Matta et al. conducted a randomized clinical trial for the FDA, published in JAMA in 2019. They applied sunscreen at the recommended 2 mg per square centimeter to 75% of body surface area, 4 times daily for 4 days, and collected 30 blood samples over 7 days. All four tested ingredients (avobenzone, oxybenzone, octocrylene, and ecamsule) exceeded the FDA threshold of 0.5 ng/mL after just a single application. Oxybenzone was the most absorbed, reaching 209.6 ng/mL in spray formulations and 169.3 ng/mL in lotion. The 0.5 ng/mL threshold is the level above which the FDA requires additional safety studies before an ingredient can be considered safe without further data.

Matta et al. published a larger follow-up study in JAMA in 2020, testing 6 active sunscreen ingredients across 4 formulation types (lotion, aerosol spray, nonaerosol spray, and pump spray). All 6 ingredients exceeded the 0.5 ng/mL threshold after a single application. Oxybenzone reached 258.1 ng/mL in lotion and 180.1 ng/mL in aerosol spray. Homosalate and oxybenzone remained above the safety threshold at day 21, a full 3 weeks after the last application. The study collected 34 blood samples per participant over 21 days and confirmed that systemic absorption occurs regardless of sunscreen formulation type.

Calafat et al. analyzed urine samples from 2,517 participants aged 6 and older in the nationally representative National Health and Nutrition Examination Survey (NHANES) 2003-2004 cycle. Benzophenone-3 (the chemical name for oxybenzone) was detected in 96.8% of samples, with a mean concentration of 22.9 micrograms per liter. Women and girls had higher concentrations than men and boys. By the 2011-2012 NHANES cycle, the mean had risen to 36.3 micrograms per liter, a 58.6% increase. The near-universal detection shows that sunscreen chemicals enter and circulate in the bodies of almost all Americans, including children. Published in Environmental Health Perspectives.

Downs, DiNardo, Stien, Rodrigues, and Lebaron (Sorbonne University/CNRS) tested 16 commercial sunscreen and anti-aging product lines containing octocrylene. Published in Chemical Research in Toxicology in 2021, they found that octocrylene breaks down into benzophenone over time. Initial benzophenone levels averaged 39 mg/kg and ranged from 6 to 186 mg/kg. After simulated aging, concentrations rose to an average of 75 mg/kg (range: 9.8 to 435 mg/kg). Benzophenone is classified as a possible human carcinogen and endocrine disruptor, and is banned as a food additive in the US due to cancer concerns. The finding means sunscreen users may unknowingly apply increasing amounts of a carcinogen as their product sits on the shelf.

The EU Scientific Committee on Consumer Safety (SCCS) issued opinions in 2021 reassessing the safety of several UV filters used in sunscreen. They concluded that oxybenzone (benzophenone-3) at the current maximum concentration of 6% in body products is not safe for consumers. The SCCS recommended reducing the maximum allowed concentration to 2.2% for body products. Similarly, homosalate was found safe only up to 0.5% in body products, far below the concentrations commonly used in US products (up to 15%). These regulatory downgrades were based on updated absorption data and endocrine disruption concerns, and represent the judgment of independent toxicologists that current exposure levels pose a risk.

Ghazipura et al. conducted a systematic review of 23 human and animal studies examining oxybenzone and reproductive toxicity, published in Reproductive Toxicology in 2017. In human studies, urinary benzophenone-3 levels in 588 adolescent males were associated with lower serum total testosterone. The review found that oxybenzone interacts with hormone receptors, alters steroid metabolism, and influences the hypothalamic-pituitary-gonadal axis. While the authors noted that evidence in humans remained limited, the consistency of endocrine disruption findings across animal and human studies raised concern about chronic exposure from daily sunscreen use.

Huo et al. published a review in 2021 examining prenatal exposure to UV filter chemicals. Oxybenzone was detected in the urine and blood of pregnant women as well as in fetal and umbilical cord blood, demonstrating that the chemical crosses the placental barrier. Women with medium to high urinary oxybenzone levels showed associations with adverse birth outcomes, including reduced birth weight in female infants. Oxybenzone is present in approximately 70% of commercial sunscreen products. The finding that these chemicals reach the developing fetus is particularly concerning given the heightened vulnerability of fetal tissues to endocrine-disrupting compounds during critical developmental windows.

Hawaii signed SB2571 into law in July 2018 (effective January 2021), becoming the first US state to ban the sale of sunscreens containing oxybenzone and octinoxate. Testing at Kahaluu Bay found oxybenzone concentrations at 262 times the EPA high-risk threshold for aquatic life. An estimated 14,000 tons of sunscreen enter coral reef areas annually worldwide. The ban represents a regulatory body accepting that the evidence of harm from these chemicals - both to marine ecosystems and by extension to humans who consume affected seafood and swim in contaminated water - is sufficient to restrict their use. Key West, Florida and the US Virgin Islands followed with similar bans.

Research from the University of Zurich found UV filter chemicals in the breast milk of Swiss mothers. At least one sunscreen chemical was detected in 85% of samples tested. Oxybenzone has also been detected in urine, blood, semen, and amniotic fluid in various studies. The presence in breast milk means breastfed infants receive direct exposure to these chemicals during a period of rapid development when the endocrine system is particularly sensitive. This pathway of exposure is in addition to any direct skin application of sunscreen on infants. The findings demonstrate that maternal sunscreen use creates an exposure route that bypasses any choice about applying sunscreen directly to an infant.