ONE WILD WORLD — NEWSLETTER

Issue #018  |  Things Companies Don’t Want You to Know  |  May 2026

In 2019, the US Food and Drug Administration ran a clinical trial on its own approved sunscreen ingredients. The results were so unexpected that the agency proposed pulling “safe” status from twelve out of the sixteen filters Americans had been using for decades. Six of them, including the most common chemical filter on the planet, were absorbing into the bloodstream at sixteen times the FDA’s own safety threshold after a single application. Multiple studies have since detected oxybenzone in human breast milk, fetal cord blood, and amniotic fluid. And the most uncomfortable question of all — the one almost no one wants to ask out loud — turns out to have a much weaker answer than you’ve been told: does sunscreen actually prevent skin cancer?

BY THE NUMBERS

For decades, the assumption baked into every public-health message about sunscreen was simple. The chemicals in the bottle stay on your skin. They block UV. They wash off in the shower. End of story.

Then, in 2019, the US Food and Drug Administration ran an actual clinical trial. Researchers asked twenty-four healthy adults to apply standard sunscreen four times a day for four days, exactly as the label instructed. They drew blood. Then they measured what was actually in it.

Six of the most widely used chemical filters — oxybenzone, avobenzone, octocrylene, homosalate, octisalate, and octinoxate — had been absorbed into the participants’ bloodstream at concentrations far above the FDA’s own safety threshold of 0.5 nanograms per millilitre. After just one application, oxybenzone showed up in the blood at levels up to sixteen times that threshold. After four days, the chemicals were still circulating systemically. The FDA repeated the experiment in 2020 with a larger group of participants. The results were the same.

The FDA’s response was unusually frank. In a 2019 proposed rule, the agency stated that out of the sixteen chemical UV filters it had approved over the years, only two — the mineral filters zinc oxide and titanium dioxide — had enough evidence to be confidently classified as Generally Recognised As Safe and Effective. The other twelve — including oxybenzone, octinoxate, and most of the workhorse chemicals in the average American sunscreen — were reclassified as Category III: meaning the FDA had no idea whether they were safe. Not safe. Not unsafe. Just unknown.

These were filters Americans had been smearing on themselves — and on their children — every summer for decades.

The reason the FDA’s 0.5 nanogram threshold matters is that any drug or chemical reaching that concentration in human blood legally requires a full toxicology assessment before it can be considered safe. The FDA’s own data showed sunscreen filters were blowing past that threshold by a factor of ten, twenty, even thirty. That toxicology assessment had never been done.

In the years since, independent researchers have started doing the work. The findings have not been reassuring.

Oxybenzone — the most-studied of the chemical filters — has been detected in human breast milk, in amniotic fluid surrounding unborn babies, in umbilical cord blood, and in urine samples from over 96% of Americans tested by the Centers for Disease Control. In laboratory cell studies, oxybenzone activates estrogen receptors at roughly 60% of the strength of the body’s own estrogen. It simultaneously blocks androgen receptors, the system that responds to testosterone. In simpler terms, it acts like a weak hormone in your body.

Oxybenzone is not the only one. Octinoxate, banned in Hawaii alongside oxybenzone, is also a confirmed endocrine disruptor. Octocrylene degrades over time into benzophenone, a suspected human carcinogen — meaning the older a bottle of sunscreen sits in your bathroom cabinet, the more carcinogen it actually contains. Avobenzone breaks down rapidly in sunlight, producing reactive free radicals on the skin. Homosalate has been linked in animal studies to disruption of estrogen, androgen, and progesterone signalling.

None of these chemicals were ever tested at the level of scrutiny we now apply to a new prescription drug. They were grandfathered in under regulatory frameworks designed for an era when the assumption was that nothing topical reached the bloodstream. That assumption is now demonstrably wrong.

Here is the part of the sunscreen story that genuinely surprises most people: the evidence that sunscreen prevents skin cancer is not nearly as robust as you have been told.

In all of medical literature, there is exactly one randomised controlled trial — the gold standard of medical evidence — that has tested whether sunscreen reduces the incidence of melanoma. It is called the Nambour Trial, and it was conducted in Queensland, Australia between 1992 and 1996. A follow-up published in 2011 reported that, after ten years, the daily-sunscreen group had developed eleven new melanomas while the control group had developed twenty-two. That sounds like a clear protective effect. Look closer and the picture is murkier: the result was only borderline statistically significant (P = 0.051), the absolute numbers were small, and the protective effect for invasive melanoma rested on three cases versus eleven.

That is the entire body of randomised evidence we have. One trial. Ambiguous numbers. From thirty years ago.

Observational studies, where you compare sunscreen-users to non-users, paint an even messier picture. A 2018 meta-analysis published in the European Journal of Cancer Prevention pooled data from 29 studies covering 313,717 participants and 10,670 cases of skin cancer. The result was striking: there was no statistically significant association between sunscreen use and reduced skin cancer risk. Not for melanoma. Not for non-melanoma. Sunscreen users in these studies were, if anything, slightly more likely to develop skin cancer than non-users — almost certainly because people who burn easily use more sunscreen, not because the sunscreen caused the cancer.

