Particulate Matter Introduction

What is Particulate Matter?

• Particulate matter, or PM, is the term for particles found in the air, including dust, dirt, soot, smoke, and liquid droplets. Particles can be suspended in the air for long periods of time.  Some particles are large or dark enough to be seen as soot or smoke.  Others are so small that individually they can only be detected with an electron microscope. 
• Some particles are directly emitted into the air (primary particulate matter). They come from a variety of sources such as cars, trucks, buses, factories, construction sites, tilled fields, unpaved roads, stone crushing, and burning of wood.
• Other particles may be formed in the air from the chemical change of gases (secondary particles). They are indirectly formed when gases from burning fuels react with sunlight and water vapor.  These can result from fuel combustion in motor vehicles, at power plants, and in other industrial processes.
• According to the EPA (See EPA Particulate Matter), the size of particles is directly linked to their potential for causing health problems.  Small particles less than 10 micrometers in diameters pose the greatest problems because they can get deep into your lungs, and some may even get into your bloodstream. Exposure to such particles can affect both your lungs and your heart.
• Small particles of concern include “fine particles” (such as those found in smoke and haze), which are 2.5 micrometers in diameter or less; and “coarse particles” (such as those found in wind-blown dust), which have diameters between 2.5 and 10 micrometers.

What are the Health Effects of Particulate Matter?

• Health studies have shown a significant association between exposure to fine particles and premature death.
• Other important effects include aggravation of respiratory and cardiovascular disease (as indicated by increased hospital admissions, emergency room visits, absences from school or work, and restricted activity days), lung disease, decreased lung function, asthma attacks, and certain cardiovascular problems such as heart attacks and irregular heartbeat.
• Individuals particularly sensitive to fine particle exposure include older adults, people with heart and lung disease, and children.
• Roughly one out of every three people in the United States is at a higher risk of experiencing fine particulate related health effects. One group at high risk is active children because they often spend a lot of time playing outdoors and their bodies are still developing. People of all ages who are active outdoors are at increased risk because, during physical activity, fine particulates penetrate deeper into the parts of the lungs that are more vulnerable to injury.

What are the Particulate Standards Promulgated by the EPA?

PM₁₀ Standards

• The United States Environmental Protection Agency (EPA) first established National Ambient Air Quality Standards (NAAQS) for total suspended particulate matter (TSP) in 1971.
• The reference method specified for determining attainment of the original standards was the high-volume sampler, which collects TSP up to a nominal size of 25 to 45 micrometers (µm).
• EPA began to review the TSP standards for PM in October 1979.  After a lengthy and elaborate process, EPA promulgated significant revisions of the original standards on July 1, 1987. In these revised standards, EPA changed the indicator for particles from TSP to PM₁₀ , the latter referring to particles with a mean aerodynamic diameter less than or equal to 10µm.
• EPA also revised the level and form of the primary standard by defining the 24-hour PM₁₀ standard as 150 µg/m³ with no more than one expected exceedance per year.   Due to a lack of evidence linking health problems to long-term exposure to coarse particle pollution, EPA revoked the annual PM₁₀ standard (previously set at 50 µg/m³, expected annual arithmetic mean) in 2006.         
• Connecticut is currently measuring attainment for the 24-hour NAAQS for PM₁₀.

PM_2.5 Standards

• The EPA promulgated NAAQS for fine particulate matter, particles with a mean aerodynamic diameter less than or equal to 2.5 µm (PM_2.5), on July 18, 1997.  The annual average NAAQS for PM_2.5 was set at 15 µg/m3 and the 24-hour average NAAQS was set at 35 µg/m³ (effective December 2006).
• CT DEEP designed a monitoring network and began PM_2.5 monitoring in 1999.
• States were required to provide EPA with recommendations by February 15, 2004 for PM_2.5 area attainment and nonattainment designations based on three years of monitored data.
• For the three-year period ending in 2004, all of the PM_2.5 monitoring sites in Connecticut measured levels below the annual and 24-hour NAAQS, except for a monitoring site in New Haven. The Stiles Street site was found to be measuring very localized conditions that are not representative of population exposure in New Haven. EPA concurred with CT DEEP that this microscale site should not be used to determine compliance with the annual PM_2.5 standard.    
• EPA subsequently promulgated a annual NAAQS on December 14, 2012 based on reviews of health studies showing adverse impacts at concentration levels lower than the 1997 NAAQS. The annual average NAAQS for PM_2.5 was set at 12 µg/m³ (micrograms per cubic meter) while the 24-hour average NAAQS was still set at 35 µg/m³.
• EPA has designated the entire state as attainment/unclassifiable for PM_2.5  .This action was effective as of April 15, 2015.

Related Links:

PM 2.5 General Information

PM2.5 Planning Efforts

SIP Revisions and Other State Air Quality Plans