Zinc oxide-induced changes to sunscreen ingredient efficacy and toxicity under UV irradiation

Sunscreen safety and efficacy is generally evaluated based upon the properties of the individual chemicals in a formulation. However, the photostability of sunscreens has been shown to be highly dependent on the mixture of chemicals present. To better understand how sunscreen formulation influences...

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Bibliographic Details
Published in:Photochemical & photobiological sciences 2021-10, Vol.20 (10), p.1273-1285
Main Authors: Ginzburg, Aurora L., Blackburn, Richard S., Santillan, Claudia, Truong, Lisa, Tanguay, Robyn L., Hutchison, James E.
Format: Article
Language:English
Subjects:
Animals
Biochemistry
Biomaterials
Chemistry
Chemistry and Materials Science
Original Papers
Particle Size
Physical Chemistry
Plant Sciences
Sunscreening Agents - chemistry
Sunscreening Agents - pharmacology
Sunscreening Agents - toxicity
Ultraviolet Rays
Zebrafish - embryology
Zinc Oxide - chemistry
Zinc Oxide - pharmacology
Zinc Oxide - toxicity
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Summary:Sunscreen safety and efficacy is generally evaluated based upon the properties of the individual chemicals in a formulation. However, the photostability of sunscreens has been shown to be highly dependent on the mixture of chemicals present. To better understand how sunscreen formulation influences stability, and to establish a foundation for probing the influence of zinc oxide additives, we formulated five different small-molecule based ultraviolet-filter (UV-filter) mixtures with a Sun Protection Factor (SPF) of 15. These mixtures contained active ingredients approved in either the United States or European Union and were designed to represent formulations of actual products on the market. We evaluated the photostability and toxicity of these mixtures in the absence and presence of zinc oxide after UV exposure for two hours. Changes in UV absorbance were minimal for all five small-molecule-based mixtures without zinc oxide. The presence of either micro- or nano-sized zinc oxide caused significant small-molecule photodegradation and the degraded mixtures exhibited higher levels of toxicity in embryonic zebrafish assays. This study suggests that caution must be taken when formulating sunscreens containing both zinc oxide and small-molecule UV-filters to avoid unintended consequences during use. Graphic abstract
ISSN:1474-905X
1474-9092
1474-9092
DOI:10.1007/s43630-021-00101-2