Heavy pesticide exposure linked to brain cancer

NEW YORK (Reuters Health) - Agricultural workers with extensive exposure to pesticides may have an elevated risk of brain cancer, new research suggests.

In a study of nearly 700 adults with or without brain tumors, French researchers found that agricultural workers with the highest level of exposure to pesticides were twice as likely to be diagnosed with brain cancer as those with no occupational pesticide exposure.

There was also evidence that people who treated their house plants with pesticides had an elevated brain cancer risk. However, the researchers caution that this has not been seen in previous studies, and more research is needed to confirm whether the connection is real.

Past studies have linked pesticide exposure among farmers to adverse effects on the brain, such as a higher risk of Parkinson’s disease.

The current study focused on residents of France’s Bordeaux region which, along with its famous wine vineyards, has one of the highest recorded rates of brain cancer in the world.

Dr. Isabelle Baldi of the University of Bordeaux and colleagues compared 221 adults who developed brain cancer between 1999 and 2001 with 442 adults from the general population who were the same age and were free of the disease.

The overall average risk of brain cancer was 29 percent higher among subjects with occupational exposure to pesticides than subjects with no exposure. There was also no strong evidence that workers with lower levels of pesticide exposure had an elevated brain cancer risk.

However, farmers, vineyard workers and others with the highest exposure had a two-fold higher risk of developing a brain tumor.

When examined by tumor type, the risk of glioma was three times higher in exposed workers than those with no work exposure to pesticides, Baldi’s team reports in the journal Occupational and Environmental Medicine.

Gliomas, the researchers note, are more common among men than women -- raising the possibility that on-the-job pesticide exposure is one reason for the discrepancy.

Regarding household pesticide use, study participants who said they used pesticides on their house plants were about twice as likely as those who never used pesticides to be diagnosed with brain cancer.

It’s not clear what to make of this finding, according to Baldi’s team. It’s possible, they note, that people with brain cancer might have been biased toward reporting household pesticide use. Other factors not measured in the study, like total exposure to household chemicals, might also account for the link, the researchers point out.

In the Bordeaux vineyards, fungicides are the most commonly used pesticides. However, the study lacked information on the specific pesticides participants used.

A better understanding of which pesticides are associated with brain cancer is now needed, the researchers conclude.

SOURCE: Occupational and Environmental Medicine, online June 2007.