Phthalates are a group of chemical compounds used as plasticizers in many household items - ranging from soaps, shampoos and cosmetics to plastic containers, toys, piping and even medicines. Due to their effects on the hormonal system, phthalates have previously been connected to reproductive problems in baby boys, but now, researchers have also linked the chemicals to abdominal obesity and insulin resistance in adult males. The new study, carried out by researchers from the University of Rochester Medical Center, adds to the growing suspicion that low-dose exposures to phthalates and other common chemicals may be reducing testosterone levels in men, and thereby contributing to rising obesity rates and related disorders like Type 2 diabetes.
The study came about after Rochester researcher Richard Stahlhut hypothesized that phthalates might have a direct link to obesity, since low testosterone appears to cause increased belly fat and pre-diabetes in men. To investigate further, the Rochester team analyzed urine, blood samples and other data from the National Health and Nutrition Examination Survey; a large sampling of the U.S. population acquired routinely by the CDC.
The researchers found that, as expected, several phthalate metabolites showed a positive correlation with abdominal obesity. In fact, men with the highest levels of phthalates in their urine had more belly fat and insulin resistance. The study also estimated that more than 75 percent of the United States population has measurable levels of several phthalates in their urine.
The new research, appearing in the journal Environmental Health Perspectives, follows on from previous work that found that phthalates depress testosterone levels in animals. In other past studies, it was found that the chemicals were linked to smaller penis sizes and a variety of testicular problems in adolescence. Phthalates have also been associated with poor semen quality in men.
"Substantial declines in testosterone levels and sperm quality have been observed over the last several decades and it urgently requires explanation," Stahlhut said. "While we can't say yet that phthalates are a definite cause, I am certain they are on the list of chemicals that demands careful study."
While a European study has previously found that routine exposure to two of the most common phthalates should not pose a risk to humans, concerns remain. "Unfortunately, there's still a lot to learn about phthalates," Stahlhut noted. "The more difficult issue is what combinations of common low-dose chemical exposures might be contributing to these problems."
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Source: University of Rochester Medical Center
