With more than 50,000 pesticide products registered for thousands of agricultural purposes in the United States, it should come as no surprise that the pattern of pesticide use is extremely complex. Growing concern about the effects of pesticides on human health and the environment has prompted closer examination of exactly where specific products are used, by whom, for what purpose, and with what result.
Detailed information on the extent of pesticide use in the United States, that is, on the amounts of pesticides used—by active ingredient, by crop, and by region—is critically needed if the quantitative risks and benefits of pesticide use are to be assessed in light of allied issues of the environment, human health, agricultural production, and economic policy goals. Yet, at present, no comprehensive set of pesticide use estimates exists or is under development at either the federal or the state level. Until this information is available, accurate assessment of the implications of adopting particular pesticide policies will be impossible.
The inadequacies, of the data now available on pesticide use in the United States can be explained in part by the complexities of the issue. For instance, the target pest of the individual compounds varies widely—from weeds, insects, and mites to fungi, rodents, and nematodes. The uses of pesticides are equally diverse: in agriculture they include seed treatment, fumigation, protection of nursery stock and livestock, and weed control on fallow land. Moreover, some pesticides are used in large quantities on only a few crops while others are used in small quantities on a large number of crops. Use of a particular pesticide on a certain crop can vary widely from state to state, and use of the same pesticide on one crop in any state can vary widely from year to year. To complicate matters further, very few pesticides are used for all of the purposes for which they are registered.
The presence or absence of an agricultural pest in any location is due largely to local geographic and climatic conditions. Growers in northern states, for example, need smaller amounts of certain pesticides because cold winters ward off pests that flourish in warmer, southern regions.
In addition, many crop diseases and insects respond to climate changes within the same region. For instance, more rainfall or warmer temperatures can greatly increase the population of a pest that normally would not appear at all or else would be present only in insignificant numbers.
Biochemical and economic factors also affect pesticide use patterns, as has been clearly demonstrated since synthetic organic compounds began to be used in agriculture more than forty years ago. As pests have become resistant to the effects of specific chemicals in some of the earlier mixtures, substitute products have been developed and marketed. In addition, the availability of more specifically targeted pesticides has, in some instances, caused shifts in use away from more broadly applicable products. Changes in packaging and marketing (e.g., offering premixed combination products) have affected the demand for and use of various products, while depressed economic conditions have sometimes led growers either to switch to less costly products or to eliminate pesticides entirely.
Agricultural and environmental policies also have had a significant effect on how and where agrichemicals are used. Some of these policies have indirectly resulted in a reduction in the use of particular products in some areas. For example, a policy change in cotton commodity programs during the 1970s led to an increase in cotton acreage in the Southwest and a decrease in the Southeast. Since fewer herbicides are needed for growing cotton in the Southwest, aggregate use of pesticides by cotton growers declined sharply.
A more current example of how policies can indirectly reduce pesticide use is the Conservation Reserve Program. This federally sponsored program is designed to divert up to 45 million acres of cropland out of production and into grassland or forest by 1990 in an effort to reduce both crop yield and erosion. Here again, in areas where pesticides are heavily used, their application would obviously decline with a significant reduction in planted crop acreages.
On a broader scale, over the past twenty years many farmers in the United States have adopted what are called Integrated Pest Management programs. These programs, promoted by the U.S. Department of Agriculture (USDA), are designed to shift growers from exclusive reliance on pest-controlling chemicals to a system that integrates various methods of pest control, including the introduction of naturally occurring control agents such as other insects.
Obviously, not all agricultural and environmental policies result in lower levels of pesticide use. For instance, a policy of encouraging limited-till and no-till fanning has been widely promoted by agricultural and environmental groups over the past several years as a means of preventing soil erosion; these practices have been widely adopted in certain regions of the country. However, because no-till methods are dependent on herbicides rather than on tillage to destroy weeds, the adoption of these methods has led to greater dependence on certain herbicides.
Agency restrictions
Restrictions imposed by governmental agencies have been a fundamental force in regulating pesticide use. In large part, these controls have been prompted by concerns for human health and the environment raised by reports of pesticide residues in human and animal tissues, in food, and in water supplies.
Most of the restrictions have come about as a result of the 1972 amendments to the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) which require the U.S. Environmental Protection Agency (EPA) to re register all previously registered pesticides on the basis of current testing requirements. FIFRA empowers EPA to cancel, suspend, or restrict a pesticide registration if the agency concludes that an unreasonable risk to human health or the environment results from its use.
As a result of FIFRA, a limited number of substances—including organochlorine pesticides such as aldrin, DDT, and dieldrin, which were widely used in agriculture during the 1950s and 1960s—have been completely eliminated from most agricultural uses. Other pesticides have been given "restricted use" designations; that is, these substances can only be applied by individuals trained and certified to do so. Restrictions governing the reentry of farm workers into sprayed fields also have been established to limit occupational exposure to certain substances. In addition, EPA sets limits on the maximum level of pesticide residues permissible in foods; the limits are determined by projecting the level of protection from potential health hazards needed over a normal lifetime.
