| John Wargo, associate professor in the School of Forestry and Environmental Studies and the department of political science at Yale University, has testified in Congress and been an advisor to federal policy makers on environmental issues. He was centrally involved in two National Academy of Science committees on the science and politics of pesticides. |
Each day, we are all exposed to a complex mixture of contaminants in food, water and air. Methods of estimating our exposure to mixtures and their toxic effects, however, are primitive and are likely the result of laws and regulations that generally support the single-media, one-pesticide-at-a-time regulation of chemicals. Real-world risk reduction will require formal scientific and legal consideration of human exposure to complex mixtures of toxic substances across the artificial environmental compartments defined by current laws.
Laws that demand analysis of single compounds within a single medium cause scarce analytical resources to be used to explore narrow questions and to identify minuscule risks. As risks approach zero, the marginal costs of risk reduction tend to increase exponentially -and to consume available resources before a search for systemic or cumulative effects can even be started. Further, the specialized knowledge produced promotes more technical regulation, which in turn directs EPA's attention to questions even more limited in scope.
The problem of estimating and managing cumulative effects from diverse compounds has many dimensions. Exposure to different compounds that each contribute to the same adverse effect may come from numerous sources, each managed independently. One example is childhood exposure to neurotoxic compounds such as heavy metals or pesticides: these chemicals are found in air, water, and food, each of which is controlled without regard to the other. Cancer risks appear to pose another type of cumulative effect problem whereby a single cell may move through several stages before a tumor begins to grow and promotion from one stage to the next may be induced by different compounds at different points in time. A final example may be our exposure to diverse chlorinated organic compounds that mimic estrogen. In these cases, each individual release of the compound into the environment seemed to pose little threat so we permitted release of minor amounts-but in an uncontrolled manner, with no one keeping track of amounts released or their distribution in the environment, accumulation in the body, or adverse health effects.
Fractured environmental law has defined the structure of EPA, the organization of its expertise, and the boundaries surrounding the questions agency scientists have normally asked. Law has shaped regulatory science by demanding answers to technical questions that are chemical-specific, medium-specific, and effect-specific-all of which are necessary for setting standards. How much benomyl, for example, will likely remain in heat-processed apple juice, and what if any cancer risk might the residues pose? Answers to these types of questions normally cause regulations to be further elaborated or qualified. Since 1970, attention has imploded on narrow topics, a trend that has caused a proliferation of regulations. It is an unfortunate irony that the comprehensive demand of current law-that each chemical be studied with equal intensity-has necessitated an incremental regulatory process that moves at a glacial pace. Quite simply, law has not directed attention or resources to examine the bigger questions, such as how are we accumulating risks across chemicals and environmental media-risks we face in daily life? The potential for contamination to flow across environmental compartments, and for people to amass exposures and risks as they move from one environment to the next, have been largely ignored.
Current law seems to reflect a highly simplified conception of nature, one that neglects important ecological processes. Although breaking nature into compartments is a necessary basis for pursuing improvements in environmental quality and risk reduction, the boundaries among the compartments are necessarily artificial. Many lessons from ecology-some of which are detailed in earlier chapters-have long warned us to consider the natural processes that connect the units. More worrisome, this entanglement between law and science gives little hope that we are even aware of the magnitude and distribution of significant threats to environmental health.
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