Secondhand smoke can triple risk of lung cancer
People who are routinely exposed to a lot of secondhand smoke, such as workers in bars and restaurants, can see their risk of lung cancer triple, a new study says. The Canadian study provides some of the most compelling scientific evidence yet for a total
The research, published in the International Journal of Cancer, found that the greater the amount of smoke in a workplace, the greater the risks. "These data absolutely back a smoking ban in all workplaces, including bars," said Dr. Kenneth Johnson, senior epidemiologist at the surveillance and risk-assessment division of Health Canada and the lead researcher.
Dr. Roberta Ferrence, director of the Ontario Tobacco Research Unit, said "What's important about this research is it demonstrates a dose-response: The more exposure you have, the higher your risk. "While this may seem obvious, it has long been contested by the tobacco industry." Dr. Ferrence said she hopes that this "strong new evidence will prompt strong new action" to expand smokefree workplace laws.
"There's an underlying [belief] that secondhand smoke increases your risk of developing lung cancer by 20-25 per cent, and maybe that can be explained away by publication bias," Dr. Johnson said. "But when you see the risk rising by 75 per cent right up to a tripling of the risk, it's hard to argue that nothing is going on."
The new research found that when the number of "occupational smoker years" (the number of smokers in the workplace multiplied by the worker's years of service) reaches 26, the risk of lung cancer has doubled. (That could mean two smoking co-workers over 13 years or five smoking co-workers over five years. It could also mean 26 customers daily for a year in a bar.) When researchers looked at the upper third of workers -- those exposed to the most secondhand smoke -- they found the lung cancer risk was more than tripled.
Since the early 1980s, more than three dozen studies have examined the impact of secondhand smoke on non-smokers, but the Health Canada research is the first original Canadian data.
In the International Journal of Cancer, Dr. Johnson wrote that it is not surprising to see higher risks associated with workplace exposure because studies have consistently demonstrated that the intensity of exposure is higher on the job than at home. The level of nicotine in the air of bars is up to 15 times higher than in the home of a smoker.