Control of Dioxins (and other Organochlorines) from the Pulp and Paper Industry under the Clean Water Act and Lead in Soil at Superfund Mining Sites: Two Case Studies in EPA's Use of Science

This paper discusses EPA's acquisition and use of science in addressing dioxins (and other organochlorines) from the pulp and paper industry under the Clean Water Act and lead in soil at large Superfund mining sites. The common thread between both cases is the challenge posed by administering national pollution control programs while considering site-by-site variability in factors that influence environmental risks. In the first case study, high levels of dioxin in fish downstream of pulp and paper mills were inadvertently detected in 1983 as part of an EPA effort to determine background levels of dioxin in areas presumed to be relatively uncontaminated. These findings quickly got the release of dioxins from pulp and paper mills on EPA's research agenda. News reports beginning in 1987 elevated the issue onto the regulatory agenda, but more than a decade has passed without EPA taking final regulatory action. Meanwhile, the pulp and paper industry has dramatically reduced, but not eliminated, dioxin discharges from mills. The key scientific issue now confronting EPA decision-makers is how much weight to give to a water quality indicator called AOX. AOX is not statistically related to dioxin at the levels under consideration. Environmentalists justify using AOX because it serves as a surrogate measure for the entire toxicologically uncharacterized "soup" of organocholorines discharged from bleaching mills. Additionally, EPA estimates that discharges of dioxin from plants at levels below the analytical detection limits will continue to result in exceedances of stringent federal ambient water quality criteria under some local conditions. Industry counters that reductions in AOX do not achieve any measurable or monetizable environmental benefits. This case illustrates EPA's use of science to evaluate the cost-effectiveness of nominally technology-based water pollution controls. In the second case study, the Superfund program does not have the option of following its standard operating procedures for evaluating risks and determining Preliminary Remediation Goals for lead-contaminated sites because EPA has no numerical health-based standard for ingested lead (the agency's goal for lead is based on the level of lead in children's bloodstream). The study, therefore, illuminates the challenges and opportunities posed by developing and using rigorous site-specific scientific information. Potentially Responsible Parties (PRPs) generated rodent bioassay data which suggested that the bioavailability of lead in soil at mining sites would be much lower than EPA's default assumption. However, the agency disputed the validity of using mature rodents as animals models for the population of concern, children. In response, EPA conducted experiments with juvenile swine. The results indicated considerable variability in the bioavailability of lead in soil among the sites tested, with some higher, some lower, and some about the same as the agency's default assumption. Consequently, EPA cannot generalize across sites where similar mining activities occurred or draw any general distinctions between different types of mining sites, as had been presumed. This case illustrates that selection of the most appropriate animal model for toxicological studies involves tradeoffs between cost, experimental power and control, fidelity to human physiology, and the value of information for decision-making. Determination of the "optimal" animal model depends on the evaluative criterion being used. Although the new scientific data generated by EPA suggests higher bioavailability of lead in soil at some sites than the agency's default assumption, in terms of the final remedy selection, it appears that all of the results will be either beneficial or essentially neutral to Large Area Lead Site PRPs because EPA deems the cost of removing the contaminated soil to be excessive.

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Discussion Paper 97-08-REV

 Record created 2017-04-01, last modified 2018-01-22

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