If you know a couple that’s having trouble trying to conceive, their couch could be part of the problem. Or their shower curtain. Or any number of other household items, depending on what they’re made of. 

New research by scientists at the University of Nottingham (UNOT) in Nottingham, England suggests that common chemicals and environmental contaminants found in the home could be causing infertility in men—and in male dogs, too.

Infertility’s been creeping up on both: The past 80 years have seen a 50% global reduction in human male sperm quality. An earlier study by researchers at UNOT showed that sperm quality in domestic dogs declined sharply between 1988 and 2014.

This got the UNOT researchers thinking: Could modern-day chemicals in the home environment be at least partly to blame?

Those researchers tackled the question in the new study by testing the effects of two specific man-made chemicals commonly found in modern-day homes: diethylhexyl phthalate (DEHP) and polychlorinated biphenyl 153 (PCB-153).

DEHP is a is a manufactured chemical commonly added to plastics to make them flexible. A colorless, nearly odorless liquid, DEHP is present in carpets, tablecloths, floor tiles, furniture upholstery, shower curtains, rainwear, toys, and shoes. The EPA considers it a probable human carcinogen, and it’s known to affect both the immune and reproductive systems in people.

PCB-153 belongs a to a class of chemicals commonly called PCBs that were used in the manufacture of paints, plastics, and rubber products (among other applications) between 1929 and 1979, at which point they were mostly banned in the US after it was discovered that the chemicals were leaching into the environment and finding their way into the food chain, causing human health problems such as cognitive deficits, increased risk of infection, premature birth, and low birthrates.

Despite the ban, traces of PCB-153 persist in the environment.

The UNOT research consisted of identical experiments in both species using samples of sperm from donor men and stud dogs living in the same region of the UK. The findings show that the chemicals, at concentrations relevant to environmental exposure, have the same damaging effect on sperm from both man and dog.

NEWStat reached out tothe study’s corresponding author, Richard Lea, PhD, associate professor of reproductive biology at UNOT’s School of Veterinary Medicine and Science, and his fellow researcher, Rebecca Sumner, PhD, a lecturer in equine science at Hartpury University in Gloucestershire, England, for some perspective. They gave their joint response in an email interview.

NEWStat: Given all the possible chemical pollutants that can found in the average home, why did you chose these particular chemicals to study?

Richard Lea and Rebecca Sumner: We chose these particular chemicals because, in our previous published work, [the majority of samples from the materials we screened—including dog food, dog sperm, and discarded tissue from routine neuterings—showed elevated levels of DEHP and PCB-153] and both are reported to be widely present in the environment. In addition, [DEHP] and PCBs have been reported to have adverse effects on reproductive function. It therefore seemed sensible to look at these chemicals as representative toxins. However, we are mindful that we are exposed to a cocktail of chemicals and testing all chemical types individually and in combination is a huge undertaking.

NEWStat: How different were the results between humans and dogs?

RL, RS: Comparing results between human and dog generally showed very similar effects on sperm motility and the fragmentation of DNA.

NEWStat: How does DNA fragmentation affect fertility?

RL, RS: DNA fragmentation is the most important component of the sperm and is therefore regarded as a measure of sperm quality and its ability to fertilize. Some studies in the human have shown that subfertility is linked with increased DNA damage.

NEWStat: What gave you the idea of including both dogs and humans in the same study?

RL, RS: The dog is “man’s best friend” and closely shares our environment. Since many chemicals are present in our homes, then both man and dog are exposed to the same pollutants. This suggests that any adverse effects of chemicals in humans will also be mirrored in the dog. Our findings support this idea.

NEWStat: Given that chemicals are so widely dispersed in so many environments, what practical steps can we take to reverse this trend in both dogs and humans?

RL, RS: You are correct in that there are many chemicals in the environment, and clearly we cannot remove or extract [them] ourselves. However, if we increase awareness of the possible dangers and sources of some chemical types, then we can take steps to reduce our own future exposures, [such as by] limiting plastic use. The other outcome we would like to see is a change in legislation and further regulation of chemical use by industry.

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