Avobenzone and Octinoxate: Silent Killers

First Posted: Mar 07, 2025 07:01 PM EST

With skin cancer rates on the rise worldwide and exposure to UV radiation from the sun accounting for 90% of nonmelanoma cases, sunscreen sales are also up. However, the public has recently started paying attention to scientific studies that show that the organic compounds that make up the majority of our sunscreens and cosmetic products might be doing harm as well as good.

Over-the-counter sun protections contain ultraviolet filters (UVFs) that are either organic (absorb and convert UV rays) or inorganic (mineral-based molecules including Zn0 and TiO2 that reflect UV rays). Organic filters are more widely used in sunscreens, and in order to provide broad-spectrum protection against UVA and UVB radiation, formulas typically have a mixture of different organic UVFs as well as inorganic ones.

In May 2024, organic UVFs, notably avobenzone and octinoxate, gained attention as lawsuits in the U.S. were brought against Walmart and Big Lots for marketing their sunscreen brands as "reef friendly" or "reef conscious" despite containing compounds that recent scientific studies have proven to be dangerous for reefs and marine ecosystems. The lawsuits claim consumers willingly pay more for products that are sustainable but rely on product labels to provide accurate information.

The average consumer is generally unaware that the products they use to protect their skin contain UVFs like avobenzone and octinoxate that have negative impacts on the environment and, ultimately, on human health. More studies need to be done, but existing scientific research conclusively shows that current regulations worldwide need to be changed in order to start protecting human and animal life.

Environmental Deterioration

UVFs reach aquatic environments either when released from swimmers' skin or from domestic wastewater inputs, and avobenzone and octinoxate have been detected in ambient water (marine and freshwater) at significant levels, particularly during tourist seasons. One study concludes that, "Serious adverse effects have been reported for several OUVFs in aquatic ecosystem, which include coral bleaching and mortality, growth retardation, and reproduction damages in marine and freshwater organisms."

The frequency and spatial extent of coral bleaching has increased dramatically over the past 20 years. Sunscreens, even at extremely low concentrations, have been found to be a main contributor to this because UVFs "are able to induce the lytic viral cycle in symbiotic zooxanthellae with latent infections." Such viral infections, along with pollution, temperature anomalies, and high irradiance, cause coral bleaching. UVFs such as avobenzone and octinoxate are therefore not "reef safe" because they cause coral bleaching and harm the marine ecosystem as they "significantly increase the viral abundance in marine bacterioplankton through prophage induction, and they also modify the carbon, nitrogen and phosphorous biogeochemical cycle in seawater."

Research on the acute and chronic effects UVFs have on aquatic organisms is limited, but studies evaluating the impact that environmentally relevant concentrations of UV filters have on Daphnia magna (water fleas) show that while not fatal, their reproductive and antioxidant defense systems are compromised and basic physiological traits and cellular defense pathways are altered. Another study that exposed zebrafish embryos to sublethal concentrations of UVFs found that they decreased thyroid hormone levels. The authors concluded that "Toxicological consequences of altered TH homeostasis, neurobehavior, and kidney function at the early life stage warrant further investigations not only in humans but also in aquatic ecosystems." On land, a study of perinatal octinoxate exposure in rats showed impacts on the reproductive (i.e., decreased sperm count) and neurological development of rat offspring.

Human Health Concerns

Such studies demonstrate that UVFs are systematically associated with various deleterious effects in all organisms observed, with strong endocrine implications, consequences for neuronal, motor, and retinal development, and consequences for the renal, hepatic, and reproductive systems. Fewer analyses have been done on human subjects, but there is a sound assumption that if aquatic organisms and rats are affected in such ways, human systems are as well.

Organic sunscreens have a higher risk of causing allergic contact dermatitis, particularly because avobenzone is unstable and does not protect against UVB rays, so it is often combined with other UVFs (such as octinoxate), which can result in breakdown products that irritate the skin. Once organic UVFs have been applied to the skin, they also easily enter the bloodstream. For example, octinoxate in urine samples has been found at levels up to 0.58 μg/g creatinine and avobenzone in plasma up to 11 μg/L, exceeding the threshold levels established by the U.S. FDA. A 2020 FDA study found octinoxate in blood samples at levels 16 times their recommended safety threshold.

Exposure to endocrine-disrupting chemicals (EDCs) during early life stages is particularly alarming because of a higher vulnerability for EDCs to disturb developmental processes with structural implications that appear later in life. Analyzing human milk provides insight into prenatal and infant chemical exposure, and one study found UVFs in 85.2% of milk samples, whereas another noted that octinoxate was present in five out of six human milk samples. This same study also confirms that some UVFs (including octinoxate) increase cell proliferation in MCF-7 breast cancer cells.

It is worth noting that some of the mothers sampled did not apply sunscreen, and this is explained by the use of UVFs as stabilizers and as protection against photodegradation in other cosmetics and personal care products (PCPs), including perfume, lip balms and lipsticks, face and hand creams, aftershaves and foundation makeup. Indeed, a Swiss study analyzed 116 such products and found that 71% contained avobenzone, 51% had octinoxate, and 78% of all perfumes contained avobenzone. This implies that UVFs are being applied on a regular basis through PCPs and are also being inhaled.

Regulatory Landscape

Considering the ubiquitous presence of UVFs in sunscreen and PCPs, one would expect these compounds to be highly regulated and measured, but that is not the case. In the EU, Regulation no. 1223/2009 of the European Commission says PCPs and sunscreens must list the products' ingredients, and UVFs must fall under specified thresholds ranging from 2–15%. In the US, manufacturers are allowed to use UVFs at concentrations higher than in the EU despite a 2021 update from the FDA that only gave a "generally recognized as safe and effective" (GRASE) label to two inorganic UVFs: zinc oxide and titanium dioxide. The FDA said that "because of inadequate data to support a safety finding," it could not give GRASE status to organic UVFs, including avobenzone and octinoxate.

However, a few locations have taken matters into their own hands. The first was the state of Hawaii, which put a law into effect in 2021 banning the sale of sunscreens containing oxybenzone and octinoxate. They were followed by Palau, the U.S. Virgin Islands, Aruba, Bonaire, and some nature reserves in Mexico. Such bans sparked the marketing of "reef friendly" sunscreens that are oxybenzone and octinoxate free, but 92% of them contain other organic filters that have a proven negative impact on hard coral and aquatic ecosystems. There is currently no legislation in place regulating which products can claim to be "reef safe," but the lawsuits against Walmart and Big Lots might change that.

Human health is closely linked to the biodiversity and effective functioning of our reef ecosystems and marine life, with an estimated half a billion people directly sustained by them. Negative effects observed in aquatic organisms and rats exposed to UVFs on the endocrine, reproductive, antioxidant defense, and neural systems (among others) point to a need to study the impacts on humans further. All these factors beg for stricter regulations on UVFs, such as avobenzone and octinoxate, that guide people towards choosing products that are safer for them and for the planet.

1 https://www.skincancer.org/skin-cancer-information/skin-cancer-facts/