Researchers working in busy roads increase the risk of breast cancer, and after finding at least six women from the same site, the disease is suffering within three years, scientists warn.
A group of women were diagnosed with cancer, believed to be the result of exhaust fumes in a car, which scientists describe as a "new occupational disease". Another group of seven women infected the disease after working in the tunnel just a few miles from the US-Canada border.
The study focused on the case of an unknown woman who worked for 20 years on an ambitious bridge between Detroit and Michigan Windsor in Ontario.
The bridge links the United States and Canada, one of the busiest trade districts in North America, with 12,000 trucks and 15,000 vehicles a day.
Assuming that traffic was similar in 20 years, when women spent 40 hours a week at their jobs, 46.8 million vehicles were exposed to an explosion.
Doctors Michael Gilbertson and Jim Proffy of the University of Stirling in Scotland believe that chemicals in traffic smoke cause cancer.
The study found that women working in traffic kiosks gave them a 16 times greater chance of breast cancer than women.