Researchers investigate the possible environmental cost of sunscreen

As the weather gets warmer and Canadians slather on sunscreen to enjoy the heat, some environmental scientists are worried about how our sun protection could be harming aquatic life once it leaves our skin.  

A portion of sunscreen is washed off our bodies when we bathe at home or go for a swim, and from there it enters lakes, rivers and the ocean. With millions of people around the world using sunscreen, the small amount that's washed off starts to add up. 

"The sunscreens that you put on, the pharmaceuticals that you take, you know a portion of these are getting back into the environment," said Brett Sallach, an assistant professor in environmental chemistry at the University of York in the U.K.

"And that's really where our research focuses to try to understand how much is being released and then what effects that might have."

New research suggests some of the components of certain sunscreens may harm both coral reefs and freshwater fish. Some of that work led to Hawaii banning sunscreens that contain the chemicals oxybenzone and octinoxate earlier this year. 

Both of those chemicals are UV filters, which are used in some sunscreens to block or absorb ultraviolet radiation. Some lab tests show that these chemicals can harm coral and could be a factor in coral bleaching.

"This isn't a vanity issue. These are compounds that are really important for human health protection. So we want to make sure we have a really good environmental risk assessment before we make draconian changes to the products that are available," said Sallach.  

The new research doesn't make Dr. Cheryl Rosen question her faith in sunscreen. She's a certified dermatologist and head of the division of dermatology at Toronto Western Hospital. 

She said the benefits of sunscreen on human health — helping prevent skin cancer, sunburns and other skin damage — are well known.

"Yes, we have to be aware of the research that's going on looking at sunscreens and their effect on coral and their effect on fish. But so far there is nothing beyond work in the laboratory to suggest that we need to avoid them," said Rosen.   

Some of that lab work is being done by environmental toxicology professor Kyungho Choi at Seoul National University in South Korea.

His work shows that UV filters can harm freshwater fish. 

Choi's been studying UV filters like benzophenone-3 (BP-3) and octyl methoxycinnamate (OMC) for eight years, and running experiments seeing how fish in the lab react after being exposed to these chemicals. 

"We have found that these compounds damage reproduction in fish and also hormonal balances," he said. "In addition, we found these compounds could damage kidney function and neurological behavioural function." 

Choi said far more work needs to be done to determine how fish in real world ecosystems could be impacted by their exposure to sunscreen. But it would be hard to determine how sunscreens alone are affecting ecosystems when there are other environmental factors at play.

Even so, "we cannot simply ignore the possibility of ecological consequences based on this experimental data," said Choi.

Sallach said the decline in coral reef health can't be entirely pinned on sunscreen's UV filters. Ocean acidification, climate change, and pollution are probably having a bigger impact on coral.

In the U.S., the National Oceanic and Atmospheric Administration has published an infographic online highlighting the dangers of sunscreen's UV filters, but a spokesperson said the agency is not doing any active research on the subject.

Nor is the federal Department of Fisheries and Oceans in Canada.  

The department is instead trying to understand the environmental effects of contaminants like microplastics, pesticides, along with oil- and gas-related contaminants, said spokesperson Carole Saindon in an email. 

Choi said he would like people to avoid going out during the hottest parts of the day to cut down on their sunscreen use and cover up using UV-protective clothing, which would also limit the amount of sunscreen needed.

If people are concerned about UV filters from sunscreen possibly damaging the environment, there are other options. Rosen suggests mineral sunscreens that contain titanium dioxide and zinc oxide. They help protect against UV light without using benzophenone UV filters.

Sallach said it will take a co-operative effort to answer lingering questions around chemicals like benzophenone UV filters and their effects on the environment.

"We really need to put programs in place," said Sallach.

"This needs to be kind of at a more global level with multiple governments working in co-ordination together, to really get an understanding of what the actual exposure of organisms in the oceans are to these compounds."