IFIC Review: Pesticides And Food Safety

Consumers demand safe food and expect it to be nutritious, easy to store, easy to prepare and available at low cost year-round. The United States can boast a long history of being able to meet these demands, with a highly productive food and fiber system envied throughout the world.1

The average American family spends only about 10 percent of its disposable income on food, less than residents of any other country.2,3 Indeed, the percentage of U.S. income spent on food purchases has dropped by 50 percent since the turn of the century. In 1994, family grocery expenditures averaged $79 per week.4

This plentiful, affordable food supply undoubtedly has contributed to the improved health and longevity of Americans. Whereas in the early 1900s the average lifespan was some 50 years, today Americans are living well into their late 70s.5

According to the National Academy of Sciences (NAS), such improvements in public health can in part be attributed to pesticides.6 Pesticides have increased crop yields and the availability and affordability of fruits and vegetables year-round. The Dietary Guidelines for Americans, issued by the U.S. Department of Agricul-ture (USDA) and the Department of Health and Human Services (DHHS), promote consumption of a wide variety of grains, fruits and vegetables as the foundation of a healthful diet.

This issue of IFIC Review takes an in-depth look at agricultural chemicals, including pertinent food safety laws and regulations, monitoring of pesticides in food, consumer attitudes and integrated pest management.

Definitions and Uses

The term "pesticides" refers to a broad class of crop-protection chemicals: insecticides, which are used to control insects; rodenticides, which are used to control rodents; herbicides, which are used to control weeds; and fungicides, which are used to control fungi, mold and mildew. Herbicides are the most widely used chemicals in agriculture.6

Pesticides help control hundreds of weed species, more than one million species of harmful insects and some 1,500 plant diseases.7 Pest problems and their management vary widely throughout the country based on climate, soil types and many other conditions. 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.8 Through the use of pesticides, growers are able to produce some crops profitably in otherwise unsuitable locations, extend growing seasons, maintain product quality and extend shelf life.9

Some pesticides currently used are naturally occurring chemicals such as sulfur. Certain plants also produce low levels of natural pesticides to self-protect against insects and other invaders.10 Farmers use both natural and synthetic chemicals as needed to control weeds, insects and diseases.

Chemical use represents a significant agricultural production cost. Thus, farmers have an incentive to use fewer, more carefully timed pesticide applications. Farmers do not use pesticides unless their potential benefits—such as improved quality, increased production, aid in harvesting and prevention of crop loss—outweigh their costs of application.10,11

Pesticide users and applicators are required by law to follow manufacturers' instructions for use. Certain pesticides can be applied legally only by certified and licensed applicators, who are subject to fines or loss of their licenses for not following label instructions.11

In addition to their use in food and fiber production, pesticides provide a host of other beneficial uses. Consumers use them in the home or yard to control termites and roaches, clean mold from shower curtains, destroy crab grass, kill fleas on their pets and disinfect swimming pools. Pesticides are also used in hospitals, hotels, restaurants and homes to destroy bacteria, fungi and germs.7

Pesticide Tolerances

The registration and use of pesticides are governed by the Federal Insecticide, Fungicide and Rodenticide Act (FIFRA) and the Federal Food, Drug and Cosmetic Act (FFDCA).

Under FIFRA, the Environmental Protection Agency (EPA) determines whether a pesticide can be registered or approved for use in the United States.8 For each chemical approved for use on a particular crop, EPA establishes a tolerance. A tolerance is the maximum residue level of a pesticide legally permitted in or on a food, feed or food constituent.10

Tolerances are based on studies conducted by the chemical manufacturer in which a pesticide is used in a variety of locations, at maximum rates, with a maximum number of applications per year, and the shortest interval between last application and harvest. The tolerance level is set at the highest maximum residue level observed at the end of the studies.12

In establishing a tolerance on a raw agricultural product, FIFRA allows EPA to consider both the risks and benefits that may result if the pesticide is used. Tests must be conducted by the manufacturer to determine whether a pesticide has the potential to cause adverse effects on humans, wildlife, fish or plants, including endangered species.13 More than 140 different studies on a chemical's toxicology, crop residues and environmental effects may be required.7 Because development of a single new pesticide can cost as much as $70 million and require years of research, manufacturers seldom assume this expense unless the new chemical can be registered for at least one major crop, such as corn, wheat or soybeans.9

