks to reasonable levels. Therefore, though the benefits of dinoseb were substantial in terms of monetary value, EPA concluded that risks of exposure to dinoseb clearly outweighed its benefits, not only in the long-term but also during the interval of time required to conduct usual cancellation proceedings. Thus, in October 1986 the Agency opted for the most drastic remedial option available under FIFRA -- emergency suspension, calling an immediate halt to the sale and use of a pesticide while cancellation proceedings are conducted.

However, in reaching a decision to immediately suspend dinoseb, EPA did not attempt to evaluate the economic benefits from use of dinoseb for each affected crop in each geographic region. Rather, the Agency focused on national impacts and on those crops involving the largest amount of use and percent of the crop treated. A more extensive analysis would not have been consistent with the Agency's concern about the imminent hazard to pregnant women exposed to dinoseb.

As a result, however, growers of certain minor crops grown in the Northwest sued EPA, asserting that the suspension was invalid because EPA did not properly conduct its benefits analysis and that there were modifications to use practices less drastic than suspension that would have sufficiently reduced the risk. The growers also complained that EPA could have delayed the suspension of use of dinoseb on their crops, which would not have occurred until several months after the suspension order was issued, while EPA completed the benefits assessments for their uses. (The suspension of the major uses of dinoseb, such as peanuts and potatoes, was never challenged.) A district judge agreed with the plaintiffs and issued an order allowing the use of dinoseb on the minor crops if a series of use precautions were observed.

An appeals court later ruled that the district judge had no authority to modify the suspension order by imposing conditions of use, but by then the use had already occurred. Meanwhile, EPA completed its assessment of the benefits of all dinoseb uses in preparing for the cancellation hearing. However, all the registrants of dinoseb eventually agreed to withdraw their registrations, making both a cancellation proceeding and further court proceedings moot.

Some of the other cases interpreting the suspension provisions of FIFRA are not consistent with the results in the Northwest dinoseb suspension case. However, if FIFRA is not amended or clarified, the need to fully assess economic benefits prior to emergency action could prevent EPA from taking timely action to protect public health. Under President Bush's food safety plan announced in October 1989, EPA would have the flexibility to order a suspension when there is substantial risk to human health without consideration of economic benefits.