The short answer, we really don’t know. But scientists are trying to find out.
Researchers at the University of York in Britain recently published the results of a sort of study on studies. The study reviewed past research conducted on the impact of sunscreens on coral reefs. The goal was to identify gaps in our understanding of the subject.
“Importantly, we needed to understand what areas could be considered priority for future attention in order to understand the impacts of these products, and hopefully prevent any further damage to the environment," said Dr. Brett Sallach, from the University of York's Department of Environment and Geography.
"Undoubtedly, products that can help protect against the harmful effects of UV radiation on human health are hugely important, and therefore we need reliable and extensive evidence to suggest any changes or scaling back of these products."
One of the major findings was a lack of long-term studies in real world environments. To this point, much of what we have learned has come from lab experiments. Translating lab results to ever-changing marine ecosystems remains a challenge.
For now, regulators and lawmakers will have to rely on our limited knowledge of sunscreen’s impact on the environment. This has led legislators in Hawaii to enact one of the stiffest sunscreen bans on the planet.
Until we know more, it is probably best to err on the side of caution. Use reef-safe sunscreens at the beach, lake, river, or anywhere else you may come in contact with marine life.