Swimming in the oceans in this sweltering heat, a favourite choice for many, and wearing a thick layer of sunscreen on our face and body before that dip, is a must too. But do you know that most sunscreens are harmful to the already endangered coral reefs? You might say that your sunscreen is “waterproof”, but reports hint at something very grave.
According to a study in Environmental Health Perspectives, an estimated 25% of applied sunscreen washes off during recreational water activities, releasing some 5,000 tons annually in reef areas alone, and many of those chemicals are toxic to corals, which are already struggling to survive due to climate-change-induced ocean warming.
Some researchers also argue that this may be a low estimate, mentioning that the experiment might not have replicated the friction caused by swimming, resulting in more sunscreen to rub off.
Coral reefs support about a quarter of all marine species despite covering just 0.1% of Earth's oceans. Already under mounting pressure from warming waters, pollution, overfishing and coastal development, reefs face an additional threat from sunscreen chemicals that can damage coral larvae, trigger bleaching and disrupt growth. Scientists say it’s a smaller stressor than climate change, but one that consumers can actually address.
The pollution doesn’t just come from swimming, but also enters waterways when people shower, wash towels or urinate after beach trips. Sewage is the largest source of sunscreen contamination in oceans, as conventional treatment plants can’t effectively remove many UV filter compounds, studies show. The chemicals flow from wastewater facilities into rivers and ultimately the sea.
While sunscreen prevents sunburn and reduces skin cancer risk, not all formulas carry the same environmental footprint.
The strongest evidence of harm centres on oxybenzone and octinoxate — two widely used chemical UV filters. A 2016 study published in Archives of Environmental Contamination and Toxicology found oxybenzone transforms coral larvae from healthy, mobile organisms into deformed, immobile ones. The chemical causes corals to expel the algae that provide much of their food and colour, a stress response known as bleaching. Bleached corals are weakened, more vulnerable to disease and can starve or die if stressful conditions persist.
Researchers also found oxybenzone damages DNA and triggers premature skeleton formation that can encase entire larvae. It can also cause corals to bleach at lower temperatures, worsening the effects of marine heat waves driven by climate change.
Not just that, scientists also have growing concerns about octocrylene, avobenzone and homosalate as well, which don’t stay put. UV filters have been detected in fish and other marine organisms, raising questions about seafood safety.
While zinc oxide and titanium dioxide are generally considered safer alternatives to chemical UV filters, they come with caveats. Experts say they should be in non-nano form, as their larger particle size makes them less likely to be inhaled or absorbed by marine organisms.
However, zinc oxide can also contain trace heavy metal impurities such as lead, chromium and mercury, and only a few products have undergone comprehensive ecotoxicity testing, so they may be better avoided.
Consumers should also pay attention to inactive ingredients, since oils, fragrances and other additives can harm marine life.
Some mineral sunscreen manufacturers add UV filters such as butyloctyl salicylic acid and ethylhexyl methoxycrylene to prevent SPF levels from degrading in zinc oxide, which is also linked to potential cancer risks and coral toxicity.
Experts recommend covering up with full-sleeved swimming costumes, rash guards, hats and shade.
If you're going for a swim and want to ditch the chemical sunscreens for the sake of saving the marine ecosystems, here are a few natural alternatives that you might try using:
Plant-based oils and butters like red raspberry seed oil and carrot oil are known to provide coverage of 25-50.
Easily available alternatives would be pure shea butter and sesame oil, providing mild protection and soothing the skin.
If you are looking for traditional or ayurvedic remedies, aloe vera helps soothe skin, providing mild UV protection. Turmeric, too, can prevent free radical damage from sun exposure, as it contains antioxidants.
If you feel unsure, prone to sunburns or really need an SPF protection, look for mineral-based products with non-nano zinc oxide or titanium dioxide as active ingredients. While research continues into how these minerals behave in marine environments, many experts consider them preferable to chemical UV filters.
Experts are also recommending avoiding aerosol sprays, which can disperse sunscreen into the air and the surrounding environment. Waiting at least 15 minutes after applying sunscreen before swimming allows it to better adhere to skin rather than wash off immediately.
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