The Bay Area Air Quality Management District (BAAQMD) is proposing changes to its Air Toxics New Source Review Program (NSR). The changes will make the BAAQMD program consistent with the latest state health risk assessment guidelines, adopted in 2003 by the California Environmental Protection Agency's Office of Environmental Health Hazard Assessment (OEHHA) after a multi-year reassessment of the science on which the evaluation of public health risks is based. This and other proposed changes to the NSR process will lower the levels of toxic air contaminants which trigger action to protect public health and the environment. Impacts of the proposed rule changes will be felt primarily at gas stations and facilities with diesel generators, where emissions are already close to the current permissible levels. However, the district feels that the more stringent requirements being proposed can be easily met with existing control technologies.
The district's Air Toxics NSR Program was established in 1987. The program requires that facilities undergo a permit review before undertaking major construction projects; the goal is to prevent increases in public health risk from projects that create new or modified sources of toxic emissions. The Air Toxics NSR Program also requires companies to update their emissions controls when modifying or replacing more polluting emissions sources. The implementation of this program along with other state and local programs has halved the average cancer risk from toxic air contaminants in the Bay Area in the sixteen years of the program's existence.
Under the Air Toxics NSR Program, assessment of risks from new and modified sources of toxic air contaminants has been accomplished using an approach known as a Health Risk Assessment (HRA). The methodology for HRAs is developed at the state level for air pollution control programs across California; it has been updated several times over the years. The current BAAQMD rule changes are being proposed to adopt the latest updates based on new developments in the underlying risk assessment science. Toxicity values and exposure assessment procedures within HRAs will be updated to conform to the statewide guidelines adopted by OEHHA in October 2003. In addition, the Air Toxics NSR health risk assessments, which currently evaluate health risks only from long-term or chronic exposure to toxic air contaminants, will now include an assessment of short- term or acute exposures.
The changes in exposure assessments include changes in assumptions about how much of a contaminant an average worker or member of the public is likely to breathe if they are located near a facility that emits air contaminants. (Cal OSHA is responsible for regulating the exposure of workers actually on the site of the emissions source.) In other words, current technology is better at estimating actual exposures, and as a result, adjustments can now be made in the levels of contaminants that need to be controlled.
Now that the risk levels will be racheted down, emissions sources that are close to current control levels will have to find ways to limit their emissions even further. These facilities include gas stations and any facility that has a stationary diesel engine, such as those used to power a back-up generator. Gas stations should be able to meet the new requirements by using existing preventative maintenance checklists to minimize emissions from fueling equipment. In a few cases, some facilities may have to limit the amount of gasoline pumped on any given day. The statewide phase-in of Enhanced Vapor Recovery systems, a program already in progress, will also help to reduce emissions from the pumping of gasoline.
Stationary diesel engines are another emissions source that may need to be adjusted to meet the new emissions levels. Diesel engines accounted for over sixty percent of the HRAs performed under Air Toxics NSR in 2002. Newly manufactured engines generally meet the new emissions levels without any problems. In most cases, existing engines can meet new requirements with add-on controls such as particulate filters, which provide eighty-five to ninety percent reductions in emissions, or diesel reduction catalysts, which cost much less but provide only a thirty percent emissions reduction.
While most of the changes in the proposed rules will have a broad-based impact, one change directly affects a specific industry sector, drycleaning. The proposed rule will remove a historical exemption for drycleaners from existing health risk limits for the used of perchloroethylene as a cleaning solvent. The exemption was put in place when perchloroethylene, a carcinogen, was the only economically viable option for the industry. In the last fifteen years, many less toxic cleaning options have been developed (see June-July 2003 issue). Seventy-five percent of new machines currently being purchased are non-perchloroethylene machines; the rule change is therefore expected to have a minimal economic impact on the drycleaning sector.
In other proposed changes, the current threshold for requiring the application of Best Available Control Technology for Toxics (TBACT) for carcinogens will be lowered to be consistent with guidelines from the California Air Resources Board issued for all thirty-five air quality management districts in California. In addition, there will be a lower risk trigger for non-carcinogenic compounds. BAAQMD has done an extensive analysis of the source categories of these compounds, and concluded that this would not add a great regulatory burden on industry, since most of these sources are organic compounds that are either carcinogens with non-carcinogenic impacts in addition to their primary impact, or already trigger risk mitigation measures under the criteria pollutant rule.
The district held five public workshops from May 30 to June 12, 2003 to present the proposed rules to the public and receive comments. BAAQMD is currently preparing documentation required under the California Environmental Quality Act (CEQA) and the proposed rule changes are likely to be adopted in the first half of 2004. Implementation of the proposed rule changes is dependent on a final piece of the OEHHA project, the release of software known as the Hot Spots Analysis and Reporting Program (HARP).
Ann Blake
For more information: http://www.baaqmd.gov; Brian Bateman, Engineering Division Director, (415) 749-4653, bbateman@baaqmd.gov.