Despite some progress, the reregistration process being carried out by EPA has moved slowly. Of the 600 individual active ingredients under review, 79 have been cancelled voluntarily or have been suspended by EPA. Furthermore, only 2 active ingredients have been assigned final regulatory standards (these standards identify the crops that an active ingredient can be used on and the conditions under which it can be applied). All of the remaining active ingredients are at some interim stage of the reregistration process.
EPA generally obtains its usage data in the form of proprietary information concerning shipments; such information is provided by the pesticide producers themselves. The agency also relies on privately operated, proprietary-data reporting services such as Doane's to supply data on the extent of usage by crop for large regions of the country.
EPA publishes data on a particular pesticide in the course of rulemaking procedures to suspend or ban such a substance. To prepare the needed estimates, EPA economists generally use ad hoc methods, since the agency does not maintain a systematic, publicly available set of usage estimates for the active ingredients commonly used in pesticides.
In addition to EPA, other public agencies have also become involved in pesticide regulation in the past few years. For instance, the Fish and Wildlife Service of the U.S. Department of the Interior is working with EPA to carry out requirements specified under the terms of the Endangered Species Act of 1973. It is developing regulations that restrict the use of sixty-eight chemicals on eight crops being grown in 373 counties on acreage considered to be unacceptably near the habitat and range of endangered species.
Agency and institutional activity to control pesticide use also has intensified at the state and local levels. For instance, most states are in the process of developing groundwater protection strategies, and some state governments are considering bans on specific substances—the state of Massachusetts in fact having recently banned alachlor, the most widely used pesticide in the United States. Evidence of groundwater contamination from pesticides has prompted state and local drinking water authorities to implement regulations for monitoring pesticides, and nonpoint-pollution planning agencies and public health authorities also are developing policies on pesticide use. Future groundwater regulations may also involve restrictions imposed for specific counties.
Mistaken assumption
It is often assumed in public policymaking agencies newly involved in this field that there is an up-to-date database on pesticide use available for each county, state, region, or watershed. However, the reports on pesticide use issued by forty-one states are flawed by major limitations in their estimates, and most of these reports are out of date in any case. Nine states—including major agricultural states such as Tennessee, North Carolina, Alabama, and Virginia—have not released information on pesticide use at all.
Comprehensive data on the subject are not available from EPA, USDA, or the Bureau of the Census. Although each of these organizations is aware of the need for the data and has made efforts to obtain them, changing administrative priorities and funding problems have curtailed their efforts. In fact, funding for USDA programs to collect and publish such information has been cut significantly over the past five years.
Three recent examples highlight the problems encountered by public agencies when they attempt to assess the risks and benefits of pesticide use:
- In 1986, there was great concern in Kansas due to a report from the National Cancer Institute linking the pesticide known as 2,4-D to cancer among farm workers. The Kansas State Department of Public Health was unable to assess the 2,4-D exposure pattern in the state, since the most current available data on pesticide use in Kansas are for the year 1978.
- Also in 1986, EPA suspended the herbicide dinoseb because of health-related concerns; in addition, study had revealed that substitute chemicals were available for the major crops on which dinoseb would usually be used. After the suspension, some growers contended that there were special cases in which substitutes would not work; had the data on such cases been more clearly understood, EPA might have granted exemptions permitting the use of dinoseb in certain instances. That was not done, and EPA is now involved in extensive litigation over its decision.
- In its 1987 report, Regulating Pesticides in Food: The Delaney Paradox, on cancer risks due to ingestion of pesticide residues in food products, the National Academy of Sciences could make only a "worst case" assessment, since detailed usage data for most of the crops and pesticides of concern were not available.
At a minimum, the lack of a publicly available pesticide use inventory tends to produce considerable frustration among those seeking information on the subject. Perhaps more significantly, public policymaking under these circumstances can all too easily become stalled or else carried out in great haste following unsuccessful efforts to gather the information needed for a well-informed decision.
Table 1. Agricultural Pesticide Use in States Ranked As Highest-volume Users
Table 2. Amounts of Ten Leading Active Ingredients Used in Agricultural Pesticides
RFF database helps fill gap
With the help of financial support from EPA, USDA, and the United States Geological Survey, Resources for the Future has begun to fill this information gap. It has gathered, mapped, and analyzed information on pesticide use pertaining to 186 active ingredients and 75 crops in all fifty states; most of the data are for the year 1982. This national database incorporates most of the agricultural uses of pesticides, categorizing them by state, crop, and active ingredient.
