Does sunscreen cause cancer?

By June 8, 2023 Health, Science

We came across the following post on the social media platform Reddit:

In the post, a user mentioned that he had found a preferred sunscreen product, but he was considering switching to a different product because it contained ‘5% octocrylene’, and he had heard that the ingredient could cause cancer.

As we researched this topic further, we found that there were other sentiments online expressing distrust of sunscreen due to the belief that it caused cancer. In one other post on Reddit, for example, a user stated that their client, in the belief that sunscreen caused cancer, had begun using olive oil instead for protection against the sun.

Recalling Past Scares

When we investigated this link, we found news reports from 2021 in which cancer-causing chemical compounds had been found in sunscreen products, prompting a recall by the brands Neutrogena and Aveeno under their parent company Johnson & Johnson (J&J). Other brands would also withdraw their products from sale following the news.

Independent testing had revealed that the products contained benzene, which increases the risk of developing leukaemia and other blood disorders. The discovery was highly concerning as the harmful compound was present in 27% of tested samples, and there is no safe level for benzene in sunscreen products.

Even so, Christopher Bunick, a dermatologist at Yale Medicine, emphasises that the presence of benzene in sunscreen is a result of unintentional contamination rather than it being a necessary ingredient. He mentions that it likely formed during the manufacturing process and remained undetected due to a lack of sufficient quality control. Crucially, he points out that it could have ‘happened to any product and not just sunscreen’.

The Octocrylene Question

When we looked up octocrylene, the chemical compound specified by the post’s author, we found that the link to cancer emanated from a study by the Laboratory of Biodiversity and Microbial Biotechnology of the Oceanological Observatory of Banyuls-sur-Mer. The laboratory is run jointly by Sorbonne University and the French National Centre for Scientific Research.

The research from 2021 found that ‘octocrylene degrades within the bottles themselves into a known carcinogenic and endocrine disrupting compound: benzophenone’. Benzophenone is a suspected carcinogen and endocrine disruptor that can cause issues with key hormones and reproductive organs. It is banned in food products and packaging in the US.

Following the release of their findings, which are published in the journal Chemical Research in Toxicology, the researchers petitioned the Food and Drug Administration (FDA), the US regulator of sunscreens, to pull products containing octocrylene from the market.

At present, octocrylene has not been banned from sunscreen products. The FDA currently recognises octocrylene as an acceptable active ingredient in sunscreen up to a concentration of 10%. The European Union has also approved octocrylene for use as a UV (ultraviolet ray) filter in cosmetic products up to a concentration of 10%, following an opinion issued by the Scientific Committee on Consumer Safety that the evidence of effects on endocrine from octocrylene were not conclusive.

Octocrylene is often used as a chemical filter in sunscreen because it is an effective and photostable absorbent of UV rays. It also has moisturising properties and works well in combination with other UV filter ingredients.

Even so, the FDA recognises that there is insufficient data to conclusively indicate the safety of octocrylene and other chemical filters (which absorb UV) in sunscreens. The FDA is currently proposing that only sunscreens containing zinc oxide and titanium oxide—mineral filters which reflect UV—are regarded as ‘generally regarded as safe and effective’ (GRASE for short).

Under the proposed order, octocrylene and other chemical filter sunscreens would not receive GRASE determination. The FDA is in the process of determining how to implement the proposed order while further studies are being conducted to determine the safety of octocrylene and other chemical filter ingredients.

Olive It Up?

Due to the uncertainty over some ingredients in sunscreen, some have mooted using herbal and plant-based oils instead, with the individual in the second post said to be using olive oil. While this is an unorthodox choice today, there is some precedent for olive oil being used as sunscreen. Ancient Greeks, for instance, were found to ‘use olive oil to protect their skin from the sun and for care after sun exposure’.

Historical practices, however, are not always a fount of wisdom. Modern scientific studies testing the sun protection factor (SPF) of various herbal and plant-based oils found that olive oil had an SPF of around 8. Though it was found to have a higher SPF than all the other oils tested in the study, it still offers far less protection than many sunscreens.

A common misconception is that the SPF value is related to the duration of skin protection provided. Rather, SPF is a measure of how much UV radiation is required to produce sunburns relative to skin that has no protection. This means that a sunscreen with high SPF value would be able to protect skin from UV radiation under much more intense solar energy than one with a low SPF value.

The FDA recommends sunscreens with an SPF of at least 15, as ‘only broad spectrum sunscreen products with an SPF of at least 15 have been shown to reduce the risk of skin cancer and early skin ageing caused by the sun when used as directed with other sun protection measures’. This means that olive oil, with its SPF value of 8, is ineffective as a substitute for sunscreen.

Sun-screening the Facts

While this factcheck focuses on octocrylene and the use of olive oil as a substitute, a review of the information available indicates that there are several lingering anxieties over the use of sunscreen.

These include concerns over another chemical filter, oxybenzone, over its ability to disrupt hormones, studies that found an association between higher sunscreen use and skin cancer, and concerns that nanoparticles in sunscreens could penetrate the bloodstream and cause health problems.

In each case, the concerns have been refuted or have not been sufficiently substantiated. In the studies that found a link between sunscreen use and skin cancer, the false association was made because individuals who used sunscreen more often were those who sunbathed or experienced sunny climates more often than others, and the higher exposure to the sun was the factor that raised the risk of skin cancer.

Nanoparticles in sunscreen have also not been shown to penetrate beyond the skin layer, and the study with the hormone disrupter oxybenzone—done in rats—required a human dose equivalent to 277 years of sunscreen use.

While some scientific studies have demonstrated the need for further research into some of the ingredients used in sunscreen, evidence indicating that they are harmful are inconclusive, and there is no evidence that sunscreens cause cancer specifically.

In contrast, exposure to UV radiation in sunlight is a major cause of skin cancer. There has been an increase in younger patients being diagnosed with cancer in Singapore, which experts have attributed to ‘low sun protection awareness’ and not treating sun protection as a priority. Moreover, limiting skin exposure to UV rays is the only preventable risk factor for skin cancer.

In conclusion, it is false that sunscreen causes cancer, and not using sunscreen may instead contribute to a higher risk of skin cancers.

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