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HONG KONG (Reuters) - Some Chinese cigarettes contain amounts of lead, arsenic and cadmium that are three times higher than levels found in Canadian cigarettes, a study has found.
While consuming such heavy metals is widely known to be harmful to health, there is little research done so far about their impact when inhaled into the body.
The researchers, who published their findings in the journal Tobacco Control on Thursday, said more investigation was needed.
"While the per-stick levels of metals are what we measured, the real issue is repeated exposure. Smokers don't smoke just one cigarette, but 20 or so a day every day for years because cigarettes are addictive," wrote lead author Richard O'Connor of the Roswell Park Cancer Institute in Buffalo, New York.
"These metals get into smokers along with a cocktail of other toxicants. The effect of cumulative exposure to multiple toxicants, including metals, is the public health question that needs to be sorted out."
The researchers used Canadian cigarettes for comparison in their study because Canadian manufacturers and importers are required to test for metals content in tobacco, and Health Canada, the country's public health agency, recently released data concerning this.
China has more than 320 million smokers and a million Chinese in the country die each year from tobacco-related illnesses. Smoking has been causally linked to hypertension, stroke, diabetes, cancer, heart and respiratory diseases, among others.
China has the world's largest smoking population and is also the biggest producer of tobacco, manufacturing 2.16 trillion cigarettes in 2007, according to the Tobacco Atlas.
O'Connor and colleagues analysed 78 varieties of popular Chinese cigarette brands and found significantly elevated levels of heavy metals, with some containing three times the levels of lead, cadmium and arsenic compared with Canadian cigarettes.
"The higher yields of cadmium and lead in cigarettes manufactured in China are worrisome given current smoking prevalence in China and China National Tobacco Company's export ambitions," the researchers wrote in their paper.
A member of the team, Geoffrey Fong from the University of Waterloo in Canada, said the heavy metals content was due to contaminated soil.
"Tobacco like other crops absorbs minerals and other things from the soil, so if the soil has cadium, lead or arsenic, they will be absorbed into the tobacco," Fong said.
(Reporting by Tan Ee Lyn; Editing by David Fox)