People who live in cities are exposed to substantial levels of air pollutants called polycyclic aromatic hydrocarbons (PAHs), according to study findings reported in the Journal of Occupational and Environmental Medicine.
This exposure may cause a small increase in the risk of cancer, researchers reported.
PAHs are released into the air by the burning of coal, wood, fuel, garbage, tobacco and meat.
In cities, the most common source of these pollutants are factories, exhaust from cars, and cigarette smoking.
When inhaled, these small particles may become lodged deep within the lungs, and may increase the risk of lung cancer.
In the study, a research team led by Dr. Denis Zmirou at Grenoble University in France measured personal exposure to PAHs during the summer and winter in Grenoble, a city of approximately 400,000 people.
During a 48-hour period, 38 volunteers carried a personal air sampler that measures air quality.
The investigators detected potentially troublesome levels of PAHs in the air, especially in areas near traffic congestion.
Levels of pollutants were 3 to 25 times higher in winter, probably due in part to PAHs given off by heaters and furnaces.
Compared with people who work in factories, ordinary city dwellers are exposed to relatively low levels of PAHs, but the pollutants are still a reason for concern, according to the study authors.
They estimated that exposure to PAHs causes approximately one case of lung cancer every two years in a city the size of Grenoble.
"Owing to the relatively low exposures encountered in non-occupational settings, the cancer risk estimated associated with the atmospheric PAHs in this study is modest, yet of public health concern," Zmirou and colleagues concluded.