August 18, 2026
The National Science Foundation (NSF) has awarded environmental health sciences associate professor Eric Vejerano a grant of nearly $620,000 to determine how and why common sunscreen ingredients form persistent free radicals (PFRs) when they are exposed to light. Funded through the NSF’s Chemical, Bioengineering, Environmental and Transport Systems Nanoscale Interactions Program, the project names Vejerano as sole principal investigator and follows directly from his lab’s recent discovery that every commercial sunscreen it tested produced these long-lived radicals under artificial light.
The new award, titled “Formation of Persistent Free Radicals in Sunscreens During Light Exposure,” moves the work from observation to mechanism. The earlier study, published in Environmental Science & Technology Letters, showed that sunscreens form PFRs. This project will explain how they form, how long they last, and how seawater changes their behavior. Vejerano’s lab will determine how sunscreen particles generate reactive chemicals in air and seawater — and what that may mean for coral reefs.
“We had shown that sunscreens produce persistent free radicals. What we did not know was the mechanism behind it,” Vejerano says. “This award lets us answer the harder questions. How do these radicals form on the particle surface? How long do they survive? And why does water sometimes shut them down and sometimes make them worse?”
Arriving at the Arnold School in 2017, Vejerano’s expertise centers on air quality –more specifically, how nanoparticles interact with environmental pollutants. A member of the South Carolina SmartState Center for Environmental Nanoscience and Risk (CENR), his NSF-funded research examines the nature, sources and impacts of persistent free radicals.
For decades, PFR research focused on particles created through combustion and other industrial processes. Vejerano’s lab has steadily expanded that picture, first by identifying biogenic PFRs in unexpected sources such as leaves, and more recently by showing that the sunscreens people apply every day can generate radicals that linger long after the light is gone. That earlier work also produced a surprise: while adding water reduced PFR output for most of the sunscreens tested, one sample produced more, raising concerns about what happens when these products wash into the ocean.
This project takes aim at that open question. Two of the most widely used active ingredients in mineral sunscreens, zinc oxide and titanium dioxide, are tiny particles that can generate reactive chemicals when sunlight strikes them. Vejerano’s team will measure how these reactive substances form and decay in both air and water, identify how sunlight and seawater change their behavior, and explain how the surfaces of the particles control the process. Using electron spin resonance spectroscopy and simulated sunlight chamber experiments, the researchers will track the radicals and the reactive oxygen species they spin off under conditions meant to mimic a coral reef.
The goal is knowledge that manufacturers, coastal managers and the public can actually use. By linking a particle’s composition and surface chemistry to how long its radicals persist, the work aims to support safer sunscreen formulations that preserve protection from the sun while reducing the risk to marine ecosystems and human health.
“Our results point to the need to reconsider certain formulations that are prone to producing these radicals,” Vejerano says. “If we understand the chemistry, we can help design products that protect people and protect coral reefs at the same time.”
The award also carries a teaching mission. Vejerano will engage graduate, undergraduate,
and high school students through hands-on research and structured mentoring, with
two graduate students each helping to guide several younger trainees per year. He
plans to work with University of South Carolina summer research internships and regional
high schools to broaden participation in environmental science and strengthen the
pipeline of students entering science, technology, engineering, and mathematics fields.
The SmartState Center for Environmental Nanoscience and Risk (CENR) investigates the effects and behaviors of manufactured and natural nanoparticles on environmental and human health. CENR also develops low-hazard and low-risk nanotechnologies for the benefit of human and environmental health.
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