The risk of ovarian cancer increases with increased exposure to diesel exhaust, according to a new study published in the International Journal of Cancer.

“Occupational exposure to diesel exhaust has been classified as probably carcinogenic and that to gasoline engine exhaust as possibly carcinogenic to humans,” Dr. Johannes Guo, of the Finnish Institute of Occupational Health, Helsinki, and colleagues write. “Earlier results concerning cancers other than lung cancer are scarce and inconsistent, and exposure-response relations have seldom been reported.”

The researchers assessed the risk a variety of cancers than may be associated with engine exhaust exposure. These included leukemia and cancers of the throat, ovaries, testes, kidney and bladder.

Between 1971 and 1995, they followed a large group of Finns, who were born between 1906 and 1945. A record linkage with the Finnish Cancer Registry was used to identify 2198 throat cancers, 5082 ovarian cancers, 387 testicular cancers, 7366 kidney cancers, 8110 bladder cancers and 4562 leukemias.

Using data from the population census in 1970, they calculated cumulative exposure (CE) to exposure to diesel and gasoline engine exhausts.

They detected a significant increased risk of ovarian cancer with increasing CE to diesel exhaust. Individuals with the highest CE had more than 3.5 times the risk of ovarian cancer. For exposure to gasoline engine exhaust, the risk was significantly increased only in those who were in the middle CE category. These individuals had a 70 percent increased risk.

A 17 percent increased risk “was found for kidney cancer among men with the lowest CE levels to diesel exhaust, but there was no increase at higher exposure levels,” Dr. Guo and colleagues write. “An excess of bladder cancer was observed only at the lowest level of exposure to gasoline engine exhaust.”

“In conclusion, our study suggests a positive exposure-response relation between occupational exposure to diesel exhaust (or a factor related to diesel exhaust) and ovarian cancer,” the authors write.

“Our results do not support previous findings suggesting an association between engine exhausts and risk of esophageal, testicular, kidney, or bladder cancers, or that of leukemia,” they add.

SOURCE: International Journal of Cancer, August 20, 2004.