What’s it all about?
- Endocrine disruptors are natural or synthetically produced chemical compounds that interfere with the production of hormones in humans and other animals that may contribute to disease and other conditions
- Common sunscreen active ingredients including Homosalate and 4-Methylbenzylidene Camphor have been deemed as potentially endocrine disrupting by the Scientific Committee on Consumer Safety (SCCS) with others still under review.
- There are difficulties in reliably determining the endocrine disruption potential of chemicals due to bans on animal testing.
- If brands avoid ingredients associated with endocrine disruption, it will contribute to an increase in the price of their sunscreens.
A deep dive into relevant sunscreen ingredients
Benzophenone-3 (Oxybenzone) is globally approved for use in sunscreen up to 5% (maximum 10% in Australia). It is a comparatively high-performance and cost effective, broad spectrum UV filter, however it is being used less frequently, particularly in Australia, as a consequence of it being a photoallergen. The SCCS has concluded that 6% (the max permissible amount in the EU) is safe when used in products for the face, hands and lips, however, recommends 2.2% in products for the body or sprays.
Benzophenone-3 has been linked to concerns around ‘reef safety’ following some arguably flawed research by a US-based environmental laboratory, suggesting it can cause coral bleaching. Benzophenone-3, like a lot of chemicals, including Zinc Oxide, is associated with aquatic toxicity, although Benzophenone-3 has been detected in the water in areas subjected to coral bleaching events, it is a phenomenon that occurs in regions of very limited human activity, including the Great Barrier Reef and correlates to increasing water temperatures.
An alternative to Benzophenone-3 is Bis-Ethylhexyloxyphenol Methoxyphenyl Triazine (BEMT, also known by the trade name Tinosorb® S) a higher-performing UVA/UVB filter that provides a comparable SPF in-silico at less than half the dosage. Despite the lower dosage, the cost is 5-6 times higher than that of Benzophenone-3, so it remains more expensive on a cost per SPF unit basis.
Octyl Methoxycinnamate (Ocinoxate)
Octyl Methoxycinnamate (sometimes referred to as ‘Octinoxate’) is globally approved for use at up to 7.5% (10% in Australia) and is a high performance and cost effective UVB filter.
It is being used less frequently as it is photo unstable (not to be confused with a photoallergen) in certain combinations particularly in mixtures with Avobenzone. Despite the photo instability, it is very effective when used correctly. The SCCS are yet to draw a conclusion on the use of Octyl Methoxycinnamate, whilst it has been associated with endocrine disruption in some studies, the SCCS will no doubt interpret the available literature and provide a detailed opinion in due course.
There is no single alternative to OMC. It’s unique as a liquid emollient with high UVB absorbance, an alternative could be a combination of other oil based UVB filters and a crystalline UVB filter to enhance the SPF.
Combinations of Octyl Salicylate, Butyloctyl Salicylate, Octocrylene, Ethylhexyl Methoxycrylene and Octyl Triazone generates comparable SPF to Octyl Methoxycinnamate when tested in-silico. The cost for an alternative system based on Octocrylene is roughly 2-3 times higher, whereas one based on Ethylhexyl Methoxycrylene is 5-6 times more expensive.
4-Methylbenzylidene Camphor (4-MBC) is an approved sunscreen ingredient in many jurisdictions up to 4%, except for the US and Japan. The US has not ‘unapproved’ the ingredient, it simply sits in a box with several other sunscreen ingredients that haven’t ever been approved. In Australia, 4-MBC is becoming increasingly rare in sunscreens as it has been associated with increased sensitisation.
As at the end of 2022, the SCCS’s official stance on 4-Methylbenzylidene Camphor is that 4% or above is not a safe level, however they are unable or unwilling to propose an acceptable limit. To date the EU has not changed the maximum dosage level from the current 4%.
An alternative to 4-MBC is Octyl Triazone, also a crystalline filter which is higher in UVB performance but slightly lower in UVA. The price of Octyl Triazone is currently less than 4-MBC, as MBC has increased in price recently, likely as it is phased out and production is scaled back.
Octocrylene is globally approved up to 10%, it has a moderate performance and is a cost effective UVB filter with powerful solubilising ingredients, capable of dissolving other more high-performing filters that would otherwise be unusable.
In 2021 the SCCS concluded that 10% (the maximum allowed in Australia) is safe in most products, however, recommends 9% in spray products, when used in conjunction with other products containing 10% octocrylene.
