State officials say air quality monitors in five Iowa counties picked up “unhealthy levels” of air pollution over the weekend and again on Tuesday. Brian Button is an air quality specialist for the Iowa Department of Natural Resources. Button says there have been elevated levels of “fine particulate matter” in the air. The particles are about the size of a human red blood cell, according to Button. He says the particles are the product of “combustion processes.” Button says they don’t know the source of the pollution yet. He says one of the things they’ll be doing is to do an intensive scientific study to determine where the emissions came from. The “microscopic particular matter” was detected in the following counties: Clinton, Linn, Palo Alto, Scott and Van Buren. Button says the pollution may have caused problems for folks with respiratory problems if they spent a great deal of time outdoors this weekend.