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National Research Council (US) Committee on Scientific and Regulatory Issues Underlying Pesticide Use Patterns and Agricultural Innovation. Regulating Pesticides in Food: The Delaney Paradox. Washington (DC): National Academies Press (US); 1987.

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Regulating Pesticides in Food: The Delaney Paradox.

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The modern increase in pesticide use demonstrates how technological advancements can be beneficial and harmful at the same time. Effectively used, pesticides can kill or control pests, including weeds, insects, fungi, bacteria, and rodents. As a result, chemical pest control has won a central place in modern agriculture, contributing to the dramatic increases in crop yields achieved in recent decades for most major field, fruit, and vegetable crops. The production systems for most crops in most regions of the United States are dependent on at least one pesticide, and often several— some for weed control, some to control insect pests, and others for the control of a variety of plant diseases. The amount of pesticide use varies by region, however. Oats in the northern plains require little or no pesticide use, whereas vegetables in humid regions of the South may require 20 or more pesticide applications in a single growing season.

The focus of this study is limited to pesticide use on food crops. Although pesticides help protect food crops from insect pests, weeds, and diseases, most are potentially dangerous substances whose use requires careful control. They work because they are toxic to target organisms or otherwise disrupt natural processes necessary for the organisms' survival. Some are toxic only to target pests and pose little threat to other life forms, including humans. Many, however, are capable of harming nontarget species.

Pesticides are dispersed widely to treat crops, pastureland, and harvested fruits and vegetables. Consequently, most pesticide applications result in some contact with nontarget crops and organisms as well as applicators (persons who apply pesticides), farm workers, food handlers, and ultimately food consumers. Drinking water is also an increasingly significant source of human exposure to pesticides. All of these routes of exposure present concerns, but this study is limited to dietary exposure from oncogenic residues in food and to the process designed to control this route of exposure.

FIFRA and the FDC Act

The societal response to the dual nature of pesticides has been the development of a comprehensive regulatory system that seeks to make possible the beneficial use of pesticides while minimizing their public health and environmental risks. The current system originated with enactment of the 1947 Federal Insecticide, Fungicide and Rodenticide Act (FIFRA). The system now is defined by a comprehensively amended FIFRA and—for pesticides likely to appear on human foods—by various provisions of the Federal Food, Drug and Cosmetic (FDC) Act. The basic goals of these statutes are to allow only those pesticide uses that (1) do not have "unreasonable adverse effects" on human health or the environment and (2) have benefits outweighing whatever risks might exist. These goals are easy to state but difficult to implement. Complex issues and scientific uncertainties arise in estimating risks and benefits of pesticide uses. There is no simple, widely accepted method for balancing risks and benefits. Moreover, the avoidance of unsafe residues requires not only an operational definition of safety but a costly and complex system for monitoring and enforcement. The responsibility for deciding which pesticides may be used and what residues can be tolerated lies with the Environmental Protection Agency (EPA).

The EPA performs two main tasks. First, under FIFRA, the EPA decides what pesticide uses can be registered or approved in the United States. A single pesticide may have many potential uses. For example, the insecticide dimethoate is used to control a variety of pests on nearly 30 different crops, including cotton, tomatoes, and corn. In this report, a pesticide use refers to the application of a pesticide on a particular crop. The EPA registers each use under a statutory standard that requires balancing of benefits of a pesticide use against its potential risks to human health and the environment.

The EPA's second main task—and the focus of this study—is the establishment of legal limits (tolerances) specifying the amount of pesticide residue that can be present in or on foods sold in interstate commerce. The EPA performs this function under the authority of the FDC Act. It is a huge administrative task. A single pesticide intended for use on a single crop is likely to leave residues on the raw agricultural commodity. It can also find its way into numerous processed food and animal products. Moreover, most pesticides are used on several crops.

