Three years ago, a plastic surgeon from New Jersey made a stark declaration on the popular “The Dr. Oz Show”: “There is a real potential for sunscreens to cause cancer, particularly breast cancer.”

He was talking about common sunscreen chemicals that may affect the function of certain hormones, such as estrogen, if they seep through the skin. But much of the research on the chemicals was performed on animals or in test tubes, not on humans, and none of the studies done on humans actually found they caused cancer.

Still, a nonprofit research organization called the Environmental Working Group, which has released its annual report on sunscreens, advises people to avoid some chemicals altogether, despite the lack of a definitive cancer link.

“It’s not 100 percent clear cut, but we think there is enough evidence to raise concerns and seek alternatives, if possible,” said David Andrews, a senior scientist with the EWG and a co-author of the group’s 2016 sunscreen guide.

The EWG bestows its highest toxicity concern rating on a common sunscreen ingredient called oxybenzone. The chemical is so prevalent in not only sunscreen, but also other cosmetics and personal care products, that a Centers for Disease Control and Prevention study in 2008 estimated it’s present in the urine of nearly 97 percent of Americans.

Some animal studies found oxybenzone exposure affected estrogen levels, although others did not. One study found it altered sperm production in mice, another found it delayed puberty in rats and another linked it to lower birth weights in human females. A number of studies found oxybenzone can cause skin irritation in humans.

One thing there is solid evidence on: Proper use of sunscreen, coupled with other sun protection practices, reduces one’s risk of getting skin cancer (some forms more than others).

That’s why one of Andrews’ main messages is not to rely solely on sunscreen. Cover up. Don’t go outside in the middle of the day if you don’t need to. Wear sun-protective clothing and wide-brim hats.

“It’s really ensuring that you’re making sunscreen just one piece of the sun-protection strategy,” he said.

‘A very contrived scenario’

Does sunscreen cause cancer?

It’s a question Dr. Oliver Wisco, a dermatologist with Bend Memorial Clinic, hears all the time when patients walk into his office. The truth is, while no existing data shows a direct correlation between oxybenzone and cancer, he said he can’t dispute the risk that’s shown up in some research.

“I think there are a lot of things we are doing to ourselves that we don’t fully understand,” said Wisco, who also performs Mohs surgeries to treat some forms of skin cancer. “For example, we used to use mercury as a medication and now we laugh at that.”

When it’s not possible to avoid the sun, Wisco recommends mineral-based sunscreens, especially those with zinc oxide as their active ingredient. Zinc — the stuff we put on babies’ butts to soothe diaper rash — is a naturally occurring mineral Wisco said he believes is safer and less likely to cause skin irritation than oxybenzone.

The most common types of sunscreen are chemical based, with active ingredients like oxybenzone, avobenzone, octisalate, octocrylene, homosalate and octinoxate. They work by creating a chemical reaction on the skin that reduces the amount of ultraviolet radiation that penetrates the skin. Physical sunscreens, those made of minerals like zinc oxide or titanium oxide, block the UV radiation.

The chemicals that comprise chemical sunscreens are designed to break down once they absorb UV radiation. Those compounds are much less stable than zinc or titanium, which don’t break down from UV exposure, Wisco said. If zinc or titanium were to penetrate a person’s skin, they would be much harder for the body to get rid of.

He added, “We have no great data at this point that says that it is harmful in any fashion.”

Octinoxate is the other chemical EWG lists in its highest toxicity concern category. Like oxybenzone, there’s lots of research showing it seeps into the skin, but a few animal and test tube studies have shown it also can affect hormones.

EWG also recommends people avoid sunscreens that contain a form of vitamin A called retinyl palmitate.

A 2012 study found it increased the number of skin tumors that appeared on mice exposed to UV radiation. The American Academy of Dermatology, in response to the study, said the type of mice used are known to develop skin cancer within weeks of UV exposure. Dermatologists routinely use forms of vitamin A for acne, Wisco said. It’s also found in lots of over-the-counter anti-aging products.

What happens to animals in studies doesn’t necessarily reflect what’s going to happen in people, said Dr. Colette Pameijera, a surgical oncologist and associate director of translational research for Penn State Melanoma and Skin Cancer Center.

