Lubin JH, Boice JD Jr, Edling C, et al.: Lung cancer in radon-exposed miners and estimation of risk from indoor exposure.

The health hazards produced by mold have been associated with sick building syndrome, but no validated studies have been able to demonstrate that normal indoor exposures to these common organisms pose a significant threat.

Studies have also found that indoor exposure to certain pollutants routinely exceed maximum Federal standards for outdoor air.

The main ways of reducing indoor exposure to radon are to make the floor a better barrier or to divert any seeping radon to the open air.

Repeated indoor exposure to the tuberculosis germ in poorly ventilated areas is the most common way to get the disease; outdoors, the sun's ultraviolet rays quickly kills the bacterium.

The malady, brought on by prolonged indoor exposure during the region's cruel five-month winter, is traditionally diagnosed when Minnesotans do peculiar things after the snow finally starts to melt.

"Evidence showing an excess risk from indoor exposure to radon remains inconclusive," he said.

From indoor exposure alone, urban children may ingest as much benzo[a]pyrene, a potent carcinogen, as they would get from smoking three cigarettes a day, according to a 1998 report in Scientific American.

"But at least the child in the developing-world city has electricity and propane as home energy, sparing constant indoor exposure to smoke," Bates continues.