BOARD MEETING DATE: April 2, 2004
AGENDA NO. 22
Notification of Recent State-Approved Health Risk Assessment Procedures
SYNOPSIS:
Rule 1402 requires a report to the Board when new or revised risk assessment guidelines are published by the state. This report will highlight key changes in several recently revised documents.
COMMITTEE:
Stationary Source, March 26, 2004, Reviewed
RECOMMENDED ACTION:
Receive and file.
Barry R. Wallerstein, D.Env.
Executive Officer
Background
Rule 1402 – Control of Toxic Air Contaminants from Existing Sources, sets limits for cancer and non-cancer risks for existing stationary sources and implements the risk reduction requirements of AB2588. The rule requires that staff report to the Board when the state Office of Environmental Health Hazard Assessment (OEHHA) revises or publishes risk assessment guidelines. Specifically, the report should describe if there are any material changes to the guidelines that affect the criteria in Rule 1402 and recommend rule amendments, if needed, to make Rule 1402 consistent with the guidelines. The key changes to the OEHHA guidelines and a related document from CARB regarding implementation are summarized in this board letter.
The changes to the risk guidelines do not change the criteria in Rule 1402, so no changes are recommended to the rule at this time. Changes will be needed to update the AQMD guidance materials to be consistent with the state guidelines. Staff will proceed to implement the revised guidelines over the next several months, as staff is trained and the AQMD’s implementation guidance documents are updated. The implementation of these guidelines would change certain risk assessments under Rule 1401, Rule 1402, and the AB2588 program.
There are several factors involved in assessing risk, including the chemical used, amount of emissions released, potency (risk values), the distance to the nearest receptor, and whether the receptor is a residence or a business. Calculations of risk include assumptions on breathing rates, length of exposure, and other parameters. Calculations can be done with several ‘tiers’, which vary from screening equations using generic default values, to very site-specific modeling. The revised state guidelines include changes to breathing rates for workers and adjustments to the length of exposure for occupational exposures, as well as some additional calculation methods.
Revised OEHHA Guidelines
There have been several recent developments in risk assessment guidance documents. In August 2003, OEHHA published revised "Air Toxics Hot Spots Program Guidance Manual for Preparation of Health Risk Assessments." This was followed by a CARB Recommended Interim Risk Management Policy For Inhalation-Based Residential Cancer Risk in October 2003. CARB published the Hotspots Analysis and Reporting Program (HARP) on their website on December 31, 2003, which is the software program that will enable implementation of the new guidelines. These three documents are the subject of the analysis required for Rule 1402.
In addition, OEHHA published a separate Guidance for School Site Risk Assessment in February 2004. A brief summary of the school guidance document is also provided for information. This document is not intended for use in the AB2588 Hot Spots Program. Staff will evaluate the use of this document in other regulatory programs and will develop an integrated recommendation for using this document later this year when the Cumulative Impact Reduction Strategies, for potential more stringent standards for facilities near schools, are developed for Rules 1401 and 1402.
Air Toxics Hot Spots Program Guidance Manual for Preparation of Health Risk Assessments
This document, which was published by OEHHA in August, 2003, incorporates by reference four technical support documents that were previously released, and replaces the 1992/1993 risk assessment guidance documents. There are updates to risk values, breathing rates, and tiered approach for performing health risk assessments. The updated risk values have been adopted by the Board through numerous Rule 1401 amendments. The guidelines are suitable for use for risk assessment, permitting under Rule 1401, and public notification and risk reduction under AB2588. The HARP software was developed to assist with the implementation. Other models are acceptable if they are shown to be consistent with the OEHHA Guidelines.
For cancer risk assessment, an analysis of a 70-year exposure is required. Consistent with previous guidelines, a 70-year assessment is appropriate to use for AB2588 public notice, risk assessment, and risk reduction plans. This can be supplemented using different exposures, but the 70-year exposure is the recommended basis for risk management decisions. For residential exposures, 9- and 30-year estimates can also be done to supplement the 70-year evaluation for public notification purposes, not risk management decisions. Nine years is the minimum time recommended for estimating cancer risks, even for children. The guidelines include exposure adjustment factors for occupational exposure estimates for workers and teachers, which also vary by their work schedule.
The guidelines include traditional methods for estimating risk using point estimates and new methods for estimating risk: stochastic (use of distributions) and derived risk (average of maximum and minimum calculated risk).
One key difference from the current guidelines is the use of revised breathing rates and exposure duration for estimating worker exposure. The revised breathing rate for workers will increase the estimated risk by 50 percent. However, a shorter exposure duration (40 years, rather than 46 years) will decrease risk estimates by about 13 percent, resulting in a net increase of 30% in cancer risk. These revisions will be added to the District guidance manuals and will not require changes to Rule 1402.
CARB Recommended Interim Risk Management Policy For Inhalation-Based Residential Cancer Risk
CARB published interim guidelines in October 2003 regarding how to use the revised guidelines for estimating risks for residential exposures. CARB recommends using the 80th percentile breathing rates (midpoint between the 50th percentile and the 95th percentile of the population distribution of the breathing rates) for most cases where default assumptions are used. This is consistent with the breathing rate in the existing guidelines. In most cases where site specific data is used, CARB recommends using the 95th percentile (high end) breathing rate.
HARP
HARP was developed by CARB, OEHHA, and a software engineering company. This computer software package can be used for developing an emission inventory database, facility prioritization calculations, air dispersion modeling, and risk assessment. It is CARB’s intention that HARP be used by air management districts, industry operators, and other parties to manage and evaluate emissions inventory data and their associated potential health impacts. This will promote statewide consistency.
CARB will be providing training on HARP starting in April 2004. AQMD staff can then start using HARP and implementing the new guidelines for AB2588 and Rule 1402 implementation.
School Site Risk Assessment Guidance
Information on this document is provided for informational purposes. Analysis of this document is not required for Rule 1402, and use of this document is not recommended for use in the AB2588 Hot Spots program.
OEHHA published risk assessment guidelines specific to school sites in February, 2004. This document provides procedures for estimating chemical exposures and health risks for children at existing and potential school sites.
The document addresses routes of exposure for children, which are more inclusive than typical risk assessments for air pollution alone, includes some child-specific health values, and identifies uncertainties and actions needed to address them. The approach includes tiers for estimation, and mathematical and site models to address populations of different ages at a school site, as well as different exposure routes. Risks per year can be calculated. Future efforts include development of age-specific toxicity values.
Public Process
OEHHA reports that they conducted extensive public outreach for the development of the revised guidance documents. These documents, and other related risk assessment documents can be viewed on CARB’s website at http://www.arb.ca.gov/toxics/harp/downloads.htm#2C. AQMD staff will update the AQMD guidance documents and perform outreach to regulated facilities to inform them of the revised procedures.
Recommendation
Staff recommends that this report be received and filed. Staff will obtain the necessary software and training, revise AQMD’s guidance documents for permitting and AB2588, and conduct outreach to potentially impacted facilities. A report to the Stationary Source Committee will be made two months prior to the application of the new AQMD risk assessment guidelines.
Staff will also address the use of the School Site Risk Assessment Guidance later this year and develop an integrated recommendation when Rule 1401 and 1402 are evaluated under the Cumulative Impacts Reduction Strategy.
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