Before registering a chemical, EPA also carefully examines research on its potential to cause cancer, birth defects, reproductive disorders, neurological effects or other adverse health effects.14

Using a computerized data base known as the Dietary Risk Evaluation System (DRES), the agency combines data on food consumption with data on pesticide residues to estimate the potential dietary exposure of the population to a particular pesticide.6,14 DRES analyzes data on 22 population subgroups including infants, children and other age groups, different ethnic groups and regional populations. EPA also calculates a cumulative lifetime exposure that integrates the exposure rates experienced beginning in infancy and childhood through a lifespan of 70 years. If risks are at an unacceptable level, EPA will not register a pesticide or will require action to reduce those risks.

Since significant numbers of people eat food raw or partially cooked, tolerances are established for raw foods. But during the registration process, EPA also examines data on the effects of processing on pesticide residues. Most pesticides begin breaking down with exposure to sunlight, rain and other elements soon after they are applied and are usually below tolerance levels before leaving the farm.11,15 In most cases, food processing methods such as washing, canning, freezing and drying further decrease the trace levels of pesticide residues in foods as eaten. Residues on the surface of produce are often further reduced by washing, peeling or other home preparation methods.

Pesticide Residue Monitoring

Under FFDCA, the Food and Drug Administration (FDA) and USDA share responsibility for monitoring levels of pesticide residues on foods. FDA enforces pesticide tolerances for all domestically produced food shipped in interstate commerce and in imported foods, except for meat, poultry and some egg products, which are monitored by USDA.16 Many agriculturally-intensive states such as California and Florida also conduct extensive pesticide residue monitoring programs.

FDA uses three approaches for pesticide residue monitoring:

  1. incidence/level monitoring
  2. regu-latory monitoring
  3. Total Diet Study16

Incidence/level monitoring is conducted to obtain information on specific commodities, pesticides or combinations thereof. Samples are collected from packing sheds, wholesale facilities or otherwise as close as possible to the point of production in the food chain. Regulatory monitoring is performed to enforce EPA tolerances. If tests confirm that any food contains pesticide residues exceeding the tolerance level or residues for which no tolerance has been established, FDA can seize the shipment, prevent further shipments, seek recalls and pursue criminal penalties. The Total Diet Study provides estimates of the intakes of pesticide residues in foods as consumed or prepared.

In 1993, FDA's regulatory monitoring program analyzed 12,751 samples of domestically produced food and imported food from 107 countries; 12,166 were surveillance samples, meaning that there was no prior knowledge that a specific food shipment contained illegal pesticide residues.16 No pesticide residues were found in 64 percent of the 5,703 domestic surveillance samples, 34 percent had detectable residues below tolerances, less than one percent had residues that exceeded EPA tolerances, and one percent had residues for which there was no established tolerance for that particular pesticide or commodity.

Of the 6,463 import surveillance samples, 69 percent had no detectable residues, 27 percent had detectable residues below tolerances, less than one percent had residues that exceeded tolerances, and three percent had residues for which there was no established tolerance.

In FDA's Total Diet Study, foods are collected four times per year, once from each of the four U.S. geographical regions.16,17 The levels of pesticide residues found, along with USDA food consumption data, are used to estimate dietary intake of pesticide residues for eight different age/sex groups. Estimated dietary intakes are then compared with a safety standard known as the Reference Dose (RfD) set by EPA or other safety standards set by international bodies.

The RfD is the amount of a chemical that, if ingested over a lifetime, is not expected to cause any adverse health effects in any population subgroup.10 It is based on the maximum dose of a chemical to which test animals can be exposed without observable biological effects. This maximum dose, also known as the no observable effect level (NOEL), is then divided by a factor of 100 to provide an extra margin of human safety. This safety fact or allows for individual variations in susceptibility to toxic substances and for species differences between humans and test animals.

