According to the Environmental Protection Agency (EPA), Particulate Matter (PM) is a "mixture of extremely small particles and liquid droplets."

Air quality professionals pay attention to particulate matter because these very small particles can cause health problems when inhaled. Specifically, particles less than 10 micrometers in diameter can pass the nose and throat and enter the lungs. A micrometer is one millionth of a meter.

Size is important to understand because the EPA classifies particulate matter as two types based on size. Alaska has problems with both types of particulate matter.

• Coarse Particulate Matter (PM₁₀) is less than 10 micrometers in diameter. It primarily comes from road dust, agriculture dust, river beds, construction sites, mining operations, and similar activities. Most people in Alaska experience PM₁₀ as dust.

• Fine Particulate Matter (PM_2.5) is less than 2.5 micrometers in diameter. PM_2.5 is a product of combustion, primarily caused by burning fuels. Examples of PM_2.5 sources include power plants, vehicles, wood burning stoves, and wildland fires.

Air pollution standards are given as a mass of material in a volume of air: micrograms per cubic meter (µg/m³). A microgram is one millionth of a gram. A paper clip weighs about a gram. Imagine chopping the paper clip into a million equally sized pieces. One of those pieces would weigh about a microgram. A cubic meter (approximately 39" X 39" X 39") describes a volume of air that is about the size of a washing machine. If you place one of the million pieces of the paper clip in the space occupied by the washing machine, you would have 1 µg/m³.

New Particulate Matter Regulations

The EPA recently updated the national standards for Particulate Matter. For PM₁₀, the EPA retained the current 24 hour PM₁₀ standard of 150 µg/m³ and eliminated the annual PM₁₀ standard. The EPA increased the stringency of the PM_2.5 standard by lowering the previous 24 hour standard of 65 µg/m³ to 35 µg/m³. EPA left the annual PM2.5 standard of 15 µg/m³ in place.

Read the state's comments on EPA's proposed particulate matter rules:

• Transmittal letter to EPA (PDF)
• Comments to EPA (PDF)

Implications for Alaska

Dust has long been a problem for rural Alaska. As populations grow and mechanized travel becomes more prevalent, the amount of dust seems to be increasing. Over the past six years, several Alaskan villages initiated PM₁₀ monitoring programs. Since EPA retained the 24 hour PM₁₀ standard, Alaskans have a standard to compare against the monitoring results. It appears a number of villages are in violation of the PM₁₀ standard.

Historically, Eagle River and Juneau have violated Clean Air Act air quality requirements for Particulate Matter (PM₁₀). Neither area continues to violate the PM₁₀ standard. The Department, together with EPA and the City and Borough of Juneau, are currently in the process of changing Juneau's PM₁₀ planning status from "nonattainment" to "maintenance". The draft maintenance documents are available for review:

• Juneau's Mendenhall Valley Proposed PM₁₀ Limited Maintenance Plan, Public Review Draft, DEC08 (PDF 396K)
• Amendments to State Air Quality Control Plan, Vol. III: appendices to Vol. II, Section III.D.3 (PDF 4.88M)
• Draft Mendenhall Valley Emission Inventory and Appendices, JAN06 (PDF 733K). This document is contained within the above amendments document.

PM_2.5 also is a problem. Until EPA revised the standard, Alaska had been in compliance with the PM_2.5 standard. PM_2.5 monitoring shows the Fairbanks North Star Borough (FNSB) exceeding the more stringent revised PM_2.5 standard; the FNSB will be in "nonattainment." A "Nonattainment Area" is any area that does not meet (or that contributes to ambient air quality in a nearby area that does not meet) the national primary or secondary ambient air quality standard for the pollutant - particulate matter in this instance.

Controlling Particulate Matter

Violations of air quality standards mean the state government and impacted communities must work together to formulate a plan to reduce particulate emissions.

PM₁₀ - The state may recommend EPA designate areas violating the PM₁₀ standard as "nonattainment." If EPA agrees, a process of planning and rule making begins for transportation related problems; these areas gain access to federal highway funds dedicated to air quality improvement. A second option might be for state and impacted communities to sign a "Memorandum of Agreement" with EPA for a pollution reduction plan. A Memorandum Of Agreement (MOA) avoids the stigma of being in "nonattainment" and provides some flexibility and timeliness in formulating a pollutant reduction plan, but does not allow special access to the air quality transportation funds.

PM_2.5 - With the new PM_2.5 standard, the EPA expects and is looking for states to designate communities in violation of the standard as Nonattainment Areas. The EPA state designated the Fairbanks North Star Borough as a Nonattainment Area for PM_2.5 in 2009.

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