Air Quality - Current Issues
Revised National Ambient Air Quality Standards for Particulate Matter
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, on September 21, 2006. The standards are scheduled to be implemented in December 2006. This page provides an overview of the revised particulate standards and what they mean for Missoula County.
The revised 2006 standards address two categories of particle pollution: PM2.5 (also called "fine particulate"), which includes particulate matter that is 2.5 micrometers in diameter and smaller; and PM10 which is smaller than 10 micrometers. (The average diameter of a human hair is 60-80 micrometers.) The 2006 standards tighten the 24-hour fine particle standard from 65 micrograms per cubic meter (ug/m3) to 35 ug/m3, and retain the current annual fine particle standard at 15 ug/m3. EPA also retained the existing 24-hour PM10 standard of 150 ug/m3 and revoked the annual PM10 standard.
EPA's scientific advisory committee recommended setting the 24-hour fine particulate standard in the range of 30-35 ug/m3 and the annual standard in the range of 13-14 ug/m3. EPA finalized the 24-hour standard at 35 ug/m3, which is at the upper end (least protective of public health) of the committee's recommended range, and EPA finalized the annual standard at 15 ug/m3, which is outside the range recommended by the committee - also in the direction of less protection for public health. In comments submitted to EPA, the Missoula City-County Health Department recommended lowering the annual standard to 13 or 14 ug/m3 and lowering the daily PM2.5 standard to 32 ug/m3.
Missoula's air quality has improved dramatically over the years. However, recent monitoring data shows that there were a handful of days each winter when particulate concentrations in the Missoula area exceeded 35 ug/m3 (see Table 1). Because current research indicates that particulate is unhealthy at levels lower than previously thought, it is important to analyze data from these "high' days more closely and evaluate how to reduce pollution under the conditions that lead to higher levels of pollution. Since Missoula is a rapidly growing community, it is important to address these issues as soon as possible.
*indicates data collected on days affected by wildfire smoke, which probably would not be used to determine compliance with standards
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 dine 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. About half of the fine particle pollution in the Missoula area comes from the transportation sector.
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.
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
Missoula City-County Health Department, in cooperation with the Montana Department of Environmental Quality, has been monitoring concentrations of particulate matter in the Missoula area since the 1970s (more about Missoula’s air quality history). Preliminary analyses of monitoring data shown in Table 1 below indicate that if the standard were applied to the period 2003-2005, Missoula would have violated the PM2.5 daily standard, and would have been designated as a ”nonattainment area” for this pollutant. Recommendations from the states to the EPA will be based on air monitoring data from 2004-2006, so we will know more about Missoula's attainment status after the end of 2006.
|Milestone||1997 PM2.5 Primary NAAQS||2006 PM2.5 Primary NAAQS|
|Promulgation of Standard||July 1997||Sep. 2006|
|State Recommendations to EPA||Feb. 2004
(based on 2001-2003 monitoring data)
(based on 2004-2006 monitoring data)
|Final Designations Signature||Dec. 2004||Dec. 2009|
|Effective Date of Designations||April 2005||April 2010|
|SIPs Due||April 2008||April 2013|
|Attainment Due||April 2010
(Based on 2007-2009 monitoring data)
(Based on 2012-2014 monitoring data)
|Attainment Date with Extension||Up to April 2015||April 2020|
If Missoula is designated as a nonattainment area, we will be required to take action to address fine particulate. The Health Department has already taken steps in this direction, which we have begun to do. After we obtain the results from this winter's study of the sources of fine particulate, the department will begin evaluating possible control strategies. 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.
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, the Air Pollution Control Board designated fine particulate as one of the highest priorities for the air program. In November 2006, the Department began a study of the sources of fine particulate in our area, which will continue through the winter of 2006-2007.
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. Keep in mind that, at this point, these are just projections based on 2003-2005 data. EPA will use 2004-2006 data to make final determinations retarding attainment.
The Missoula area is currently a nonattainment area for PM10 due to past violations of the standards. Since Missoula is currently meeting the standards, the Health Department has been preparing the documents necessary for EPA to redesignate the Missoula area from a “nonattainment area” to a “maintenance area” for PM10. Recent research of health effects has highlighted the need to analyze the sources of and take steps to minimize PM2.5 pollution in our area. The department, in consultation with the Air Pollution Control Board and other stakeholder groups, is in the process of evaluating how to best use the department’s resources to protect and enhance public health.
- 4-12-06 issue review by DEQ
- 5-2-06 presentation to Air Quality Advisory Council
- 5-11-06 memo to Air Pollution Control Board
- 5-18-06 presentation to Air Pollution Control Board
- 6-9-06 Comments to EPA
- 2005 PM2.5 data
- 1995-96 PM2.5 sources pie chart
- 6-22-06 memo to Air Pollution Control Board
- July 2006 recommendation regarding PM activities
- November 2006 PowerPoint presentation
Clean Air Scientific Advisory Committee:
- Clean Air Scientific Advisory Committee Recommendations Concerning the Proposed National Ambient Air Quality Standards for Particulate Matter
Environmental protection Agency:
State and Territorial Air Pollution Program Administrators (STAPPA) and Association of Air Pollution Control Officials (ALAPCO):
- Comments on PM NAAQS Proposal and Monitoring Regulations - Attachment (April 17, 2006)
- Comments on PM NAAQS Proposal and Monitoring Regulations - Cover Letter (April 17, 2006)
- Testimony on EPA’s Rule Revisions on the PM NAAQS/Monitoring Package (March 8, 2006)
- Comments on PM2.5 Implementation Rule Proposal – Attachment (January 31, 2006)
- Comments on PM2.5 Implementation Rule Proposal – Letter (January 31, 2006)
- Testimony on PM2.5 Implementation Rule Proposal (November 30, 2005)