University of Michigan School of Public Health researchers have conducted a study that explores “relationships between urinary concentrations of 13 phthalate metabolites and serum total T levels among men, women, and children when adjusting for important cofounders and stratifying by sex and age.” John Meeker & Kelly Ferguson, “Urinary Phthalate Metabolites Are Associated with Decreased Serum Testosterone in Men, Women, and Children from NHANES 2011-2012,” Journal of Clinical Endocrinology & Metabolism, July 2014. Phthalates are found in plastics and some personal-care products. The researchers found reduced levels of circulating testosterone associated with increased phthalate exposure in certain populations, including boys ages 6-12 and men and women ages 40-60. Of the 13,431 subjects screened in the 2011-2012 NHANES cycle, only the 2,208 participants with both T and phthalate metabolite levels were included in this study.

The researchers found that women ages 40-60 with increased phthalate concentrations were associated with a 10.8- to 24-percent decline in testosterone levels, while boys ages 6-12 with increased concentrations of metabolites of a phthalate known as DEHP had a 24- to 34.1-percent decrease in testosterone levels. Study co-author John Meeker said that the findings “may have important public health implications, since low testosterone levels in young boys can negatively impact reproductive development, and in middle age can impair sexual function, libido, energy, cognitive function and bone health in men and women.” See Endocrine Society Press Release, August 14, 2014.

According to a news source, the U.S. Centers for Disease Control and Prevention (CDC) withdrew certain data released in July 2014 from NHANES 2011-2012, indicating that it had discovered an error in sampling weights. Among the biomonitoring data corrected in updated tables posted to the CDC Website were measurements of exposure to phthalate metabolites. Because the data corrected involved information released long after this paper was prepared and peer-reviewed, it is unlikely that the observed associations would be affected. See Bloomberg BNA Product Safety & Liability Reporter™, August 18, 2014.