Living Peacefully with the Sun
- Francesca Bell-Miller
- Jun 18
- 7 min read
Updated: 1 hour ago
Sunscreen Protects Skin, But Can Be Toxic to Marine Life
Day after day, the Sun provides the heat and light that allows life to flourish on Earth. Its powerful rays impact the wind, clouds, ocean currents, and countless other essential activities on the planet.
But due to the Sun’s high temperatures, especially in summer months, humanity is constantly seeking peaceful coexistence with it.
A robust “sun protection” industry has emerged to literally block sunrays, sparing people from dangerous sunburns and even cancer. Yet, concerns have now risen about the chemical components in sun products that can threaten fragile environments, such as coral reefs.
As a result, the industry is doing introducing products it deems “reef friendly,” according to The New York Times.
The Sun’s Powerful Rays
The Sun emits energy in a spectrum, from infrared radiation (which is felt as heat) to visible light and invisible light, including ultraviolet (UV) waves. Research has shown that unprotected exposure to certain types of UV radiation, specifically UV-A and UV-B, causes skin issues—including cancer—as well as eye damage. One in five Americans will develop skin cancer by age 70, says the Personal Care Products Council, a trade group for manufacturers of cosmetics and products such as sunscreens.
To deal with UV radiation, people have taken to using topical sun protection, with specific properties depending on the country. There are two types of sun protection: physical blockers that reflect UV rays (sunblock) and chemical blockers that absorb UV rays (sunscreen). The terms “sunblock” and “sunscreen” are often used interchangeably.
Given the “consistent growth” of the sun protection skin care industry, … the use of topical sun protection raises concerns of it leaching into the environment.
However, given the “consistent growth” of the sun protection skin care industry—with revenue projected to reach about $13.5 billion by 2028, according to Market.us Media—the use of topical sun protection raises concerns of it leaching into the environment. It is thus important to be aware of the properties of topical sun protection and its potential environmental impacts.
Physical and Chemical Blockers
The first sunscreens were developed over the 1880s and early 1890s, until emerging as ready-to-buy topical creams, such as Coppertone and Glacier Cream in the 1940s, according to a published history by Baylor University Medical Center.
Physical blockers, more commonly known as mineral sunscreens, reflect UV radiation away from the skin. Zinc oxide or titanium dioxide (also known as inorganic UV filters) are typically the active ingredients in mineral sunscreens. In micronized sunscreens (with very small particle sizes), however, “the mechanism of action is similar to that of chemical filters,” says a 2020 study, such as for zinc oxide and titanium dioxide.
Top examples of mineral sunscreens include products like MDSolarSciences Mineral Moisture Defense SPF 50 and Australian Gold Mineral SPF 50, according to Forbes magazine.
Chemical filters or blockers have active ingredients that absorb UV rays before the skin can soak them up. Also known as organic UV filters, these include oxybenzone, avobenzone, octisalate, octocrylene, homosalate, and octinoxate, and 55 different types are registered for use worldwide. Oxybenzone, for example, is used in cosmetics but is known to cause eye and respiratory irritation and is “very toxic to aquatic life.”
Chemical sunscreens without oxybenzone include products like Banana Boat Light As Air SPF 50+, Solimo Sheer Face Sunscreen SPR 50+, and Black Girl SPF 30, according to The New York Times.
The US set standards in 1999 for the maximum concentration of active ingredients in sunscreen. For example, titanium dioxide and zinc oxide can be up to 25%, while others such as oxybenzone and dioxybenzone can be up to 6% and 3%, respectively. Concentration limits vary worldwide based on different regulations.
Given these limitations, along with how the absorbed UV spectrum varies with each active ingredient, a single sunscreen may have a combination of various active ingredients. Typically, three to eight organic UV filters—up to 15% of the sunscreen’s total mass—can be found in a single sunscreen.
SPF and UV Protection
The US Food and Drug Administration (FDA) defines SPF (sun protection factor) as a measurement of the amount of (absorbed) UV radiation required to produce sunburn on protected skin versus unprotected skin. This means that SPF is not directly correlated with the amount of time spent under the sun, as the sun’s intensity varies throughout the day. Other factors such as skin color (with lighter skin absorbing more solar radiation) and weather (with clouds absorbing some of the solar radiation) can affect the amount of UV radiation required before sunburn.
Thus, a higher SPF value means a protected person can tolerate a higher amount of UV radiation before getting sunburned.
According to Raman Madan, MD, a dermatologist with Northwell Health, SPF values can be expressed in a different way: SPF 2 “protects against 50% of UVB rays” and SPF 10 to 100 protects against 90% to 99% of UVB rays. “The difference between SPF 30 and SPF 100 is marginal at most,” he says.
