Air quality of the great indoors

Submitted by Ned Rozell
Phone: 907-474-5823
11/15/07

The National Safety Council once reported that Americans spend 90 percent of their lives inside buildings. The council didn’t say how Alaskans affected that number, but it’s a good bet most of us spend a lot more time indoors in winter. With this inner migration comes the peril of breathing mold spores, overshot hair spray, gases wafting from new carpet, the feces of dust mites, and other indoor pollutants.

Maggie Isbell once did a study of indoor air pollution in Alaska, specifically two compounds in gasoline that often find their way into Alaska homes from engines stored near or inside the house. Isbell earned a degree with her work from the University of Alaska Fairbanks Department of Chemistry and Biochemistry. She spent a one winter and summer sampling air in Fairbanks homes and checking it for levels of benzene and toluene. Found in higher levels in Alaska gasoline than gasoline sold in the lower 48, benzene has been linked to cancer. Found in carpet glues and paints, toluene is toxic to the nervous system in high doses.

Isbell sampled the air from homes that had attached garages. She installed little air pumps in living rooms and other areas in which people spent much of their time. The pumps pulled air through a tube filled with absorbent material. Isbell later analyzed the air for concentrations of benzene and toluene, which probably entered the house through the garage.

She figured that the chemicals escape from cars and smaller engines, such as those in lawn mowers, chain saws, snowmachines, weedwhackers, and motorcycles. Many of these engines allow gas to evaporate through gas caps or vapor seals. When she began the study, Isbell thought levels of benzene and toluene would be much lower in summer, when people left windows and doors open. She found the opposite. Levels of both compounds were higher in summer, though nowhere near toxic concentrations. Why was the indoor air worse in summer?

Isbell thought there may have been several reasons. Wintertime temperatures encourage the mixing of air due to the difference between cold outside air and the warm air indoors. Just opening a door in wintertime allows an impressive air exchange. Air tends to sit in place in summer, when there’s little temperature difference between outdoors and indoors. Warmer temperatures in summer also tend to evaporate more gasoline, liberating benzene and toluene into the air. The heat from just-used lawnmowers and other small engines stored in the garage has the same effect.

Isbell said the levels of benzene and toluene she measured were low, but small doses of any toxin over a long period of time are dangerous. She recommends that people store gasoline-powered engines outside in a shed, not in their homes or attached garages.

"If you have to start up the engine in winter, just drag it into the garage for one night to warm it," she said.

This column is provided as a public service by the Geophysical Institute, University of Alaska Fairbanks, in cooperation with the UAF research community. Ned Rozell is a science writer at the institute. To view past columns or to subscribe, visit www.gi.alaska.edu/ScienceForum/index.html.