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Executive summary
We conducted a safety review of 4-Methylbenzylidene camphor (4-MBC), an active ingredient in therapeutic sunscreens.
This safety review was dependent on national and international safety assessment reports and peer reviewed publications investigating the safety and toxicokinetics of 4-MBC, where available.
However, based on the data considered in this safety review, the TGA recommends regulatory controls for 4-MBC to restrict its permitted concentration and use in therapeutic sunscreens.
The two main issues considered in this safety review were the evidence for the ability of 4-MBC to penetrate the skin to reach viable cells systemically and the potential toxicity exerted by 4-MBC.
Based on the data available, a Margin of Safety (MoS) was determined for 4-MBC using the Australian Sunscreen Exposure Model (ASEM) which underwent public consultation in 2024. A MoS of 100 or more is considered to be satisfactory for controlling for the risks to human health and safety from long-term use of an ingredient by the Australian population. The MoS was calculated based on the current maximum permitted concentration in therapeutic sunscreens (which are regulated as listed medicines).
However, it is important to note that the concentration of 4-MBC in products can be less than the maximum permitted amounts; and that some products contain a combination of active ingredients.
The ASEM has been used to calculate the highest estimated average daily sunscreen exposure modelled to account for use of therapeutic sunscreens applied long-term to the face and body by children and adults. The MoS using the highest estimated sunscreen exposure for application of a general sunscreen to the body, at the maximum permitted concentration, was less than 100. Hence, the ASEM was utilised to estimate alternative exposures based on specific parts of the body e.g. head, face and/or hands. In this case, the MoS was more than 100 and considered low-risk for long-term use when limited to the face and hands at concentrations between 16.5% and 3.8%, depending on the type of product and the directions for use (e.g. limited to face-only use).
The limitations of this review are:
- The toxicological endpoints, (NOAELs), were collected from published international safety assessment reports and scientific literature. As full data sets, including all raw study data, were not available for independent corroboration of the findings from these reports and literature, this review was dependent on the veracity of the details provided in those reports and literature.
- Consumer products other than sunscreens that contain the same active ingredient were not considered in this review.
- The exposure to metabolites or impurities of the active ingredient has not been considered in this review.