Although there is no general consensus amongst scientists, most sunscreens are suspected to harm coral reefs and other marine life.
Oxybenzone or benzophenone-3, a common chemical found in most chemical sunscreens, is one of the bad performers. It is found to be toxic to the symbiotic algae that live within corals (which performs vital duties to the coral polyps) and it stunts the growth of corals. It is believed that Oxybenzone damages coral DNA, causes deformities on the coral, initiates endocrine disruption (= interference with hormone systems) and makes coral more susceptible to coral bleaching. It also has a negative impact on the well-being of other marine life like fish, invertebrates, shellfish, etc.
Harmful are not only the particles and/or chemicals that come off while swimming but also what travels through sewage systems when washed off in the shower. Also, as sunscreen chemicals are absorbed by our skin and excreted by urine, they end up in the ocean eventually through this route.
The damaging effect of oxybenzone and in which concentrations this chemical is harmful is disputed amongst scientists. Some research, also disputed by others, consider mineral sunscreens including zinc oxide or titanium dioxide that are “non-nano” in size safe. Important to check the ‘’non-nano’’ of these products which explains the particle size. Smaller particles (‘nano’) can be ingested by the coral polyps and are still harmful.
What to do?
Unfortunately there is no scientific consensus yet on this issue. Protecting yourself from the sun is important, especially in the tropics. If you want to protect marine life, the choice for good protective clothing and staying less in the sun is a far better idea than using a lot of sunscreen. Especially if you go swimming, diving, surfing, needless to say that good sun-protective clothing is better for you and for the environment.
Chemical sunscreen, in more detail:
Oxybenzone, also called benzophenone-3 (trade names Milestab 9, Eusolex 4360, Escalol 567, KAHSCREEN BZ-3), is not the only wrong-doer. There are more chemicals in many sunscreens that can damage the reef and marine life. Screening chemical sunscreen for environmental friendliness requires more research on other chemicals that it contains like octinoxate, methyl paraben and many more. You can use as a guide a checklist of known environmental pollutants the Haereticus Environmental Laboratory published (unfortunately in the ingredient lists on sunscreens many synonyms are used for the chemicals):
- oxybenzone (=benzophenone-3),
- octinoxate (=ethylhexyl methoxycinnamate)
- 4-methylbenzylidene camphor (=Enzacamene or 4-MBC),
- para-aminobenzoic acid (PABA),
- any form of microplastic sphere or beads,
- any nano-particles.
In Mexico, areas popular with snorkelers such as Xel-Há on the Rivera Maya and Chankanaab Beach Adventure Park in Cozumel ban the use of non-biodegradable sunscreen. At the seven Solmar Hotels & Resorts in Los Cabos, guests may purchase biodegradable sunscreen on-site and are advised in advance that it is the only kind permitted in area preserves such as Cabo Pulmo National Marine Park. A bill to ban the sale of sunscreens containing oxybenzone and octinoxate was passed by the Hawaii state legislature in May 2018 and will now go to the governor’s office for his signature. If signed, the ban would start in 2021. Hawaii is set to become the first state in the US to ban the sale of sunscreen chemicals that are toxic to coral reefs and marine life.