Air Quality - PM2.5 Information
Missoula County Particulate Matter (PM2.5) Information
Updated 6-3-2009
The Clean Air Act requires the Environmental Protection Agency (EPA) to adopt National Ambient Air Quality Standards (“standards”) that are protective of public health and provide an adequate margin of safety. Because recent studies indicate that particulate matter (PM) in ambient air has health effects at lower concentrations than previously thought, in December of 2006 the US EPA promulgated new standards for particulate matter 2.5 microns or smaller (PM2.5). This new standard lowered the permissible 24 hour level of PM2.5 from 65 micrograms per cubic meter (µg/m3) to 35 µg/m3.
Based on monitoring results from 2004-2006, Missoula was non-attainment for the 24-hour PM2.5 standard. Because we exceeded the 24-hour standard based on the 2004-2006 data, Montana was required by the EPA to propose a non-attainment area for PM2.5.
The US EPA uses 9 criteria, or factors, to determine the appropriate size of a non-attainment area. States must submit an analysis of these 9 factors, along with a proposed non-attainment boundary, for any areas that are not meeting the federal standard. Because the Missoula Air Pollution Control Board has been designated as the lead planning agency for Missoula County air quality, the Missoula Health Department prepared an analysis of the 9 factors and the Board adopted a proposed boundary which was forwarded to the Montana Department of Environmental Quality (DEQ) on November 15, 2007. DEQ reviewed the proposal to ensure it met federal requirements, and submitted Missoula’s proposal to the Governor, along with a proposed separate non-attainment boundary for Ravalli County. By law, the Governor had to submit proposed non-attainment boundaries with supporting documentation to the US EPA by December of 2007. The US EPA was then required to make non-attainment area designations by December of 2008.
Based on monitoring results from 2005-2007, which were barely below the 24-hour standard, the US EPA did not designate Missoula as non-attainment for the 24-hour PM2.5 standard.
Download a copy of the Missoula County 9 Factor Analysis here.
Download a PDF map of the proposed non-attainment area boundary
Download a Google Earth map of the proposed non-attainment area boundary
Where does our fine particle pollution come from?
Fine particles can be emitted directly (like smoke from a fire) or they can form from chemical reactions of gases such as sulfur dioxide, nitrogen dioxide and some organic gases. Fine particle pollution comes primarily from combustion sources such as woodstoves, outdoor burning, vehicle engines and industrial processes. Road dust and other types of dust contribute also to fine particulate in the air. However, in the winter months - when Missoula has the highest levels of pollution - dust is not as much of an issue because the ground is often wet or frozen. According to the results of a recent Chemical Mass Balance study conducted in Missoula, over half of the wintertime PM2.5 emissions come from residential wood burning.
What are the health effects of particulate matter?
Numerous studies link particle levels to increased hospital admissions and emergency room visits, as well as deaths from heart or lung diseases. Long-term exposures have been associated with problems such as reduced lung function, the development of chronic bronchitis, and premature death. Short-term exposures to particles (hours or days) can aggravate lung disease, causing asthma attacks and acute bronchitis, and may also increase susceptibility to respiratory infections. In people with heart disease, short-term exposures have been linked to heart attacks and arrhythmias. Healthy children and adults have not been reported to suffer serious effects from short-term exposures, although they may experience temporary minor irritation when particle levels are elevated.
What effect will attainment of the standards have on public health?
According to EPA the benefits of meeting the revised 24-hour PM2.5 standards include an estimated reduction in:
- 1,200 to 13,000 premature deaths in people with heart or lung disease
- 2,600 cases of chronic bronchitis
- 5,000 nonfatal heart attacks
- 1,630 hospital admissions for cardiovascular or respiratory symptoms
- 1,200 emergency room visits for asthma
- 7,300 cases of acute bronchitis
- 97,000 cases of upper and lower respiratory symptoms
- 51,000 cases of aggravated asthma
- 350,000 days when people miss work or school
- 2 million days when people must restrict their activities because of particle pollution-related symptoms
What happens if Missoula becomes a non-attainment area for fine particulate?
If Missoula is designated as a non-attainment area in the future, we will be required to take action to address fine particulate matter. In an attempt to maintain our PM2.5 attainment status and keep decisions more locally based, the Health Department has already taken steps to address the sources of fine particulate matter, PM2.5. Other agencies and the public will have many opportunities to participate in the process of making any changes to the Air Pollution Control Program as a result of the new standards.
What is the Health Department doing to address fine particulate pollution?
Because current research indicates that Missoula's levels of fine particulate are sometimes in the unhealthy range, the Department has already taken steps to address this type of pollution. In September of 2006, the Air Pollution Control Board designated fine particulate as one of the highest priorities for the air program. During the winter of 2006-2007, the Department conducted a study of the sources of fine particulate in our area. The results of this study indicated that over half of the PM2.5 emissions in the wintertime are from residential wood burning. In 2009, the Department proposed regulations that would allow only clean burning wood burning devices to be installed in Missoula County.
Download a full copy of the report here.
Download a pie chart showing sources of Missoula's winter PM2.5
Will other communities be designated as non-attainment areas?
According to EPA's analysis of 2003-2005 data, 143 counties in the U.S. exceeded the new fine particulate standards. 56 of these counties exceeded both the annual and 24-hour standards, 70 (including Missoula) exceeded only the 24-hour standard, and 17 exceeded only the annual standard. According to DEQ's analysis of 2003-2005 data, the following Montana communities are demonstrating noncompliance with the 24-hour standard: Missoula, Libby, Hamilton and Butte. Helena, Whitefish and Kalispell have the potential for noncompliance with this standard, and Libby is also likely to violate the annual standard for fine particulate.
Based on 2004-2007 data, Missoula, Hamilton and Butte have been designated as in attainment for the 24-hour standard. Because of mountain valley topography and frequent winter inversions, many communities in Western Montana are at risk of exceeding the national PM2.5 24-hour standard.
