Study finds herbalists at higher urinary cancer risk

A small new study from Taiwan links a widely banned substance traditionally used in Chinese medicine to an elevated risk for kidney and bladder cancers among professional herbalists.

Herbs, such as fang chi, that contain the plant-derived aristolochic acid, are known to cause cancer as well as kidney failure, and the current study suggests that working with these herbs raised urinary cancer rates among Taiwanese herbalists who handled fang chi before its ban in 2003.

"This is the first study that looks at an occupational group that has been heavily exposed to aristolochic acid," said the study's lead author Dr. Hsiao-Yu Yang, an occupational medicine professor at Tzu Chi University in Taiwan.

Previous research has found that Chinese herbalists have three times higher risk for urinary system cancers compared with the general population, but those reports didn't connect the pattern to a specific work-related factor.

To see whether fang chi exposure could be involved, Yang's team used national databases to track 6,564 Chinese herbalists working in Taiwan between 1985 and 1998. In 2002, the herbalists took surveys about their recollections of processing medicines such as fang chi in their practices.

The occupational researchers honed in on 24 herbalists who had contracted cancer of the urinary system, including the kidneys, bladder and urethra, and compared that group with 140 herbalists who were healthy at the time of the 2002 survey.

About two-thirds of the herbalists in both groups were women.

Herbalists who packed or sold fang chi had 2.6 times the risk of urinary cancer compared with herbalists who avoided fang chi in their practice, Yang's team reports in the Journal of Urology. Those who ground the herb had 2.2 times higher risk.

The results took into account other potentially cancer-causing factors such as cigarette smoking, use of hair dyes or exposure to arsenic from deep-water wells.

AN ONGOING THREAT

In 2001, the U.S. Food and Drug Administration warned consumers of the dangers of aristolochic acid-containing herbs, and regulations established in the Europe Union in 2004 effectively banned the substance. However, Internet sites still sell the processed drug or source plant, which remains legal in China and several other countries.

For Yang, the study also highlights the fact that little-regulated Chinese herbal medicines in many cases still contain aristolochic acid.

"We want to push our government to prohibit all drugs that contain aristolochic acid," Yang said. One example, xi xin, a common cold medicine still in use in Taiwan, contains aristolochic acid, he pointed out.

Yang and colleagues also found that 19 percent of Taiwanese herbalists had traces of aristolochic acid in their blood three years after the ban, indicating that the drug was probably still in use.