What you need to know before stepping out in sun

Just in time for Memorial Day weekend, it’s time for a primer on sunscreens and sun exposure.

Both Consumer Reports and the Environmental Working Group have just released reports to help consumers make more informed choices in seeking protection against ultraviolet B — the radiation that causes sunburn — and ultraviolet A — the radiation that penetrates deeper into the skin than UVB rays and causes tanning and wrinkling of the skin. Both UVB and UVA can raise your risk of developing skin cancer.

Consumer Reports, in its online report published May 18, claims that not all SPF ratings on various brands provide a reliable measure of how much protection they’re providing. The sun protection factor is the number you see on the bottle that measures how well a sunscreen guards against UVB rays.

Theoretically, if your skin would normally burn after 10 minutes in the sun, wearing an SPF 15 sunscreen would allow you to stay in the sun for 150 minutes without burning. According to the Mayo Clinic, when applied correctly, a sunscreen with an SPF of 30 will provide slightly more protection from UVB rays than does a sunscreen with an SPF of 15. But the SPF 30 doesn’t provide twice the protection. And sunscreens with SPFs greater than 50 increase protection only slightly.

The Environmental Working Group, a nonprofit dedicated to protecting human health and the environment, released its 11th annual sunscreen guide to help folks understand sun protection products sold in the U.S.

Its goal is to get the Food and Drug Administration to provide safer products for consumers.

“People are really misled by marketing,” said Sonya Lunder, senior analyst and lead author of the guide.

According to its website, EWG assessed more than 880 beach and sport sunscreens, 480 moisturizers and 120 new lip ingredients. Products were rated based on: ingredients, UVB protection, UVA protection, UVB and UVA ratios and sun stability.

Not much has changed since the first guide, Ms. Lunder said.

Scientists and trade groups disagree on the safest but most effective ingredients in sunscreens. The EWG, noting that sunscreens

were designed initially to guard against sunburn but not skin cancer prevention, is most troubled by the use of oxybenzone, a chemical filter in many products. It can cause allergic skin reactions and in laboratory studies it is a weak estrogen and can disrupt hormones, according to the EWG. “In a recent evaluation of CDC-collected exposure data for American children, researchers found that adolescent boys with higher oxybenzone measurements had significantly lower total testosterone levels,” according to the report. This ingredient has been removed from many cosmetics over such concerns, the EWG said.

Another worrisome ingredient, according to Ms. Lunder, is retinyl palmitate, which is composed of palmitic acid and retinol (Vitamin A). Data from an FDA study indicate that retinyl palmitate, when applied to the skin in the presence of sunlight, may speed the development of skin tumors and lesions.

Despite the growing use and acceptance of sunscreens, the National Cancer Institute notes that the rate of melanoma — the most lethal skin cancer — continues to rise and has tripled over the past 35 years.

EWG says that “higher SPF values [are] ‘inherently misleading.’ ” If applied evenly on the skin every two hours, SPF 50+ works almost the same as SPF 100+.

The EWG urges consumers to look for sunscreens that contain mineral filters, such as zinc oxide, titanium dioxide or Mexoryl SX. These are overall safer, they do not break down in the sun as easily, and they still protect against UVA rays.

The only way for consumers to know about the safety of their products is to read labels and practice proper sun habits beyond simply using sunscreen.

Although the EWG has been updating its reports annually for 11 years, the FDA has been slow to make changes.

Ms. Lunder said that noticeable changes in the safety of sunscreens will not be made until the FDA alters its regulations.