Oxybenzone makes corals 10 times more prone to viral infections, threatening 10% of the world's reefs.
This episode of Chemistry in its Element, presented by Katrina Kramer, examines the controversial sunscreen ingredient oxybenzone. It explores the compound's function, its disputed environmental impact, and the scientific debate surrounding its use. The discussion is framed by the context of increasing extreme heat and the human reliance on sun protection.
On August 16, 2020, Death Valley recorded a potential century-high temperature of 54.4°C, illustrating the trend of more frequent hot spells. Historical sun protection includes a powder invented by the Samabajau people of Southeast Asia. Modern sunscreen began with chemist Franz Greiter, who developed Glacier Cream after a severe sunburn in 1938. Oxybenzone is a pale yellow, organic solid that absorbs UVA and UVB rays, converting the energy into heat. Approved in the US in the 1980s, it is found in about 70% of sunscreens. The controversy stems from studies linking it to coral bleaching, where stressed corals expel their symbiotic algae. A 2016 bleaching event killed 30-50% of corals on Australia's Great Barrier Reef. A seminal 2008 study found coral fragments exposed to oxybenzone were more prone to viral infections and bleaching. A highly cited 2015 study showed oxybenzone is toxic to coral cells and disrupts larval development.
Researchers detected oxybenzone in waters near Hawaii and the Virgin Islands at concentrations from micrograms to over a milligram per liter. In response, Palau became the first country to ban oxybenzone in 2020, imposing a $1,000 fine on sellers. Critics, including a U.S. Personal Care Products Council scientist, argue the bans are misguided and could limit access to effective sunscreens. Some scientists contend the lab studies don't reflect real-world conditions and that focusing on oxybenzone distracts from larger threats like agricultural runoff and global warming. A recent Dutch study suggested oxybenzone might even weaken corals' defenses against rising water temperatures. As an alternative, scientists are investigating shinorine, a UV-absorbing compound produced by marine algae and cyanobacteria.
The tone is educational and narrative, weaving historical anecdotes with clear scientific explanations of complex environmental chemistry. The style is factual and measured, presenting competing viewpoints without definitive conclusion.
Listeners interested in environmental science, consumer product chemistry, or marine conservation will find this episode compelling. Those seeking a simple, definitive verdict on sunscreen safety might find the nuanced debate frustrating.
