Development of a Relative Source Contribution Factor for Drinking Water Criteria: The Case of Hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX)

ABSTRACT

The consideration of multiple or cumulative sources of exposure to a chemical is important for adequately protecting human health. This assessment demonstrates one way to consider multiple or cumulative sources through the development of a relative source contribution (RSC) factor for the explosive hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), using the Exposure Decision Tree approach (subtraction method) recommended by the U.S. Environmental Protection Agency. The RSC factor is used to ensure that the concentration of a chemical allowed by a regulatory criterion or multiple criteria, when combined with other identified sources of exposure common to the population of concern, will not result in unacceptable exposures. An exposure model was used to identify relevant potential sources for receptors. Potential exposure pathways include ingestion of soil, water, contaminated local crops and fish, and dermal contact with soil and water. These pathways are applicable only to areas that are in close proximity to current or former military bases where RDX may have been released into the environment. Given the physical/chemical properties and the available environmental occurrence data on RDX, there are adequate data to support a chemical-specific RSC factor for RDX of 50% for drinking water ingestion.

Key Words:

• Relative source contribution
• hexahydro-1
• 3
• 5-trinitro-1
• 3
• 5-triazine
• RDX
• explosives
• exposure

ACKNOWLEDGMENTS

We thank James Daniel of the Army Environmental Command, Shannon Cunniff, and Paul Yaroschak of the Department of Defense, Chemical and Materiel Risk Management Directorate for their continued interest in and support of this effort. We also thank Steven S. Kueberuwa, Manager, OW Health Advisory Program, US EPA, and Dr. Michael Dourson of TERA for a critical review of the article. We also thank Ms. Melissa Kohrman-Vincent of TERA for her assistance in organizing data and preparation of the article. This work was funded by the U.S. Army Environmental Command, Aberdeen Proving Ground, MD.

The opinions expressed in this document are those of the authors and not necessarily those of the U.S. Army.

Notes

Editor's note: The NPL is the list of uncontrolled hazardous waste sites that the USEPA has determined that require remediation under the provisions of the federal Comprehensive Environmental Response, Compensation, and Liability Act (also knows as the Superfund Act).