Environmental correlates of intercity variation in age-adjusted cancer mortality rates.

Factors contributing to urban differences in cancer mortality rates are difficult to specify because of migration and the delay between exposure to carcinogens and manifestations of the disease. Proxy measures for prior migration, motor vehicle emissions, industrial pollution, factors in the water supplies, and climate, explain more than half the intercity variation in age-adjusted cancer mortality rates among 98 cities in the U.S. in 1970. The potential importance of these environmental factors as the "urban factor" in cancer is discussed.