$486 ENVIRONMENT REPORTER : * the point where predicted concentrations of the pollutant of control efficiency, technical feasibility, and costs and the are highest. Maximum individual risk is expressed as a reductions in risk that they achieve. means that & person spending @ lifetime at the point of maximum exposure faces an estimated increased risk of cancer of one in 10,000. (For comparison, the average SUMMARY OF EPA'S INTENTIONS TO REGULATE BENZENE EPA listed benzene as a hazardous air pollutant in 1977. [n 1980 and 1981, EPA proposed emission standards for four probability, a risk of one in ten thousand, for example, lifetime risk of contracting cancer in the United States is currently about 2.5 in ten, 30 eliminating a risk of one in ten thousand reduces the overall lifetime risk of contracting cancer by less than 0.1 percent.) Estimates of maximum individual risk must be interpreted cautiously, however, since few peopie reside at the points of maximum concentrations and even fewer spend their whole lives at such bocations. The second measure, “total population impact,” takes account of people exposed at all concentrations, low as well as high. It is expressed in terms of annual number of cancer cases, and provides a measure of the overall impact on public health. A total population impact of 0.05 per year, for example, means that the modeling predicts that emissions of the specific pollutant from the source category will cause one case of cancer every 20 years. Such figures should not be viewed as precise, however, nor even as best estimates of the likely effects. They, together with the estimtes of maxzimum individual risk, are intended to give an indication of a plausible upper-limit situation. In the same vein, s plausible lowerbound estimate of the risk would be zero. The two estimates taken together provide a better de actiption of the magnitude and distribution of risk in a community than either number taken alone. “Maximum individual risk” tells us the worst risk, but not how many people bear that risk. “Total population impact” describes the overall! health impact on to the entire exposed population. but not how much risk the most exposed persons bear. Two chemicals or regulations could have sisnilar population impacts, but very different maximum individual risks. or vice versa. Consequently, any sensible “risk management” system cannot rely on either measure alone, both are important. Risk Management Given the linear no-threshold assumption regarding risks from pollutants such as benzene, the only absolutely risk- free approach to setting a standard would be to reduce exposures to zero. It does not appear that Congress intended Section 112 standards to cause widespread distribution of the national economy. Moreover, while Section 112 requires standards to protect the public health, this does not mean that EPA must eliminate all risks. For carcinogens (asbestos and vinyl! chloride) EPA has reduced human health risks by setting Section 112 standards that reflect identified emission control techniques. Thus, EPA has sought to establish an approach to risk management thatallows for an appropriate contro] of emissions of hazardous air pollutants without an automatic closing of all sources of the pollutant. This risk management approach that EPA bas adopted for Section 112 pollutants is as follows: 1) The agency should evatuate all source categories of the pollutant to determine which categories cause significant public health risks. source categories (maleic anhydride plants, ethylbenzene and styrene plants, benzene storage vessels and fugitive emissions from petroleum refineries and chemical manufac- turing plants) and began work on a Afth standard for coke by-product recovery plants that will be proposed. I. Intent to promulgate Anal benzene standard.for fugitive benzene emissions from petroleum refineries and chemical manufacturing plants. EPA estimates that the contro! of sorne 229 sources will reduce benzene fugitive emissions from existing petroleum refineries and chemical manufacturing plants from about 7900 megagrams per year to about 2500 megagrams per year. As a result of this emission reduction, the standard would reduce the estimated maximum lifetime risk for the most exposed individual from 15 chances in 10,000 to 4.5 in 10,000, and would reduce the estimated annual incidence of cancer from new and existing plants from an estimated 0.45 to 0.14, or an approximate 70 percent reduction. Benefits to » air and water quality will result from the new standard because the controls utilized in implementing the standard will also reduce emissions of other potentially toxic hydrocarbons and because leak control techniques would reduce the amount of benzene and other organic compounds enter- ing wastewater systerns. . The standard will iimit benzene emissions fromm new and existing fugitive emissions sources containing 10 or more percent by weight benzene in the petroleum refining and chemical manufacturing industries. The standard allows no detectable emissions due to leaks from safety /relief valves and product accumulator vessels, requires a leak detection and repair program for pipeline valves and existing pumps and compressors; and requires certain equipment for sew pumps, new compressors, sampling connections, and openended valves. Public hearings were held on the proposed standard for fugitive sources and the comments received are being considered in the final rule. {l. Intent to propose benzene emission standard for coke by-product recovery plants: The proposed standard would reduce benzene emissions from severa! emission sources at new and existing coke by- product recovery plants through a combination of emission, equipment, work practice, and operational requirements. The 55 existing coke by-product plants account for an estimated 29,000 megagrams of benzene emissions yearly. or some 53 percent of all benzene emissions from stationary sources. EPA's proposalcalls for a reduction of some 25,500 megagrams, or an 68 percent reduction in emissions. The proposed controls would reduce the maximum individual~ risk from 83 chances in 10,000 to $.§ in 10,000, The number ee of cancer incidences would change from 2.60 per year to-> ¢L an 0.23 per year. In addition to the reduction of benzene emissions. the 2} The source categories that are judged to cause significant risk are then evaluated EPA examines the various options available to reduce emissions from these sources, including controls similar to those imposed under Section agency projects that nationwide emissions of nonbenzene Organic pollutants, which include volatile organic compounds, naphthalene, polynuclear aromatic hydrocarbons, and lighter organic compounds, would also be reduced from their current estimated level of 165,000 megagrams pet ards) and closing the plant. Options are examined ip terms reduction. 111 of the Clean Air Act (New Source Performance Stand- 12-23-33 year to about 41.000 megagrams per year, a 75 percent Pubsehed by THE BUREAU OF NATIONAL AFFAIRS INC.. Washengion. 0.C. 20037 cee ee eee ee ee ee sally