On the basis of field testing to measure residue levels, the EPA establishes tolerances to cover all expected residues on food. Over 8,500 food tolerances for all pesticides are currently listed in the Code of Federal Regulations (CFR). Approximately 8,350 of these tolerances are for residues on raw commodities (promulgated under section 408) and about 150 for residues known to concentrate in processed foods (promulgated under section 409). Table 1-1 shows the number of tolerances issued for insecticides, herbicides, and fungicides, which are the major classes of pesticides.

TABLE 1-1. Section 408 and 409 Food Tolerances Listed in the CFR.


Section 408 and 409 Food Tolerances Listed in the CFR.

The EPA's tolerance-setting task is made complicated by divergences between FIFRA and the FDC Act. Most notably, some legal standards within the FDC Act apply to pesticide residues present in or on raw commodities and some apply to pesticide residues in processed foods. In deciding whether to establish a raw agricultural commodity tolerance for a fresh food such as tomatoes, the EPA is authorized to balance the benefits of using the pesticide to produce a crop against the potential human health effects of any residue that would result—a process similar to that undertaken when the pesticide is considered for registration under FIFRA.1

Some processed foods contain higher levels of residues than allowed by the raw commodity tolerance because residues concentrate during processing. An example is the fungicide benomyl, which concentrates in processed tomato products. This phenomenon can have important regulatory implications because the FDC Act does not allow the EPA to consider the benefits of a pesticide's use in setting tolerances for residues that concentrate in processed foods. Tolerances for such residues are instead set under the same risk-only standard that governs intentional food additives: a residue must be proven safe.2

The Delaney Clause and the Purpose of This Report

The regulatory consequences of residue concentration in processed food are profound if a pesticide has been found to induce cancer in experiments on animals. Such a residue, or food additive for legal purposes, is subject to the FDC Act's most famous provision—the Delaney Clause. The EPA has interpreted the Delaney Clause as generally prohibiting the establishment of any processed-food tolerances for an oncogenic pesticide (a pesticide capable of inducing tumors), regardless of whether or to what extent its residue is judged to pose a hazard to human health. It is this policy that has occasioned the current study.

The objectives of this study are to describe and, to the greatest extent possible, estimate the consequences for public health and agricultural innovation of these dichotomous standards for setting pesticide tolerances. The EPA's request for this study followed its recognition that the procedures necessary to implement the two standards had grown exceedingly complex and sometimes produced results that were difficult to reconcile scientifically. Moreover, the agency realized that an increasing number of regulatory decisions would hinge on its policies for dealing with oncogenic residues in processed foods as the results of new residue chemistry and chronic toxicity studies became available as part of its ongoing pesticide reregistration process.

In describing the need for the study, EPA officials anticipated that application of the Delaney Clause could have a major impact on pesticide availability. Agricultural producers could face high costs if they were forced to adjust cropping patterns and pest control methods. In addition, the agency emphasized a potential paradox. Adherence to the strict standard of the Delaney Clause in establishing new tolerances could preclude commercial introduction of potentially lower-risk pesticides. These lower-risk pesticides would then be stopped from replacing older, potentially more hazardous compounds that have not been fully tested or, if tested, have not been brought into compliance with all current statutory requirements. The EPA was also concerned that actions dictated by the law's preoccupation with oncogenicity might make it more difficult to address other health and environmental hazards.

The EPA asked the National Research Council's Board on Agriculture to study the current system for tolerance setting, especially as affected by the Delaney Clause. The agency also asked the board to evaluate the clause's impact on the EPA's ability to accomplish the central goals of pesticide regulation enunciated by Congress: permitting beneficial uses of pesticides while minimizing public health and environmental risks. The board appointed the Committee on Scientific and Regulatory Issues Underlying Pesticide Use Patterns and Agricultural Innovation to respond to these questions.

The Committee's Tasks

The committee began by developing an analytical framework and a data base to assess the impact of the current system (and possible alternatives) on the future availability of pesticides and on human exposure to oncogenic pesticide residues. As explained in Appendix B, the committee, with the EPA's cooperation, assembled an extensive data base. This data base covers 289 registered pesticide active ingredients currently used on food crops by

  • Tolerance levels,
  • Crop use,
  • The likely need for processed food tolerances (because residues tend to concentrate),
  • Potential human exposure based on average dietary consumption patterns,
  • Regulatory status and history, and
  • Toxicological properties.

