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What is particulate matter?
Particulate matter (PM) is a complex mixture of solid and liquid particles that are suspended in air. These particles typically consist of a mixture of inorganic and organic chemicals, including carbon, sulfates, nitrates, metals, acids, and semi-volatile compounds.
The size of PM in air ranges from approximately 0.005 to 100 micrometers (µm) in diameter – the size of just a few atoms to about the thickness of a human hair. Researchers have defined size categories for these particles differently. For the purposes of this fact sheet, PM is defined by three general categories commonly used by the U.S. Environmental Protection Agency (U.S. EPA): coarse (10 to 2.5 µm), fine (2.5 µm or smaller), and ultrafine (0.1 µm or smaller).
Research suggests that particle size is an important factor that influences how particles deposit in the respiratory tract and affect human health. Coarse particles are deposited almost exclusively in the nose and throat; whereas, fine and ultrafine particles generally are able to penetrate to deep areas of the lung. Fine and ultrafine particles are present in greater numbers and have greater surface area than larger particles of the same mass, and they are generally considered to be more toxic.
How can particulate matter affect my health?
Over the past fifteen years an increasing number of studies have reported associations between the levels of PM in the air and adverse respiratory and cardiovascular effects in people (e.g. increases in daily mortality, illness, hospital admissions and emergency room visits). Scientists have observed these associations even at relatively low ambient levels that are prevalent in the U.S. and Western Europe. Research is currently underway to better understand the nature of the relationship between PM and disease – especially how PM affects human health.
The health effects of PM are likely to depend on several factors, including the size and composition of the particles, the level and duration of exposure, and age and sensitivity of the exposed person. Symptoms of exposure may include a sore throat, persistent cough, burning eyes, wheezing, shortness of breath, tightness of chest, and chest pain. PM may also trigger asthma or may lead to premature death, particularly in the elderly who have preexisting cardiovascular and respiratory diseases.