Perchloroethylene Unit Risk Factor – Review Draft for Scientific Review Panel on Toxic Air Contaminants

The Office of Environmental Health Hazard Assessment (OEHHA) is releasing a draft document for review by the Scientific Review Panel on Toxic Air Contaminants (SRP) that summarizes the derivation of an updated inhalation cancer Unit Risk Factor (URF) for perchloroethylene (PCE or tetrachloroethylene).  URFs are used to estimate lifetime cancer risks associated with inhalation exposure to a carcinogen. 

A draft of the PCE URF document was released for a 45-day public review and comment period on February 16, 2016.  Four sets of comments were received.  Based on these comments, OEHHA revised the document and provided it to the SRP.  OEHHA made further revisions based on comments from one of the two SRP lead reviewers, Dr. Stanton A. Glantz.

The draft document released today incorporates all revisions since the release of the February 16, 2016 draft.  A document copy showing additions and deletions from the initial SRP review draft version denoted by underline/strikeout is additionally being provided.  Responses to the public comments are also being released at this time.  The document will be reviewed and discussed by the SRP at its meeting on June 24, 2016, in Sacramento, CA.

OEHHA is required to develop guidelines for conducting health risk assessments under the Air Toxics Hot Spots Program (Health and Safety Code Section 44360(b)(2)).  In implementing this requirement, OEHHA develops new URFs and revises existing URFs for many air pollutants.  The existing inhalation URF for PCE was revised using the most recent “Air Toxics Hot Spots Program Technical Support Document for Cancer Potency Factors,” finalized by OEHHA in 2009.

The proposed values for PCE are as follows:

  • Inhalation Cancer Unit Risk (URF): 6.1 x 10-6 (µg/m3)-1
  • Inhalation Cancer Slope Factor (CSF): 2.1 x 10-2 (mg/kg-day)-1

OEHHA is not seeking further comments from the public on the draft document.

Please direct any inquiries concerning technical matters or availability of the documents to:

Dr. John Budroe
Chief, Air Toxicology and Risk Assessment Section
Air, Community, and Environmental Research Branch
Office of Environmental Health Hazard Assessment
1515 Clay Street, 16th Floor
Oakland, CA, 94612

Telephone: (510) 622-3145

Information about dates and agenda for meetings of the Scientific Review Panel can be obtained from the California Air Resources Board web page at: