Experts agree sunscreen is essential and recommend mineral formulas as the safest choice, especially for children.
You might have heard from a social media post or a friend that sunscreens can be toxic. And more and more cosmetics products on the U.S. market contain sunscreen ingredients.
Should you avoid sunscreen?
The answer is no, says Leila Deravi, associate professor of chemistry and chemical biology at Northeastern University.
“Absolutely everybody should wear sunscreen because it does protect against skin cancer,” she says.
However, some chemicals in sunscreens and other cosmetic products can become toxic, Deravi says, if they exceed the threshold levels recommended by the U.S. Food and Drug Administration.
Sunscreens are classified as over-the-counter drugs, Deravi says, because their manufacturers claim they help prevent skin cancer. That is why ingredients in sunscreens are divided into active ingredients — ultraviolet radiation filters — and other inactive ingredients.
“That’s why you can’t just throw in any sort of active ingredient,” Deravi says. “You have to have validated that it protects against skin cancer, which means it blocks UV rays.”
There are two types of chemicals used in sunscreens for their UV filtering properties: chemical filters and mineral filters.
Chemical filters penetrate skin and absorb ultraviolet radiation, converting it into heat that is then released from the skin, helping protect against sunburn, premature aging and cell DNA damage.
Mineral filters such as titanium dioxide and zinc oxides sit on the surface of skin and reflect sunlight.
Both types of sunscreens can be equally effective. The tradeoff with mineral sunscreens, Deravi says, is that they create a white cast on skin, which many people don’t like.
Many manufacturers now add iron oxide, often used in makeup, to create tinted mineral sunscreens. Iron oxide is a naturally occurring mineral, Deravi says, which is used as an antioxidant and is absolutely harmless.
The FDA recommends using broad-spectrum sunscreens that protect from both UVA and UVB rays of sunshine. While UVA rays are associated with photoaging, UVB rays are the ones that cause skin cancer.
In 2019, the FDA proposed a reassessment of sunscreen safety. Two randomized clinical trials, conducted by the FDA and Spaulding Clinical Research and published in the Journal of American Medical Association in 2019 and 2020, found that certain chemical sunscreen ingredients are absorbed into the bloodstream.
The studies tested six active ingredients — avobenzone, oxybenzone, octocrylene, homosalate, octisalate and octinoxate — in four formulations such as lotion, aerosol spray, nonaerosol spray and pump spray.
All active ingredients were systemically absorbed into the bloodstream of all participants. Plasma concentrations exceeded the FDA threshold, even when sunscreen was applied only once on day one and re-tested on day 21.
The most common side effect was rash.
While the FDA called for further research, it did not label the ingredients unsafe. The organization still strongly advises all Americans to use sunscreen alongside other sun protective measures such as clothing and hats.
After reviewing safety data, the FDA proposed classifying zinc oxide and titanium dioxide as generally recognized safe and effective (GRASE) at concentrations of up to 25%.
Aminobenzoic acid (PABA) and trolamine salicylate were deemed not GRASE due to risk outweighing benefit, effectively banning them from U.S. over-the-counter sunscreens.
The FDA also proposed to consider not GRASE due to insufficient safety data such active ingredients as cinoxate, dioxybenzone, ensulizole, homosalate, meradimate, octinoxate, octisalate, octocrylene, padimate O, sulisobenzone, oxybenzone and avobenzone.
While not banned, new products with these ingredients won’t be approved unless manufacturers submit new safety data.
Benzophenone-3, commonly known as oxybenzone, is a chemical compound with well-documented toxicity, says Julia Varshavsky, assistant professor of public health and health sciences at Northeastern.
Benzophenone-3 has been linked to harmful health effects in both animal and human studies. But determining toxic levels of UV filters, such as oxybenzone, for humans, Varshavsky says, is difficult because researchers cannot ethically test high doses in people.
“How our risk assessment decisions are made on chemical safety in the United States is through what’s called dose response assessment,” she says. “They will expose animals or whatever it is to different levels of exposure to see where the toxic effect is. But you can’t do that with humans because we can’t expose people on purpose to things that might be harmful.”
Varshavsky led an observational study of pregnant women in Puerto Rico, examining the impact of benzophenone-3 exposure during pregnancy. Benzophenone-3 is a type of phenol, an aromatic organic compound used in cosmetics products and food packaging for its UV-absorbing properties.
The study found associations between phenol and paraben exposures during pregnancy and increased risk of hypertension, or high blood pressure, during pregnancy. This condition not only raises the risk of cardiovascular disease later in life for the mother, Varshavsky says, but can also affect the child’s health.
“Phenols have been associated with a lot of different potentially toxic molecular actions,” she says. “For example, a lot of them are hormone disruptors.”
Phenols can impact hormone signaling in the body that governs reproduction, development and daily functions. They can also induce oxidative stress and inflammation, Varshavsky says, both linked to disease.
“They have been linked to gestational hypertension and preeclampsia, which is a dangerous hypertension disorder of pregnancy,” she says.
Phenol exposure has been associated with impaired placental development by inhibiting vasodilation, the widening of blood vessels critical for healthy fetal growth.
Another paper recently published by Emily Zimmerman, professor and chair of the communication sciences and disorders department at Northeastern, showed a connection between exposure to phenols, including benzophenone-3, and disrupted infant sucking and feeding patterns that are associated with decreased cognition later in childhood.
Oxidative stress, inflammation and endocrine disruption caused by oxybenzone, Varshavsky says, can lead to various health issues in non-pregnant people as well.
Even mineral filters like titanium dioxide and zinc oxide can be unsafe at high concentrations, Deravi says.
“Titanium dioxide is a known semiconductor and photocatalyst,” she says.
Uncoated titanium dioxide can trigger photochemical reactions when exposed to UV light, which can lead to unintended reactions, degrade other ingredients in the formulation and damage skin cells. But many manufacturers often use titanium dioxide particles coated with silica or alumina nowadays that inhibit the photocatalytic activity, making titanium dioxide safe and stable.
Varshavsky recommends people who are concerned about toxic chemicals exposure to use mineral-based sunscreens.
“We know that’s really important for skin cancer,” she says.
She also advises to look for fragrance- and paraben-free products because they typically don’t have known “bad actors” in them.
Deravi recommends only using mineral sunscreens on children.
“That’s because the skin of kids is more permeable, so it allows for more things to pass through it,” she says.There are a number of resources, Varshavsky says, that can help limit daily exposure to toxic chemicals in general. Varshavsky recommends a free Detox Me app, created by Silent Spring Institute, the Environmental Working Group’s Skin Deep Cosmetics Database and Clearya app, which helps shop for safe household and personal care products online at Amazon, Target, Sephora, iHerb and Walmart websites.