ABSTRACT
Life Cycle Assessment
(LCA) is a framework for comparing products according to their total
estimated environmental impact, summed over all chemical emissions and
activities associated with a product at all stages in its life cycle
(from raw material acquisition, manufacturing, use, to final
disposal). For each chemical involved, the exposure associated
with the mass released into the environment, integrated over time and
space, is multiplied by a toxicological measure to estimate the
likelihood of effects and their potential consequences. In this
paper, we explore the use of quantitative methods drawn from
conventional single-chemical regulatory risk assessments to create a
procedure for the estimation of the cancer effect measure in the impact
phase of LCA. The approach is based on the maximum likelihood
estimate of the effect dose inducing a 10% response over background, ED10,
and default linear low-dose extrapolation using the slope ßED10
(0.1/ED 10). The calculated effects may correspond to
residual risks below current regulatory compliance requirements that
occur over multiple generations and at multiple locations; but at the
very least they represent a "using up" of some portion of the human
population's ability to accommodate emissions. Preliminary
comparisons are performed with existing measures, such as the US EPA’s
slope factor measure q1 *. By analysing bioassay data
for 44 chemicals drawn from the EPA’s Integrated Risk Information
System (IRIS) database, we explore estimating ED10 from more
readily available information such as the median tumour dose rate TD50
and the median single lethal dose LD 50. Based on the TD
50, we then estimate the ED10 for more than 600
chemicals. Differences in potential consequences, or severity,
are addressed by combining ßED10 with the measure
Disability Adjusted Life Years per affected Person, DALYP.
Most of the variation among chemicals for cancer effects is found to be
due to differences in the slope factors (ßED10)
ranging from 10-4 up to 104 [risk of cancer /
mg/kg-day].
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