Many studies of the harmful effects of secondary smoke on non-smokers have either understated or overstated those effects, depending on which elements in smoke were chosen for scrutiny, says a Brigham Young University scientist.

"Although environmental tobacco smoke, or secondary smoke, has been determined to be biologically harmful, especially to very young children, we don't really know which compounds or subsets of compounds in secondary smoke cause health problems," says Delbert J. Eatough, a BYU professor of chemistry."What we do know from our research is that if you measure the concentration of nicotine only, you can easily underestimate the impact of secondary smoke by a factor of up to 10." Those who base their studies on measuring particles suspended in the air can overestimate its impact.

Through their research, Eatough and co-workers have shown that nicotine in environmental tobacco smoke (ETS) is dominant in the gaseous phase but dissipates rapidly in the atmosphere - making it highly unreliable as a marker or tracing element when trying to determine what people really are exposed to by breathing ETS.

"Nicotine has been used extensively as a marker, but we are just now beginning to understand its weaknesses," explains Eatough.

Current epidemiological data suggest that exposure to secondary tobacco smoke leads to an increased incidence of respiratory disease, the impairment of lung development in small children and the development of lung cancer, he says.

Recent studies are attempting to determine how much ETS people are exposed to in a variety of indoor situations.

Other studies focus on measuring breathable particles suspended in the air, which actually overestimate ETS exposure, because they don't distinguish between tobacco smoke particles and those generated by other sources, Eatough says. Such factors as dust, cooking, wood stoves, animals and people contribute to the total number of particles suspended in the atmosphere.