Chemistry of sunscreen

Me, hiding from the sun

It’s summer time!

It’s time for longer days, walks, sea, beach, hiking and nature.

But it is also time for sunscreens.

Have you ever ask yourself how do sunscreens protect our skin from the sun? Here, you will find the answer.

Sunscreens protect from the UV light emitted from the sun. UV light is a particular kind of light of the electromagnetic spectrum.

The electromagnetic spectrum

UV light (or rays) can be divided into three sub-types:

  • UV-A : 95% of the solar UV radiation is UV-A. This kind of light caused indirect DNA damage and contributes to skin cancer,
  • UV-B: 5% of the solar UV radiation is UV-B. This kind of light causes direct DNA damage and is the major contributor to skin cancer,
  • UV-C: it is filtered by the ozonosphere and doesn’t reach the Earth.

Sunscreen lotions contain molecules which are able to block UV-A rays only, or UV-B rays only, or both of them.

Organic UV-rays blockers

Menthyl anthranilate, for example, is a great UV-A blocker, homosalate is an excellent UV-B blocker and oxybenzone is able to block both UV-A and UV-B rays.

Protect our skin is of vital importance, but the use of sunscreen has also a negative effect on the coral reef.

Oxybenzone and other chemicals of sunscreens induce the bleaching of corals, which is the first signal of their death.

The concentration of oxybenzone is so elevated in the Hawaii (0.8 – 19.2 ug/L) that the government will ban sunscreens containing oxybenzone from 2021.

What is the solution to protect both our health and the coral reef?

Inorganic UV-rays blockers

Data show that sunscreens based on inorganic minerals, such as titanium oxide and zinc oxide, seem to be the safest for the coral reef, while protecting our skin from the UV light.

References:

Danovaro et al., “Suncreens cause coral bleaching by promoting viral infections”, (2008), https://doi.org/10.1289/ehp.10966

Lee Granger and Brown: “The chemistry and HPLC analysis of chemical sunscreen filters in sunscreens and cosmetics”, (2001), https://doi.org/10.1081/JLC-100107346

Raffa et al., “Sunscreen bans: Coral reefs and skin cancer”, (2018), https://doi.org/10.1111/jcpt.12778

Compoundchem: https://www.compoundchem.com/2014/06/05/sunscreenchemicals/

Cen: https://cen.acs.org/environment/pollution/Periodic-Graphics-Sunscreen-coral-reef/97/i28

Published by Martina Bodner

Biotechnologist, PhD Candidate in Food Chemistry, Science Teacher, STEM and autism advocate, mother.

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