Smoke from wildfires originating in Canada blanketed Des Moines on May 7, reducing visibility and raising concerns about pollution in much of the state.

A thick blanket of smoke from wildfires that originated in Canada hovers over Des Moines on May 7, and causes the EPA to issue an “Unhealthy for Sensitive Groups” alert.

The Environmental Protection Agency issued an “Unhealthy for Sensitive Groups” alert in six locations to notify “asthmatics, individuals with heart or lung disease, as well as the elderly and children” that they may experience adverse health effects because of poor air quality.

Outdoor air quality is measured by levels of particulate matter (PM). The EPA 24-hour health threshold for PM is 35 micrograms per cubic meter. Daily average PM concentrations on May 7 in Waterloo, Cedar Rapids, Viking Lake, Lake Sugema, Des Moines, and Emmetsburg were 37.2, 37.6, 40.0, 47.4, 50.7, and 61.0 microgram per cubic meter, respectively.

The data used for air quality measures is supplied to the EPA by the Hygienic Laboratory on behalf of the Iowa Department of Natural Resources.

“The Ambient Air Quality staff members routinely are on call for weekend duty, and monitor the status of the network,” said Amanda Hughes, supervisor of Ambient Air Quality. “They alert the IDNR (via email) if any exceedances are observed in 1-hour, 12-hour and 24-hour intervals.”