Why use biodegradable sunscreen in La Paz? What the rules and science say
Because it's required and because it protects the sea. To swim with whale sharks, Mexico's official standard NOM-171-SEMARNAT-2018 prohibits using non-biodegradable sunscreens or tanning products before getting in the water [1]. Also, a lab study found that oxybenzone, a common UV filter, deforms and damages coral larvae [2].
In La Paz the sun is strong and you'll spend hours on the boat. Sunscreen isn't optional. But the one you choose does matter, and not just for you.
What the rules say
The standard regulating whale shark swimming states that, before entering the water, users must not use non-biodegradable sunscreens or tanning products [1]. That's why only biodegradable sunscreen is allowed on whale shark tours.
What science says: oxybenzone and corals
A study published in 2016 tested in the lab the effects of oxybenzone (benzophenone-3), a very common UV filter in sunscreens, on coral larvae (called planulae) and on coral cells [2].
- Oxybenzone turned planulae from mobile larvae into deformed, immobile forms [2].
- The authors describe it as a skeletal endocrine disruptor for coral [2].
- Its toxicity was higher in light, i.e. the conditions of a sunny, shallow reef [2].
- The study also measured oxybenzone contamination in waters of Hawaii and the US Virgin Islands [2].
Why it matters in the Sea of Cortez
Because the reefs here are alive and recovering. Cabo Pulmo, for example, increased its fish biomass almost sixfold in a decade thanks to protection [3]. Being careful about what we bring into the water is part of keeping it that way.
How to protect yourself without harming the sea
- Use biodegradable sunscreen and check that it doesn't contain oxybenzone.
- Apply it early, before heading out, so it absorbs instead of washing off in the water.
- Cover up: long-sleeve rash guard, cap and sunglasses with a strap. Less exposed skin, less sunscreen.
- Don't apply sunscreen right before jumping in with the whale shark.
See the full list in what to bring on a boat tour in La Paz.
Experience it with Keabelmet
Frequently asked questions
Is biodegradable sunscreen required in La Paz?
For whale shark swimming, yes: NOM-171-SEMARNAT-2018 prohibits using non-biodegradable sunscreens before entering the water [1].
Why does oxybenzone harm corals?
In the lab it deformed and immobilized coral larvae and acted as a skeletal endocrine disruptor, with higher toxicity in light [2].
What if I don't have biodegradable sunscreen?
Cover up with a rash guard, cap and long sleeves, and pick up a biodegradable one in La Paz before your tour.
Scientific sources
The wildlife, season and geography facts in this article come from these publications. The [n] citations in the text link here.
- Secretaría de Medio Ambiente y Recursos Naturales (Semarnat) (2019). NOM-171-SEMARNAT-2018, observación y nado con Tiburón Ballena (Rhincodon typus). Diario Oficial de la Federación, 19 de noviembre de 2019. sidof.segob.gob.mx/notas/docFuente/5579132
- Downs, C. A., Kramarsky-Winter, E., Segal, R., Fauth, J., Knutson, S., Bronstein, O., Ciner, F. R., Jeger, R., Lichtenfeld, Y., Woodley, C. M., Pennington, P., Cadenas, K., Kushmaro, A. & Loya, Y. (2016). Toxicopathological effects of the sunscreen UV filter, oxybenzone (benzophenone-3), on coral planulae and cultured primary cells and its environmental contamination in Hawaii and the U.S. Virgin Islands. Archives of Environmental Contamination and Toxicology 70(2): 265–288. doi.org/10.1007/s00244-015-0227-7
- Aburto-Oropeza, O., Erisman, B., Galland, G. R., Mascareñas-Osorio, I., Sala, E. & Ezcurra, E. (2011). Large recovery of fish biomass in a no-take marine reserve. PLoS ONE 6(8): e23601. doi.org/10.1371/journal.pone.0023601