“They use astronomical doses in animals that are not necessarily realistic,” she said. “It’s a very contrived scenario, frankly.”

Melanoma rates increasing

Despite widespread sunscreen use, CDC data show melanoma rates increased in the U.S. by 1.5 percent among men and by 1.1 percent among women between 2002 and 2011.

Wisco said that could be because doctors are getting better at detecting cancerous lesions on the skin. He pointed out that fewer people are dying from melanoma. Indeed, statistics from the National Cancer Institute show the five-year survival rate from melanoma increased from 82 percent in 1975 to about 93 percent in 2008.

Wisco said his bigger concern these days is overdiagnosis. Sometimes tests for cancer in moles can appear ambiguous to doctors, who then err on the side of treating a potential cancer.

Melanoma’s origins could also play a role in that trend. The link in studies between sunscreen use and decreased skin cancer risk has always been stronger when it comes to more common forms like squamous cell carcinoma and basal cell carcinoma, both of which are far less likely than melanoma to be life-threatening.

While studies since at least 2011 have shown sunscreen to be effective in reducing one’s risk of melanoma, Wisco said one’s genetic risk tends to play a bigger role compared to other forms of skin cancer.

Surprisingly, some of the earliest studies investigating the link between sunscreen use and melanoma actually found subjects had higher risks of melanoma when they used sunscreen. Wisco said that’s because after applying the sunscreen, people tended to spend more time in the sun assuming they were safe.

Pameijera compares the phenomenon to using birth control.

“Just because you’re using birth control doesn’t mean you can run around and have sex with lots of people,” she said. “That’s not necessarily a good behavior.”

Similarly, just because someone is wearing sunblock doesn’t mean they can go tanning all day, Pameijera said. The problem there is the sun behavior, not the tanning.

Vitamin D without the sun

Another common remark Wisco hears from his patients is that they purposely spend time in the sun to get enough vitamin D, which is produced in the body when skin is exposed to sunlight. He advises against this.

People need no more than 15 minutes of sun exposure three times per week on the surface area no larger than their hands and face to get adequate vitamin D, Wisco said.

“In Bend, we get that,” he said.

In truth, though, people don’t need to rely on the sun to get their vitamin D, Wisco said. They can get it from foods that contain vitamin D, either naturally or through fortification, or take supplements.

“You shouldn’t get the sun you don’t need,” he said.

When it comes to choosing a sunscreen, Wisco recommends choosing a mineral-based product, preferably zinc oxide, with a sun protection factor of 50 or higher. People really only need SPF 30, but almost no one applies enough to actually achieve an SPF 30, he said. In addition, he tells people to always wear a wide-brim hat and clothing with an Ultraviolet Protection Factor rating of at least 50, which can be found at most sporting goods stores.

SPF only refers to the protection the sunscreen provides from UVB radiation, the rays that make people burn. UVA rays, however, cause just as much damage to the skin, even though they don’t cause visible changes, and there is no good scale to rate UVA protection, Pameijera said. She always recommends people reapply every two hours. Broad-spectrum products are good choices, too, as that means the product includes both UVA and UVB protection.

Austin Britts, the co-founder of Zealios, a Bend company that makes personal care products designed for endurance athletes, said he supports the EWG’s work researching sunscreens. Zealios’ sunscreen, Sun Barrier SPF 45, was not rated in this year’s report. However, Britts said he thinks they can take their caution a bit too far. For example, Sun Barrier contains both retinyl palmitate and octinoxate. Britts said he doesn’t think those chemicals pose any risk to users.

“There is no real reason to take it out,” he said of retinyl palmitate.

Sun Barrier’s active ingredient is zinc oxide, which Britts said blocks 98 percent of the UVA and UVB spectrum and the protection lasts longer than other types of products. It also dries within 15 minutes of application, he said. For his part, Wisco said he prefers Sun Barrier because it goes on easily.

Britts said there are lots of products on the market today that are labeled as being natural or organic, but don’t necessarily work as well. He thinks Sun Barrier walks the line between using safe ingredients and working well.

Britts added, “We’re not scared to use synthetic ingredients that aren’t all-natural or organic if it’s going to make the product perform better and feel better.”

— Reporter: 541-383-0304,

tbannow@bendbulletin.com