On-the-job lead exposure tied to stomach cancer

Last Updated: 2007-11-09 14:05:49 -0400 (Reuters Health)

By Amy Norton

NEW YORK (Reuters Health) - Men exposed to certain forms of lead at work may face an elevated risk of stomach cancer, a new study suggests.

Canadian researchers found that among nearly 4,300 men between the ages of 35 and 70, those who'd been exposed to lead in certain jobs had a heightened risk of stomach cancer.

The risk was specifically linked to working around organic lead -- mainly in jobs where men were exposed to leaded gasoline in its liquid form -- and to jobs where they breathed in large amounts of gasoline fumes.

"Our study suggests that workplace exposure to organic lead, especially from leaded gasoline, could increase stomach cancer risk," lead researcher Dr. Marie-Claude Rousseau told Reuters Health.

She and her colleagues at the University of Quebec report the findings in the American Journal of Epidemiology.

Lead is a toxic metal that is present in the air, soil and water, though public health efforts in recent decades have reduced environmental levels -- by taking lead out of gasoline and paints, for example.

Men in the current study were diagnosed with cancer in the 1980s, and were exposed to leaded gasoline before lead additives were phased out. However, a variety of jobs can potentially expose workers to lead, including construction work, welding and any industry that manufactures lead-containing products, such as lead-acid batteries.

While lead exposure is known to have serious health effects -- which, in adults, include high blood pressure and damage to the kidneys, brain and nerves -- its relationship to cancer is less clear. Inorganic lead, which is breathed in through lead dust and fumes, has been classified as a "probable" carcinogen, based on animal research and limited studies in humans.

However, Rousseau said, "it is still unclear as to whether people exposed to organic lead have higher risks of developing cancer."

For their study, she and her colleagues used information from 3,730 Canadian men who were diagnosed with cancer between 1979 and 1985, as well as 533 men from the general population who were studied for comparison.

Rousseau's team found that compared with the general population, men who'd ever been exposed to organic lead on the job had a three-fold higher risk of stomach cancer. An elevated risk was also seen among workers with a substantial exposure to gasoline emissions -- at least five years of moderate to frequent exposure.

No other form of cancer was linked to lead exposure, and men who worked around inorganic lead showed no heightened cancer risk.

This does not, however, mean that working with inorganic lead poses no cancer risk, according to Rousseau. Results from any one study, she said, should not be given too much weight, and other research suggests that inorganic lead is a carcinogen.

As for exposure to everyday levels of lead in the environment, studies so far have not shown a link to cancer, Rousseau said.

"One likely explanation is that normal environmental levels of lead are usually much lower than those experienced by workers," the researcher added.

SOURCE: American Journal of Epidemiology, November 1, 2007.