After a relatively smog-free summer, Bay Area residents may be surprised this winter by a increase in the number of Spare the Air Tonight advisories. Advisories are issued when the Bay Area Air Quality Management District (Air District) predicts levels of air pollution that will exceed air quality standards. Last summer's Spare the Air program, from June 3 to October 18, predicted 7 days when high ozone levels were expected. In actuality, the national 1-hour ozone standard of 12 parts per hundred million (pphm) was exceeded on 2 days. On 16 days, the more stringent state 1-hour standard of 9 pphm was exceeded, and on 7 days, the new national 8-hour standard of 8 pphm was exceeded.
This winter the new National Ambient Air Quality Standard for fine particulate matter (PM) 2.5 microns or smaller in diameter (PM2.5) will be added to the program, which previously included forecasts only for carbon monoxide and particulate matter 10 microns or smaller in diameter (PM10). Because it is more stringent, the PM2.5 standard is expected to be exceeded more regularly than the PM10 standard was in the past.
More than a third of PM is the result of woodburning in fireplaces and stoves, about a third is from motor vehicles, and the rest is dust from roads, construction activities and agriculture, and other dust and combustion sources. Build-ups of particulates occur on cold nights with no breezes, when an inversion layer traps air pollutants at ground level and prevents their dispersal.
The Spare the Air Tonight program will begin on December 2 and continue through January 31. Advisories will be posted at 10 a.m. if a high level of PM2.5 is expected that night, signalling that woodburning fireplaces and stoves should not be used and motor vehicle use should be curtailed.
Particulate matter consists of particles of solids and liquids, small enough to be suspended in the air. The smaller the particles, the more deeply they can be inhaled into the lungs. Larger particles don't penetrate deeply into the lungs and will be coughed out, while the fine particles will penetrate so deeply that they cannot be dislodged, and will remain there. Besides being irritants, the particles may be composed of toxic materials or carry toxic substances with them, further increasing the harm they can do.
Health effects of PM can be acute—shortness of breath, coughing, or wheezing—and can contribute to infections such as bronchitis, or exacerbate chronic respiratory and cardiac conditions. Over a period of time, exposure to high levels of PM may actually cause such conditions as emphysema and cardiac and respiratory diseases to develop. Children, the elderly, and people with lung and heart disease are especially susceptible to injury. When there are high PM levels in the air, the number of hospital admissions and emergency room visits by people with cardiac and respiratory diseases increases, and the death rate from these diseases rises.
Besides PM, woodsmoke contains other air pollutants or pollutant precursors—nitrogen oxides, sulfur oxides, carbon monoxide, volatile organic compounds, polycyclic aromatic hydrocarbons, and other air toxics. Woodburning stoves and fireplaces contaminate not only outdoor air but indoor air as well with their emissions.
In addition to the Spare the Air Tonight program, the Air District has developed a model woodburning ordinance for cities and counties to abate the PM and other air pollutants from woodsmoke. The ordinance, affecting new construction and some remodels, prohibits the installation of any woodstove except a pellet stove or an EPA-certified stove. The sale, but not the installation, of woodstoves that are not EPA-certified is illegal. Fireplaces must be gas-fired or have EPA-certified inserts. Traditional woodburning masonry fireplaces or factory-built fireplaces are not allowed, and the conversion of a gas fireplace to woodburning is not permitted. These provisions can be enforced through the local building permit process.
An optional provision would make the observance of Spare the Air Tonight alerts mandatory rather than voluntary. Another optional provision would prohibit burning of certain unsuitable fuels, such as garbage and plastics.
To date, 21 cities and 4 counties have adopted woodburning ordinances. They are:
The Air District will provide technical assistance to cities and counties to help them adapt the model ordinance to fit the needs of their communities.
In order to mitigate its emissions of PM10 from October to March each year, the Los Esteros Critical Energy Facility in northern Santa Clara County will fund two programs to be administered by the Air District. They are a woodstove and fireplace replacement/retrofit program and a lower-emitting school bus program. The power plant will contribute $510,500 to the programs.
The stove and fireplace program will be voluntary, on a first-come, first-served basis. Residents within a 3-mile radius of the facility will be able to replace an operational non-EPA-certified stove or fireplace with a natural gas stove or fireplace insert and, in return, will receive an incentive payment of $500 from the Air District.
The school bus program will replace older, high-emitting buses with cleaner or alternative fuel buses. The program will pay at least 75 percent of the cost of a bus, and the school district 25 percent or up to $25,000. Priority will be given to the three school districts closest to the facility, and to replacing older diesel buses.
The relationship between the PM emissions from the stacks of the facility and the emission reductions from the two programs is not pound-for-pound. Instead, the amount of PM from the stacks that would have to be offset was estimated from the height of the stacks, the velocity of the emissions as they leave the stacks, and the amount of mixing and dilution that could be expected before the PM reaches ground level. The woodstove and fireplace program and the school bus program were then calculated to offset this amount of PM, based on woodburning patterns in north Santa Clara County and the state Air Resources Board guidelines for emissions from school buses.
Adelia Sabiston
For more information about the model ordinance, contact the Air District public information officeat (415) 749-4900.
For information about the Woodstove and Fireplace Replacement/Retrofit Program, contact Ralph Borrmann at rborrmann@baaqmd.gov or (415) 749-4791.
For information about the Lower-Emitting School Bus Program, contact Michael Murphy at mmurphy@baaqmd.gov or (415) 749-4644.