DES MOINES– Several Iowa monitoring sites recorded exceedances of the National Ambient Air Quality Standard for fine particulate matter last month, including two measurements that were more than twice the national standard.
Smoke from wildfires in the western U.S. and Canada were evident across much of Iowa towards the end of July. While many news outlets reported on smoke, official data from regulatory monitors is only available after laboratory analysis.
Smoke levels were heaviest in northwest Iowa, where DNR monitors measured exceedances at three monitors on July 30, with another exceedance measured in Des Moines on Aug. 1. These exceedances were primarily due to wildfire smoke.
Emmetsburg, Sioux City and Council Bluffs sites recorded 24-hour fine particle levels of 76.5, 79.4 and 42.2 micrograms per cubic meter (µg/m3) respectively. The Des Moines site recorded a fine particulate concentration of 37.3 µg/m3 on Aug. 1. The national standard is 35 µg/m3 for a 24-hour average.
When 24-hour fine particulate averages are above the standard, air quality is considered unhealthy for sensitive groups. Averages greater than 55 µg/m3 are considered unhealthy, meaning more people may experience health effects. Asthmatics, those with respiratory difficulties or heart disease, the elderly, children and pregnant women are most likely to suffer adverse health effects from inhaling small particles. DNR encourages these groups to limit outdoor activity when air quality pollutants exceed the standard.
To determine particulate levels, Iowa’s regulatory monitors collect air samples on filters over a 24-hour period. The State Hygienic Laboratory then processes the filters to determine final concentrations. Iowa’s fine particulate matter levels exceeded the national standard twice in February this year.
Find current fire and smoke plumes on the U.S. Environmental Protection Agency’s National Fire and Smoke map. Check EPA’s AirNow for current and predicted air quality in your area.