Sunscreen chemicals, particularly those containing oxybenzone and octinoxate, pose threats to coral reefs. Last year, Hawaii even prohibited sunscreens using chemicals that impact their reefs – a ban that will go into effect in January 2021. Now, a new study suggests that another chemical found in sunscreen and other personal care products, octocrylene, could also be harmful to corals.
Moisturizing agents, tanning oils, hair spray, and cosmetics all contain octocrylene. According to the study, corals can easily absorb octocrylene, which can be toxic at high concentrations. However, the ocean is dynamic and capable of diluting octocrylene that humans introduce into seawater near corals. Thus, the researchers studied how the corals responded to both toxic and non-toxic amounts of octocrylene. They worked with corals from the Arabian Sea near Oman and exposed them to octocrylene at a naturally-occurring, non-toxic level (5 micrograms per liter of seawater) and then three more concentrated levels that represent the longer-term accumulation of octocrylene in the ocean (50, 300, and 1000 micrograms per liter of seawater).
After 7 days, the researchers found that octocrylene accumulated in corals in a cryptic way – as fatty acid esters – that may have prevented previous studies from accurately detecting the chemical and its effect on corals. The corals that had to endure the two highest concentrations of octocrylene were inactive. But even corals immersed in seawater with 50 micrograms of octocrylene per liter of seawater (which is ten-fold greater than what has been found in seawater surrounding coral reefs) absorbed octocrylene at toxic enough levels that upset their metabolisms. Additionally, the corals had elevated levels of the metabolite acylcarnitine, which indicates that the octocrylene had disrupted the corals’ physiology.
The well-documented impacts of common sunscreen chemicals on coral reefs created a market for “reef safe” sunscreens. What remains to be seen is if we will soon be seeing more “reef-safe” hair and skin care products.