The use of sunscreens is essential to protect the skin from UV exposure, but they may enter waterways damaging the ecosystem
There is a correlation between climate change and the incidence of skin cancer. In the United States, for example, over 30,000 additional melanoma and nonmelanoma diagnosis per year are today attributed to the depletion of the ozone layer (J Am Acad Dermatol. 2017 Jan;76(1):140-147). Moreover, it is assumed that a 2°C rise in temperature may result in a 10% increase of the number of skin malignancies yearly due to a higher exposure to ultraviolet (UV) light without protective clothing.
The growing incidence of skin cancer entails more interest in sun safety strategies, particularly the use of sunscreens. The history of sunscreens dates back to 1928, when the first product appeared on the US market; however, the highest increase in their sales has been noted in the last 20 years. Despite the effectiveness of sunscreens is proven, their use has a drawback: it is estimated that roughly 14,000 tons of sunscreen enter waterways across the globe every year, with an estimated 25% of the total being deposited in water, and additional amounts released in the ecosystem from wastewater (Environ Health Perspect. 2008 Apr;116(4):441-7).
UV filters are crucial sunscreens ingredients that protect people from harmful UV rays, but they may cause harm to the environment when released into the water. Overall, UV filters can be divided into organic (chemical) and inorganic (physical). Organic filters protect the skin due to complex chemical reactions upon UV exposure, while inorganic filters reflect, scatter, and partly absorb sun rays. Several examples of known organic UV agents are oxybenzone, dibenzoyl methane, benzophenone, salicylate, cinnamate, camphor derivatives, or p-aminobenzoic acid. Many organic UV filters are found to accumulate in water because of their chemical properties, and unwanted by-products may be formed due to their instability in water.
Coral reefs are particularly susceptible to the active ingredients in commercial sunscreens, but adverse effects are not limited to corals only. The first study linking organic UV filters to coral bleaching was published in 2008 (Environ Health Perspect. 2008 Apr;116(4):441-7). Eight years later, scientists found that oxybenzone is particularly toxic to corals compared to other sunscreen ingredients and can cause not only bleaching but also DNA damage, abnormal growth, and developmental deformities in baby corals (Arch Environ Contam Toxicol. 2016 Feb;70(2):265-88). Further research confirmed these observations also in other organisms, such as anemones and close relatives of coral (Science. 2022 May 6;376(6593):644-648). In green algae, sunscreen byproducts impair growth and photosynthesis; in mussels and sea urchins, it can lead to the deformation of young. In larger sea animals, like fish or dolphins, chemicals accumulate in tissue decrease fertility, and can even be transferred to the young (Arch Environ Contam Toxicol. 2016 Feb;70(2):265-88).
Some organic UV filters are also known to cause negative side-effects in humans, including skin reactions, and have been detected in human urine, blood, and breast milk (JAMA. 2020 Jan 21;323(3):256-267). Physical or inorganic sunscreens are considered to be less toxic and safer for human use than organic UV filters since they do not penetrate deep into the skin. Similarly, inorganic filters that most commonly contain titanium dioxide (TiO2) or zinc oxide (ZnO) are considered more environmentally sustainable.
Based on published research, some places around the world now ban the use of the most damaging ingredients, such as oxybenzone and octinoxate. These include, among others, Hawaii, the US Virgin Islands, and Thailand. Also, regulatory agencies and policymakers are moving toward promoting safe and environmentally friendly UV filters. For example, in the European Union and in the US, only ingredients included in specific lists of safe compounds can be used. But there is definitively a high need for more research and development of new, highly effective, and safe sunscreens – both to humans and the environment.
There is no perfect option that will be 100% safe for the environment while providing the highest protection to our skin. However, there are a few easy steps that each of us can follow to balance the risks and benefits related to sunscreens, e.g. read labels and be discerning (not every “environmentally friendly” label means that the sunscreen is truly safe for the environment); avoid sunscreens containing harmful substances, such as oxybenzone, benzophenone-1, benzophenone-8, OD-PABA, 4-methylbenzylidene camphor, 3-benzylidene camphor, nano-titanium dioxide, methyloxycinnamate, nano-zinc oxide, octinoxate, octocrylene, homosalate, and octisalate; opt for lotions instead of spray-on products (most of the sunscreen ends up in the environment without staying on and protecting your skin) and finish sunscreens already purchased (they will eventually end up in the environment); and finally do not forget about other means of skin protection such as wearing hats and long sleeves, seeking shade between 10 am and 2 pm.
We, as sunscreen users, need at least to be conscious of both their protective effect against skin cancer and potential environmental harm, to make decisions that can protect both our health and that of the environment.