Each collection in the Total Diet Study from 1987 to 1993 contained more than 200 items representative of some 5,000 different foods commonly consumed in the United States, including fresh, frozen and packaged foods, wine and fast foods.16 Each food item was analyzed for about 200 different pesticide residues. The findings from reports over the last seven years continue to demonstrate that pesticide residue levels in foods are generally well below EPA tolerances and represent no appreciable public health risk.

Pesticide Residues in Perspective

Pesticide residues in food and water are expressed as parts per million (ppm), parts per billion (ppb), or parts per trillion (ppt). The following comparisons may help put these quantities into perspective.37

  • 1 ppm = 1 gram (g) of residue in 1,000,000 g of food; 1 inch in 16 miles; 1 minute in 2 years; 1 cent in $10,000; or 1 pancake in a stack 4 miles high.
  • 1 ppb = 1 g of residue in 1,000,000,000 g of food; 1 inch in 16,000 miles; 1 second in 32 years; or 1 cent in $10 million.
  • 1 ppt = 1 g of residue in 1,000,000,000,000 g of food; 1 inch in 16 million miles; 1 second in 32,000 years; 1 square foot of floor tile on a floor the size of the state of Indiana.

Pesticides and Children

In the late 1980s, questions arose about the safety of pesticides in the diets of infants and children. Using data from its Total Diet Study for 1985 through 1991, FDA conducted a special analysis of pesticide residues in infant foods and adult foods eaten by infants and children.17 A total of 33 different types of infant foods were studied including cereals, combination meat and poultry dinners, desserts, fruits and fruit juices, vegetables and infant formulas. Almost all the findings were well below EPA tolerances for each commodity/pesticide combination studied.

At the request of Congress, the National Academy of Sciences (NAS) established a committee in 1988 to study the scientific policy issues related to pesticides and children's diets. Experts in pediatrics, toxicology, reproduction, food science, nutrition, statistics and epidemiology studied the evidence for five years.

In 1993, the NAS committee concluded that although the food supply in the United States is safe, certain regulatory improvements are needed to better account for differences between children and adults, which may affect their health risks from pesticides (6). Particularly needed are better data on children's dietary patterns and more uniform analysis and reporting of pesticide residues on foods as eaten. EPA is working on implementing these and other NAS recommendations.

In response to the NAS findings, the American Academy of Pediatrics (AAP) reaffirmed its position that, "The risks of pesticides in the diet are remote, long-term and theoretical, and there is no cause for immediate concern by parents. The risks to children over their lifetime of experiencing the major chronic diseases associated with the typical American diet far exceed the theoretical risks associated with pesticide residues."18 The AAP, as well as the American Medical Association (AMA), the American Cancer Society, the American Dietetic Association, the Institute of Food Technologists, the American Institute of Nutrition and the American Society for Clinical Nutrition encourage parents to feed their children more, not less, of a variety of fruits and vegetables.19

The Delaney Clause

As part of a 1958 amendment to FFDCA, the Delaney Clause prohibits any additive in processed food if it is shown to induce cancer in experimental animals. Under FIFRA, a tolerance is granted for a pesticide on a raw agricultural commodity if the benefits of its use outweigh any risks. However, according to the Delaney Clause, if any new pesticide concentrates in processed food and is found to cause cancer at any level, it is not permitted. Thus, EPA's tolerance-setting task is complicated by differences between FIFRA and FFDCA.8

Registration of a new chemical may be denied if it is found to cause cancer at any level in animals even though EPA is convinced that it would pose less risk and provide essentially equal food-production benefits.8

Although originally intended to provide more protection from substances that cause cancer, NAS concluded in 1987 that the Delaney Clause actually may increase human cancer risks by inhibiting the development and registration of less hazardous pesticides that could be substituted for older chemicals. New pesticides are subjected to stringent safety tests using the modern analytical equipment, which allows the detection of residues as low as parts per trillion.

The NAS, EPA, FDA and most scientific experts have recommended updating the Delaney Clause to a negligible risk standard.8 In essence, a negligible risk standard for pesticides means that the chance or probability that a cancer will result from consuming fruits and vegetables treated with pesticides is so low that it is considered negligible or non-existent.