The committee carded out a series of analyses using the data base. From the results, the committee estimated the effects of different regulatory strategies across all registered pesticides. Based on risk assessment and other analytic methods routinely used by the EPA, this data base analysis has yielded approximate answers to such general questions as—

  • How large is the potential human oncogenic risk from pesticides in the diet?
  • What pesticides pose the most significant risks?
  • What crops account for the greatest exposure and largest risks?
  • What general conclusions can be drawn regarding the characteristics of the most hazardous and least hazardous pesticides?

The committee's report of data responsive to these questions, primarily in Chapter 3, must be interpreted with great caution. It is especially important to note that only estimated cancer risks and no other human health risks were assessed. Further, estimates of oncogenic risks are derived using methods designed to identify conservative upper bounds on potential human risk. The estimates presumably overstate true human risk. But with these caveats the analysis provides some important insights, which are described below.

The potential impact of the Delaney Clause on the availability of pesticides and human exposure to oncogenic pesticides is explored in Chapters 4 and 5. In these chapters, four scenarios, or theoretical policy constructs, were evaluated to determine which approach or approaches to tolerance setting will maximize the availability of useful pesticides while minimizing public health and environmental risks.

Throughout the study, the committee has been impressed by the complexity of the tasks that Congress has delegated to the EPA. The committee has come to appreciate the sometimes perplexing scientific and administrative issues posed by each regulatory decision. Before the agency can sanction a new chemical use or restrict or eliminate an old risk, it must assemble and evaluate large amounts of scientific and economic data. It must deal with an array of sometimes competing considerations. It must pay attention to consistency among decisions, especially when far-reaching impacts on the public health, environment, and economy are potentially at stake. It must regularly incorporate scientific advances in risk assessments. In spite of scientific advances and an exponential increase in data that must be evaluated in estimating risks and benefits of pesticide use, the EPA shoulders these complex tasks with budget constraints and limited resources that have shrunk considerably since 1980.

A major part of the EPA's difficulty in reaching and defending regulatory decisions is caused by the law itself rather than the amount or complexity of data. By statute, the propensity of a pesticide residue to concentrate in processed food has been made the linchpin for determining which of two quite different statutory standards applies to the tolerance-setting decision. For oncogenic pesticides that do concentrate, the agency's exercise of scientific judgment is curtailed because the Delaney Clause purports to demand not only zero risk but zero exposure. As a result, agency resources have been diverted toward inquiries regarding the fact and extent of concentration, which may often be insignificant in terms of public health protection, but of great consequence in practice. The committee began the study with the understanding that the Delaney Clause could have substantial impacts on the pesticide program, but was unsure of how to characterize or measure the impacts. The report's analyses shed new light on these impacts.

The committee hopes that this study will provide a framework for policymakers in the EPA, the Congress, and elsewhere to make informed judgments about whether the current system for tolerance setting should be changed. The committee offers some general conclusions concerning the desirability of change and suggests how the prospective consequences of alternative policies should be analyzed. If further refined, the analytical framework and data base used herein may help clarify whether strict adherence to the Delaney Clause contributes to or detracts from achievement of Congress' goals.


1. "In establishing any such regulation [raw agricultural commodity tolerance] the Administrator shall give appropriate consideration . . . (1) to the necessity for the production of an adequate, wholesome, and economical food supply." 21 USC § 346(b).

2. "No such regulation [food additive tolerance] shall issue if a fair evaluation of the data before the Secretary fails to establish that the proposed use of the food additive under the conditions of use to be specified in the regulation, will be safe." 21 USC § 348(C)(3)(A).

Copyright © 1987 by the National Academy of Sciences.
Bookshelf ID: NBK218046


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