Drivers' smoking give passengers high levels of secondhand smoke

Smoking tobacco while driving might seem harmless. But smoking drivers are subjecting themselves—and their passengers—to extremely unhealthy levels of air pollution, say scientists. The study, conducted by British researchers and due to be published in the journal Tobacco Control, was the largest of its kind and examined more than 100 car trips made by 17 drivers, 14 of whom were smokers.

Thirty-four of the trips were smoke-free and averaged about 7.4 micrograms per cubic meter (μg/m3), well below the 25 μg/m3 safe level as recommended by the United Nations' World Health Organization. But in trips with smoking drivers, scientists found interior pollution averaged 85 μg/m3. The levels of particulates in the car's interior varied according to the number of cigarettes smoked and the length of the trip. But the study says that peak levels of pollution averaged about 385 μg/m3 for trips with smokers.

And on one occasion, scientists found a reading as high as 880 μg/m3. What's more, even with the cars' air conditioning on or the windows open for ventilation, passengers were still exposed to air pollution levels that exceeded WHO's guidelines. "Children are likely to be at greater risk from [secondhand smoke] exposure due to their faster breathing rates, less developed immune system and their inability to move away from the source in many home and car settings," wrote the study authors. Several states, including Arkansas, California, Hawaii, Louisiana, Maine, and Maryland, and countries have banned or are considering banning drivers smoking in private cars.