REVIEW OF EPA, ATSDR, AND CDC COMMENTS ON THE ARMY'S RISK-ASSESSMENT REPORTS ON ZINC CADMIUM SULFIDE
THE U.S. ARMY REQUESTED that the U.S. Environmental Protection Agency (EPA), the Centers for Disease Control and Prevention (CDC), and the Agency for Toxic Substances and Disease Registry (ATSDR) review its health risk-assessment reports for the tests conducted with ZnCdS.
The Subcommittee on Zinc Cadmium Sulfide had the opportunity to review comments by EPA, CDC, and ATSDR experts on the Army's risk assessments for releases of ZnCdS in Corpus Christi, TX, and Minneapolis, MN. A total of 7 EPA experts wrote comments, which were summarized by Hugh McKinnon (director of EPA's Health Assessment Group). Comments from experts at the CDC and ATSDR were also available.
EPA reviewed the Army Environmental Health Agency's risk-assessment reports for Corpus Christi, TX, and Minneapolis, MN. EPA indicated
general agreement with the Army's conclusion, stating that "if the exposure calculations are even close to correct (that is, within a hundredth to a millionth of the actual exposure), the test sites appear to pose no human health risk." However, EPA suggested several possible improvements in the documents. As stated by Robert Huggett, assistant administrator for research and development at EPA, "We found the Army's conclusion of no health threat is likely correct but too narrowly stated."
EPA suggested that the Army's assessment documents discuss exposures of sensitive subpopulations, such as children and debilitated adults. There was also concern that inhalation was the only exposure route considered and that neglect of the dermal and oral routes led to underestimation of the cadmium exposure. EPA concluded that some assumptions made can result in underestimates of exposure, perhaps by wide margins, and recommended that the margins of uncertainty be presented, in addition to the estimates themselves. EPA suggested that the Army's assessment of exposure downwind of the dispersion devices did not represent the maximal ZnCdS concentrations, which would be upwind of the monitored areas (closer to the dispersion device).
ATSDR AND CDC REVIEWS
ATSDR's and CDC's reviews of the risk associated with ZnCdS dispersion tests concluded that the tests would result in negligible increases in background concentrations of cadmium and zinc in air, soil, and water. The ATSDR and CDC reviewers concurred with the conclusion of the Army that the ZnCdS tests posed negligible health threats to residents of the Corpus Christi and Minneapolis test areas.
In general, the reviewers did not deal in depth with the methodology of measurement, computation of exposures, or translation of exposures to health risks. In addition, most did not comment on the lack of attention to risks other than cancer in the Army's documents.
Some reservations were expressed regarding routes of exposure other than inhalation, possible bioaccumulation, risk to special populations, and margins of uncertainty, but the reviewers' comments generally were not detailed.