Overview of the Standing Operating Procedure (SOP) for the development of Provisional Advisory Levels (PALs)

Abstract

Provisional Advisory Levels (PALs) are concentrations in air and drinking water for priority toxic chemicals. This article summarizes the Standing Operating Procedure (SOP) currently in place for the data-driven development of chemical-specific PALs. To provide consistency and transparency, and to avoid faults of arbitrariness, the SOP was developed for guidance in deriving PAL values. 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. The SOP for PAL development focuses on (1) data acquisition and analysis, (2) identification of a chemical-specific critical effect, (3) selection of a quantitative point-of-departure (POD), (4) uncertainty analysis and adjustments, (5) exposure duration adjustment and extrapolation, (6) identification of special concerns and issues, and (7) verification, documentation, and dissemination of PALs. To avoid uncompromising rigidity in deriving PAL values and to allow for incorporation of new or refined methodologies, the overall procedure is fluid and subject to modification. The purpose of this publication is to provide a summary of this SOP.

Keywords::

• PAL
• Risk Assessment
• SOP
• inhalation
• drinking water

Acknowledgements

The authors are grateful for the scientific rigor provided by the members of the Expert Consultation Panel in development of the PAL process. Individuals from several different US EPA offices have also contributed to the review process. The authors are grateful for the assistance of Debra Stewart in preparation of this manuscript.

Declaration of interest: This work was prepared under two Interagency Agreements (IAGs): IAG No. 1824-S870-T1 with the U.S. Department of Energy and IAG No. DW-89-92241401 with the U.S. Environmental Protection Agency. The Oak Ridge National Laboratory is managed and operated by UT-Battelle, LLC for the U.S. Department of Energy under contract DE-AC05-00OR22725. The views expressed in this paper are those of the authors and do not necessarily reflect the views or policies of the US Environmental Protection Agency.