A new study published December 1, 2020 in Oncotarget revealed that the common sunscreen ingredient benzophenone-3, also known as oxybenzone or BP-3, can play a role in the development of mammary gland tumors, according to new research in mice. The study showed estrogenic activity as a proliferative stimulus to MCF-7 breast cancer cells.
Oxybenzone is an easily absorbed chemical that is also a suspected endocrine disrupting chemical (EDC), substances that interfere with hormonally regulated processes the body uses for a wide range of functions, including mammary gland development.
Nearly all mice developed two kinds of aggressive breast cancer tumors. The first, known as epithelial tumors, retain many of the properties of normal mammary gland cells. The second, known as spindle cell tumors, lose most of the properties of normal cells and develop into a deadly, often triple negative form of breast cancer known as claudin-low breast cancer.
A recent report in the Journal of the American Medical Association found that after just one heavy application of sunscreen, blood levels of BP-3 exceeded the Federal Drug Administration’s guidance for chemicals at a threshold of toxicological concern, and the Centers for Disease Control found Oxybenzone in 98% of adult urine samples.
Using a mouse model where the mammary glands lacked a gene often mutated in human breast cancer as a proxy for women growing from puberty into adulthood, the researchers put the mice under three distinct dietary regimes: a lifelong low-fat diet, a high-fat diet during puberty switching to a low-fat diet during reproductive years, and vice versa.
The experiment split mice on these three diets into two groups. One of these groups was fed BP-3 daily at a dose equivalent to a heavy application of sunscreen on a beach day.
Over the course of a year and a half of treatment, the researchers collected tumors from the mice and found robust evidence for the adverse effects of diet and Oxybenzone on breast cancer development.