Regulatory Policy, New Technology, and Mother Nature

Much of the legislation introduced in the 1970s to regulate pesticides was in response to concerns over the effects of pesticide use on human health and the environment. The 1972 amendments to the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) required the U. S. Environmental Protection Agency (EPA) to reregister all of the approximately 600 active pesticide ingredients approved for use up to that time. The reregistration process requires a review of all existing data on each active ingredient and submission of additional test data needed for an evaluation of the risks and benefits it poses. In this way older pesticides are evaluated according to current regulatory standards and testing procedures. Lately, interest in the reregistration process has sharply increased as a result of fears for public health and farmworker safety from pesticide exposure.

Due to advances in the fields of toxicology and analytical chemistry, recently developed pesticides have had to meet more rigorous testing requirements in order to be registered than those developed in the past. New compounds must now demonstrate low toxicities to humans, fish, and wildlife in order to gain approval. The pace of reregistration of older compounds, once slow, has been accelerated by the deadlines set by the 1988 amendments to FIFRA. Within the next few years, the EPA will make decisions affecting the registration of a large number of both new and old pesticides.

One of the factors considered in the EPA's risk/benefit analyses of previously registered pesticides is the availability of substitutes for the active ingredients in question. In many cases, a compound meeting the new requirements is registered for use on the same crops and to control a similar spectrum of pests as an older chemical suspected of posing a greater risk to human health and the environment. Many advocate banning these older chemicals soon after the newer, less toxic alternatives have been made available.

Newcomers raise concerns

It turns out, however, that there is a new set of concerns arising from some of the properties of the newer pesticides. The very characteristics that make them less of a threat to the environment and public health—namely, their low rate of application and specific mode of action—also make them vulnerable to resistance by the pests they are designed to control.

The recent history of the pesticides 2,4-D and chlorsulfuron clearly illustrates that substitution of one product for another may resolve one set of problems but create another set of its own. Sold under the product name of Glean, chlorsulfuron was registered for use on wheat in 1983. It was the first of the class of sulfonylurea herbicides whose mode of action is the inhibition of a single enzyme system. Chlorsulfuron has demonstrated neither mutagenic nor teratogenic properties and exhibits low toxicity to fish and wildlife. It is applied at a low rate of 0.02 pounds per acre and has residual activity in the soil for as long as three or four years. Because its residual activity can injure other crops, its use is most prevalent in continuous wheat and wheat/fallow rotations in the Great Plains. Chlorsulfuron gained wide acceptance rapidly, and began to replace 2,4-D in many areas where monoculture wheat is grown. Compared to phenoxys, it normally controls many more of the weeds in wheat.

Chlorsulfuron's "rival," the phenoxy herbicide 2,4-D, is still the most widely used herbicide in U.S. small grain production. Originally registered for use as a pesticide in 1948, 2,4-D is a systemic herbicide that is absorbed by plant foliage and stem tissue and is translocated to the actively growing parts of the plant, where it affects the plant's growth. Its mode of action is complex and not well understood, but it acts as an auxin, causing the plant to grow disoriented and too rapidly. Although 2,4-D has been widely used for forty years, it has multiple sites of action, and no significant resistance problems have occurred. It does not persist in the soil but is degraded within one to two weeks. It is generally applied at a rate of about 0.5 pounds per acre. In the 1980s, 2,4-D continues to be used on about one-third of the nation's wheat acreage.

Like many of the older pesticides, 2,4-D has been under suspicion in connection with risks its use may pose to human health. The Environmental Protection Agency has issued a registration standard for 2,4-D which mandates that workers wear protective clothing when handling it. The EPA has also proposed that use of 2,4-D be restricted in certain counties where it might pose a threat to endangered species. In addition, the agency is monitoring for groundwater contamination by 2,4-D in areas of high vulnerability to the leaching of soluble pesticides. The EPA has also identified certain data gaps while evaluating the environmental and health effects of 2,4-D, and has called for additional studies.

An important lesson can be drawn from the recent experience with 2,4-D and chlorsulfuron: newer, less toxic compounds should not be automatically viewed as complete replacements for the older compounds. It is probably wiser to plan on their coordinated use. If many chemicals are banned or withdrawn from use, it may be necessary to develop and register new compounds at a much faster pace to keep ahead of resistance and other unforeseen problems. This is easier said than done, as it is becoming increasingly difficult and costly for the chemical industry to find new and better herbicides. Therefore, it may be advantageous to keep the older chemicals available as insurance if the new chemistry fails.

Concern over weed resistance, however, is only part of the issue facing those who must make decisions on how to regulate pesticides. Pesticides also need to be evaluated in terms of their long-term benefits for agriculture and the agronomic practices they promote. If the pool of available, effective pesticides is limited, a farmer's management options may also be limited. Lately there has been much promotion of the benefits to agriculture from both crop rotation and reduced tillage. Sometimes tradeoffs must be made.

The use of chlorsulfuron, for example, is credited with certain benefits to the environment and to agricultural productivity. Its use has permitted less frequent tillage of fields, resulting in large reductions in soil erosion, water loss, and sedimentation in some areas of the Great Plains. In other areas its use has increased retention of soil moisture, thus boosting yields. However, chlorsulfuron severely limits a grower's options in rotating crops. In other words, the consequences of promoting the use of one pesticide over another can affect much more than wildlife and human health.

What role for government?

What is the appropriate role for the federal government to assume when agricultural problems arise from pesticide use? Both Israel and Great Britain have banned the further use of chlorsulfuron. However, a U.S. court ruled in 1978 that the EPA did not have the authority under FIFRA to ban pesticides on the basis of lack of effectiveness. The assumption was that the marketplace would eliminate nonperforming pesticides. In the case of chlorsulfuron, the manufacturer took steps to limit use of the product before resistance to it became widespread. Because the manufacturer chose to act quickly and responsibly, massive crop failures may have been averted. The response of the marketplace in this case could have come too late.

These lessons suggest that pesticide rulemaking needs to encompass a broader range of objectives than the reduction of risk to the environment and human health. Concerns for efficacy, the likelihood of pest resistance, indirect environmental effects, and the promotion of sound agronomic practices ought to be taken into account. Also to be taken into account are the distributional consequences of pesticide policies—particularly command-and-control policies. Since these policies target specific active ingredients used on specific crops, the burden of the policies is felt most by those who use the restricted ingredient and especially by those whose possible pest management options are limited. Having those who use the pesticide bear the cost of the policy honors the "polluter pays" principle but does not address the issues of equity and fairness.