Male Fertility Is Plummeting—and Scientists Have Now Found Household Chemicals Could Be to Blame

Sperm quality among men has dropped in recent decades, and scientists believe household chemicals could be partly to blame—and dogs may have the same problem.

The researchers behind the small study investigated the potential effects of DEHP, a chemical used to make plastic and is found in such items as furniture, flooring, carpets, upholstery, toys and shoes. They also tested polychlorinated biphenyl 153: the banned chemical that lingers in the environment and has been linked to male infertility.

The British authors of the study published in the journal Scientific Reports set out to understand whether these chemicals contributed to the 50 percent reduction in sperm quality among men between 1938 and 2011, and a drop of 30 percent in dogs over a period of 26 years. They took nine samples of sperm from men and 11 stud dogs who lived in the same area of the U.K. Separate samples of sperm were treated with incrementally increased doses of the substances.

In vitro tests on the cells suggested the chemicals affected how sperm swam, and appeared to cause DNA fragmentation in which genetic material in the sperm became abnormal. The results indicated that domestic dogs were a "mirror" of the decline in male reproductive health, the authors said.

As the fertility of dogs appears to be comparable to that of humans, this could provide a new approach for researching reproductive health as it is easier to control factors such as diet in animals.

Richard Lea, lead author of the study and associate professor and reader in reproductive biology at the University of Nottingham School of Veterinary Medicine and Science, said in a statement: "Our findings suggest that man-made chemicals that have been widely used in the home and working environment may be responsible for the fall in sperm quality reported in both man and dog that share the same environment.

"Our previous study in dogs showed that the chemical pollutants found in the sperm of adult dogs, and in some pet foods, had a detrimental effect on sperm function at the concentrations previously found in the male reproductive tract," he said.

Co-author Rebecca Sumner commented: "We know that when human sperm motility is poor, DNA fragmentation is increased and that human male infertility is linked to increased levels of DNA damage in sperm. We now believe this is the same in pet dogs because they live in the same domestic environment and are exposed to the same household contaminants."

Gary England, a professor of comparative veterinary reproduction and dean of the School of Veterinary Medicine and Science, said: "An important area of future study is to determine how the region in which we live may impact sperm quality in both man and dog."

The team is the latest to investigate the potential harms of chemicals on fertility. Last year, the consumer advocacy group Which? warned that some popular slime-toy products could contain chemicals that negatively affect fertility.