Frequent Questions=20

Answers to the following questions = can be=20 found by scrolling down or by clicking on the question of interest. If = you need=20 further information, please use the cont= act=20 information provided.

What = is=20 PM_2.5?

Where = does=20 PM_2.5 come from?

Who = is most at=20 risk?

How = can I find=20 out about PM_2.5 levels in my community?

What = does=20 nonattainment mean?

What = does=20 designation mean?

What = will my=20 area need to do to improve air quality if it is designated nonattainment = for=20 PM_2.5?

What=20 information does EPA use to determine whether an area should be a = "nonattainment=20 area?"

How = can I=20 participate in the designation process?

What = is EPA=20 doing to reduce PM_2.5 levels?

What = is the=20 litigation history of the PM_2.5 standards?

Where= can I go=20 for further information?

What is PM_2.5? =

Particulate matter, or PM, is the term for particles found in the = air,=20 including dust, dirt, soot, smoke, and liquid droplets. Particles can = be=20 suspended in the air for long periods of time. Some particles are = large or=20 dark enough to be seen as soot or smoke. Others are so small that = individually=20 they can only be detected with an electron microscope.

Many manmade and natural sources emit PM directly or emit other = pollutants=20 that react in the atmosphere to form PM. These solid and liquid = particles come=20 in a wide range of sizes.

Particles less than 10 micrometers in diameter (PM₁₀) = pose a=20 health concern because they can be inhaled into and accumulate in the=20 respiratory system. Particles less than 2.5 micrometers in diameter=20 (PM_2.5) are referred to as "fine" particles and are = believed to=20 pose the greatest health risks. Because of their small size = (approximately=20 1/30th the average width of a human hair), fine particles can lodge = deeply=20 into the lungs.

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Where does PM_2.5 come = from?=20

Sources of fine particles include all types of combustion = activities=20 (motor vehicles, power plants, wood burning, etc.) and certain = industrial=20 processes. Particles with diameters between 2.5 and 10 micrometers are = referred to as "coarse." Sources of coarse particles include crushing = or=20 grinding operations, and dust from paved or unpaved roads. Other = particles may=20 be formed in the air from the chemical change of gases. They are = indirectly=20 formed when gases from burning fuels react with sunlight and water = vapor.=20 These can result from fuel combustion in motor vehicles, at power = plants, and=20 in other industrial processes.=20

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Who is most at risk?

Roughly one out of every three people in the United States is at a = higher=20 risk of experiencing PM_2.5 related health effects. One = group at=20 high risk is active children because they often spend a lot of time = playing=20 outdoors and their bodies are still developing. In addition, = oftentimes the=20 elderly population are at risk. People of all ages who are active = outdoors are=20 at increased risk because, during physical activity, PM_2.5=20 penetrates deeper into the parts of the lungs that are more vulnerable = to=20 injury.

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How can I find out about = PM_2.5 levels in=20 my community?

Air quality forecasts are often given with weather forecasts on = local=20 television and radio stations, and may be found on the weather page of = your=20 newspaper. Another way to learn about unhealthy exposures is to check = daily=20 Air Quality Index forecasts. Visit http://www.airnow.gov/ to find the = forecast=20 for an area near you.

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What does nonattainment = mean?

The Clean Air Act identifies six common air pollutants that are = found all=20 over the United States. These pollutants can injure health, harm the=20 environment and cause property damage. EPA calls these pollutants = criteria air=20 pollutants because the agency has developed health-based criteria=20 (science-based guidelines) as the basis for setting permissible levels = in the=20 air we breath. PM_2.5 is a criteria pollutant. EPA = establishes=20 national ambient air quality standards for each of the criteria = pollutants.=20 These standards apply to the concentration of a pollutant in outdoor = air. If=20 the air quality in a geographic area meets or is cleaner than the = national=20 standard, it is called an attainment area; areas that don't meet the = national=20 standard are called nonattainment areas.

In order to improve air quality in a nonattainment area, states = must draft=20 a plan known as a state implementation plan (SIP). The plan outlines = the=20 measures that the state will take in order to improve air quality. = Once a=20 nonattainment area meets the standards and additional redesignation=20 requirements in the Clean Air Act [Section 107(d)(3)(E)], EPA will = designate=20 the area to attainment as a "maintenance area."

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What does designation = mean?

States and tribes submit recommendations to the EPA as to whether = or not an=20 area is attaining the national ambient air quality standards for a = criteria=20 pollutant. The states and tribes base these recommendations on air = quality=20 data collected from monitors at locations in urban and rural settings. = After=20 working with the states and tribes and considering the information = from air=20 quality monitors, EPA will then "designate" an area as attainment or=20 nonattainment for the PM_2.5 standard. If an area is = designated as=20 nonattainment it signifies to the public that the air in the area is = unhealthy=20 to breathe.

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What will my area need to do to improve = air quality=20 if it is designated nonattainment for PM_2.5? =

States with designated nonattainment areas are required under the = Clean=20 Air Act to develop a State Implementation Plan and submit it to EPA = within=20 three years (around April 2008). (Tribes may elect to develop tribal=20 implementation plans but are not required to do so.) This plan must = include=20 enforceable measures for reducing air pollutant emissions leading to = the=20 formation of fine particles in the atmosphere. The plan must also = provide=20 steps for the area to attain the PM_2.5 standards as quickly = as=20 possible, and the area must show how it will make reasonable progress = toward=20 attaining the standards.=20

In assessing how quickly an area can attain the standards, states = should=20 consider the air quality improvements that can be achieved from a = combination=20 of national, state, and local measures. For example, states should = take into=20 account existing emission reduction programs (e.g. national emission standards for cars = and=20 trucks; and the Clean Air = Interstate=20 Rule to reduce powerpolant emissions; or local efforts such as diesel engine retrofit = programs),=20 plus any new programs or regulations that can be implemented within = the state=20 or local nonattainment area.

