Recent research by a group of Italian scientists led by Roberto Danovaro suggests that many common sunscreen ingredients cause coral bleaching. To read my summary of how this happens as well as my criticism of the research, read my previous post.
Most news blurbs and blogs are reporting the culprit sunscreen chemicals as "a paraben preservative, cinnamate, benzophenone and a camphor derivative." If you go to check the list of ingredients on your sunscreen bottle, though, that list won't be much help unless you're an organic chemist. I want people to be able to make informed decisions about the kind of sunscreen they choose to slather up with, which is why I wrote this post.
While doing research about various sunscreen ingredients to write this post, I came across an excellent online database called Skin Deep created by the Environmental Working Group. They have rated hundreds of sunscreens by dozens of brands for their chemical safety and effectiveness in providing UVA and UVB protection. You can also read about specific ingredients and find products that contain the ingredients you specify.
These four common sunscreen ingredients were found to cause coral bleaching (at potentially unnaturally high concentrations?) by Danovaro et al.:
Butylparaben (this is not an active ingredient but a common preservative in cosmetics)
These three ingredients did not cause significant coral bleaching:
Butyl methoxydibenzoylmethane (Avobenzone)
All of the active sunscreen ingredients tested by Danovaro et al. were chemical absorbers (molecules that absorb UV rays before they damage your skin). Sunscreens with physical blockers (zinc oxide and/or titanium dioxide) rather than chemical absorbers are considered safer for you and the environment. Skin Deep has a list of the 141 safest (for humans) sunscreen products, many of which lack the chemical absorbers listed above (although many of these products still contain ingredients listed above that caused coral bleaching, so read thoroughly).
Skin Deep also has product lists for active ingredients and ingredient combinations, such as zinc oxide, titanium dioxide, or zinc oxide and titanium dioxide together. You can look up your sunscreens to learn about the ingredients, or you can use the database to search for a new, better, safer sunscreen.
Some coral reef parks such as Xel-Ha and Xcaret in Mexico have restrictions on what kind of sunscreen you can use in the park. The requirements range from "...it must have the legend 'Oil Free' and natural ingredients. You can also choose any brand if it is labeled 'Paba Free' or 'Bio-degradable' " (Xcaret) to "biodegradable tanning product" (Xel-Ha). Both of these guidelines are vague and there are plenty of oil free and Paba-free sunscreens with the compounds found to cause coral bleaching. Danovaro et al.'s results as well as future research on this topic will hopefully help coral reef managers develop sound guidelines for sunscreen restrictions based on scientific research.