Federal regulators will require sunscreen manufacturers to test their products' effectiveness against sun rays that pose the greatest risk of skin cancer. Under new rules being announced Tuesday, they also will have to follow stricter guidelines when describing how well their products work against ultraviolet B rays.
Currently, the Food and Drug Administration only requires testing for ultraviolet B rays that cause sunburn. That's what the familiar SPF measure is based on.
Starting by next summer, products must be tested for how well they deflect the more dangerous ultraviolet A rays. UVA rays are most commonly linked to skin cancer.
The federal government first announced plans for sunscreen standards in 1978. The process was delayed by difficulties assessing UVA protection.