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What information does EPA use to = determine whether=20 an area should be a "nonattainment area?"

The Clean Air Act defines a nonattainment area as the area that is=20 violating the national ambient air quality standard OR a nearby area = that is=20 contributing to a violation of the PM_2.5 standards. The=20 PM_2.5 standards are based on averaging air quality = measurements=20 both annually and on a 24 hour basis. The annual standard for = PM_2.5=20 is met whenever the 3 year average of the annual mean PM_2.5 = concentrations for designated monitoring sites in an area is less than = or=20 equal to 15.0 =B5g/m³. The 24 hour standard for = PM_2.5 is=20 met whenever the 3 year average of the annual 98th percentile of = values at=20 designated monitoring sites in an area is less than or equal to 35=20 =B5g/m³.

In addition to air quality data, EPA guidance on the PM_2.5 designations = process=20 also discusses other important factors, including emissions of = pollutants that=20 lead to PM_2.5 formation, population, commuting patterns, = and=20 expected growth, that states should evaluate in order to determine = whether a=20 county is a likely contributor to the area=92s air quality = problem.

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How can I participate in the = designation=20 process?

You can follow the designation process for the PM_2.5 = standard in=20 your state by contacting your state environmental agency, attending = public=20 hearings related to the designations process in your area, and keeping = informed about the current status of the designations process from = this Web=20 site and state Web sites. Information such as the latest list of = counties=20 having violating monitors for PM_2.5, and technical data to = be=20 considered in designating nonattainment areas, can be found at the PM_2=
.5=20 Designations Technical Information Page

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What is EPA doing to reduce = PM_2.5=20 levels?

EPA has a number of programs already in place that will help reduce = emissions from power plants, cars, and other sources of emissions that = lead to=20 the formation of fine particles. More information on these programs = can be=20 found on the following sites:

Programs in = Place

- Efforts to = Reduce=20 PM - General overview.

- Tier II=20 standards for passenger cars and light trucks - Finalized February = 2000.

- NOx SIP = Call=20 - Regional strategy to reduce nitrogen oxides from eastern = states. =20 Primarily designed to meet the ozone NAAQS, but will provide some = benefits in=20 terms of reduced levels of nitrate fine particles.

- Diesel Engine Retrofit = Programs -=20 Voluntary programs to reduce diesel engine emissions.

- Clean Air Nonroad Diesel = Emissions=20 Rule - a comprehensive national program requiring stringent = emissions=20 controls on diesel engines used in construction, agriculture, and = mining and=20 significantly reducing the sulfur content of diesel fuel.

- Clean Air Interstate Rule - = Permanently=20 caps powerplant emission of particle forming sulfur dioxide = (SO₂)=20 and nitrogen oxides (NO_x) in the eastern US.

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What is the litigation history of the = 1997=20 PM_2.5 standards?

After EPA promulgated the PM_2.5 and 8-hour ozone = standards in=20 July 1997, several industry organizations and state governments = challenged=20 EPA's action in the U.S. Court of Appeals for the District of Columbia = Circuit=20 (the D.C. Circuit). On May 14, 1999, the three-judge panel of the D.C. = Circuit=20 held in a split decision that the Clean Air Act, as applied by EPA in = setting=20 the 1997 standards for PM and ozone, was unconstitutional as an = improper=20 delegation of legislative authority to EPA. The ruling did not = question the=20 science or decision-making process used to establish the standards. = The Court=20 remanded the PM_2.5 standards to EPA but did not vacate = them. In=20 June 1999, the Department of Justice (DOJ) and EPA petitioned the = Court for a=20 rehearing en banc with the entire D.C. Circuit Court. On October 29, = 1999, the=20 Court denied the petition for rehearing.

The DOJ and EPA then filed a petition for certiorari with the = United States=20 Supreme Court in December 1999 to appeal the decision of the D.C. = Circuit, and=20 the Supreme Court issued its decision to hear the appeal in November = 2000. The=20 Supreme Court issued its decision on the merits of the appeal on = February 27,=20 2001. In that decision, the Supreme Court held that EPA's approach to = setting=20 the National Ambient Air Quality Standards in accordance with the CAA = did not=20 constitute an unconstitutional delegation of authority. The Supreme = Court=20 unanimously affirmed the constitutionality of the CAA provision that=20 authorizes the Agency to set national air quality standards, stating = that this=20 provision "fits comfortably within the scope of discretion permitted = by our=20 precedent." The Supreme Court also affirmed that the CAA requires EPA = to set=20 standards at levels necessary to protect the public health and = welfare,=20 without considering the economic costs of implementing the standards. = The=20 Supreme Court remanded several other issues back to the D.C. Circuit,=20 including the issue of whether EPA acted arbitrarily and capriciously = in=20 establishing the specific levels of the standards.

The D.C. Circuit heard arguments in this remanded case in December = 2001,=20 and issued its decision on March 26, 2002. The D.C. Circuit found that = the=20 Agency had "engaged in reasoned decision making," rejecting the claim = that the=20 Agency had acted arbitrarily and capriciously in setting the levels of = the=20 standards. This last decision by the D.C. Circuit gave EPA a clear = path to=20 move forward with implementation of the PM_2.5 = standards.

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Where can I go for further=20 information?

If you would like further information, please visit the Cont= act=20 Us page.

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Frequent Questions=20

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