Nanomaterials in sunscreens
How do sunscreens work?
To avoid sunburn, we use sunscreens to protect our skin from UV rays (UVB and UVA rays). Sunscreen filters work in two different ways. Some of them are mineral-based and use nanoforms of chemicals, such as titanium dioxide (TiO2) and zinc oxide (ZnO), to reflect the UV rays away from the skin. Mineral filters are effective immediately once applied. Chemical sunscreen filters contain substances like oxybenzone. They need to be applied before exposure to the sun as they protect from sunburn by absorbing the UV rays.
The concentration of UV filters used in sunscreens is dependent on the desired sun protection factor (SPF). The concentration levels are controlled and, should not exceed 25% of the final product composition for mineral filters or 10% for chemical filters.
Why are nanomaterials used in sunscreens?
Mineral UV-filters contain nanoparticles and give longer protection as they are more stable compared to chemical filters. ZnO is considered to give the most effective protection. Sunscreens containing ZnO and TiO2 nanoparticles allows a non-white finish, similar to chemical-based sunscreens.
Is it safe to use sunscreens that contain nanoparticles?
The Scientific Committee on Consumer Safety (SCCS) has raised concerns over the safety of sprayed sunscreen products which contain TiO2 as it is suspected to cause cancer if inhaled.
To protect people, any product containing TiO2 above a certain limit must contain a warning on its label stating: ‘Warning! Hazardous respirable droplets may be formed when sprayed. Do not breathe spray or mist.’
Sunscreens and the environment
Although data on environmental impact is limited, chemical filters, such as oxybenzone, have been associated to coral bleaching and have been reported as endocrine disruptors. Due to these findings, for example in Hawaii, its use has been restricted as a precautionary approach.
There are only a few studies available on mineral filters. It is difficult to reproduce reliable conditions with all environmental variables, sunscreen components and their interactions in a laboratory setting.
Variations of particle size, shape or surface coating may also impact the hazard potential of products. Although zinc is an essential nutrient, it may be toxic in high doses, particularly for aquatic organisms.
Both zinc oxide and zinc chloride have a harmonised classification which means they are toxic to aquatic life at concentrations below 10 milligrams per litre. For titanium dioxide, there is currently no harmonised classification related to its environmental effects.