Some people are trading chemical sunscreens in favour of mineral versions because of fears over toxicity, pollution and effectiveness. Is there actually any difference?

Mineral sunscreen is having a moment. Amid concerns that so-called "chemical" sunscreens may be bad for our bodies, brains, and even coral reefs, mineral-based formulations have become the fastest-growing share of the global sunscreen market.

But debates over "chemical" versus "mineral" sunscreens are riddled with misconceptions. Many commonly repeated claims – such as mineral sunscreens not containing chemicals; that chemical sunscreens have been proven harmful; or that chemical sunscreens absorb UV, while mineral ones only reflect it – are misleading, even false.

The confusion begins with terminology. "Everything is a chemical," points out Brian Diffey, emeritus professor of photobiology in dermatological sciences at the UK's University of Newcastle and inventor of sunscreen's UVA star rating. What people call "chemical" filters are more accurately termed organic, since they contain carbon-hydrogen bonds, says Diffey. Inorganic filters (often called mineral), primarily titanium dioxide and zinc oxide, lack those bonds. All are chemicals.

Seeking to protect our skin and bodies from the Sun is not a new trend – nor are sunscreens, organic or inorganic. Ancient Mesopotamians used umbrellas; ancient Greeks, wide-brimmed hats. Along with various coverings, people applied concoctions to the body. In Africa, the use of ochre-based pastes, still used as sunscreen by people such as the Himba in Namibia, dates back at least 285,000 years, while the Roman writer Cornelius Celsus advised slathering the skin with olive oil.

It wasn't until the 19th Century, however, that scientists discovered ultra-violet radiation (UVR) – and realised that some ingredients, like quinine sulphate (derived from a tree bark), could absorb it. Scientists duly recommended it as a sunscreen. By 1930, researchers had found a number of other ingredients that absorbed UVR, including aesculin (from trees such as horse chestnut) and larch bark tannin. Though they wouldn't meet today's SPF standards, in terms of how they protected the skin, they all were organic ("chemical") sunscreens.

Later, dozens of other ingredients were added to this list – including those produced by mixing together different substances in a laboratory to induce a chemical reaction. Often referred to as "synthetic chemicals", these types of ingredients – including avobenzone, oxybenzone, octisalate and octinoxate – have been found to absorb UV rays far more effectively than their predecessors. Another type of sunscreen came to market, too: "mineral" sunscreens.

While they might seem more "natural", the titanium dioxide and zinc oxide in today's sunscreens are usually lab-produced.

At first, it was thought that organic sunscreens absorbed UVR, while inorganic sunscreens physically reflected and scattered UVR away from the skin – a belief that was perpetuated further in a 1970s United States Food and Drug Administration (FDA) monograph.

This idea is still commonly heard today, including from seemingly authoritative sources. It also is partly why inorganic sunscreens sometimes are also called "physical sunscreens", implying that they block out UV rays like an umbrella deflects raindrops.

"People say that mineral or inorganic sunscreens reflect ultraviolet radiation," says Antony Young, professor emeritus of experimental photobiology at King's College London and a lifelong researcher of sunscreen efficacy. "And that's........

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