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PM2.5 SIP Development: Background
The Clean Air Act requires the U.S. Environmental Protection Agency (EPA) to set National Ambient Air Quality Standards (NAAQS) for air pollutants that impact human health and the environment. NAAQS are set for the following six pollutants: Carbon Monoxide, Lead, Nitrogen Dioxide, Particulate Matter 10, Particulate Matter 2.5 (PM2.5), Ozone, and Sulfur Dioxide.
The Clean Air Act requires that each pollutant undergo a five year review. In 2006, EPA tightened the PM2.5 standard from 65 µg/m3 (micrograms per cubic meter), which Utah attained, to 35 µg/m3, which resulted in seven Utah counties not attaining the standard.
Nonattainment
As result of this noncompliance, EPA designated Utah and Cache counties to be in their own "nonattainment" areas for PM2.5 and combined the counties of Box Elder, Davis, Salt Lake, Weber, and Tooele into one large nonattainment area. A nonattainment area is useful to achieving compliance with the NAAQS because it gives an area, or airshed, the opportunity to establish a baseline emissions inventory, run models that will predict success for emissions reductions strategies, and ultimately measure the improvements made in meeting the standard.
Once these nonattainment designations were formalized by the EPA in December 2009, a three year window began for the Utah Division of Air Quality (DAQ) to develop a plan to bring the counties into compliance with the standard. This plan is called a State Implementation Plan, or SIP.
PM2.5
PM2.5—approximately 1/70th the size of a human hair—can aggravate heart and lung diseases and has been associated with a variety of serious health problems, including heart attacks, chronic bronchitis, and asthma. Sources of PM2.5 include fuel combustion from automobiles, power plants, wood burning, industrial processes, and diesel-powered vehicles such as buses and trucks. In September 2006, the EPA dramatically strengthened the fine particle standards to protect public health, tightening the 24-hour standard from 65 to 35 micrograms per cubic meter.
PM2.5 is measured in micrograms per cubic meter or µg/m3. The standard of 35 µg/m3 can be described as one grain of table salt, which is approximately 35 µg/m3, in a one liter bottle filled with air. It does not take very much PM2.5 mass to exceed the standard.
PM2.5 Formation
SIP development is a complicated process anywhere, but Utah's unique geography and weather, when combined with emissions, creates an interesting dynamic when it comes to PM2.5 formation that isn't found in many other places in the world.
About 75% of all PM2.5 found on DAQ's monitoring filters is created by secondary particulate formation. Secondary particulate formation is what happens when precursor emissions, usually the gases NOx and SOx and VOC, react in the atmosphere and combine to create PM2.5.
The other 25% of PM2.5 is considered primary, because it is directly emitted as a particle, and enters the atmosphere as soot from roadways or tailpipe emissions.
As Utah works on the SIP, soot and precursor emissions reductions will factor into solutions that help Utah meet the standards.
Attainment Process
DAQ is working with a number of stakeholder workgroups to develop emissions reductions strategies. This workgroup process will take place throughout most of 2011 and into 2012.
Once DAQ has a list of strategies, they will run them through a model that incorporates chemistry, physics, and meteorology. The model is intended to get to identify the most production reduction strategies like identifying solution using a scalpel rather than a hatchet. Ultimately, solutions that are the most technically sound, feasible, cost effective, and potentially supportable in the community will be the ones included in the SIP.
For more information please visit these links:
- DAQ's Choose Clean Air Campaign
- DEQ Acronyms Page
- EPA's Basic Information on PM
- Science and Health Behind Particulate Matter
To receive information about the SIP development process, workgroup strategy meetings, and public hearings, please sign up for our county specific listservs.
