Two new studies published this month suggest that exposure to common endocrine disruptors may reduce fertility in men. Both reports examined phthalates, chemicals that are used to produce plastics and other products, and found that male infertility may partially result from these common chemicals. The two studies, published separately, add to a growing literature indicating that exposure to endocrine disrupting chemicals is bad for male reproductive health.
The first report, published in Environmental Science and Pollution Research International focused on the men in couples seeking fertility treatments in New Delhi, India. The couples, having been unsuccessful in previous attempts to conceive, were brought in and men had blood tested for levels of phthalates while their semen was tested as well. The results showed a positive relationship between the level of phthalates DEHP, DBP and DEP in the blood with male infertility, specifically problems with sperm, including sperm concentration, sperm motility and DNA damage. Those men with more phthalates had more significant problems with their sperm, likely contributing to their inability to produce offspring.
The second report, published in the journal Fertility and Sterility examined hundreds of couples in Michigan and Texas who were trying to get pregnant. This study differed from the previous study as the couples were not seeking any treatment for problems with fertility, and had simply decided to stop using contraceptives and try to conceive. The scientists found that increased levels of the phthalates mMP, mBP, mBzP and mECPP were found in significantly higher levels in men than in women for couples that were unable to achieve pregnancy during the five years that the study ran.
Furthermore, mMP, mBP and mBzP were associated with the amount of time required for successful impregnation. Given that these associations were not seen in women, it was speculated that male infertility, specifically, was partially to blame for longer times to conception and that this result was associated with the chemicals commonly found in certain types of plastic. Additionally, the researchers stated that the decrease in fecundity seen in their subjects was equal to that associated with both smoking and obesity.
Previous research has shown that Bisphenol A (BPA) and the phthalates can be associated with decreased success of fertility treatments amongst people seeking help conceiving. Just last month, Bisphenol A or BPA levels in pregnant women were found to be associated with increased risk of miscarriage in couples who had sought assistance in achieving a pregnancy, and that this was due to problems that occurred both before and after implantation of the embryo. BPA has also been previously found to impair sperm production in animals and damage the DNA in human sperm as well.
These are not the only health problems associated with these common plasticizers. Behavioral changes in preschool aged girls have been found as have increases in obesity and diabetes. BPA and certain phthalates, including DEHP, have also been associated with reproductive cancers in both men and women.
These chemicals can be found in a variety of products, including plastics, tin food containers, medical tubing, dental sealants, PVC, compact discs, electronics and even makeup. In addition, other studies have documented the presence of some of these compounds in soil and household dust; however, the concentrations in those matrices are thought to be too low to be dangerous to humans.
Overall, research suggests that exposure to some of the chemicals used to make plastics may partially result in male infertility. Scientists hope that future research will determine the mechanisms by which these problems occur. Until then, they say limiting exposure to these compounds is the best bet.
By Bryan A. Jones