Management of Carcinogenic Air Emissions: A Case Study of a Power Plant

An adjudicatory hearing to determine the potential adverse effects of the carcinogenic and mutagenic emissions from a diesel power plant at Harvard University was conducted by the Massachusetts environmental agency. Emissions from the plant were characterized through monitoring of fine particles, soluble organic extract and 11 indicator compounds, and comparing them with automotive diesel emissions. Quantitative risk assessment included assessment of the facility's contribution to ambient background and a comparison with emissions from mobile sources. The aggregate risk of cancer associated with 40 years of plant operation was estimated to range between 0 and 4 per 1.66 million people exposed. In 1986 the plant was permitted to operate on the grounds that the risks were not unreasonable. The significance of the decision extends beyond this one case; 1) in its decision the agency focused only on public health issues and disregarded all other social and economic costs or benefits; 2) the agency rejected a zero risk standard for carcinogens by explicitly accepting a small but nonnegligible risk as "reasonable"; 3) the agency did not define an absolute standard of risk acceptability and, therefore, implicitly recognized the attendant uncertainty. The case also illustrates a strong subjective component present in all risk assessments.