Household Chemicals Can Reduce Male Fertility—but Dogs Can Help. Here's How.
A recent study published by the journal Scientific Reports found that exposure to certain man-made chemicals can negatively affect sperm function and quality in domestic dogs—as well as humans.
The study, conducted by scientists at the University of Nottingham, measured sperm motility after exposure to two kinds of chemicals commonly found in household products: diethylhexyl phthalate (DEHP) and polychlorinated biphenyl 153 (PCB153).
Sperm motility is the ability of sperm to move freely on its own and is often cited as a marker of overall male reproductive health. Decreased sperm motility is associated with male infertility.
The researchers found that varying levels of exposure to DEHP and PCB153 had significant inhibitory effects on sperm motility in both dogs and humans, meaning that exposure to these chemicals at certain levels could contribute to a decline in male fertility.
Over the past few years, scientists have been increasingly concerned about the significant decline observed in male reproductive health. The authors of this study had previously identified declines in the sperm quality of domestic dogs and sought to identify environmental factors that could contribute to the decline of reproductive health in both.
DEHP and PCB153, the chemicals tested, are widely found in a number of products used by humans and dogs. DEHP is a plasticizer, used in common household products like carpets, flooring, upholstery, clothes, wires and toys to increase flexibility and reduce brittleness. PCB153, while banned globally, is still found in a range of foods, including wet and dry dog food.
Richard Lea, a co-author of the paper and an Associate Professor and Reader in Reproductive Biology at the School of Veterinary Medicine and Science at the University of Nottingham, said: “this new study supports our theory that the domestic dog is indeed a 'sentinel' or mirror for human male reproductive decline and 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."
Sentinel species are animals that are used as predictors of various risk to humans. A classic example would be the “canary in the coal mine”, where birds were placed in coal mines to detect the presence of carbon monoxide. When the birds would keel over, dead from carbon monoxide poisoning, it was time for humans to get out of the mine—because they were next.
In this case, domestic dogs are the “canary in the coal mine”, by being studied for the negative reproductive effects of exposure to chemicals. They are easy to study since there is widespread access to sperm samples from a controlled breeding population of domestic dogs, allowing for controlled experiments on the effects of chemicals like DEHP and PCB153 on their sperm health. Yet more importantly, domestic dogs inhabit the same environment as humans, exposing them to the same sort of potentially harmful chemicals as their human companions.
Dr. Rebecca Sumner, the lead author of the study, drew a link between domestic dog infertility and that of human males: "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. This means that dogs may be an effective model for future research into the effects of pollutants on declining fertility, particularly because external influences such as diet are more easily controlled than in humans."
The study is significant in that it established domestic dogs as helpful test subjects to gauge the environmental impacts of various household chemicals on the reproductive health of humans, without causing the domestic dogs any harm.