(UtiliPoint.com - Feb. 10, 2006)

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By Bob Bellemare President and CEO

Many articles about pollution control focus on pollutants such as ozone (smog), carbon monoxide, lead, nitrous oxides, and sulfur dioxide. All these pollutants are regulated by the U.S. Environmental Protection Agency (EPA) but there is one other pollutant of concern—particulates. Just prior to the Christmas break, the EPA announced proposed revisions to its national air quality standards for fine particle pollution and for certain coarse particles. Under the proposal, states would need to be in compliance with the new standards as soon as April 2015 for new limits on fine particles, and 2018 for coarse particles. Particulate Emission Background

Particulate pollution is a mixture of solid particles and liquid droplets found in the air. Some particulate matter (PM), such as dust, soot, or smoke, is large or dark enough to be seen with the naked eye. Others are so small that they can only be detected using a microscope.

These particles come in many different shapes, sizes, and chemical composition. Particulate matter includes both “primary” PM, which is directly emitted into the air, and “secondary” PM, which forms indirectly through atmospheric chemical reactions from fuel combustion and other sources. Soot (carbon) is an example of a primary PM that is emitted from cars, trucks, forest fires, coke ovens, coal combustion and industrial processes. Dust from unpaved roads, stone crushing, and mining are other examples of primary PM emissions,

Secondary PM forms in the atmosphere from gaseous reactions. Some of these reactions require sunlight and/or water vapor to form. Examples of secondary PM include nitrates that form from car, truck, and power plant emissions. Sulfates are another common secondary PM caused by reactions of sulfur dioxide emissions from power plants and the burning of oil. Ammonia, from sources such as fertilizer and animal feed operations, also contribute to the formation of ammonium sulfate and nitrate. .

The type and nature of PM emissions do vary substantially across the United States. In the eastern U.S. there are more sulfates than in the West. Southern California has more nitrates than other areas of the country. Carbon (soot) is a substantial component of fine PM across the United States.

Particulate matter varies greatly in size. The largest particles can be 40 micrometers (μm) in diameter or even larger, which is about half the thickness of a human hair. EPA regulations, however, focus on particles that are 10 μm (PM10) in diameter or smaller because these particle sizes are most likely to penetrate into the lower respiratory tract when inhaled. “Fine particles” are classified as PM2.5, because they have total particle size less than 2.5 micrometers. Major sources of PM2.5 include sulfate and nitrate compounds, dust and ash.

Particulate Matter (PM) sizes (source: EPA)

The EPA reports that scientific studies show links between PM and numerous adverse health effects. Long-term PM exposure is associated with decreased lung function and chronic bronchitis. Short-term PM exposure can cause heartbeat irregularities, aggravated asthma, and heart attacks. Another adverse impact of PM is it is a major source of haze and causes soiling and erosion damage to structures.

PM Regulations

The EPA first established regulations for “total suspended particulate” (TSP) in 1971. The standards were revised in 1987 when TSP was replaced by regulations for particulate matter under 10 micrometers (PM10) in size. In 1997 the EPA put in place standards for PM2.5 because these finer particles are more closely associated with serious health effects. These standards include limits on both 24 hour and annual emissions.

The recently proposed revisions call for doing away with PM10 standards and replacing them with standards that fall into two categories: "fine particles" (PM2.5), and "inhalable coarse particles" (PM10-2.5), which are smaller than 10 micrometers in diameter but larger than PM2.5. Using air monitoring data from 2005-2007, states would be required to designate attainment (compliant) and nonattainment (noncompliant) areas. The EPA will make a final determination of attainment and nonattainment designations by December 2009, which would then become effective in April 2010. States would then have three years to develop “State Implementation Plans” (SIPs) for how nonattainment areas will come into compliance with the PM 2.5 standards by April 2015.

For course particle (PM10-2.5) standards, the EPA will only designate attainment and nonattainment areas until it has three consecutive years of monitoring data. The proposed timeline anticipates SIPs will be filed before July 2016 and states would need to comply with the new standards by July 2018.

Under the proposal, the 24-hour fine particle (PM2.5) standard will be lowered from the current level of 65 micrograms per cubic meter (µg/m3) to 35 µg/m3, although the EPA is currently soliciting public comment on setting the standard even lower—somewhere between the range of 30 and 35 µg/m3. The annual standard of15 µg/m3 is expected to remain unchanged, although the EPA is seeking comments on changing that standard to as low as 12 µg/m3.

The current standards for coarse particles (PM10) were set in 1987 and limit these emissions to 24-hour standard of 150 µg/m3, and an annual standard of 50 µg/m3. The proposed revisions would modify this definition to cover only particles between 10 and 2.5 micrometers in diameter (PM10-2.5), from certain sources such as high-density traffic on paved roads, industrial sources and construction surfaces. Generally these sources are found in urban areas. The proposed definition would not include coarse particles from agriculture or mining sources.

The new PM10-2.5 standard would be a 24-hour standard set at 70 µg/m3. There would no longer be an annual standard because in the EPA's view scientific studies indicate there is not a significant public health risk associated with long-term exposure to coarse particles.

The EPA is now taking comment on the proposed changes and will issue final standards by September 27, 2006.

Impact of PM Regulations

U.S. direct emissions of PM10 have decreased approximately 25 percent since 1988 when about 3.4 million tons of PM10 was emitted. About 40 percent of this amount comes from fuel combustion, another 40 percent from industrial processes, and 20 percent from transportation. Paving dirt roads, adding pollution control on coal power plants, and better soil management in agricultural business have helped to lower these emissions.

PM Historical Reductions (source EPA)

The EPA estimates that PM2.5 emissions are about 30 percent lower than they were 25 years ago in 39 major cities where they monitor these emissions. A key factor in this reduction has been the lowering of sulfur dioxide emissions from coal power plants as these plants have implemented scrubbing equipment in response to EPA's Acid Rain program.

Much of the existing and proposed emission standards for other pollutants will also have a beneficial reduction in particulate emissions, so the overall impact of the new restrictions will likely be isolated to only certain areas in the United States. EPA modeling indicates the main areas of potential impact under the new standards would be central and southern California and some areas in the Midwest and Appalachian regions.

In all likelihood the measures power plants are taking to come into compliance with other emission regulations will help keep most areas in compliance with the new standards and therefore little, if any, additional investments will be needed. Power plants in certain regions such as California and the Appalachia may, however, find themselves in a nonattainment area and could see an impact from the proposed standards. There will be plenty of time to study and plan for the new regulations since their real impact will not be felt until well in to the next decade.

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