Researchers sampled the air in workplaces that allow smoking and found that contrary to the tobacco industry's claims, workers are exposed to dangerous levels of secondhand smoke.
Nicotine levels in offices studied were more than triple the amount considered hazardous by U.S. regulatory standards, the researchers found in what is believed to be the largest study on secondhand smoke in the workplace.
"The tobacco industry says work exposures are trivial compared to home exposures," said lead researcher S. Katharine Hammond, an associate professor of public health at UC Berkeley. "And this paper says that's clearly not true."
A spokesman for the tobacco industry said the study's methods were faulty and that its conclusions contradict other research.
The findings appear in Wednesday's issue of the Journal of the American Medical Assn. The study was conducted in Massachusetts, when Hammond worked at the University of Massachusetts Medical School in Worcester.
The researchers placed 25 fiber disks treated to react to nicotine at each of 25 work sites, including fire stations, newspaper publishing facilities, textile drying plants and various manufacturing plants. The disks were left for a week in offices, cafeterias and production areas.
Nicotine levels ranged from 8.6 micrograms per cubic meter of air in open offices where smoking was allowed to 1.3 micrograms where smoking was restricted and 0.3 microgram where smoking was banned. In non-office areas, the levels were 2.3 micrograms, 0.7 microgram and 0.2 microgram, respectively.
Exposure to an average of 2.3 micrograms of nicotine per cubic meter of air for eight hours a day over 40 years creates a lung cancer risk of 3 in 10,000, the researchers said, citing previous research.
Secondhand smoke is believed to have an even greater effect on heart disease. Studies have estimated that secondhand smoke may cause 30,000 to 50,000 U.S. nonsmokers to die each year from heart disease, compared to 3,000 similar deaths from lung cancer, the researchers said.
Hammond said she believes the Massachusetts work sites are typical of other U.S. workplaces.
Tom Lauria, a spokesman for the Tobacco Institute, a Washington-based trade group, said Hammond's method of monitoring at fixed locations failed to account for varying amounts of time employees actually spent at those locations.
"To measure workplace exposure properly, both concentration and length of exposure must be measured," he said.
Other research has found much lower workplace concentrations, Lauria added, citing a study by Oak Ridge National Laboratory in 16 cities.
"Preliminary results from the Oak Ridge study show as much as 13 times less exposure in the workplace than at other locations," Lauria said.
He also said it has not been scientifically established that secondhand smoke contributes to lung cancer, as the government says.
Hammond said the Oak Ridge study has not yet been published in a scientific journal and subjected to review by experts.
The U.S. Environmental Protection Agency in 1993 classified secondhand smoke as a serious cancer threat and issued guidelines urging every company to have a policy protecting nonsmokers from involuntary exposure.
Michael Eriksen, director of the Office on Smoking and Health at the Centers for Disease Control and Prevention, said Hammond's study is not only the largest, but is one of the first to show the relationship between secondhand smoke and work-site smoking policies.