Abstract
In compliance with Homeland Security Presidential Directive No.8, the US EPA National Homeland Security Research Center, in collaboration with the Department of Energy, is developing health-based Provisional Advisory Levels (PALs) for priority toxic industrial chemicals, pesticides, and chemical warfare agents in air and drinking water. The PALs Program will provide exposure levels to assist emergency response decision-making, and to serve as criteria for determining re-use and re-entry into affected areas resulting from transport/storage accidents, natural disasters, and subversive activities. PALs are applicable at federal, state, and local levels, and are intended for use in homeland security efforts, public health, law enforcement, and emergency response, as well as decisions by water utilities, and national and regional EPA offices. PALS have not been promulgated nor have they been formally issued as regulatory guidance. They are intended to be used at the discretion of risk managers in emergency situations when site specific risk assessments are not available. Three levels (PAL 1, PAL 2, and PAL 3), distinguished by severity of toxic effects, are developed for 24-hour, 30-day, 90-day, and 2-year durations of potential drinking water and inhalation exposures for the general public. Draft PALs are evaluated both by an EPA working group, and an external multidisciplinary panel to ensure scientific credibility and wide acceptance. In this issue, we present background information on the PAL program, the methodology used in deriving PALs, and the technical support documents for the derivation of PALs for acrylonitrile, phosgene, hydrogen chloride, and hydrogen sulfide.
