Sunscreen Lotions: Do They Block More Than Just Sun?
Using a cell-proliferation assay, which measures increased growth in a cultured breast cancer cell-line following exposure to estrogen or estrogen-like chemicals, Schlumpf found that eight out of ten sunscreen-filters tested positive.
“Of the ones we tested, we did not find many UV-filters that were inactive.”
But cell-proliferation assays don;t measure activity in living creatures, and as many scientists will note, activity “in the test-tube,” does not necessarily imply activity in the body.
Estrogen has many different roles in the body, from maintaining normal brain function to essential roles in breast development, puberty and pregnancy. In mammals, estrogen stimulates growth of the uterus, and over the years, scientists have employed uterine growth as a sensitive marker of estrogenic activity in living animals. Using this assay, Schlumpf and her colleagues reported in the journal Toxicology that six out of nine sunscreen filters tested positive for uterine growth in rats. The researchers noted, however, that effective concentrations of sunscreens were well above those we, or our kids are likely to encounter after a weekend in the sun.
Haven’t these products passed a battery of tests before reaching our skin? Why, if these chemicals have been in use for decades, are we just finding out about these endocrine disrupting properties now? Turns out they are tested, but, as “Over-the Counter” drugs, not as rigorously as prescription drugs, or even some pesticides and industrial chemicals.
Although I couldn’t get a straight answer from the FDA when I asked if these chemicals had been tested specifically for endocrine disrupting activity, they did respond that it is suggested, but not required that chemicals such as sunscreen filters be tested for adverse effects on endpoints like fertility and embryo or fetal toxicity. As a toxicologist, I understood this to mean they’ve likely not been tested for the subtleties of endocrine disruption. And these days, it seems the more researchers look, the more they find chemicals capable of endocrine disruption.
Marianne Balmer, another Swiss researcher from the Swiss Federal Research Station, measured quantities of UV-filters in both Swiss lakes and in fish tissues. “For small rivers, wastewater treatment plants were the main source of UV-filters. But, in lakes used for recreational activities, direct imputs, washing off from the skin during bathing, may contribute significantly to the UV-filter load,”
Closer to home, some UV-filters have turned up in coastal waters receiving sewage treatment effluents in New York and in California where researchers reported finding male fish carrying not only sperm but eggs as well, (although they cannot at this time point to any one environmental chemical as the cause). The United States Geological Survey has added sunscreen-filters to their growing list of chemicals detected in our nation’s waters, and they are currently developing methods for detecting UV-filters in sediments.
When asked for thoughts on the application of UV-filters to infants, young children, and/or pregnant women, those considered most sensitive to the impacts of endocrine disrupting chemicals, Dr. Schlumpf replied, “ I wouldn’t advise pregnant women and small kids to put on tons of sunscreen, but I would recommend they protect their skin. Not being in the sun all the time will reduce the amounts of sunscreen used greatly.”
My kids aren’t so small anymore, but now, besides the tube of sunblock, I’ve got a couple of SPF-30 t-shirts tucked away in the beach-bag.