Occupational exposure to lead dramatically increases the risk of devloping and dying from brain cancer, according to a report published in the International Journal of Cancer. The report by leading epidemiologists analyzed over 300,000 workers and found the riskiest occupations were welders, auto mechanics, heavy equipment mechanics. Individuals heavily exposed to lead at work were more than two times as likely to die from brain cancer as nonexposed workers.
This study reviewed job categories reported for 317,968 adults who participated in the National Longitudinal Mortality Study from 1979 to 1989. The investigators compared the 119 brain cancer deaths that occurred in this group over nine years of follow-up to lead exposure based on a job exposure matrix that rated each occupation for likelihood and intensity of exposure. Overall, 19% of the cohort was deemed occupationally exposed to lead.
The research found that jobs with low exposure to lead had a hazard ratio of 0.7. The hazard ratio doubled to 1.4 for jobs considered to have medium exposure to lead. However the hazard the ratio jumped to 2.2 for jobs where high exposure to lead was probable. Three occupations contributed to all the brain cancer deaths in the medium to high intensity group, they were: automobile mechanics with a 2.30 hazard ratio, heavy equipment mechanics with a 3.15 hazard ratio, and welders and flame cutters 5.12 hazard ratio.
Scientists have always thought that lead was a carcinogen. Lead passes through the blood-brain barrier, making the brain especially sensitive to the toxic effects of of the substance. The effects of lead exposure are usually not evident for many years after the exposure has ceased. The reports authors believe that lead inhibits DNA synthesis and repair, oxidative damage and interaction with DNA-binding proteins and tumor suppressor proteins.
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