Study links sunscreen to impaired male fertility

Certain sunscreen chemicals may impair men’s ability to father children in a timely manner, according to a recent National Institutes of Health study that an expert in male infertility called “interesting but very preliminary.”

Study authors, from the NIH and the New York state Department of Health’s Wadsworth Center, agreed that the results are preliminary and noted that additional studies are needed to confirm the findings.

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Benzophenone (BP)-type ultraviolet (UV) filters comprise a class of about 29 chemicals commonly used, among other purposes, in sunscreens and other personal care products to protect skin and hair from sun damage. Some of these chemicals, upon being absorbed by the skin, can interfere with the body’s hormones and endocrine system processes. Researchers found that men with high exposure to UV filters BP-2 or 4OH-BP had a 30% reduction in fecundity, the biological ability to reproduce.

“In our study, male fecundity seems to be more susceptible to these chemicals than female fecundity. The women participants actually had greater exposure to the UV filters overall, but their exposure wasn’t associated with any significant pregnancy delays,” said Germaine Louis, PhD, of the NIH’s Eunice Kennedy Shriver National Institute of Child Health and Human Development in Bethesda, MD in a news release. “Our next step is to figure out how these particular chemicals may be affecting couple fecundity or time to pregnancy-whether it’s by diminishing sperm quality or inhibiting reproduction some other way.”

Study findings were published online in the American Journal of Epidemiology (Nov. 13, 2014).

The researchers studied 501 couples that were trying to conceive a child. The couples were part of the Longitudinal Investigation of Fertility and the Environment (LIFE) study, established to examine relationships among fertility, lifestyle factors, and exposure to environmental chemicals. Researchers recruited the study participants from 16 counties in Michigan and Texas in 2005 through 2009. Female participants ranged from 18 to 44 years of age, and the men were over 18; none had a medical diagnosis of infertility.

The researchers followed the couples until pregnancy or up to one year of trying, to record the time it took for the women to become pregnant. They also tested participants’ urine samples and measured concentrations of five selected UV filters associated with endocrine-disrupting activity. The researchers controlled for age, body mass index, and smoking, among other factors.

Their findings suggest that some, but not all, UV filters may be associated with diminished fertility in men, independent of their partners’ exposure. The researchers observed effects among men with the highest exposure (the 75th percentile and above) to UV filters BP-2 or 4OH-BP.

Next: Two limitations

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The researchers pointed out two limitations of the study. First, they tested single urine samples from participants to assess chemical exposure, but participants’ levels of exposure may have changed over the course of trying for pregnancy. The researchers also had no data on what specific products the participants used that contained the UV filters.

“The results, in essence, are interesting, but very preliminary,” James M. Hotaling, MD, MS, of the University of Utah Health Care in Salt Lake City, told Urology Times. “You have to remember that they were checking these compounds in the urine, and all of these compounds have a half-life in the range of hours. The urine tests are just reflecting what these individuals did a day ago, not over a long period of time. The other issue is that there’s a blood-testis barrier, so it’s unclear how much of this is actually getting into the spermatogonial stem cells, where the sperm are being produced.

“I don’t think we should advise men not to use sunscreen at this point. I would need to see a lot more data,” Dr. Hotaling said.

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