Octocrylene has been associated with the formation of Benzophenone, a widely recognised toxin, whilst not considered an endocrine disruptor, it is a possible human carcinogen. Benzophenone is a degradation product with an increased rate of formation in the presence of water and accelerated by exposure to higher temperatures
An alternative to octocrylene is another liquid emollient that provides comparable solubilising power; Ethylhexyl Methoxycrylene (and SPF booster), however the cost is 3-8 times more.
Whilst there is no existing evidence to support the suggestion, it may be expected that Ethylhexyl Methoxycrylene may be similarly associated with the degradation and formation of Benzophenone. Likewise, there is potential for it being harmful to aquatic life, it is currently considered non-hazardous.
Homosalate is globally approved for use up to 10% (15% in Australia), it is a low performance but cost effective UVB filter. Despite its average performance as a sunscreen, as a liquid emollient with UV absorbance it is useful in solubilising other active ingredients and as a result it is incredibly common in sunscreens.
The SCCS 2021 opinion concluded that Homosalate acts as an endocrine disruptor and that levels above 10% Homosalate are unsafe, recommending a maximum 7.34% in products intended for the face and 0.5% for body(1).
Of all the chemicals of concern that have been reviewed by the SCCS regarding endocrine disruption, Homosalate stands as the ONLY sunscreen active that can be considered an EDC with a resulting change to the maximum permissible limits and it is likely that it will be banned entirely in the EU.
Finding alternatives to Homosalate can be difficult, particularly to avoid other ingredients with negative press such as Octyl Methoxycinnamate. As Homosalate is a liquid emollient with UV absorbance and some level of solubilization capacity for crystalline UV filters it is fairly unique. One possible alternative is Octyl Salicylate (a permitted sunscreen active) whilst this is comparatively priced, it does have a lower maximum permitted dosage. Another alternative is Butyloctyl Salicylate (an SPF booster) which is roughly twice the price of Homosalate.
Parabens are a group of chemicals based on a ‘para-hydroxybenzoate’ structure that are highly effective preservative ingredients globally approved in cosmetics with dose-based limitations, in addition to use in food and pharmaceuticals.
Parabens are becoming less common in cosmetics as a consequence of negative press (derived from flawed research) and a resulting brand preference to make ‘paraben free’ claims.
The SCCS found parabens are not a concern at the current maximum recommended dosages, which vary on the specific paraben (methyl, ethyl, butyl, propyl etc). The lower molecular weight, short chain options including Methylparaben and Ethylparaben are deemed entirely safe as they quickly metabolise into non-toxic p-hydroxybenzoic acid, whereas for the higher molecular weight, long chain types including Butylparaben and Propylparaben the metabolism is less clear based on current data.
Many alternatives to parabens are available, most of which are equally effective, whilst they may be more expensive in comparison, the dosages are low in contrast to those of sunscreen ingredients.
Testing EDC’s and animal testing
Industrial and other mixed-use chemicals will continue to be tested using an array of animal based screening methods to determine whether they disrupt the endocrine system. However, as a consequence of bans on animal testing in cosmetics, there will be issues in continuing to determine whether a potential EDC used solely in cosmetics is an actual EDC.
Whilst in-vitro methods are being developed as a substitute for in-vivo/animal testing, there are currently no valid methods for determining the endocrine disrupting potential of an ingredient.
We are surrounded by endocrine disruptors and other toxic substances, these chemical compounds aren’t dangerous by default, and often they’re essential to our health. Identifying a hazard exists and understanding it is simply the first step in determining how we can safely co-exist with it.
In the case of sunscreens, 4-Methylbenzylidene Camphor, Benzophenone-3 (Oxybenzone) and Homosalate have been identified as potentially endocrine disrupting by the SCCS at currently approved maximum usage limits, and further limitations on their use proposed which will likely be implemented into law in Europe. How this impacts other regions from a legal perspective is uncertain, the SCCS opinion in the absence of any other similarly robust evaluation of the available literature should be, and likely will be, heavily considered by sunscreen brands into the future.
Other sunscreen actives including Octocrylene have not been deemed endocrine disrupting by the SCCS, with others including Octyl Methoxycinnamate and many more yet to be evaluated.
With the move away from common sunscreen ingredients like Homosalate, sunscreen reformulations are expected in the coming years. Due to comparable and cost-effective alternatives not yet existing, the cost of sunscreens is anticipated to increase for the consumer as a result of the more expensive sunscreen ingredients, but also the costs of sunscreen reformulation, SPF and broad spectrum testing and stability testing.
NOTES: (1) It may be worth noting the difference between recommendation between face and body, this is no doubt linked to ‘the dose makes the poison’ whereby the amount applied to the face is considerably lower than that applied to the body, hence the risk is higher when applying to the body resulting in a recommendation for those products to have a lower dose.