Dogs: Defenders of your home, your family, and….. your sperm?

_ By Daniel Merino

  • Two chemicals found in plastics and electronics significantly lower the quality of human sperm.
  • The chemicals, DEHP and PCP153, were found in human semen at levels similar to those that harmed sperm in the lab.
  • Researchers tested dogs for the same chemicals and found similar concentrations in dog semen as well as similar harmful effects to sperm quality.
  • Dogs could be used as “canaries in the coal mine” to test for environmental pollutants that decrease male fertility.

Human pollution is everywhere. Our waste can be found at the bottom of the ocean, in outer space, in our water supply, and yes, even in the food we eat. This is unfortunately not new, but scientists have found something a little more personal to be worried about when it comes to pollution. Some of the chemicals we put in plastics and electronic devices are finding their way into our bodies and they may be causing low fertility in men.

Warning label on the bottom of a cup.

In a study published last month, researchers tested how two common chemicals affect the quality of both human and dog sperm. The chemicals, a plasticizer called DEHP and an electrical insulator called PCB153, turn sperm into terrible swimmers and also harm the all-important DNA they contain.

To test the effects the two chemicals have on sperm wasn’t all that complicated for the scientists. First, they established baseline concentrations for each chemical using samples they obtained from nine men and eleven dogs. Then, they simply cleaned the samples to make sure there was no cross contamination and introduced them to solutions with DEHP and PB153. The team tested different concentrations ranging from no contamination all the way up to 100 times the baseline amounts as well as each chemical’s effect alone or together.

The chemical structure of DEHP, a plasticizer that is getting into food and hurting sperm.

The scientists found that the pollutants lowered motility – the ability of an individual sperm to swim – and increased genetic fragmentation, both measures that are linked to infertility in human men.  When they exposed human and dog sperm to both chemicals at once, as is much more likely the case in real-world scenarios, the effects were just as bad and often worse than exposure to just one or the other. They also found that higher concentrations of the chemicals had a greater effect on the overall quality of sperm.

The researchers, supported by the University of Nottingham, wanted to determine two things with this study. First, they wanted to see how the chemicals affected sperm in both dogs and humans. It, unsurprisingly, isn’t good to expose sperm directly to man-made chemicals. Second, they wanted to see if the concentrations of the pollutants and the harm they caused to sperm were comparable between dogs and humans.

The hundreds of thousands of dogs that get neutered each year in the US could be canaries in the coal mine when it comes to environmental chemicals.

The answer to that second question is yes, and raises an interesting possibility for future studies and ways to protect against environmental chemicals that hurt fertility in men. Since most dogs are neutered, at least in the United States and other developing countries, it would be relatively easy to take samples from the testes of these animals. Since there is a strong correlation between the concentrations of DEHP and PCB153 found in dogs and humans, dogs could potentially be a way to easily and test for changes in the chemical environment that might lead to fertility problems in men. This could very well be the strangest canary in the coal mine situation ever.

Male fertility has fallen over recent decades, and difficulty conceiving a child is a real and painful problem for people around the world. Scientists have found that the overall quality of human sperm has been decreasing dramatically, potentially by as much as 50% since 1938, and this is likely a contributing factor when couples can’t conceive a child. This study is among a growing number that show how specific chemicals can harm sperm in men, but it is the first to establish a connection between man and mans best friend, albeit a bit of a weird one.

This is only one study and the small number of sampled individuals (on both the dog and human side), as well as not knowing what the dogs and humans were exposed to, make further studies necessary. But it does provide more than enough evidence to pursue this connection further.

Your pup may already be protecting your home and your children, but in the future, he just might have a role in protecting the other little guys you may be worried about.