This summer, against the backdrop of record-shattering heatwaves and the typical desire to hit the beach, some people may be wondering if the lotion we slather on to protect against the Sun is just as dangerous as the skin cancer sunlight can generate.
Since the dawn of humanity, we've depended on the Sun to survive. Our solar system's star drives weather on Earth, influences ocean currents, climate and makes plant life possible. But only relatively recently have humans developed mechanisms to protect ourselves from it as much as physically possible when exposed. Of course we're talking about sunscreen. While there is evidence that Ancient Egyptians and Greeks used mixtures of plant extracts to prevent tanning (they likely didn't know about the harmful effects of ultraviolet radiation from the Sun), the first sunblock was developed less than a century ago.
Today, there are many to choose from and the importance of its use is emphasized in the mere fact that rates of melanoma have been rising rapidly over the past few decades.
However, sunscreen has a PR problem. One in which headlines often point out that some sunscreens have previously included carcinogenic or potentially carcinogenic chemicals. Indeed, in July 2021, Johnson & Johnson recalled five aerosol sunscreen products because they had been contaminated with benzene, a known carcinogen. The presence of the chemical wasn't intentional.
In 2019, the FDA requested additional safety data on sunscreen components from manufacturers, heightening fears around safety and sunscreen. Consumer watchdogs like the Environmental Working Group often publish warnings about the potential health risks of sunscreen chemicals. And it's not just the potential to harm human health, but also the environment. In 2018, Hawaii banned sunscreens that contain octinoxate and oxybenzone fearing that they could damage coral reefs. Concerns have also been raised about the use oxybenzone, a potential hormone disruptor, in sunscreen.
The seeming catch-22 of sunscreen has made it difficult for some people to choose the right sunscreen — or wear it at all. However, in the United States, skin cancer is the most common type of cancer. It's estimated that one-fifth of Americans will develop some form of it in their lifetimes — a striking statistic to dermatologists given it's also one of the most preventable cancers. While most cancers are caused by genetic mutations in DNA that trigger genes in normal cell growth to become oncogenes, skin cancer is caused by excessive sun exposure. And most Americans don't wear sunscreen regularly.
"There are more skin cancers than all other cancers combined in the United States," Dr. Darrell S. Rigel, a clinical professor of dermatology at Mount Sinai Icahn School of Medicine and former president of the American Academy of Dermatology, told Salon. "Melanoma, the most dangerous kind of skin cancer, is the most common cancer in women ages 25 to 29 and the second most common after breast cancer in women ages 30 to 34. It strikes younger, and we are seeing younger and younger people get it."
Rigel said when weighing the risk of chemicals in sunscreen and getting skin cancer, what is really happening is that people are weighing an "unproven risk with a proven benefit."
"It's an unproven hypothetical risk that has actually been disproven in some studies, versus a proven risk," Rigel said. "But I'm biased because I see all the people who get skin cancer, but the people who get skin cancer, they virtually all say 'I wish I protected myself from the sun years ago.'"
The sun gives off two kinds of damaging rays: UVA light, which causes wrinkles and UVB, which causes sunburn. Both contribute to the development of skin cancer. (There are also UVC rays, which are far more dangerous than UVA or UVB, but they luckily don't reach the Earth's surface.) Sunscreen works by blocking UV light via physical or chemical filters or both. Sunscreens that contain titanium dioxide and zinc oxide create a physical barrier between the skin and the Sun. These sunscreens physically reflect light off the skin. Then there are chemical sunscreens that are designed to absorb UV rays, acting as sponges that turn damaging rays harmless.
"There's been some evidence that some of the chemical sunscreens are absorbed into the bloodstream after being applied to the skin, especially when they're applied to a large surface area of the skin," Dr. Bruce A. Brod, a clinical professor of dermatology at University of Pennsylvania Perelman School of Medicine, told Salon. "But we don't have any evidence to show that chemical sunscreens that are absorbed in the skin are harmful."
Indeed, two separate FDA studies published in 2019 and 2020 found that ingredients commonly found in chemical sunscreens, including oxybenzone, can be absorbed in the skin and linger for days. However, what Brod and other dermatologists are quick to point out is that there is no evidence to suggest that it's harmful and causes cancer. In both studies, the authors emphasized that their findings did not mean people should refrain from wearing sunscreen.
"The benzene issue was a one-off. There were some impurities in the production process, but it's been fixed," Rigel said, adding that a separate study found that exposure to benzene in a sunscreen — assuming you used it everyday for a year — was still less than the amount of benzene inhaled when filling up a tank at the gas station.
The tide is turning on research suggesting that sunscreen poses environmental risks, too. Aaron Boyd, a PhD candidate at the University of Alberta in Edmonton, Canada, recently demonstrated how exposure to sunscreen may actually be a lower risk for small aquatic animals compared to some tests done on each individual chemical.
"Researchers overwhelmingly perform studies testing the toxicity of UVFs [ultraviolet filters] in isolation by exposing test organisms to one chemical at a time," Boyd said in a media statement, describing an experiment on water fleas. "In fact, less than 3% of aquatic toxicology studies published to date have investigated whole sunscreen mixtures, leaving a massive knowledge gap to be addressed."
When it comes to sunscreen, the FDA isn't responsible for safety testing. Instead, it sets the standards that companies have a responsibility to follow. However, the FDA has proposed experiments to be done to better understand the effects of sunscreen.
"But those experiments are basically done every weekend in the summer when tens of millions of people are using sunscreen. And they're not seeing any of those hypothetical risks," Rigel said. "So the bottom line with that, is it's not a major risk to wear sunscreen. The flip side is what's the risk of not using sunscreen, right? That is a proven risk and the risk is skin cancer."
