|
||||||||
|
PUBLIC HEALTH Common Industrial Ingredient Appears Able to Stifle SpermPhthalates make perfumes linger longer, impart enough give to nail polish to prevent chipping, strengthen tool handles to resist breaking, and most often, show up as a softener in plastic to make the versatile and flexible polyvinyl chloride (PVC), used in items from building products to toys to medical devices.
Fewer and misshapen sperm were associated with the highest phthalate levels, according to the latest findings from HSPH and Massachusetts General Hospital researchers. The study team includes (l to r) Nelta Mercedt-Lozius, Linda Godfrey-Bailey (seated), Russ Hauser, Isaac Schiff, and Susan Duty. (Photo by Steve Gilbert) Now it appears that some phthalates (pronounced THAL-ates) may also make human sperm lethargic, misshapen, and less numerous, according to School of Public Health researchers and their colleagues. The report, published in the May Epidemiology, provides some of the first human reproductive data on phthalates, which may be present in nearly everyone by virtue of continual exposure to phthalate-containing products in daily life.
Documenting Sperm DamageThe latest finding is based on a study of 168 men from the infertility clinic at Vincent Memorial Obstetrics and Gynecology Service Andrology Laboratory and IVF Unit at Massachusetts General Hospital. Researchers found low sperm concentration and sperm motility in men with high urinary levels of MBP, an active phthalate metabolite of two kinds of phthalate, the smaller DBP molecules used in personal care products and the larger BBP used to soften plastic. A similar low sperm concentration was associated with high levels of MBzP, another phthalate metabolite of BBP. In an earlier study in the January 2003 Environmental Health Perspectives, Duty and her colleagues found that higher urinary levels of MEP, but not other phthalates, were associated with sperm DNA damage.Interestingly, MEHP, the phthalate metabolite of DEHP, the plastic-softening phthalate with the highest public profile for its use in intravenous tubing and other medical devices, showed no strong associations with semen quality in the adult men in the study; however, animal studies have shown testicular toxicity from prenatal and prepubescent exposures. "In contrast, DBP can apparently disrupt male reproduction at all stages of life," wrote environmental epidemiologist Jane Hoppin of the National Institute of Environmental Health Sciences, in an accompanying commentary. The Take-home MessageThe authors say these are preliminary results in the search for environmental agents that may contribute to declining sperm quality over the last 50 years. Based on this work alone, "it is not warranted to alarm the public," said senior author Russ Hauser, HSPH assistant professor of occupational health. "Furthermore, it is difficult to make recommendations on the important sources of phthalates, because they are in so many products. It is difficult to even begin studying the proportional contribution of various sources of phthalates to human body burden."Yet, even with little human data, public concern has been high enough to affect policy in several countries. Three years ago, the Centers for Disease Control and Prevention first reported that four phthalate monoesters, including MEP, MEHP, and MBP, were detectable in most people in the latest U.S. surveys that collect biological samples and information about health and diet, known as the National Health and Nutrition Examination Survey, or NHANES. High levels of some phthalates, especially in women of reproductive age, prompted a coalition of organizations to test 72 name brand beauty products, such as deodorant, shampoo, and nail polish. According to their report published last summer, "Not Too Pretty," none of the 52 phthalate-containing products lists the chemical on its label. Two years ago, an expert panel commissioned by the U.S. National Toxicology Program expressed "serious concern" for neonatal males exposed to DEHP, which leaches from PVC medical devices. The European Union and Japan have placed emergency bans prohibiting plastic children's toys from containing DINP, another phthalate. In new draft guidelines, the U.S. Food and Drug Administration warns that DEHP in medical devices may pose a health risk to certain vulnerable groups, such as male fetuses and neonates and prepubescent boys. The guidelines recommend that manufacturers label DEHP-containing products and that exposures be minimized through the use of alternative products, said Ted Schettler, an internist at Boston Medical Center and science director of the Science and Environment Network, a member of the coalition Healthcare Without Harm. "This whole family of chemicals has been used in commerce for 50 years," he said, "and we're only now getting around to looking at these effects." --Carol Cruzan Morton |