Environmental Impacts of Sunscreen
Sunscreen leaches into the marine environment, whether directly (from swimming) or indirectly (such as from wastewater), resulting in UV filters being absorbed by marine species.
A 2022 study, for example, estimated that a thousand swimmers could deposit more than 36 kg (79 lbs.) of sunscreen per day into the water. The researchers said the freshwater “beach showers” in tourist locations were especially likely to transfer sunscreen into coastal waters.
According to a 2022 study by the National Academies of Science (NAS), measurements of most organic UV filters in water were below 1 microgram per liter (µg/L), with the exception of five UV filters in the range of 1 to 10 µg/L. While this is below the Environmental Protection Agency’s standard of 1,000 µg/L for “highly toxic,” some UV filters (such as for zinc oxide, oxybenzone, and dioxybenzone) had organisms with lethal concentrations under this threshold, along with three UV filters (avobenzone, octocrylene, and octinoxate) having organisms with lethal concentrations under 100 µg/L.
The study also acknowledges that “[t]he compounds used as UV filters are not used exclusively in products marketed as sunscreens. Many different products may contribute to the release and detection of UV filters in the environment.”
A 2025 review by University of Plymouth researchers of studies on the impacts of UV filters on marine organisms goes through a list of species and UV filter(s) tested on each species. For example, titanium dioxide was found to cause rapid bleaching, growth inhibition, and reduced moisture content in corals (Zoanthus sp.), skeletal malformations in sea urchins (Paracentrotus lividus), and death for zooplankton (Brachionus plicatilis) used for fish larvae feed.
Zinc oxide was found to inhibit growth in various algae and cellular damage in the Mediterranean mussel (Mytilus galloprovincialis).
It was estimated … that 25% of the sunscreen used by 78 million tourists—or about 4,000–6,000 tons—leached into reef areas in tropical countries.
It was estimated in a 2008 study, for example, that 25% of the sunscreen used by 78 million tourists—or about 4,000–6,000 tons—leached into reef areas in tropical countries. Since then, the 2025 review claims that “6,000–14,000 tons of UV filters wash into coral reef zones every year.”
UV filters such as oxybenzone and benzophenone-2 are a concern, as sunscreen with oxybenzone has been banned in Hawaii since 2021 and benzophenone-2 is a genotoxicant (or causes genetic damage) to corals. One 2015 study goes as far as to say that oxybenzone, also a genotoxicant to corals, “poses a hazard to coral reef conservation and threatens the resiliency of coral reefs to climate change.” A blog by the Victoria University of Wellington claims that at “concentrations comparable to one drop in 6 and a half Olympic-sized swimming pools, these compounds are a detriment to coral species.”
Unfortunately, traditional sewage and water treatment technologies, such as ozonation, cannot remove most UV filter compounds from the water, so overuse should be avoided. There has been research, however, on using biodegradable microbeads to absorb the oxybenzone and then removing the microbeads through the use of magnets.
Recommendations
In light of NAS’s 2022 study, the National Oceanic and Atmospheric Administration recommends mineral sunscreen over those with chemical UV filters, seeking shade between 10 am and 2 pm, using umbrellas and hats, as well as wearing UV protective clothing as an alternative. When applying sunscreen, the FDA recommends 2 milligrams per square centimeter of skin, which is the same amount used for testing SPF.
Consumers can begin to look for “reef safe” notations on the sunscreens they buy, said The New York Times, noting that Hero Superlight Sunscreen SPF 30 and Vanicream Facial Moisturizer with SPF 30 were examples of such products.
A group called Save the Reef, which has a Reef Safe Sunscreen Guide, urges consumers to check ingredients and avoid 10 items.
According to Harvard Health, everyone should use sunscreen because “we are all at risk of the adverse effects of UV radiation and can benefit from protection,” even more so for those with lighter skin.
“We recommend sunscreen for skin cancer prevention, including melanoma prevention, which has been demonstrated in cohort studies as well as prospective randomized trials,” says Dr. Jennifer Lin of Harvard Medical School in a 2021 interview. Regardless of skin color, “people looking to ward off the aging effects from sun would still benefit from sun-protective habits, which include sunscreen, sun-protective clothing, and sun avoidance,” she adds.
*Francesca Bell-Miller is a freelance writer and editor who currently resides in New England. She has worked on articles, newsletters, memoirs, and novels and aspires to publish her own novels. She believes strongly in the magic of language & storytelling.
Danika Cantrell, a freelance writer, assisted with research for the article.
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