Risk Management Actions Related to the OEHHA Guidelines

This page last reviewed August 15, 2014

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ARB and the Air Districts are working closely together to develop a comprehensive multi year plan for incorporating the OEHHA Risk Assessment Guidance Manual into State and local air toxics programs.  This page will have periodic updates on ARB’s actions.  Click here to sign up for the ARB listserve for Risk Management Actions Related to the OEHHA Guidelines.   


The Office of Environmental Health Hazard Assessment (OEHHA) is in the process of updating the draft OEHHA Guidance Manual (Guidance Manual) designed to improve the way the State estimates potential lifetime health risks from toxic air contaminants.  The public comment period for this document ends on August 18, 2014.  The Guidance Manual makes adjustments based on new science regarding exposures for people of all ages and provides methods for quantifying increased childhood sensitivity to air toxics.  Over the past 10 years, scientific advances have shown that early-life exposures to air toxics contribute to an increased lifetime risk of developing cancer and other adverse health effects, compared to exposures that occur in adulthood.

Why is OEHHA updating their Risk Assessment Guidelines?

The Guidance Manual is part of California’s ongoing effort to address health risks from toxics in the air.  A 1999 state law, SB 25 by Sen. Martha Escutia, requires that the special susceptibility of infants and children be considered in assessing the health risks associated with air toxics.  The U.S. Environmental Protection Agency also takes into account the increased susceptibility of infants and children to toxic chemicals in their programs.  

The Guidance Manual summarizes three technical support documents focused on non cancer health factors, cancer potency factors and age sensitivity, and exposure assessment, respectively.  The Guidance Manual weaves together the information from all three documents and provides a method for using the information to estimate health risks from air pollution sources as called for under the Air Toxics Hot Spots Information and Assessment Act.  The three technical documents underwent public and peer review and were finalized in 2008, 2009, and 2012.

The methodologies contained in the Guidance Manual seek to develop more representative estimates of the potential risk from exposure to the emissions of air toxics.  Although, control measures using the best available control technology have reduced, or in some cases eliminated, exposures and potential health impacts over the past 25 years, the new risk methodologies will result in higher estimated risks for many situations than would have been calculated by the existing risk methodology.  In some cases, the new estimated inhalation cancer risk would be only slightly higher than the current estimate; while in other cases, the new estimated inhalation cancer risk could be up to three times higher.

In addition, data from ARB’s statewide air toxics monitoring network shows there has been a reduction in cancer risk of approximately 80 percent since 1990.  Emission reductions from technological controls and other measures required by state and local regulations occurred even while the population and number of vehicles in California both rose by approximately 8 million and the economy increased by 70 percent.

What are the next steps once the OEHHA Guidance Manual is finalized?

ARB and the Air Districts are working closely together to develop a comprehensive multi-year plan for incorporating the Guidance Manual into State and local air toxics programs.  This general plan was discussed on July 24, 2014 at the ARB Board meeting.  The Board presentation is available here

Please consult this webpage in the future, or join the listserve, for any updated information related to ARB’s plan for incorporating the new science into ARB’s Air Toxics Program.  For information on air district activities, please contact the individual Air Pollution Control or Air Quality Management District of interest.