Effects of Benzophenone Ingredients in Your Sunscreen

Introduction

Sunscreens aim to block ultraviolet (UV) rays that can cause photodamage or contribute to carcinogenesis using organic or inorganic filters. The main active ingredient in 70-80% of sunscreens today is the organic filter oxybenzone.¹ Oxybenzone, also known as Benzophenone-3, is an aromatic hydrocarbon used as an ultraviolet light filter in sunscreens.^2,3 It absorbs short wave UVB light, which largely contributes to the development of skin cancer and is a factor in photoaging, and short-wave UVA light, which plays a larger role in photoaging. Organic filters such as oxybenzones are widely used in sunscreen formulations and personal care products as a photo-stabilizer to prevent color and odor changes. In fact, the US Centers for Disease Control and Prevention estimates that 96.6% of the US population is exposed to oxybenzone.³

Exposure and absorption

Oxybenzones have been measured in human urine, breast milk, and serum samples in many places across the world.^1,2 A randomized controlled study investigated daily application of oxybenzone-containing sunscreens and found oxybenzones present in samples of plasma and urine, indicating that there is substantial skin penetration, uptake, and urinary excretion of this compound in adults.⁴ Nonetheless, disruption of the hypothalamic-pituitary axis as it relates to reproduction was not observed. It should be noted that children have a higher surface area to volume ratio and more immature drug elimination mechanisms, so the impacts on this population requires further investigation.

The potential for biological effects of oxybenzones was first published by Schulmpf et al.⁵ who reported estrogenic activity via increased uterine growth upon oral administration of oxybenzones in immature rats. A more recent study calculated the number of years a person would need to apply sunscreen daily in order to reach the level of exposure investigated in the rat study and concluded that it would be unattainable in a typical lifespan.⁶ Even so, much controversy still exists.

Developmental impacts

Oxybenzone has also been investigated as a disruptor for normal development. Kim and Choi¹ argue that receptor binding assays using oxybenzones display adverse endocrine impacts, such as anti-androgen and anti-estrogen activity. Huo et al.⁷ also investigated the effects of prenatal oxybenzone exposure and Hirschsprung’s disease, which is a failure of neural crest cell migration in the intestine during embryogenesis. They concluded that maternal oxybenzone exposure was associated with fetal development of Hirschsprung’s disease, likely due to chemical inhibition of cellular migration.

Dermatologic impacts

A review article outlined several studies which identified oxybenzone as a photoallergen associated with contact dermatitis,⁸ photocontact allergy and contact urticaria.² The American Contact Dermatitis Society identified benzophenones as the 2014 Allergen of the Year, with oxybenzone as the most frequent and common reactor of this class. It was found in 68% of the 201 sunscreens tested. Oxybenzones were also found to have high rates of cross-reactivity octocrylene, another active sunscreen ingredient, and ketoprofen, a topical nonsteroidal anti-inflammatory.⁸

Environmental impacts

Oxybenzones can enter the environment through several routes: from chemical manufacturing and runoff, by washing off into the water from applied sunscreens, and by accumulating in municipal water sources (oxybenzones are not well filtered with our current water treatment practices).³ The presence of oxybenzones has been shown to affect the ecosystems where it is found. Animal studies report oxybenzones in the tissues of wild-living fish in many areas of the world and some studies link oxybenzone exposure to impaired reproductive function in these species related to its estrogenic properties.³ Additionally, it is estimated that up to 14,000 tons of sunscreen, some of which contain up to 10% oxybenzone, are released into coral reef areas each year, which puts them at risk for bleaching.⁹ Corals “bleach” by expelling the algae living in their tissues when under stress, which can be exacerbated from chemicals such as oxybenzones and octinoxate. This can lead to reef death, which is an increasing problem worldwide.¹⁰

Alternatives

The U.S. Food and Drug Administration has approved two inorganic filters for use in sunscreens: zinc oxide and titanium dioxide. These molecules reflect, absorb, and refract UV photons, providing sun protection.¹¹ Zinc oxide has a broad UVA-UVB absorption curve and titanium dioxide provides better UVB protection. Nanoparticles of these compounds are often used to prevent a chalky appearance on the skin and adding iron pigments can conceal the white appearance of these sunscreens. Upon investigation, nanoparticles of zinc oxide and titanium dioxide are advantageous in creating a non-greasy formulation that is transparent, inexpensive, and resistant to degradation from UV radiation.¹²

Importantly, the human health risks with these inorganic filters are very low because there is no percutaneous absorption of these compounds; however, there is a potential inhalation absorption risk, so spray products with nanoparticles are not recommended.¹¹ As of now, the known environmental risk is low, but increased usage and additional studies may reveal more.

Practical Tips

1. Oxybenzones are harmful to coral and other aquatic species, so avoiding products with this ingredient is a helpful step to protecting the environment.
2. Oxybenzones are a potential contact and photocontact allergen, so consider avoiding sunscreens using this active ingredient if they cause irritation.
3. Zinc oxide and titanium dioxide-containing sunscreens are good alternatives to oxybenzones and other organic UV filters, with lower risk of harm for the environment and body.