What sunscreen has been proven to do, beyond reasonable doubt, is prevent sunburn and reduce the risk of squamous cell carcinoma — a non-aggressive form of skin cancer that almost never kills anyone. That is a genuine benefit. It is just not the benefit that has been used to sell sunscreen as a public-health imperative for the last forty years.

There is one more uncomfortable wrinkle in the sunscreen evidence base, and it concerns human behaviour. In 1999, a group of European researchers ran a double-blind randomised trial. They gave young adult volunteers either SPF 10 or SPF 30 sunscreen, told them to use it as they normally would on holiday, and then measured how long they spent in direct sun.

The SPF 30 group sunbathed, on average, twenty-five percent longer per day than the SPF 10 group. Three hours versus two-point-four hours. Same beach. Same volunteers. Different bottle.

The researchers replicated the trial the following year using personal UV dosimeters strapped to participants’ wrists, and confirmed it: a higher SPF directly causes people to stay out longer. The total UV dose received over the day was, in many cases, no different between the two groups. In some cases, it was higher for the SPF 30 users.

In other words: the sunscreen does not extend your safe time in the sun by a factor of thirty. It extends your sense of safety by a factor of thirty. Those are very different things, and the gap between them may be the reason that, despite the global sunscreen industry growing into a $13 billion business, melanoma rates in countries like Australia, the United States, and the UK have continued to climb almost every year for the last forty years.

There are two simple reasons the regulatory situation in the United States hasn’t changed even after the FDA’s own 2019 and 2020 findings. The first is industry resistance. The chemical filter market in the US generates billions of dollars a year for the companies that make sunscreens, and removing GRASE status from twelve filters at once would, in effect, force a complete reformulation of the entire American sunscreen industry within a few years. The industry response to the FDA’s 2019 proposed rule was, predictably, to demand more data, more time, and more delays.

The second reason is more uncomfortable. Public-health authorities have spent forty years telling people that sunscreen is a public-health imperative. Walking that back — even partially, even with appropriate nuance — would mean admitting that the certainty of the message went well beyond the certainty of the evidence. That is a very hard admission for any health agency to make. So the situation has remained frozen: the chemicals stay on the shelves, the public-health messaging stays the same, and the underlying evidence keeps quietly accumulating in journals nobody outside dermatology bothers to read.

In December 2025, after twenty-six years of paralysis, the FDA finally proposed approving its first new sunscreen filter since 1999 — bemotrizinol, a broad-spectrum chemical that’s been used safely in Europe for over twenty years. As of this writing, in spring 2026, even that has not been finalised.

A 2019 FDA trial that showed sunscreen chemicals enter the bloodstream at sixteen times the safety threshold. Twelve out of sixteen filters reclassified as “unknown safety.” Oxybenzone in breast milk and amniotic fluid. A single ambiguous randomised trial supporting forty years of public-health certainty. And the small, awkward fact that higher SPF may simply mean longer sunbathing.

Sunscreen is not a public-health miracle. It’s a behavioural patch with unknown chemistry, sold as a certainty by an industry that never had one.

SOURCES

Matta M.K. et al. — “Effect of Sunscreen Application Under Maximal Use Conditions on Plasma Concentration of Sunscreen Active Ingredients: A Randomized Clinical Trial”, JAMA (May 2019) — the original FDA absorption study

Matta M.K. et al. — “Effect of Sunscreen Application on Plasma Concentration of Sunscreen Active Ingredients: A Randomized Clinical Trial”, JAMA (January 2020) — follow-up larger study

US FDA — Proposed Rule: Sunscreen Drug Products for Over-the-Counter Human Use, 84 FR 6204 (February 26, 2019) — GRASE Category III reclassification

Green A.C. et al. — “Reduced Melanoma After Regular Sunscreen Use: Randomized Trial Follow-Up”, Journal of Clinical Oncology (2011) — the only RCT melanoma data ever published

Silva E.S.D. et al. — “Use of sunscreen and risk of melanoma and non-melanoma skin cancer: a systematic review and meta-analysis”, European Journal of Cancer Prevention (2018) — the 313,717-participant null result

Autier P. et al. — “Sunscreen use and intentional exposure to ultraviolet A and B radiation: a double blind randomized trial”, British Journal of Cancer (2000) — the SPF behavioural-paradox study

Krause M. et al. — “Sunscreens: are they beneficial for health? An overview of endocrine disrupting properties of UV-filters”, International Journal of Andrology (2012)

DiNardo J.C. & Downs C.A. — “Dermatological and environmental toxicological impact of the sunscreen ingredient oxybenzone/benzophenone-3”, Journal of Cosmetic Dermatology (2018)

Centers for Disease Control and Prevention — National Health and Nutrition Examination Survey (NHANES), data on oxybenzone detection in US population

Environmental Working Group — “The trouble with sunscreen chemicals”, EWG Guide to Sunscreens (annual report, 2024 edition)

Cochrane Skin Group — systematic review of sunscreen use and skin cancer prevention (2015)