At issue, however, is how to define negligible risk. The debate focuses on two points:

  1. Should Congress define negligible risk, and
  2. How much discretion should be given to the regulatory agencies to determine risk assessment. Congress has been debating this issue for many years.

Consumer Attitudes

According to the Food Marketing Institute's (FMI) 1994 consumer survey, seven out of 10 shoppers are completely or mostly confident in the safety of the food supply.4 When asked their views on an unaided basis about food safety threats, consumers reported food spoilage as their primary food safety concern.

Yet while pesticides are not top of mind for most consumers, still they are an underlying concern. When asked in the FMI survey specifically about pesticide residues, 72 percent of respondents said they are a very serious health hazard. This finding outranks concerns about antibiotics and hormones, nitrites, irradiated foods and food additives. Other surveys show that Americans will reduce their consumption of fruits and vegetables when issues related to pesticides undermine their confidence in food safety.12,20

Why do consumers' attitudes toward pesticides and other health risks differ from those of health authorities? According to the National Research Council, experts usually base their determinations of the seriousness of a risk on quantitative risk assessments or numerical probabilities.21 Consumers' risk perceptions tend to be based on qualitative attributes of risk such as if the risk was previously known or unknown, voluntary or involuntary, or controllable or uncontrollable.

A 1989 report by the Natural Resources Defense Council (NRDC) was a watershed event in the crisis of consumer confidence over American food safety.20 NRDC declared that Alar, a growth regulator used mainly on apples, was a potent cancer-causing agent. Although government and health experts disputed NRDC's allegations, public uncertainty over the safety of apples continued for several months and apple sales dramatically declined. To consumers, Alar represented an involuntary, uncontrollable and invisible risk with alleged serious health consequences. The pesticide was subsequently withdrawn from the market voluntarily by its manufacturer. Upon further testing, EPA concluded several years later that the health risks associated with Alar were greatly exaggerated.22

With less than two million American families actively engaged in farming, many consumers have lost touch with the complex food chain. Consequently, they are not familiar with farming and do not fully appreciate the multiple pest, weed and insect pressures that can devastate entire crops. Morever, information received from the media about pesticides may be inaccurate, confusing or incomplete. Many journalists lack sufficient understanding of agriculture or scientific methods to critically analyze new reports.23,24 Risks related to cancer are seldom put into perspective.

The most often cited evidence that pesticides represent a significant risk comes from interpretations of animal toxicity studies.11 These studies show that roughly 20 percent of pesticides are capable of causing cancer when fed daily to laboratory animals at high levels over a lifetime. Much of the concern linking pesticides and cancer, for example, arises from adverse results in which pesticides are tested at very high doses in laboratory rats and mice.

According to AMA, there is no scientific evidence supporting a link between the proper application of pesticides and any adverse health effects in humans.25,26 Furthermore, human epidemiology does not support the hypothesis that cancer or other human illnesses are related to pesticides as food residues.11,27

Although most pesticide residues are typically well below tolerance levels before leaving the farm gate, consumers can take further steps to reduce their potential exposure to any remaining residues on fruits and vegetables. USDA, FDA and the American Dietetic Association recommend that produce be washed under tap water without soap before serving. This helps remove microorganisms, dirt and any pesticide residues that may remain on the produce. Consumers should peel away and discard outer leaves, skin or rinds, and scrub hardy vegetables, like potatoes and carrots, if the fiber-rich skins are to be eaten.

Qualitative Factors Affecting Risk Perception and Evaluation

The following are some qualitative factors affecting consumers' perceptions and evaluations of various health risks.39

Condition Related to Increased Concern Condition Related to Decreased Concern
Unfamiliar Familiar
Mechanisms or process not understood Mechanisms or process well understood
Personally uncontrollable Personally controllable
Involuntary exposure Voluntary exposure
Risk to vulnerable populations or future generations No risk to vulnerable populations or future generations
Unclear benefits Clear benefits
Effects irreversible Effects reversible
Caused by human action or failuress Caused by acts of nature
Inequitable distribution of risks/benefits Equitable distribution of risks/benefits

How is Risk Calculated?

