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Brain cancer is one of the most dreaded forms of cancer. Research published in the International Journal of Cancer shows that occupational exposure to lead may significantly increase the risk for this condition. To evaluate the risk of occupational lead exposure on the development of brain cancer, researchers studied reported job categories for over 300,000 participants in the National Longitudinal Mortality Study. The researchers estimated lead exposure based on a job exposure matrix, in which certain jobs are known to have much higher lead exposure than others. Nearly one in five study participants was deemed to be exposed to lead. Lead exposure was estimated in the 119 people who developed brain cancer and compared to those who did not develop this condition. Those who had jobs that had any potential lead exposure were 50% more likely to develop brain cancer, even after adjusting for age and gender. The riskiest jobs included auto mechanics, heavy equipment mechanics and welders and flame cutters. A dose-response relationship was also noted. Those with medium exposure were 1.4 times more likely to develop cancer, and those with a high exposure were 2.2 times more likely to develop brain cancer. Lead can enter the blood stream and gain access to the brain, where it can accumulate and reside for many years. For this reason, the effects of lead may be seen long after the occupational exposure has ceased. Lead is thought to cause cancer by altering the synthesis and repair of DNA- the building blocks of cells, and cause oxidative damage. The study is not without controversy. It should be noted that a job matrix may be considered to be a crude method to estimate lead exposure. In addition, other researchers, combining the results of numerous studies, failed to support a link between lead and brain cancer.
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