Adding all of the estimates on the use of individual pesticides in all states and by crops, RFF estimates that a total of 661 million pounds per year of active ingredients are applied in agriculture nationwide. An estimated 85 million pounds of alachlor are applied each year, primarily on field corn (not to be confused with sweet corn) and soybeans. Next to alachlor, atrazine—another herbicide used primarily on field corn—is most heavily used, in amounts of about 79 million pounds each year. Together, these two substances account for 25 percent of the pesticides used for agricultural purposes nationwide. Among the fifty states, Iowa and Illinois emerge as the largest users of pesticides, accounting for 21 percent of the national total.
One of the major applications of the RFP database so far has been the quantification of the benefits of using pesticides on field corn and soybeans. In-house research is being carried out with the aid of a national agricultural economic assessment model, also developed at RFF.
According to the database, almost 100 percent of the total acreage used for producing field corn and soybeans in the United States is sprayed with a herbicide. In fact, among the ten states rated as the highest-volume users nationwide, the pesticides in eight states were used principally on field corn and soybeans (see table 1). Likewise, most of the top ten active ingredients in pesticides (by volume) owe their high-ranking status to use on these crops (see table 2). The database also indicates that approximately one-half of the aggregate volume of pesticides employed in U.S. agriculture is used on field corn and soybeans. Corn earworm moths like this one destroy nearly 4 million acres of corn and other field crops in the United States each year. Insecticides are used extensively in an effort to reduce their numbers. The lack of a comprehensive national database on pesticide use makes it impossible to determine precisely where and in what quantities these pesticides are applied.
RFF's quantitative assessment has been aided by the fact that yield effects and other information about pesticide use on field corn and soybeans are fairly well documented (which is not necessarily the case for other crops). For instance, it is clear from examining field corn and soybean growers' annual cost-of-production budgets that while herbicide costs are relatively small on a per acre basis, the increased yields due to this application usually account for the margin needed to show a profit.
Pesticide use patterns for field corn and soybeans also show that many different herbicides are available and are used throughout the country. However, because of regional farming practices and growing conditions, certain herbicides provide particularly large yield benefits in certain regions.
For example, atrazine is widely used on field corn acreage in the Chesapeake Bay region. USDA has estimated that without atrazine, weeds would cause field corn yield losses in Maryland and Delaware to rise from 5 to 18 percent, even allowing for the substitution of alternative chemicals. If atrazine were banned, the increased yield loss plus the increased cost of switching to more expensive chemicals would translate into an aggregate profit loss of $184 million to field corn farmers in the Bay region.
The Chesapeake Bay region also illustrates the trade-offs involved in designing pesticide use policies to protect human health or, alternatively, to protect the environment. On most of the soybean acreage in the region, no-till or limited-till farming is used. From an environmental perspective, these methods offer advantages over traditional tillage practices because less sediment is lost through surface runoff and deposited in the bay. Almost 100 percent of the soybean acreage in the region is treated with linuron, the only herbicide recommended for no-till soybeans there.
Linuron, however, ranks very high in the National Academy of Sciences' study of dietary risk from ingestion of pesticide residues in foods. Ironically, this high ranking is due to residues of linuron in meat products: the pesticide is used on soybeans that are consumed as feed by cattle and hogs, which leads to the residues in the meat products.
RFF's database has also begun to be used in studies by other organizations that rely on such information to assess the risks, benefits, and trade-offs involved in pesticide use policymaking. The Economic Research Service (ERS) of USDA has used the database to estimate the extent of potential national groundwater contamination resulting from the use of highly soluble pesticides in agriculture.
Using RFF data to show the intensity of use of known leaching chemicals (those that are water-soluble) by county, ERS has superimposed these estimates onto another national database that classifies counties according to their vulnerability to groundwater leaching. The result is that ERA has identified about 1,400 counties—roughly half of the nation's counties—that have significant potential for leaching of intensively used soluble substances. Findings also suggest that there are strong regional patterns involved and that most of the southeastern United States falls into this category of potential risk.
More to be done
The work that is being done at RFF and elsewhere is, in one sense, only a beginning. Through such efforts, some of rile costs, benefits, and trade-offs of regulating pesticides can be addressed during the regulatory process at present, but most remain unquantifiable. Much of the current legislation relating to pesticide use does not require such quantification, since it does not require that a comparison of risks and benefits be carried out before decisions are made.
However, questions of trade-offs in pesticide use continue to be asked, and with recent, fresh concerns arising over health effects, these issues are becoming even more pressing. While the "big picture" of the comparative risks and benefits of the 200 most commonly used active ingredients in pesticides remains unattainable at the present time, the need for such information is crucial if regulatory decisions on these issues are to be made in the longer-term interest of all those affected by them.
Leonard P. Gianessi is a fellow in the Renewable Resources Division at RFF. He has served as project director of the pesticide use data collection effort at RFF since its inception in 1983.
A version of this article appeared in print in the October 1987 issue of Resources magazine.
