Tanning beds can ring up a steep bill—a whopping $343 million each year in medical costs in the US alone.

Indoor tanning has long been tied to skin cancer, the most common type of cancer in the US. It’s estimated that 30 million people—nearly 25 percent of whom are teenagers—head to tanning beds at least once a year.

And the health care costs of the habit can add up, health economists report in a new study published Tuesday in the Journal of Cancer Policy.

Tanning beds emit UV-A rays, which can damage DNA, and UV-B rays, which can burn the skin and increase the risk of skin cancer. Research has shown that indoor tanning before age 35 raises the risk of melanoma up to 75 percent.

Health care researchers at the University of North Carolina focused on melanoma and two other types of skin cancer, basal cell carcinoma and squamous cell carcinoma.

The researchers looked at all skin cancer cases in 2015, and then applied data on indoor tanning prevalence and relative risk of skin cancer after using a tanning bed to those numbers. They estimated that there were 263,600 cases of skin cancer in 2015 that could be attributed to the use of tanning beds.

The researchers then summed up the average annual cost of treating patients with each type of cancer, which totaled more than $343 million each year.

“Our findings highlight both the negative health and negative financial impacts associated with indoor tanning,” the authors wrote.

The Food and Drug Administration has taken steps in recent years to rein in use of tanning beds. In 2014, the agency announced that manufacturers would be required to put a black-box warning on tanning beds that states they shouldn’t be used by anyone under 18. The FDA also classified tanning beds as moderate-risk products in 2014, giving health officials the authority to review tanning beds for safety before they hit the market.

The Affordable Care Act aimed to reduce use of tanning beds, too, by implementing a 10 percent excise tax on indoor tanning services.

A couple caveats: The new numbers are just an estimation—it’s impossible to nail down the cause of each individual case of skin cancer. The results also don’t include costs associated with other health problems blamed on tanning beds, such as burns.

But the study’s authors said they are hopeful that putting an estimate on the social costs of indoor tanning will help reduce use of the devices.

Republished with permission from STAT. This article originally appeared on February 28, 2017