Until now, only UVB radiation from solar rays was known to cause a genetic mutation.
But researchers found the same mutation in the skin of mice treated with UVA. The agency decided to reclassify all types of ultraviolet radiation — UVA, UVB and UVC — as carcinogenic to humans or Group 1 carcinogens.
Previously, the three UV types were grouped as probable carcinogens.
Kathy Banks, chief executive of The Sunbed Association, a European trade association of tanning bed makers and operators, disputed the classification of tanning beds as carcinogenic.
"The fact that is continuously ignored is that there is no proven link between the responsible use of sunbeds and skin cancer," Banks said in a statement.
Most people who use tanning beds use them less than 20 times a year, she said.