Air Quality: EPA's Integrated Science Assessments (ISAs)
(PDF, 2228 pp, 1,105 MB,
Particulate matter (PM) is a complex mixture of extremely small particles and liquid droplets in the air. Particulate matter causes concern because it is associated with serious health effects such as aggravated asthma, difficulty breathing, chronic bronchitis, decreased lung function, and premature death. PM contributes to haze and can harm the environment by changing the natural nutrient and chemical balance of the soil.
EPA scientists are conducting research to better understand which attributes of particulate matter cause ill health effects, who may be most susceptible to these effects, how particles form in the atmosphere, and what the contributions are from various sources in different regions of the country.
The Clean Air Act requires EPA to periodically review the science for six major air pollutants, including PM. EPA's National Center for Environmental Assessment develops Integrated Science Assessments (ISAs) that summarize the science related to the health and ecological effects caused by these pollutants. ISAs provide a comprehensive review of the policy-relevant scientific literature published since the last National Ambient Air Quality (NAAQS) review and are a critical part of the scientific basis for establishing the NAAQS. EPA released the Integrated Science Assessment for Particulate Matter in Dec 2009. [See the history of PM for more detailed information]
[Update] In December 2012, EPA released a provisional assessment of recent studies on particulate matter collected since the release of the 2009 ISA on PM.