(NEW YORK) -- Indoor tanning increases the risk of two types of common skin cancers, especially among those exposed before the age of 25, a new review of previously published studies shows.
This international study, published Tuesday in the journal BMJ, combined the results of 12 studies on nearly 81,000 people.
By comparing the data linking indoor tanning and skin cancer, researchers estimated that the activity may account for more than 170,000 cases of non-melanoma skin cancers -- basal cell and squamous cell carcinomas -- in the United States each year. In particular, exposure to indoor tanning before the age of 25 was linked to an increased risk for basal cell carcinoma, according to the study.
These findings show that "indoor tanning is dangerous, especially for young people," said study senior author, Dr. Eleni Linos, assistant professor in the department of dermatology at the University of California San Francisco.
Specifically, Linos and her colleagues found that those who reported ever using indoor tanning had a 67 percent higher risk for developing squamous cell carcinoma and a 29 percent higher risk for basal cell carcinoma.
There are several types of skin cancer, according to the National Cancer Institute website. Basal cell carcinoma and squamous cell carcinoma form in the higher layers of the skin, while melanoma originates in the cells that create pigment. It is melanoma that is the most deadly form, but non-melanoma cancers strike many more Americans -- more than an estimated two million in this year alone. Linos added that non-melanoma skin cancers affect nearly one in five Americans over the course of their lifetimes.
"With this study, we finally have strong evidence that tanning beds contribute to all types of skin cancer including basal cell, squamous cell and melanoma," Linos said. "The risk of all three types of skin cancer is significantly higher in young people. This means there is a clear cancer risk for teenagers who use tanning beds, and it's hard to argue with regulations to protect children from cancer."
She said that while non-melanoma skin cancers are less deadly, their impact is enormous.
"Their treatment adds up to the fifth-most costly cancer for Medicare," she said, citing research that showed that the cost of diagnosing and treating these types of skin cancers ranges from $1,200 to $2,100 per case.
Cancer experts not involved with the study called the findings startling.
"This data is really strong," said Dr. Otis W. Brawley, chief medical officer of the American Cancer Society. "We have been very concerned for a long time that tanning beds clearly cause cancer and we have been recommending against their use."
These findings may renew calls to better regulate indoor tanning, according to the study authors.
"A national ban for those under 18 is a first step, because that is the group at highest risk," Linos said, adding that many states are already doing this.
Representatives from the tanning industry balked at the idea of bans and stiff regulations for a practice they said comes with health benefits that may offset the risks.
"Tanning beds are a good source of vitamin D, which is associated with many health benefits," said John Overstreet, executive director of the Washington D.C.-based Indoor Tanning Association.
Such an argument may not be enough to convince many health experts, however. In 2009, the World Health Organization placed all forms of indoor tanning in the same category as such cancer-causing agents as tobacco smoke and asbestos.
"Vitamin D is important for general health, and can be obtained both through sunlight but also through the diet," Linos said. "The risks of indoor tanning outweigh the benefits, especially for young people."
Moreover, she added, tanning beds are typically used by young healthy women who are not at risk for Vitamin D deficiency and conditions linked to low vitamin D levels.
Copyright 2012 ABC News Radio