ASDWA Provides Insights on EPA’s Draft IRIS Toxicological Review of Inorganic Arsenic

ASDWA submitted comments to EPA on December 14 in response to the Agency’s Draft IRIS Toxicological Review of Inorganic Arsenic. EPA released the draft for public comment ahead of the Agency’s Science Advisory Board (SAB) review. The Integrated Risk Information System (IRIS) program within EPA’s Office of Research and Development develops “impartial toxicity information independent of its use by EPA’s program and regional offices to set national standards and clean up hazardous sites.” Among other actions, IRIS assessments are used by EPA to inform the maximum contaminant levels (MCLs) within drinking water regulations. The reference doses (the maximum acceptable oral dose of a toxic substance, below which no adverse non-cancerous health effects should result from a lifetime of exposure) and cancer slope factors within the draft review are significantly stricter than those used to inform the existing arsenic MCL of 10 parts per billion.

ASDWA’s comments outline the possible implications of these findings and emphasize support for EPA to use the best available peer-reviewed science when making regulatory decisions. The association notes that the Agency is currently working on completing the Fourth Six-Year Review, a periodic requirement to review all existing NPDWRs, including arsenic, and revise them, if needed, every six years. Therefore, the final IRIS toxicological review may have an immediate impact on the Agency’s decision-making process for the existing arsenic MCL. ASDWA emphasizes that because of this, the review of the document by the SAB must be thorough and based on the best available peer-reviewed science. The association’s letter supports the SAB’s review of the draft IRIS toxicological review as “a critical step in assisting the Agency in its review of the current arsenic NPDWR and to help the Agency balance the potential health benefits with the anticipated costs of compliance.”