U.S. EPA Revises National Air Quality Standards

September 25, 2006

DES MOINES - On September 21, the U.S. Environmental Protection Agency announced revisions to its National Ambient Air Quality Standards. These standards address fine and coarse particulate pollution, also known as particulate matter (PM). Currently, 141 counties across the nation fail to meet the new standards.

Based on the most recent three years of data (2003-2005), Muscatine and Clinton would not meet EPA’s revised 24 hour fine particulate standard, and several other eastern Iowa counties are close to violating the new standard. EPA predicts that new nationwide emissions reduction requirements for power plants will result in attainment with new standards throughout Iowa when it becomes applicable in 2015.

“Until emissions controls are put in place, Iowans are likely to see an increase in the number of unhealthy air days associated with the new lower fine particulate standards,” said Sean Fitzsimmons, senior environmental specialist with the Iowa DNR. “Analysis of Iowa’s fine particulate air monitoring data from the past seven years shows an average of three days each year where monitored levels exceeded the old health threshold, versus seven days a year when the new threshold is applied.”

Particulate matter is a generic term used to describe microscopic sized soots and aerosols. Because small particles can penetrate the deepest parts of the lungs, exposure increases the likelihood of symptoms in sensitive individuals, including children, the elderly and those with heart and lung disease. Particulate matter can be emitted directly, such as in smoke from a fire or emissions from a boiler or gasoline or diesel engine, or it can form from chemical reactions of gases such as sulfur dioxide, nitrogen dioxide and some organic gases in the atmosphere.

The new standards address two categories of particulate pollution: fine particles and inhalable coarse particles. Fine particles are less than 2.5 micrometers in diameter and are referred to as PM2.5, while particles of less than 10 micrometers are referred to as PM10.

EPA strengthened its previous daily fine particle standards - by nearly 50 percent - from 65 micrograms of particles per cubic meter to 35 micrograms of particles per cubic meter of air. The 24-hour or daily standard is met when the 3-year average of a site's annual 98th percentile values is 35 micrograms per cubic meter or less. EPA is retaining its existing daily PM10 standard of 150 micrograms per cubic meter and revoking its existing 50 microgram per cubic meter annual standard.

Iowans can keep track of current fine particle levels by logging on to EPA’s Airnow Web site at www.airnow.gov.