Sunscreen Lotions: Do They Block More Than Just Sun?
Slip, slop, slap. Sunscreens are a summer staple. When the kids were young, I slathered the stuff all over them. As a toxicologist, I knew better. As a mother, I just wanted the convenience of allowing them a day at the beach, free to play in surf and sand without fear of sunburn.
From my own work, I know that any additional chemicals we add to our bodies and our environment come with some risk. As a mother and a consumer, I want to believe that all those federal protections really work. I want to believe that something that comes in pink bottles with pictures of beach balls and kids splashed across the front of them is safe.
My kids are now nine and twelve. Roughly ten years and countless pink bottles later, I read that those UVA- and UVB-chemical blockers, the active ingredients we look for in our sunblock, can now be categorized as endocrine disruptors, a group of chemicals which includes pesticides, plasticizers, and natural and synthetic hormones. Chemicals that interfere with normal development and reproduction.
Ever since the Federal Food and Drug Administration first approved of sunscreen products for the protection against skin cancer in the 1970’s, the sunscreen industry has thrived, growing into a nearly billion dollar business. During the summer months, young and old alike entrust their skin to the protective qualities of an array of sunblock crèmes and lotions, applying the stuff liberally, several times a day.
The sun’s ultraviolet rays can damage skin in at least two ways. The longer UVA rays that constitute the majority of sun’s ultraviolet light reaching the earth are responsible for “tanning” and penetrate deep into the skin, while the shorter UVB rays penetrate fewer layers of skin, causing “sunburn.” While the UVA rays are blamed for premature ageing of the skin, both rays are capable of causing skin cancers.
Sunscreen filters work by absorbing the sun’s high energy rays and chemically converting that potentially harmful energy into heat and less energetic, less harmful rays. But, it may just be that the chemical structures necessary for absorbing and converting UVA and UVB rays, are also capable of combining with chemical receptors in the body that, under normal circumstances combine only with our natural chemical messengers like estrogens (female hormones) and androgens (male hormones.)
“I first became interested in UV-filters after a colleague reported their presence in human breast milk,” says Margret Schlumpf, from the University of Zurich, who discovered that the majority of sunscreens filters tested are endocrine active in mammals. It turns out that once applied to the skin, some UV-filters are absorbed and distributed throughout the body with some ending up in baby’s milk.
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.
As a mother, I was satisfied by this news, that over the years I hadn’t caused inadvertent sex-reversal in either of my children (although sometimes I think delayed puberty might not be such a bad thing,) but I wondered about those federal protections.
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.
In essence we are exposed to mixtures of chemicals, albeit at low concentrations, that may be capable of greater activity when combined. When I asked Dr. Schlumpf if any one sunscreen is likely to have more than one endocrine disrupting or estrogenic chemical (increasing the total amounts of these chemicals to which one might be exposed,) she replied, “Many have more than one UV-filter. Then there are some synthetic perfumes, and other chemicals like pthalates, those chemicals commonly found in cosmetics and plastics (that can also serve as endocrine disruptors.)” And that’s just in one lotion.
Schlumpf isn’t the only researcher concerned about the impacts of sunscreen filters. Karl Fent’s laboratory at the University of Applied Sciences Basil, Switzerland, reported on the estrogenic activity of UV-filters in fish in the January 2006 issue of Toxicological Sciences. When asked why fish, he responded, “We did an earlier study with UV-filters in frogs and wondered about other important aquatic species. Residues of UV-filters are found in fish.”
Ten out of the twenty-three sunscreen filters tested by Fent’s group had estrogenic properties, and three out five tested were active in live-fish, capable of inducing production of egg-yolk protein, a common test for estrogenic activity in egg-laying animals.
Though Fent noted that, “Profound effects occurred at concentrations higher than in the environment so the question of impact on wild fish populations is open.”
This is especially true when one considers that for each complex mixture of endocrine disrupting chemicals in any one brand of sunscreen that washes off our skin while swimming or later, in the shower, there are hundreds if not thousands of other endocrine disrupting chemicals that make their way from our homes and our bodies into the aquatic environment.
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.
