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.
How the study was done
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, Dr 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 practises.
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 practise, Dr Yang's team reported online in the Journal of Urology. Those who ground the herb had 2.2 times higher risk.
The results were adjusted to account for other potentially cancer-causing factors such as cigarette smoking, use of hair dyes or exposure to arsenic from deep-water wells.
A good sign
In 2001, the US. 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 Dr 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," Dr Yang said. One example, xi xin, a common cold medicine still in use in Taiwan, contains aristolochic acid, he pointed out.
Dr Yang and colleagues also found that 19% 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.
That possibility is among the reasons at least one expert dismissed the new study as flawed.
"It's a low quality study, and I wouldn't rely on it at all," said Dr Mikel Aickin, methodology editor at BMC Complementary and Alternative Medicine, who was not involved in the research.
The report's main weakness, Dr Aickin said, was that many of the herbalists personally used fang chi outside of the clinic, making it impossible for researchers to determine whether the increases in urinary system cancer came from a work hazard or personal consumption.
The claim that handling fang chi is an occupational danger to herbalists isn't true, Dr Aickin said. "It's really just a very clumsy study that's rediscovered what's already known about the carcinogenesis of taking it as a treatment. They're producing nonsense," he added.
Dr Yang agreed that the study could not determine whether the Chinese herbalists put themselves at additional risk by personally consuming fang chi.
"This occupational group may also take fang chi - I cannot say that it is not impossible that the disease comes from taking the herbs - but their occupation contributes to the etiology greatly," Dr Yang said.
"Now that this paper is out, I suspect and hope that there will be more interest in worker safety in this industry," said Dr Steven Given, dean of clinical education at the American College of Traditional Chinese Medicine in San Francisco. "I think this is a very good sign."
Checklist for doctors
Beyond herbalists, and despite near-worldwide bans, cases of aristolochic acid-linked cancers and other illnesses continue to crop up from the Balkans to Beijing.
Fang chi was traditionally used to treat arthritis and swelling, but aristolochic acid has been found in a wide variety of dietary supplements and alternative medicines.
"This is a potential global disease," said Dr Graham Lord, a nephrologist at King's College London who worked on the first case of kidney failure from aristolochic acid reported in the UK.
"It may be under-recognised, but in the last two or three years, there has been an increasing number of epidemiological studies coming out showing that there could be potentially tens of thousands of patients out there that have been exposed," Lord said.
Doctors may not immediately associate kidney diseases with the ingredient that contaminates some herbal preparations and can be easily bought over the Internet, experts said.
'It's quite hard to diagnose, there is no simple test that you can perform, it's a fairly specialised form of testing," Dr Lord said.
To help in the diagnosis, Dr Lord and colleagues in Belgium are currently working on a checklist for doctors to help determine if aristolochic acid is at the root of a patient's kidney failure or urinary system cancer.
(Reuters Health, November 2012)
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