For a lot of people, beach trips and lake excursions are never complete without a tall bottle of sunscreen to smother their skin with before going off for a swim.
However, a recent report found that chemical ingredients in sunscreen that leach off of the skin while swimming might be detrimental to freshwater organisms.
In a major breakthrough, researchers from the University of Alberta in Canada found that long-term exposure to ultraviolet (UV) filters – the ingredients in sunscreen that block or absorb UV light – is lethal for some organisms living in freshwater habitats.
Their findings appeared online in Science of The Total Environment.
Long-term exposure to chemicals could affect entire ecosystems
Scientists know that UV filters, the main ingredients in sunscreen, can damage coral reefs and poison saltwater fishes. But little is known about the effects of UV filters on organisms living in freshwater environments.
To this end, the researchers examined the effects of UV filters on water fleas (Daphnia magna), a small aquatic crustacean often found in freshwater habitats.
Water fleas are a promising candidate organism to examine because of their integral role in the food web within their habitats. Various fish larvae use these invertebrates as their main source of food, which explains their abundant numbers.
Water fleas are also sensitive to environmental stressors. This nature allows for the identification of subtle but relevant changes in the invertebrates’ behavior upon the introduction of contaminants.
For their experiment, the scientists exposed the water fleas to three UV filters (avobenzone, oxybenzone, and octocrylene) and checked in on them at the 48-hour (acute exposure) and two-week (chronic exposure) marks.
The treatment groups also consisted of either individual UV filters or a mixture that contained equal concentrations of all three UV filters.
The researchers found no significant behavioral impairment in the water fleas after 48-hour exposure to the mixture of UV filters. However, the group noted a minor change in how the fleas responded to light stimuli.
Meanwhile, exposure to the UV filters over a two-week period proved to be more disruptive and detrimental for the fleas.
In particular, chronic exposure to the mixture of UV filters led to a 50 percent increase in mortality after five days, resulting in some deaths.
Furthermore, chronic exposure led to a 100 percent increase in mortality after seven days. On day 10, all of the remaining daphnids that survived the 50 percent increase in mortality also died.
The researchers then exposed a second batch of water fleas to lower concentrations of the UV filters, but this did not lower the mortality rate.
These results offer insight into how UV filter contamination could affect entire freshwater ecosystems, said lead author Aaron Boyd.
Because water fleas are an important part of the food chain, major losses to their population as a result of UV filter contamination could place the species that use them for food at great risk of starvation.
Organisms could recover from the harmful effects of exposure to UV filters
Despite these grim results, Boyd and his colleagues found a silver lining. The detrimental effects of the UV filters wore off over several weeks after the contaminants were removed from the water fleas’ environment.
Furthermore, UV filters were found to be short-lived in freshwater environments. Therefore, removing the contaminants offers a reasonable chance for exposed organisms to recover from the harmful effects of UV filters. (Related: Extremely toxic sunscreen ingredients you want to avoid.)
That being said, UV filters are notorious for accumulating inside bodies of living organisms. Therefore, the next step now would be to conduct further testing to see if the effects of the UV filters do not occur in post-exposure generations.
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