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• What are the PM Eftecte • oncern7 • • The characteristics, sources, end potential health effects of larger or "coazse" fraction particles -• (from 2.5 to 10 micrometers in diameter) and smaller or "fine" particles (smaller than 2.5 micrometers in diameter) are very different. • Coarse particles come from sources such as windblown dust from the desert or ngricuhural 5elds and dust kicked up on unpaved roads by vehicle traffic. • I~ine particles are generally emitted from activities such as industrial end residential combustion and front vehicle exhaust. Fine particles aze also formed in the atmosphere wlicn gases such as sulfur dioxide, nitrogen oxides, and volatile organic compounds, emitted by combustion activities, aze trarufontted by chemical reactions in the air. - Coarse particles can accumulate in the respiratory system and aggravate health problems such as asthma. EPA's scientific review concluded that fine particles, which penetrate deeply into the lungs, are more likely than coarse particles to contribute to the health effects (e.g., premature mortality and hospital admissions) found in a number of recently published community epidemiological studies at concentrations that extend well below those allowed by the current PMto standards. • These recent community studies find that adverse public health effects are associated with exposure to particles at levels well below the previous PM standards for both short-term (liom less than 1 day to up to 5 days) and long-term (from generally a year to several years) periods. • These heahh effects include premature death and increased hospital admissions and ~ emergency room visits (pritrtarily the elderly and individuals with cardiopulmonary disease); increased respiratory symptoms and disease (children and individuals with cazdiopulmonary disease such as asthma); decreased lung function (particularly in children and individuals with esthtna); and alterations in lung tissue and sttvetttre and in EPA's Revised Particulate Matter Standards Page 4 of 6 respvatory tract defense rrtecharristns. • EPA believes that the new standards will protect and improve the Gves of millions of Americans. • EPA's final rules, in addition to regional haze rules, address the so-called "welfare" effects from particles for which the previous PMtp secondary standards did not provide adequate protection. Chief among those is visibility impairment. Fine particulate matter adversely impacts visibility because i[ scatters and absorbs light.