Ensuring Clean Water for California

California Association of Sanitation Agencies

USEPA Cancer Slope Factor for Inorganic Arsenic

On February 19, 2010 US EPA proposed a revised cancer slope factor (CSF) for inorganic arsenic, which represents a 17-fold increase in carcinogenity. The CSF is used in the Integrated Risk Information System (IRIS), which is used in risk assessments conducted by EPA and its contractors. The proposed CSF change will greatly impact all aspects of wastewater and water treatment facilities if approved as is.  Moreover, in CASA’s view, EPA has mis-interpreted and mis-represented the science and the data to arrive at much more conservative values than are warranted.  CASA submitted comments on the proposal on April 20, 2010 and would like to sincerely thank Dr. Rosalind Schoof of Environ in Seattle and Dr. Rufus Chaney of USDA in Beltsville, MD for their invaluable counsel and input on these comments. CASA met with EPA during its DC Conference in March 2011 and were informed that the proposal was undergoing revisions and would then be subject to internal peer review. It is not anticipated that there will be another round of external review and public comment but stay tuned for further developments.

Comment Letter Regarding Proposed IRIS Inorganic Arsenic Cancer Slope Factor Background document regarding land application limits for arsenic
Biosolids regulations cancer slope inorganic arsenic


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