Sunscreen Safety: a Review of Recent Studies on Humans and the Environment

Purpose of Review To provide an up-to-date synopsis of the literature on the safety of sunscreen active ingredients in humans and the environment and highlight regulatory changes in the USA. Recent Findings Currently, as per the US Food and Drug Administration, the only ultraviolet filters generally recognized as safe and effective are inorganic zinc oxide (ZnO) and titanium dioxide (TiO2). In vivo human systemic absorption studies found that common organic filters attain sufficient plasma concentrations to require carcinogenicity and reproductive studies. In vivo human skin penetration studies showed ZnO nanoparticles (ZnO-NP) did not penetrate the stratum corneum. Limited quantities of TiO2-NP may be absorbed systemically. In laboratory settings, corals exposed to oxybenzone manifested concentration-dependent toxicity and bleaching. In response, bills passed in Hawaii and elsewhere ban sales of oxybenzone-containing sunscreens. ZnO-NP, but not TiO2-NP, caused coral bleaching under controlled conditions. The collective knowledge on sunscreen safety is continually evolving, with many preliminary findings. Studies on the effects of systemic absorption of organic filters in humans are forthcoming; importantly, there has been no evidence of harm over decades of use. Organic (less so inorganic) filters caused coral bleaching in controlled environments, but filter concentrations may not have been realistic, and bleaching is predominantly driven by other factors. No present evidence suggests any marketed sunscreens should be avoided. For consumers with concerns, inorganic ZnO and TiO2 are supported by the most reassuring data at the time of writing.