It’s a mantra pretty much every kid in Australia has grown up hearing. “Don’t forget your sunscreen!”

In a country with the highest skin cancer rate in the world, it’s a critical message. But just what products should they slip, slop, slap onto their skins?

Sunscreens and other cosmetic products containing UV filters are widely available in Australia. The market for sunscreen and other skincare products reached nearly $700 million in 2023 and is expected to grow 4.29 per cent annually until 2028.

But in recent years, several studies have raised concerns around the safety of some chemical sunscreens, questioning their impact on both human health and fragile marine and coral ecosystems.

As authorities including Australia’s Therapeutic Goods Administration (TGA) assess the data, experts are raising further questions about safe doses of certain chemicals used in sunscreens – given their presence in many products and how often they are applied – and the ripple effect of this on the environment in which they are used.

Skin in the game: The human impact

In 2021, a study in an American toxicology journal found octocrylene, an ingredient contained in some sunscreens, degrades into a chemical compound called benzophenone.

The International Agency for Research on Cancer, an intergovernmental agency of the World Health Organisation classifies benzophenone as “possibly carcinogenic to humans.”

The Europeans were quick to act. In July 2022, the European Commission amended its recommendations, limiting the concentration of ultraviolet (UV) filters octocrylene and benzophenone-3 in cosmetic products. This followed a March 2021 investigation into the safety of the chemical compounds in cosmetics by the Scientific Committee on Consumers Safety (SCCS).

In America and Europe, octocrylene was approved for use at a maximum concentration of 10 per cent. This applied to the application of a single product containing the UV filters, and was in line with the recommendations published by the SCCS.

But the concentration levels individuals are exposed to can surpass this safe dosage when a person applies multiple products – such as skin creams, sunscreen and makeup – each containing the chemical. Reapplication of sunscreen during sun exposure, as recommended by the Cancer Council, may also raise the dosage risk.

However, this scenario is complex, says Dr Alain Khaiat, an adviser for the ASEAN Cosmetics Association, as sunscreen is frequently rubbed off a person’s skin when they swim or towel dry.

People who use multiple products or have concerns can use physical sunscreens instead, said Rosemary Nixon, a dermatologist at Skin Health Institute, a research, education and clinical not-for-profit funded by large pharmaceutical companies.

Physical sunscreens contain tiny particles of minerals such as titanium dioxide or zinc oxide, Nixon said, which work by reflecting or absorbing the sun’s rays.

Nixon said more studies should be conducted to understand how much chemical sunscreen ingredients get absorbed into the skin to fully understand the scale of their impact on human health.

“It’s certainly raised some issues but there’s a lot more information we need,” Nixon said.

Baywatch: the marine impact

Humans are not the only ones potentially at risk from the chemical compounds. They can also have detrimental effects on marine species according to Dr Amelia Wenger, a research fellow at the University of Queensland’s Centre for Biodiversity and Conservation Science.

“With fish you can see behavioural changes [of a type] that would tend to happen before you see some sort of sublethal or acute impacts,” she said.

A study published by toxicologists in 2015 also found certain chemical ingredients in sunscreens make corals more susceptible to bleaching by reducing their resilience to climate change.

Following the report, the Hawaii Senate passed a bill in 2020, prohibiting the sale and distribution of sunscreens containing oxybenzone and octinoxate from July 2021.

To further protect reef ecosystems from chemical contaminants, the government proceeded to extend the ban to two other chemicals, octocrylene and avobenzone. Since January this year, no one in Hawaii has been able to purchase a sunscreen containing those ingredients without a prescription.

Acting chief scientist at Great Barrier Reef Marine Park Authority (GBRMPA), Dr Jessica Stella, said although banning chemical sunscreens was not a long-term solution to preserving coral reefs, as the GBRMPA recognised climate change to be the biggest threat, it would certainly be a step forward.

“We are open to any option that might relieve any pressure on the reef,” Stella said.

Stella added people wanting to engage in reef-friendly practices should consider “less toxic, more natural” alternatives to chemical sunscreens such as mineral-based versions or UV-protecting clothing.

Queensland University’s Wenger said protecting coral reefs from chemical contaminants has benefits extending beyond coral preservation.

“A huge amount of our fish globally comes from coral reefs and a lot of people are dependent on coral reefs [for] food and livelihood security.”

Coral reefs also offer coastal protection benefits, Wenger said.

“The Great Barrier Reef provides an amazing buffer for North Queensland from tsunamis, from storms, from sea level rise impacts, from climate change; all of that sort of just slows down wave energy and so without that then you’re starting to get much greater impacts from coastal erosion [and] from storms.”

But Wenger stressed that banning chemical contaminants from sunscreens was not enough to preserve coral reefs, which are facing intense threats from climate change and other factors, including tourism.

“I think looking at how to have sustainable tourism more holistically … is going to give our reefs a much better chance of survival,” she said.

“I would also encourage people to look at what’s the sustainability rating of the company that they’re using to go and visit reefs, the hotels that they’re staying at – do they have any policies related to wastewater management? Do they have policies related to sourcing fish sustainably … is there a solid waste management plan related to plastics?

“The sum of all those parts is going to be better than just saying I’ve bought a reef-safe sunscreen and now I don’t really have to think about the impacts of tourism on reefs more generally.”

Australian regulator slow to act

There has been no ban or restriction on sunscreens containing octocrylene and benzophenone in Australia.

A spokesperson for the TGA said the regulator was aware of the research that has emerged, and that “a testing project investigating impurities in sunscreens is currently underway.”

“The TGA is also reviewing the safety of benzophenone and testing sunscreens on the ARTG [Australian Register of Therapeutic Goods] for this impurity.”

While Europe and America consider sunscreens to be cosmetic products and over-the-counter medicine respectively, Australia classifies them as therapeutic goods, since they’re used to prevent skin cancers.

Because of this, the assessment process required to evaluate chemical sunscreens can therefore take longer to complete. Once finalised, the TGA also has a legal obligation to contact product sponsors and give them an opportunity to respond to the findings before taking any further steps.

The regulator did not respond to a question about when the result of this process might be publicly available.

“The TGA will take action if products are found to contain unacceptable levels of benzophenone to ensure the ongoing safety and quality of Australian sunscreens,” the TGA spokesperson said.

Dr Khaiat, an adviser for the ASEAN Cosmetics Association,  said convincing federal agencies responsible for the regulation of chemical sunscreens to approve the use of new ingredients to replace existing ones would be arduous.

“The amount of data you have to submit to the SCCS for example to get a sunscreen product approved is huge,” he said.

He also warns that consumers concerned about chemical risks do not inadvertently increase potential hazards to their health.

“We don’t want people to stop wearing sunscreens,” Khaiat said.

“It protects the skin from ultraviolet light and reduces risk of skin cancer.”