In the past 80 years, the quality of human sperm has declined by 50 percent — not only is sperm count down, but the sperm that do exist aren’t as mobile as their predecessors.

In 2016, a team of researchers from the University of Nottingham published a study noting that domestic dogs were experiencing a decline in sperm quality, too. This led them to wonder if something in the modern home environment might be contributing to the quality decline in both humans and dogs.

Based on a follow-up study, that guess appears to be correct — and the “something” at the center of it is human-made chemicals.

Double Damage

In a study published in the journal Scientific Reports on Monday, the University of Nottingham team details how it tested the impact of two human-made chemicals on the sperm of both humans and dogs.

One chemical, DEHP, is an additive that increases the plasticity of a material. It’s found in everything from carpet and upholstery to clothing and toys.

The other is polychlorinated biphenyl 153 (PCB153), an industrial chemical that once had a wide variety of applications. Though banned from production globally since 2001, PCB153 is still found in abundance in the environment — including in both human and dog food.

When the researchers incubated sperm from human and dog donors with concentrations of the chemicals comparable to those found in the natural environment, they found that the chemicals had the same damaging effect on both species’ sperm, decreasing its motility and increasing damage to its DNA.