Risk = exposure x toxicity

Risk of harm from a chemical depends on both the level of exposure to the chemical and on the toxicity of the chemical.10 Therefore, to quantify potential risks from consuming minute quantities of a particular chemical residue in food, scientists consider the toxicity of the chemical, the residue content of foods and the amounts of these foods eaten by population subgroups.

Population subgroups such as infants, children, women, women of child-bearing age and ethnic subgroups may be considered in risk assessments in addition to the total U.S. population. The groups considered depend on the toxicologic characteristics of a particular chemical. Risk assessments that consider regional and seasonal variations also are performed.

Exposure = residue concentration in food x amount of food consumed

Potential exposure to a chemical in a specific food is assessed by multiplying the residue concentrations in food times the amount of food consumed by each person in the population. This exposure is expressed as milligrams of residue per kilogram of body weight per day (mg/kg BW/day). Potential dietary exposure to a chemical is assessed by adding together residue intakes from all foods.

Different assumptions regarding residue concentrations in food may be used to assess exposure. A worst-case exposure scenario may be calculated using tolerance levels for pesticides in food. This exposure assessment is the theoretical maximum residue contribution. Exposure may also be calculated using anticipated residue levels.10,12

Integrated Pest Management

Concerns about environmental and worker protection have led to new approaches to reduce the reliance on pesticides in growing food and fiber.

One leading approach, Integrated Pest Management (IPM), involves the carefully managed use of an array of pest control tactics Ð including biological, cultural and appropriate chemical methods Ð to achieve the best results with the least disruption of the environment.26,28

Examples of IPM methods include cultivating pest-resistant plant varieties, adjusting planting times to avoid pest infestations, using beneficial or predatory insects such as ladybugs and parasitic wasps to control crop-destroying bugs, stationing pheromones or "sex perfume" traps to disrupt insect reproduction cycles and destroying pest-nesting areas by plowing under harvested crops or shredding leaf litter on orchard floors.29

When pesticides are used in IPM, it is common to routinely scout fields for pests. Chemical spraying is done only when these pests reach predetermined threshold levels, rather than spraying on a regular schedule.29-31

Although the concept of IPM has its roots in the 1950s, recently it has captured renewed interest. Many of the nation's leading food processors are working with their contract growers to research and develop new IPM strategies.11,19 Companies view IPM as an opportunity to reduce chemical risks to farm workers and the environment, while improving public confi-dence in food safety.

Estimates of IPM use on fruits, vegetables and major field crops range from 15 to 50 percent depending on the IPM operating principles used.30,31 In 1993, the USDA Extension Service allocated $8.5 million to 50 states and six territories supporting 750 full-time employees working on IPM projects.28

In September 1993, the Clinton Administration announced a national goal to have 75 percent of all farms using IPM techniques by the year 2000.28 By establishing this goal, the Administration recognized IPM as a valuable component of sustainable agricul-tural production systems while maintaining profitability. Government agencies have joined forces with various commodity groups to develop cooperative programs to achieve the Administration's goal.32

In some areas, growers are already ahead of the curve. For example, more than 90 percent of Washington apple growers reportedly use some IPM methods to control pests and diseases.33 In California, where the majority of U.S. agricultural commodities are produced, farmers have adopted IPM techniques in growing numbers, resulting in substantial reductions in pesticide use.9 Hundreds of IPM research projects have been funded through California's Statewide IPM Program since its establishment in 1980.

A key element in farmers' adoption of IPM techniques is profitability. A study of 49 economic evaluations of IPM programs in crops such as cotton, soybeans, vegetables, fruits, peanuts, tobacco, corn and alfalfa found that pesticide use decreased for seven of the eight commodities following the implementation of IPM techniques.34 Additionally, yields increased for six out of seven commodities, and net returns increased in all seven commodities for which changes were measured.

Much has been written about the potential benefits of biotechnology as part of IPM. Biotechnology allows researchers to select a specific genetic trait in a plant or other organism and move it into the genetic code of another plant.35 After a trait has been moved, the newly modified plant exhibits a specific characteristic, rather than the random alteration that occurs with traditional breeding.

