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ENVIRONMENT REPORTER
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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
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