标题：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
摘要：This paper discusses EPA's acquisition and use of science in addressing dioxins (and otherorganochlorines) from the pulp and paper industry under the Clean Water Act and lead in soil atlarge Superfund mining sites. The common thread between both cases is the challenge posed byadministering national pollution control programs while considering site-by-site variability infactors that influence environmental risks. In the first case study, high levels of dioxin in fishdownstream of pulp and paper mills were inadvertently detected in 1983 as part of an EPA effortto determine background levels of dioxin in areas presumed to be relatively uncontaminated. Thesefindings 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 adecade has passed without EPA taking final regulatory action. Meanwhile, the pulp and paperindustry has dramatically reduced, but not eliminated, dioxin discharges from mills. The keyscientific issue now confronting EPA decisionmakers is how much weight to give to a water qualityindicator 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 entiretoxicologically uncharacterized "soup" of organocholorines discharged from bleaching mills.Additionally, EPA estimates that discharges of dioxin from plants at levels below the analyticaldetection limits will continue to result in exceedances of stringent federal ambient water qualitycriteria under some local conditions. Industry counters that reductions in AOX do not achieve anymeasurable or monetizable environmental benefits. This case illustrates EPA's use of science toevaluate the cost-effectiveness of nominally technology-based water pollution controls. In thesecond case study, the Superfund program does not have the option of following its standardoperating procedures for evaluating risks and determining Preliminary Remediation Goals for lead-contaminated sites because EPA has no numerical health-based standard for ingested lead (theagency'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 bioassaydata which suggested that the bioavailability of lead in soil at mining sites would be much lowerthan EPA's default assumption. However, the agency disputed the validity of using mature rodentsas animals models for the population of concern, children. In response, EPA conductedexperiments with juvenile swine. The results indicated considerable variability in thebioavailability of lead in soil among the sites tested, with some higher, some lower, and some aboutthe same as the agency's default assumption. Consequently, EPA cannot generalize across siteswhere similar mining activities occurred or draw any general distinctions between different types ofmining sites, as had been presumed. This case illustrates that selection of the most appropriateanimal model for toxicological studies involves tradeoffs between cost, experimental power andcontrol, fidelity to human physiology, and the value of information for decisionmaking.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 atsome sites than the agency's default assumption, in terms of the final remedy selection, it appearsthat all of the results will be either beneficial or essentially neutral to Large Area Lead Site PRPsbecause EPA deems the cost of removing the contaminated soil to be excessive.