The potential environmental benefits of biotech-nology in IPM throughout the world are tremendous. For example, biotechnology can be used to modify crop plants to protect themselves against insects, rather than rely solely on surface application of pesticides. Crops naturally resistant to plant viruses can reduce the need for insecticides used to control virus-spreading aphids, thereby reducing worker and environmental risks from pesticides.

More research needs to be done to identify suitable IPM techniques for different crops, climates, soil conditions and pest and weed pressures.30,31 Thus far, most IPM techniques have been developed to control insects and plant diseases. Weed scientists need more information on the biology and ecology of alternative weed control in order to further develop suitable IPM techniques.36 As new research becomes available, farmers also need education and training to help adapt the findings to their particular crop and agricultural setting.

Natural Toxins

Substances that are capable of causing cancer are virtually everywhere, even in natural compounds. The FDA estimates that the intake of carcinogens from man-made pesticide residues is extremely small compared to carcinogenic residues that plants produce naturally.

According to Bruce Ames, a professor of molecular biology and biochemistry at the University of California, more than 99.99 percent of the pesticides Americans ingest are "nature's pesticides" or "natural toxins."11,24,38

Americans ingest in their diet at least 10,000 times more by weight of natural pesticides than they do of man-made pesticide residues. Natural toxins are present in all plants and such food products as beans, lettuce, apple juice, wine, black pepper, spinach, peanut butter and many others. Of the known natural toxins, which concentrate in parts per thousand versus parts per billion in synthetic pesticides, none has been shown to cause cancer.24,38


The use of agricultural chemicals in relation to food safety will continue to be a complex subject. Some studies have shown that pesticides may affect ground-water, wildlife and occupational workers if the chemicals are not used in accordance with the law. But the future looks promising as food scientists, research-ers, government officials and manufacturers search for methods to improve agricultural techniques while reducing pesticide-related risks. Today's consumers can feel confident that they can choose from an abundant and safe food supply for themselves and their families.


1) National Academy of Sciences, National Research Council. Sustainable Agriculture Research and Education in the Field. National Academy Press, Washington, D.C., 1991.

2) Council for Agricultural Science and Technology. Pesticides—Minor Uses/Major Issues. Ames, IA, 1992.

3) Korb, P. and Cochrane, N. World Food Expenditures. National Food Review, 12(4):26, 1989.

4) Food Marketing Institute. Trends in the United States—Consumer Attitudes and the Supermarket. Washington, D.C., 1994.

5) United States Department of Health and Human Services, National Center for Health Statistics. Health United States 1992 and Healthy People 2000 Review. U.S. Government Printing Office, Washington, D.C., 1992.

6) National Academy of Sciences, National Research Council. Pesticides in the Diets of Infants and Children. National Academy Press, Washington, D.C., 1993.

7) National Agricultural Chemicals Association. From Lab to Label—The Research, Testing, and Registration of Agricultural Chemicals. Washington, D.C., 1993.

8) National Academy of Sciences, National Research Council Board on Agriculture. Regulating Pesticides in Foods—The Delaney Paradox. National Academy Press, Washington, D.C., 1987.

9) University of California Division of Agriculture and Natural Resources. Beyond Pesticides—Biological Approaches to Pest Management in California. Agriculture and Natural Resources Publications, Oakland, CA, 1992.

10) Chaisson, C.F., Petersen, B., and Douglass, J.S. Pesticides in Food, A Guide for Professionals. American Dietetic Association, Chicago, IL, 1991.

11) Hotchkiss, J.H. Pesticide residue controls to ensure food safety. Critical Reviews in Food Science and Nutrition, 31(3):191-203, 1992.

12) California Agriculture, 48(1):6-35, January/February 1994.

13) United States Environmental Protection Agency: Prevention, Pesticides, and Toxic Substances. EPA's Pesticide Programs. Washington, D.C., May 1991.

14) United States Environmental Protection Agency: Prevention, Pesticides and Toxic Substances. For Your Information: Protecting The Public From Pesticide Residues in Food. Washington, D.C., March 1993.

15) Elkins, E.R. Effect of commercial processing on pesticide res