The Office of Environmental Health Hazard Assessment (OEHHA) released the Air Toxics Hot Spots Draft Guidance Manual in June 2014 and has been updated to incorporate new health studies. The draft Guidance Manual, part of California’s ongoing effort to address health risks from toxics, is open for public comments through August 4, 2014. The draft OEHHA risk assessment guidelines may trigger more stringent emission limits and rules for various areas, including the South Coast basin. Ways of calculating potential life time health risks have been updated in the draft Guidance Manual.

Based on the new scientific studies regarding early-life exposure to air toxics, OEHHA has made adjustments to estimating health risk. The draft Guidance Manual summarizes three Technical Support Documents focused on non-cancer risk, cancer risk, and exposure assessment. The Guidance Manual consolidates the information presented in these documents and provides methods for estimating health risks from subject facilities under the Air Toxics Hot Spots Information and Assessment Act.

A higher risk prioritization for many facilities may be expected. According to SCAQMD, the updated guidelines will create significant policy implications. SCAQMD indicated that OEHHA guidelines will cause cancer risks from emissions at many facilities to rise by a factor of three or more. Facilities may also be required to conduct health risk assessments as a result of the proposed guidance. SCAQMD is currently in the process of evaluating which district rules will be impacted by OEHHA's guidelines. Once OEHHA approves the changes to the guidelines, California Air Resources Board will develop a software program for the hot spots program to incorporate the changes to help estimate risks. The software is expected to be available for use in early 2015.