In a study published Jan. 15 in the journal Environmental Health Perspectives, researchers reported that oxybenzone, an ultraviolet filter used in sunscreen, and propylparaben, an antimicrobial used in cosmetics and personal care products, may damage DNA in breast cells at acute exposures.

Oxybenzone and propylparaben are xenoestrogens, which are chemicals that mimic the female sex hormone estrogen in the body. Some types of breast cancer cells, called estrogen receptor-positive breast cancers, require estrogen to grow. 

The team found that only cells with estrogen receptors were affected by exposure to the two chemicals and that cells without estrogen receptors were unaffected. The researchers relied on breast tissue cells cultivated in the lab and on mouse mammary glands for their investigations. 

Previous related research has focused on levels of xenoestrogens needed to activate specific genes in breast cancer cells or accelerate their growth. The chemical levels needed for those types of impacts exceed the levels that most women would typically be exposed to by ordinary cosmetic and personal care product usage. This study demonstrated that levels 1/10th to 1/30th of previously determined concentrations were enough to trigger changes in breast cancer cell DNA.

D. Joseph Jerry, professor of veterinary and animal sciences at the University of Massachusetts Amherst and a study co-author, said in a university press release that the U.S. Food and Drug Administration generally uses cells without estrogen receptors when testing these chemicals for toxicity.

Jerry cautioned that more research is needed before general consumer advisories can be made, especially regarding the use of sunscreens for the prevention of skin cancer. However, he noted, oxybenzone and propylparaben may present a “significant hazard” for women at high risk of breast cancer and those with a history of estrogen receptor-positive breast cancer.

A study published a week later on Jan. 21 found that six sunscreen chemicals, including oxybenzone, were absorbed in a single application and that chemical concentrations exceeded the FDA threshold for needing additional safety studies.

A 2019 study found a link between exposure to phthalates, parabens and phenols, endocrine-disrupting chemicals commonly found in personal care products, and the early onset of puberty in girls. Early onset of puberty is concerning due to its association with increased risk of breast and ovarian cancers and mental health problems.  

According to the nonprofit Environmental Working Group, oxybenzone is used in 60% of non-mineral sunscreens in the U.S. Oxybenzone has been found in human breast milk, amniotic fluid, urine and blood.