Four chemical mixtures were developed from the initial 11 chemicals. The resulting mixtures were also been tested on human fetal testes. The scientists observed that the mixtures inhibited testosterone production in human fetal testes. The research team also developed a mathematical equation that determined the potential side effects of a mixture of endocrine disruptors. According to the experts, the study serves as the pioneering research on how a mathematical equation can predict the onset of adverse medical conditions following chemical exposure.
"There is a very precise critical window during the first trimester of fetal development during which simultaneous exposure to weak doses of multiple endocrine disruptors may represent a risk to the development of the child’s genitals and reproductive system. It is particularly concerning as the individual potency of these chemicals can be exacerbated by up to a factor of 1,000. All the experimental data from different models lead us toward the same conclusions. This experimental proof of concept study shows that intensifying research into identifying the real mixtures to which individuals are exposed, and testing the effects on appropriate models, is a necessity,” study leader Bernard Jégou states in a press release.
Another study shows that prenatal exposure to endocrine disruptors not only affects reproductive health, but may also impact brain development. A team of scientists pooled data from the EDEN Mother-Child Study Group with a total cohort population of 529 young boys born between 2003 and 2006 and their mothers. According to the researchers, all of the mothers had been exposed to endocrine disruptors such as bisphenol A, triclosan and dibutyl phthalate (DBP). The findings showed that the chemicals induced behavioral problems in young boys.
"Exposure to bisphenol A was associated with increased relationship problems at three years and hyperactivity problems at five years, thus confirming that the effects of bisphenol A on the behavior observed in laboratory animals also occur in humans at low levels of exposure," the researchers explain.
Likewise, the scientists observed that exposure to DBP is associated with increased emotional and relationship problems such as internalizing behavior at three years old. Triclosan is also found to raise the odds of emotional problems at ages three and five. The research team adds that the chemical is shown to reduce in head circumference at birth.
According to the experts, triclosan interacts with the thyroid axis, which plays a central role in fetal brain development. However, the findings did not show a direct correlation between endocrine disruptors and neurodevelopmental conditions such as autism spectrum disorder. (Related: Plastics chemicals BPA, BPS linked to altered brain development.)
"The observed associations between BPA, MnBP, and behavior in boys are consistent with previous findings. Further health impact assessment studies based on dose–response functions corrected for exposure misclassification are required to quantify the public health burden possibly entailed by such associations," the researchers report in the Environmental Health Perspectives journal.