The word is currently facing several health crises: in between ever-growing obesity, antibiotic resistance, and rampant antivaxxing, there’s no shortage of medical issues around the planet. But one particular issue rarely makes the headlines, despite its potentially devastating effects: the sperm crisis.

Common house chemicals can cause a decline in sperm quality. Image credits: Tim Collins.

Researchers carrying out several studies on male fertility were dumbfounded to learn that the sperm count (especially in the western world) has decreased by 50% in only a few decades. While this is not a reproductive apocalypse just yet, it’s a great concern — and it’s not really clear what’s causing it. To make matters even more puzzling, studies have found that dog fertility is experiencing a similar decline, again, without a clear cause.

There’s probably not one single cause for this phenomenon — Presumably, there is a sum of different environmental factors, and understanding and quantifying their effect is not an easy task. However, researchers working in the UK have found at least one potential factor affecting male fertility: two home chemicals.

In a new paper published in Scientific Reports, a team from Nottingham University set out to test the effects of two specific man-made chemicals: the common plasticizer DEHP, which is widely abundant household items like carpets, flooring, upholstery, clothes, wires, toys, and even food and the persistent industrial chemical polychlorinated biphenyl 153, which although banned globally, remains widely detectable in the environment including food.

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Researchers tested the effects of these two chemicals on sperm coming from human males and male dogs coming from the same area in the UK (in order to minimize environmental geographical differences). They found that both substances, at concentrations commonly found in homes, can damage both man and dog sperm quality.

Rebecca Sumner, who carried out the experimental work as part of her PhD said that in both groups of subjects, the effect was reduced sperm motility and increased fragmentation of DNA.

“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.”

This isn’t the first study to raise concerns about common household chemicals. Since the declining sperm count issues seems to be largely limited to the Western World, the cause is presumably something associated with a Western lifestyle — and common chemicals are one of the common denominators.

The one silver lining, researchers say, is that now we know that dogs can serve as a proxy for future studies, which could be very useful for future research. Also, since humans and dogs share the same living environment but vastly different diets, this seems to be a nod pointing at the living environment as a main source of sperm quality decline.

“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,” said Associate Professor Richard Lea, who led the project.

Next, researchers want to study geographical variations in how sperm quality is affected.

“Since environmental pollutants largely reflect a Western way of life such as the effects of industry, the chemicals present in the environment are likely to depend on the location. An important area of future study is to determine how the region in which we live may effect sperm quality in both man and dog,” concludes Professor Gary England.

The study “Independent and combined effects of diethylhexyl phthalate and polychlorinated biphenyl 153 on sperm quality in the human and dog” by Sumner et al has been published in Scientific Reports.