Tuesday Air Quality Unhealthy Across Much of Iowa

February 2, 2005

For more information, contact Brian Button with the Department of Natural Resources at 515-281-7832.

DES MOINES-Air quality across large areas of Iowa was unhealthy for sensitive groups on Tuesday due to microscopic sized particulate matter, and similar conditions are expected to persist through Wednesday for central and eastern counties, the DNR reported today.

Western counties from a line extending west from Atlantic, Denison and Estherville are receiving a new air flow today.

As a precaution, persons in the affected counties with heart or lung disease including asthmatics, children and older adults should cut back or reschedule strenuous activities such as exercise until conditions improve, say state officials. A clean air mass is expected Thursday.

On Tuesday, the Air Quality Index measured 119 in Linn County, 113 in Polk County, 108 in Clinton County, 107 in Scott County and 104 in Palo Alto County. Surrounding areas experienced similar levels. All other areas of the state are experiencing elevated, but moderate pollution levels. Widespread areas of the Upper Midwest, Great Lakes and Ohio Valley are experiencing similar conditions.

The Air Quality Index (AQI) reports pollution levels using a color-coded and numerical range for pollutants. The higher the AQI, the poorer the air quality. An AQI of 1 to 50 is green or good, 51 to 100 is yellow or moderate, 101 to 150 is orange or unhealthy for sensitive groups, 151 to 200 is red, unhealthy for everyone. Rarely monitored are purple for very unhealthy (201 to 300) and maroon for hazardous (301 to 500.)

“There is relatively little difference between surface and air temperatures up to about 8,000 feet and this is limiting air mixing,” said the DNR’s Brian Button. “This can elevate pollution levels across multiple states as emissions are not diluted. A new air mass is expected to move into the region Wednesday night, and air quality conditions should improve by Thursday,” he said.

Particulate matter is a generic term to describe microscopic sized soots and aerosols. Because small particles can penetrate the deepest parts of the lungs, increasing the likelihood of symptoms in sensitive individuals, including children, the elderly and those with heart and lung disease.

Particles are directly released as smoke when coal, gasoline, diesel fuels and wood are burned. Particles also form from chemical reactions of nitrogen oxides, sulfur oxides, organic compounds and ammonia.

Hazy skies are often associated with higher particulate levels, which scatter light in the atmosphere. Particulate pollution can form year-round, unlike summertime ozone smog, which requires hot, sunny conditions.

Iowa’s air quality still meets federal health standards, but an increase in the number or severity of days with unhealthy air could pose clean up efforts. Iowa typically has several days of unhealthy air annually.