Assessing The Risky Job Of Risk Assessment
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LEAD: EARLY this century, the principal insecticide used on fruits and vegetables went by the elegant appellation ”Paris green.” Today’s chemists have a less appetizing name for the toxin - lead arsenate. EARLY this century, the principal insecticide used on fruits and vegetables went by the elegant appellation ”Paris green.” Today’s chemists have a less appetizing name for the toxin - lead arsenate. Banning outright such unquestionably dangerous products was the easy part of protecting health and the environment. As scientists learn about the delayed effects of more subtle poisons, regulators face much harder judgment calls. For example, traces of the common solvent methylene chloride contaminate many sources of drinking water; how much of the suspected carcinogen does it take to make the water unsafe? The exhaust of garbage incinerators contains tiny amounts of dioxin, a highly toxic product of combustion; how much can a neighborhood reasonably tolerate in its air? The science of risk assessment seeks to quantify such hazards. But it is laden with opinion as well as fact. And, since environmentalists and industry beseige Government regulators with conflicting demands, politics also becomes an ingredient in the equations of risk. In recent weeks, the Environmental Protection Agency demonstrated the controversial nature of this inexact science when it decided that several pollutants, including dioxin, methylene chloride, lead and arsenic are not as harmful as previously believed. In the new risk assessment for dioxin, the E.P.A. proposes to lower its safety threshold by a factor of 17. No one really knows how harmful tiny amounts of dioxin can be. The precision implied by assigning numbers to risk is somewhat illusory, but regulators need exact figures on which to base rules. The Dow Chemical Company, one of the companies involved in litigation over the defoliant Agent Orange, which contained traces of dioxin, applauded the new risk levels. ”Reconsidering any standard by updating the science is always a good idea,” said Kenneth L. Burgess, a company spokesman. More : query.nytimes.com |