The study was led by a group of US scientists from the University of Michigan School of Public Health and published in the peer-reviewed Journal of Clinical Endocrinology & Metabolism and compared individuals with high exposure to phthalates to those with lower exposure.
The cross-sectional study examined exposure in to phthalates and testosterone levels in 2,208 people who participated in the US National Health and Nutrition Examination Survey, 2011 – 2012 by measuring for 13 substances in volunteers urine samples, while testosterone was measured using blood samples.
Data linked high levels of phthalate to drop in testosterone
Of a range of data, the study found that in boys aged 6 – 12 increased concentrations of metabolites of a phthalate called di-(2-ethylhexyl) phthalate, or DEHP, was linked to a 24 to 34.1 percent drop in testosterone levels.
The study ultimately concluded that those individuals with higher levels of exposure to phthalates found in plastics and some personal care product tended to have reduced levels of testosterone.
In both sexes testosterone is seen as being of vital importance to physical growth, brain function and strength, but for men it is particularly important as is the main determining sex hormone.
Evidence of impact on reproductive development
“We found evidence reduced levels of circulating testosterone were associated with increased phthalate exposure in several key populations, including boys ages 6-12, and men and women ages 40-60," said one of the study's authors, John D. Meeker, MS, ScD, of the University of Michigan School of Public Health in Ann Arbor, MI.
"This 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."
What has sparked interest in endocrine disruptors such as phthalates is the fact that over the past 50 years there has been clear evidence that testosterone levels are declining in men, which has led to a rise in the number of medical related issues, as well as genital malformation in newborn boys.
Steps to limit exposure?
"While the study's cross-sectional design limit the conclusions we can draw, our results support the hypothesis that environmental exposure to endocrine-disrupting chemicals such as phthalates could be contributing to the trend of declining testosterone and related disorders," Meeker said.
"With mounting evidence for adverse health effects, individuals and policymakers alike may want to take steps to limit human exposure to the degree possible."