Tanning beds now rank alongside cigarettes and asbestos as a top-level cancer threat, the World Health Organisation's cancer research agency announced Wednesday.
Classified in 1992 and a "probable" cancer agent, research since then has left no doubt that soaking up UV rays at tanning salons significantly enhances the chances of developing the disease, the International Agency for Research on Cancer (IARC) found.
"The use of sunbeds is carcinogenic to humans. It causes melanoma of the skin, and melanoma of the eye," said Vincent Cogliano, an IARC researcher who led the new assessment.
"I cannot see any reason why a healthy person should use them," he told AFP by phone.
The risk of melanoma -- the most lethal form of skin cancer -- increases by 75 percent when use of tanning devices starts before the age of 30, according to the findings, published in the British medical journal The Lancet Oncology.
The link between artificial tanning devices and cancer is not new. The WHO and national health agencies have long cautioned against using sunbeds, much as they have warned about the ill effects of overexposure to the sun.
But threshold of scientific proof is high, and required additional research on animals as well as epidemiological studies of cancer rates among humans before sunbeds could be labeled -- along with tobacco, asbestos and alcohol -- as a carcinogen.
Cogliano said it is not the IARC's role to issue recommendations, but that he hoped the new evaluation would focus attention on the issue.
"We are not a regulatory agency. We publish the scientific results so that the public health agencies can take action as they see fit."
Physicians hailed the decision, and called for tighter regulations for the multi-billion dollar tanning industry.
"We welcome the recognition that sunbeds are carcinogenic," said Nina Goad, spokeswoman for the British Association of Dermatologists.
"It is high time that steps were taken to regulate the industry, to prevent children using sunbeds, and to ensure that sunbeds are subject to health warnings like other known carcinogens."
"We have been trying for a long time to call the attention of the government to the potential risks," said George Reuter, head of France's National Union of Dermatologists.
The tubes emitting UV rays vary in intensity and can "become more dangerous over time," highlighting the need for stricter oversight, he told AFP.
Both associations stopped short of calling for an outright ban.
"The solution is to inform the public, not to outlaw sunbeds," said Reuter, adding that many dermatologists in France tell their patients not to exceed 10 sessions in year.
Those who use the devices to stay tanned year round are especially at risk, he added.
"People have the right to make their own health choices. Other known carcinogens are not banned, so I don't think you want to set a precedent with sunbeds," Goad said by phone.
Sunbeds are more common in northern Europe and the United States than most other regions. According to a survey conducted last year, some 14 million Germans aged 18 to 45 use them, with a quarter starting before the age of 17.
Earlier studies indicate that nearly a quarter of the adult population in many European countries -- including France, Belgium, Germany and Sweden -- have used sunbeds, which emit a higher concentration of UV rays than sunlight.
The sunbed association, and industry lobby group based in Britain, disputed the IARC's reclassification of tanning devices as carcinogenic to humans.
"The relationship between UV exposure and an increased risk of developing skin cancer is only likely to arise where over-exposure -- i.e. burning -- has taken place," it said in a statement.
