Ultraviolet light — like the harsh sunlight at the beach — can cause mineral-based titanium dioxide sunscreen to leach metals and inorganic material into the water, according to a preliminary study published yesterday.

The new research introduces the possibility that titanium dioxide sunscreen is not as safe for ocean life and human health as previously thought.

“It’s kind of horrifying,” said Craig Downs, a researcher with Haereticus Environmental Laboratory, who reviewed the paper before its publication. “It solidifies further the concept that sunscreen pollution is a major problem in high-tourist areas.” 

Downs is most concerned about the amount of heavy metals — such as lead, nickel, cobalt and aluminum — that researchers found in titanium dioxide sunscreens.

Many conscious consumers have been told that mineral-based sunscreens, with active ingredients of zinc oxide or titanium dioxide, are the eco-friendly option because they do not contain two chemicals linked to coral bleaching: oxybenzone and octinoxate. 

Products with oxybenzone and octinoxate will be banned in Hawaii starting in 2021, specifically because they are linked to coral bleaching and hormone changes in marine life. Downs participated in the research that lead to this ban, but doesn’t think it goes far enough.  

“There’s a reason it’s called sunscreen pollution,” he said. “Whatever you have on your skin is going to come off your skin and get in the water.” 

The laboratory study found UV light increases how quickly titanium dioxide sunscreen leached trace metals into the water. These compounds could negatively impact marine life if they’re deposited into the water in large amounts. 

“The normally low environmental concentrations of some elements and the toxicity of others could be having a serious adverse effect on marine ecology in the Mediterranean Sea,” the Spanish researchers wrote. “This risk must not be ignored.”  

More research is needed to determine what the real-world effects of these heavy metals have on ocean health and if Hawaii’s waters have already been affected by heavy metals from these sunscreens. 

But Downs said the study has really alarmed him, and he’s planning a trip to test Hawaii’s waters for such heavy metal pollution. 

“Aluminum can be incredibly toxic for fish,” he said. “For Hawaii that’s a really big concern.” 

But it’s not just fish that researchers are worried about. The study also found these sunscreens can cause eutrophication — an increase in the levels of nitrogen and phosphorus in the water that allows coral-harming algae to grow. 

“That means when you get 6,000 tourists at Hanauma Bay and they all have sunscreen, not only are they putting in oxybenzone and heavy metals, but they’re also causing eutrophication of that bay, and that’s bad,” he said.

It’s still important to protect your skin from the cancer-causing UV rays. Conscious consumers can invest in more UV-blocking clothing, wear hats and avoid the beach during the sunniest parts of the day.

Downs said sunscreens with titanium dioxide can still be safe — if they’re from high-quality manufacturers. 

“In cheap sunscreens you’re going to find more heavy metals,” he said. Sunscreen brands that use pharmaceutical-grade titanium dioxide will be safer for the environment and your health, but pricier. 

Other mineral sunscreens that have zinc oxide as their active UV-blocking ingredient are still considered safe for reefs. But just like mineral sunscreens with titanium dioxide, Downs predicts research will find that low-quality zinc oxide can also deposit harmful heavy metals into the environment. 

“This is the major take-home message: you get what you pay for,” he said.