In compliance with the Air Toxics Hot Spots Information and Assessment Act, AB 2588, as amended, the Office of Environmental Health Hazard Assessment (OEHHA) finalized and adopted its Air Toxics Hot Spots Program Guidance Manual for Preparation of Health Risk Assessments, in March 2015. Also, to provide the software program for evaluating health risks according to the new manual, the California Air Resources Board (ARB) has released its Hot Spots Analysis and Reporting Program, Version 2 (HARP 2).  

The updated guidance manual and software tool are important for planning healthy communities, addressing air pollutant exposure risks of projects, and conducting environmental impact analysis under the California Environmental Quality Act (CEQA).

The 2015 manual has been prepared by OEHHA, in collaboration with ARB, for use in conducting health risk assessments under the Air Toxics Hot Spots Program. It supersedes and replaces the 2003 manual.  The manual has been updated based on three support studies regarding the scientific basis for determining risks, including for non-cancer risk assessment, cancer potency factors, and methods for exposure assessment. These studies underwent public and peer review during the last few years. The 2015 manual, three technical support studies, and HARP 2 software package provide the information necessary to conduct effective and reliable health risk assessments for toxic air contaminants.  

Key differences from the previous guidance include the use of age-sensitivity factors for estimating cancer risk, changes to the duration of exposure for residents and workers, breathing rates, fraction of time residents spend at home, and the incorporation of uncertainty factors into Reference Exposure Levels. As a result, the new assessment methods can demonstrate a substantially higher health risk for residential uses and other sensitive receptors near emission sources than the previous guidance would have indicated. The AERMOD air pollutant dispersion model is now embedded as a module of the HARP 2 software package. This is important because the U.S. Environmental Protection Agency has approved AERMOD as the replacement for the prior model, called ISC3, which was used in the earlier version of HARP.

If you have questions about how to apply the updated manual and HARP 2 to a Community Risk Reduction Plan, project planning effort, or CEQA document, please contact Ascent Principal Honey Walters, Senior Air Quality Specialists Austin Kerr or Poonam Boparai, or Senior Sustainability Planner Erik de Kok.