New research from the Department of Environmental Health Sciences has revealed that common sunscreen ingredients produce persistent free radicals (PFRs) when exposed to light. Led by associate professor Eric Vejerano, the study involved testing seven commercially available sunscreens, including four mineral-based formulations. The findings, published in Environmental Science & Technology Letters, shed light on the photochemical behavior of sunscreens, which may affect their safety and performance evaluations.
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Vejerano noted that while it was previously known that light exposure caused mineral sunscreens to generate transient free radicals, this study discovered the generation of long-lasting free radicals as well. He stated, "This can happen during routine sunscreen use with unknown impacts to human and environmental health."
Vejerano joined the Arnold School in 2017 and specializes in air quality and the interaction of nanoparticles with environmental pollutants. His research, supported by the National Science Foundation, focuses on the sources and impacts of persistent free radicals. Historically, research on PFRs has centered on industrial processes. However, Vejerano's lab has identified PFRs from natural sources, such as plant material, which contribute significantly because plants make up 82% of the Earth's land biomass.
In this study, the team provided the first evidence that commercial sunscreens can produce PFRs that continue to exist long after light exposure ceases. Various laboratory tests revealed that while light exposure increased PFR production, adding water reduced PFR output in most cases. Intriguingly, one sunscreen sample showed increased PFR generation upon contact with water, raising concerns about potential effects on aquatic ecosystems, notably coral reefs.
The research estimates that around 10 PFRs may form per gram of sunscreen, suggesting that a typical application of 20-40 grams could result in the formation of 200-400 PFRs, although the amount may vary across different products.
Vejerano emphasized the importance of reassessing certain sunscreen formulations that are more likely to produce PFRs. He stated, "Understanding how sunscreen ingredients behave in the environment may help us guide the development of products that better protect marine ecosystems while reducing risks to human and environmental health."
The SmartState Center for Environmental Nanoscience and Risk (CENR) focuses on the effects of both manufactured and natural nanoparticles on health and the environment, while also developing safer nanotechnologies.