ARS Scientist Shines Light on Sunscreen Absorption
A young soybean field in Wisconsin. Soybean oil can be processed to create natural sunscreen. (Photo by Michael Russelle)
Many people work hard to achieve a bronze summer tan. Medical professionals, though, often urge the plentiful application of sunscreen to ward off sunburn and potential skin cancers. But, just how healthy is that sunscreen? One scientist with the Agricultural Research Service (ARS) says there are problems – and he has a burning desire to create better options.
For William Hart-Cooper, research chemist at the ARS Bioproducts Research Unit (BRU) in Albany, CA, both human and environmental health are at stake. For people, the issues with petroleum-based sunscreens often revolve around not only skin sensitivity, but how their external application can affect the body internally.
Many popular sunscreens contain hydrophobic (water-repelling) molecules that penetrate the skin and enter the bloodstream. These carbon-based synthetic “chemical” sunscreens are usually made from a petroleum-based source and can interfere health and development. “It’s been studied pretty extensively, including by the FDA” Hart-Cooper said. “Once applied, they penetrate though the skin very quickly and into the bloodstream – within an hour – and remain there for weeks.”
Repelling water is good in a sunscreen, from a performance standpoint, but it’s a different story after they enter the bloodstream. Hart-Cooper said that some studies have shown that these molecules mimic the activities of certain hormones, becoming what’s known as endocrine disruptor chemicals (EDC).
According to the National Institutes of Health, EDCs interfere with hormone activities and may have lasting effects on the body, including affecting reproduction, breast development and cancer, prostate cancer, the thyroid, metabolism, and obesity.
“I think there's a lot of concern that these chemicals, once they penetrate your skin, can influence your hormone systems and development, especially in younger people and children,” Hart-Cooper said.
Fortunately, there are other options available. Hart-Cooper noted that consumers should read ingredient labels when purchasing UV (ultraviolet light) blockers and avoid those containing homosalate, octinoxate, and oxybenzone. “Those are all carbon-based synthetic molecules… and are often referred to as chemical sunscreens.”
Mineral-based sunscreens, usually made with some sort of modified zinc oxide or titanium dioxide, are also available. While these are safer alternatives, people often prefer the chemical sunscreens because they don’t leave a white paste or a film on the skin.
As it turns out, the sunscreen that’s safer for people is also safer for the environment; many scientists believe chemical sunscreens contribute to coral bleaching. “Bleaching” occurs when environmental stressors cause coral to expel the algae they contain, turning the coral white. While not immediately fatal, bleaching may eventually cause coral reefs to starve to death. This problem is exacerbated by the persistence of conventional sunscreens, which show little to no biodegradation in the marine environment.
Hart-Cooper explained that chemical sunscreens can become more toxic as they're exposed to sun or metabolized by different microbes. His work builds on that of previous ARS scientists who have, like him, sought to create sunscreens that are made from natural products that don’t create these toxic effects.
Some of that work by ARS scientists from the ARS Renewable Products Technology research unit in Peoria, IL, involved using coconut or soybean oil, and resulted in a class of sunscreens that are based on of plant oils. As part of a collaboration between the two labs, ARS scientists observed that these new sunscreens significantly biodegrade within weeks, at least 20 times faster than conventional sunscreens.
Other natural food ingredients are also working their way into sunscreens. One example is a modified version of vanillin, a naturally occurring compound that gives vanilla its flavor and scent. Once the modified vanillin comes into contact with water, like a large lake or the ocean, it breaks back down into harmless particles that rapidly biodegrade.
Ultimately, Hart-Cooper said, the sunscreens that he and colleagues are developing offer multiple advantages.
“[We’d] be reducing overall chemical use compared to some of those traditional [sunscreen] chemistries,” Hart-Cooper said. “There are a lot of aesthetic benefits to using chemical sunscreens, as long as you can address the human and environmental toxicity issues.
“The second advantage is [that] it isn't going to linger around for months or years and end up bioaccumulating in in aquatic organisms. It'll immediately start dissociating just by being diluted.” – by Scott Elliott, ARS Office of Communications