Riding in a car with a smoker is just as bad for your health or may even be worse than hanging out in a smoky bar, according to U.S. researchers.
A small study by Johns Hopkins Bloomberg School of Public Health in Baltimore set out to test exactly how much second-hand smoke people were exposed to when they sit with a smoker under normal driving conditions rather than in a laboratory.
They found that nicotine levels in smokers' cars were up to twice the level found in bars and restaurants.
"No matter how much you had your windows down or the air conditioner on or any other driving conditions, you could always measure tobacco smoke and in most cases you could measure very high concentrations," researcher Ana Navas-Acien told Reuters Health.
To conduct the study, Navas-Acien and her colleagues recruited 17 smokers and five non-smokers, all of whom drove their own car to and from work every day for at least 30 minutes each way.
The researchers put two air monitors in each car for a 24-hour period, one in the front passenger seat headrest and one in the back seat to measure nicotine levels and analyzed 44 samplers.
They measured nicotine because it is an easy-to-measure gauge of second-hand smoke levels, Navas-Acien said, although cigarette smoke contains many other harmful substances. Nicotine levels were undetectable in the non-smokers' cars but in smokers' cars the concentrations averaged 9.6 micrograms of nicotine per cubic meter.
This is up to 50 percent higher than concentrations typically measured in public or private places where smoking is allowed such as bars and restaurants.
For every cigarette a person smoked, the air nicotine concentration doubled.
"This is because the car is a very small place," said Navas-Acien.
The researchers' study, published in the British Medical Association journal Tobacco Control, said their findings supported "the need for education measures and legislation that regulate smoking in motor vehicles when passengers, especially children, are present."