Although summer may be coming to a close, the debate on sunscreen safety rages on.
Earlier this summer, the U.S. Food and Drug Administration declined to put warning labels on sunscreens that contain nanomaterials, while requiring other labeling information.
Sunscreen manufacturers increasingly are producing sunblocks with nanoscale ingredients, such as titanium dioxide and zinc oxide, because they rub on clearly without leaving a white film or paste.
Indeed, when Consumer Reports, a Yonkers, N.Y.-based organization, looked into the situation, it found that even sunscreens labeled as nano-free had nanoscale particles.
Scientists worry these nanoparticles, which are measured in nanometers, might be dangerous to human health. They say these particles have fundamentally different physical, biological and chemical properties than their larger counterparts.
"The worry is that these particles could generate free radicals or get some place in the body that larger-sized molecules otherwise wouldn’t be able to get to," said Carolyn Cairns, a scientist with Consumer Reports.
She also pointed to more widespread environmental effects.
"What happens to these chemicals when they wash off your body and get into the water column?" she said. "Or when you put it on burnt, damaged skin?"
And a growing chorus of environmentalists are saying that while there’s not enough research showing the chemicals are safe, the research that has appeared is ominous.
In a study published last year in the journal Toxicological Sciences, an Australian researcher wanted to see what happened to these chemicals after being applied to the body for several days in a row.
So Brian Gulson, a retired professor of environmental science at Macquarie University in Sydney, collected two groups of volunteers at the beach and had them apply sunscreen for five consecutive days.
One group applied a sunscreen with nano-sized zinc particles – 19 nanometers in size. The other group applied a sunscreen with a slightly larger-sized particle – 100 nanometers -- though still in the nano realm.
Gulson found that after just two days, the volunteers had trace amounts of the chemical in their blood.
Gulson points out that both formulas were absorbed by the skin – not just the smaller, nano-sized one. He said the levels detected in the blood were extremely low.
But for environmental groups like Friends of the Earth, that little bit is enough to cause concern.
In 2010, the group kicked off a public relations campaign highlighting nanoparticle concerns and urged the federal government to do more research and warn consumers with labels. In 2006, the group released a report addressing many of these concerns.
“What many beachgoers and others enjoying the summer sun don’t know is the sunscreens they’re using contain manufactured nanoparticles that pose health risks,” said Ian Illuminato, the organization's health and environment campaigner. “What more and more studies are showing is manufactured nanoparticles may damage cells and have harmful health repercussions. They also pose risks to workers and the environment, and there’s no evidence that they make sunscreens more effective at blocking the sun’s harmful rays.”
Cairns, from Consumer Reports, agreed. She says there is no evidence that nanosunscreens work any better than those labeled nano-free, though her organization's study showed that even those labeled nano-free had nanoparticles.
And even if they were without the nano-sized chemicals, other active ingredients in sunscreens may not be so safe either, said Jennifer Sass of the Natural Resources Defense Council, an environmental organization in Washington, D.C.
For instance, a carbon-based chemical called octyl methoxycinnamate has shown the potential for toxicity in laboratory animals.
So does that mean consumers should avoid sunscreen? Cairns said consumers still should use sunscreen if spending time in the sun. But floppy hats, long-sleeved clothing and pants can help to minimize the amount of sunscreen needed.
"I just use it on my face and hands," said Sass, who covers the rest of her body in clothing.
She also advises that people stay out of the sun during the peak hours between 10 a.m. and 2 p.m.