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Spring Thaw Causes Elevated Levels of Wintertime Haze
Posted: 03/07/2014

Elevated fine particle (PM 2.5) pollution levels were observed at Viking Lake State Park on Thursday. Levels rose overnight across much of Iowa, but should fall later today as a cold front moves eastward through the state and winds increase.


The DNR recommends that Iowans with respiratory or heart disease, the elderly, and children limit prolonged outdoor exertion until the cold front passes through later today.


The EPA’s 24-hour health threshold for PM 2.5 is 35 micrograms per cubic meter. Levels of 37.1 were recorded yesterday at Viking Lake. 


The daily average, as of 10 a.m. today, was 43.2 at Waterloo, 40.4 at Clinton, 39.5 at Emmetsburg, 39.2 at Davenport, 36.9 at Lake Sugema, 37 at Cedar Rapids, 35 at Iowa City, 34.1 at Muscatine and 25.2 at Des Moines.

Nitrate is a primary component of winter time haze in Iowa. Nitrate formation is enhanced during prolonged periods of high humidity and near freezing temperatures that sometimes occur during a spring thaw. Fine particles are also emitted by vehicle traffic and other combustion sources and by chemical reactions in the atmosphere.  Stagnant air masses do not allow the fine particles to disperse, and pollutant levels rise.


EPA’s national air quality map is available online at

For more information contact John Gering, DNR, 515-725-9530 or