Acute health reference values: overview, perspective, and current forecast of needs.

A number of organizations have developed acute inhalation health reference values, each with (1) a specific purpose, (2) populations to protect, (3) exposure scenarios (accidental releases, workplace, routine excursions of ambient levels), and (4) severity of adverse health effects considered in their development. The first section of this article reviews the existing values from different organizations and describes their purposes and method of development. The second part of the article provides a comparative review of how the values were derived, the critical endpoints considered for each value, the populations being protected by each value, and the potential for use outside of their intended purpose (e.g., Homeland Security, regulatory analysis, etc.). Additionally, an analysis of the acute inhalation reference values that was developed in support of the Office of Air and Radiation's residual risk assessment for hazardous air pollutants is presented and reviewed. The third and final part of the article focuses on the efforts of the U.S. Environmental Protection Agency (EPA) to develop a set of less-than-lifetime reference values, along with a discussion of how that effort fits with the existing sets of values described in the prior sections.