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STRONG VOICES

Janet Gray, Ph.D.
Janet Gray, Ph.D.

As author of our 2008 and 2010 State of the Evidence reports, Dr. Gray drives the science behind all our work.

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Sunscreens (UV Filters)

CATEGORY*: Endocrine disruptor

FOUND IN: Sunscreens

THE GIST: You shouldn’t have to choose between skin cancer and breast cancer. Research has found that many sunscreens contain chemicals that are estrogenic, disrupt the endocrine system and can play a significant role in breast cancer development. For example, octyl-methoxycinnamate, which is estrogenic and has thyroid hormone-disrupting effects, is found in over 800 sunscreens. Homosalate, a hormone-disrupting UVB blocker, is an ingredient in over 400 sunscreens.

State of the Evidence on Sunscreens (UV Filters)

Growing concern about exposure to ultraviolet radiation from the sun and the risk of skin cancer has led to widespread use of sunscreens. Many sunscreens contain some chemicals (also used in various cosmetics) that are not only estrogenic but also lipophilic (fat-seeking).

TIPS FOR PREVENTION

Avoid sunscreens containing octyl-methoxycinnamate and homosalate, and find a safer sunblock online.

More sunscreen tips >

Studies show these chemicals are accumulating in wildlife and humans (Hayden, 1997) and are found in human urine and breast milk samples following application (Felix, 1998; Kunz, 2006). NHANES data indicate that over 96 percent of U.S. adults have detectable levels of bexophenome-3 (Bp-3) in their urine (Calafat, 2008c).

In a study of six common sunscreen chemicals, five of them exerted significant estrogenic activity, as measured by the increase in proliferation rates of human breast cancer cells (MCF-7 cells) grown in vitro. These chemicals were 3-(4-methylbenzylidene)-camphor (4-MBC), octyl-methoxycinnamate (OMC), octyl-dimethyl-PABA (OD-PABA), bexophenome-3 (Bp-3) and homosalate (HMS) (Krause, 2012; Schlumpf, 2001). The results for 4-MBC have been replicated in another laboratory (Klann, 2005). 

In a common experimental procedure (the yeast assay) that measures the strength of a compound’s estrogenic response, mixtures of low concentrations (below the “no observed effect concentration”) of chemicals similar to those found in sunscreens had a synergistic effect – in other words, a greater effect in combination than individually (Kunz, 2006). Other studies indicate that in addition to acting like estrogen in many cellular pathways, compounds found in sunscreens can also antagonize, or work against, the effects of the natural estrogen estradiol in other pathways (Krause, 2012).

A recent laboratory rat study has demonstrated that application of OMC to the skin of the animals enhances the penetration of the endocrine-disrupting herbicide 2,4-D (Brand, 2007).

*For chemicals that have been shown to be carcinogens, we provide classifications from two authoritative bodies: the International Agency for Research on Cancer (IARC, an international body) and the National Toxicology Program (NTP, a division of the U.S. Department of Health and Human Services). We have categorized endocrine-disrupting compounds where the body of peer-reviewed research indicates a strong foundation for doing so.