Waiting to Inhale: Reducing Fine Particulate Matter

Concerned over adverse health effects of fine particulate matter (PM), the 2003 California legislature enacted SB 656 requiring the state Air Resources Board (CARB), together with local air pollution control and air quality management districts, to prepare a list of readily available, feasible, and cost-effective measures to reduce PM emissions.

Particulate matter consists of liquids and solid particles suspended in the ambient air. The particles vary widely in composition and come from many sources. PM includes soot from combustion sources such as motor vehicles, industrial facilities, power plants, wood burning, and cooking; dust from construction operations, agriculture, unpaved roads and trails, and stone crushing; and secondary PM resulting from the reaction in the atmosphere of precursor pollutants such as oxides of nitrogen, sulfur oxides, volatile organic compounds, and ammonia. The particles may be toxic, or they may have toxic substances adhering to them.

Particles larger than 10 microns generally don't penetrate far when inhaled and may be expelled by coughing or sneezing. Fine PM, smaller than 10 microns (PM₁₀), may be inhaled deep into the lungs where it may not be expelled and can remain. Acute symptoms caused by PM include breathing problems in people with respiratory disease, coughing, and wheezing. Long-term exposure to PM can cause chronic respiratory diseases such as asthma, or cancer when the PM is from a toxic air contaminant. During periods of high PM levels in the air, increased numbers of emergency room visits, hospital admissions, and premature deaths in people with respiratory and cardiac conditions have been recorded.

In the Bay Area, the principal sources of PM_2.5 (PM 2.5 microns or less in diameter) have been found to be on- and off-road motor vehicles, wood burning and cooking, and secondary PM sources related to fuel combustion processes. The Community Air Risk Evaluation Program was begun last year to identify communities with high risks from air toxics, including gathering data on exposure to diesel exhaust.

Both CARB and the U.S. Environmental Protection Agency (EPA) have set health-based standards for PM; the state standards are more stringent than the federal. Both have set standards for both annual and 24-hour levels of PM₁₀, and both have annual standards for PM_2.5 . As yet, only the EPA has set a 24-hour standard for PM_2.5. The Bay Area has attained the federal standards, but not the state standards. (See table below.)

Each local air quality agency that had not met state PM standards was required to review the the list of 103 rules, regulations, and programs identified under SB 656 and to identify those that applied to the sources of PM creating problems within its jurisdiction. The measures were screened for those which met certain criteria, including cost effectiveness. The agency could prioritize them for implementation, noting those that have already been adopted.

In preparing its SB 656 Implementation Schedule, the Bay Area Air Quality Management District (Air District) determined that 62 of CARB's 103 measures to reduce PM had already been adopted, or the Air District had equivalent measures, and 15 either had no sources in the Bay Area, or would yield no significant reductions. Eight are included as control measures and ten as further study measures in the proposed 2005 Ozone Strategy. Ten wood burning measures have been identified for further study and evaluation.

Four measures are being proposed for the Implementation Schedule—amendments to two wood burning measures, a new rule to control emissions from stationary and portable internal combustion engines, and a new rule on commercial broiling operations. One of the wood burning measures is to lower the threshold of expected PM concentrations for issuing alerts in the winter-time "Spare the Air Tonight" program, which urges voluntary curtailment of driving and wood burning on cold nights with little air movement, when wood smoke and auto emissions are likely to linger at ground level. The other wood burning measure adds more outreach and resources to educate the public and to amend the existing model wood burning ordinance.

The Air District collaborates with local communities in programs offering rebates for turning in gas lawn mowers and buying electric ones, and programs such as the Santa Clara Woodstove Rebate Program to replace old, polluting stoves with EPA-certified devices.

The Air District also administers a variety of incentive programs that reduce motor vehicle emissions. The Carl Moyer Program provides funds for retrofitting or repowering diesel engines to make them cleaner than regulatory requirements. These grants are available for on- and off-road vehicles, locomotives, marine vessels, agricultural pumps, forklifts, airport ground support equipment, and auxiliary power units.

The Air District offers incentives to fleet owners to purchase cleaner vehicles through such programs as the Transportation Fund for Clean Air, the Low Emission School Bus Program, and the Refuse Truck Incentive program. The Vehicle Buy-back Program offers financial incentives to get older, inherently more polluting vehicles off the road.

As part of the SB 656 requirements, CARB must report to the California Legislature by January 1, 2009, on the actions taken to reduce PM emissions through adoption of the 103 measures on air district Implementation Schedules statewide, and make recommendations for further measures.

For more information: http://www.baaqmd.gov/pln/pm/sb656_staff_report.pdf

Standards are for particulate matter in ambient air, expressed in micrograms per cubic meter. Most recent change in status was 11/23/2004.