No, sunscreen chemicals do not bleach the Great Barrier Reef

For the sixth time in 25 years, the Great Barrier Reef is whitewashing. During bleaching events, people point the finger at several causes, including sunburn. Why sunscreen? The snookerler washes away some of the active ingredient and goes into the rocks, polluting the area. If so, could this be the cause of the reef bleaching? Literally, no. In my new research, I looked at the evidence for sunscreen as a risk for corals, and found that the chemicals in sunscreens pose a risk to corals under laboratory conditions, and that they are found only to a very limited extent in the real world environment. This means that when coral bleaching occurs, it is more likely to be caused by rising sea temperatures due to ocean heat waves and climate change, as well as land flow.

Why are we so concerned about the environmental impact of sunscreen?

After applying sunscreen, the active ingredient can seep into our skin. When we take a shower after bathing, soap and detergent can further remove this sunscreen chemical and send it to our wastewater systems. They go through treatment plants that cannot be effectively removed and end up in rivers and oceans.

If so, it is not surprising that freshwater and seawater pollution has been detected around the world, from Switzerland to Brazil and Hong Kong. Pollution is highest during the summer months, when people often go swimming, and it rises within hours of bathing. Four years ago, the Pacific island nation made headlines around the world by announcing plans to ban all sunscreens containing specific synthetic active ingredients due to concerns about the risk to the Palau coral reefs. Similar bans have been issued in Hawaii, as well as in a number of other popular tourist destinations in the United States and the Caribbean. The ban is based on independent scientific studies and commission findings that the waters of beaches, rivers and lakes have been polluted by a specific active ingredient in sunlight. In particular, there are nations that have banned this active ingredient, such as Bonaire and Mexico, and local economies that rely heavily on local, summer tourism. For these areas, bleaching coral is not only an environmental disaster but also an economic disaster if tourists choose to move elsewhere.

How do we know that sunscreen is not an issue?

So, if the pollution problems in these active ingredients are justified, how can we be sure that they are not the cause of the Great Barrier Reef bleaching? Simply put, the concentration of chemicals is low enough to bleach. The synthetic ingredients used in many products are highly hydrophobic and lipophilic. This means they avoid water and love fats, which make them harder to dissolve in water. They mostly like to stay on the skin until they break. For this reason the levels in the environment are very low. How low? Think nanograms per liter (0.00000000001 nanograms) or micrograms (0.00001 micrograms per liter). Significantly higher levels are found only in sewage sludge and some sediments, not in the water itself.

So how do we compare this with studies showing that sunlight can damage corals? Under laboratory conditions, many sunscreen active ingredients have been found to harm plant organisms such as corals, clams, fish, crustaceans, and algae and phytoplankton. The key phrase above is “under laboratory conditions”. These studies show that sunspots are a real threat to coral reefs, but it is important to know the context. Such studies are usually carried out under artificial conditions in which natural processes cannot be explained. They usually do not take into account the breakdown of chemicals due to exposure to sunlight or water currents and tides. These tests also use sunscreen concentrations that are thousands of times higher than the real world pollution level in the collected samples – milligrams per liter. In short, laboratory-only studies do not provide a reliable indication of what happens to these chemicals under real-world conditions.

If it is not sunscreen, what is it?

According to the 2019 Outlook Report of the Coral Management Board, the biggest threat to the reef is the direct human use of landfills such as climate change, coastal development, pesticides, herbicides and other pollutants, and illegal fishing. Rocks. Corals derive their distinctive color from zooxanthellae, a single-celled organism that grows and lives in corals. Importantly, these organisms grow only under very specific conditions, including narrow temperature zones and light levels. When conditions leave the zooxanthellae’s favorite zone, the zooxanthellae die and the corals turn white. As a result, the most likely cause of this whitewash is climate change, which has increased ocean temperatures and acidity, resulting in floods, storms and hurricanes blocking light and raising the ocean floor.

So should you worry about the impact of your sunlight on the environment? No. Sunscreen should remain a key component of our sunscreen strategy as a way to protect the skin from UV damage, prevent skin cancer and delay the visible signs of aging. Our coral reefs face bigger problems than protection from the sun.


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