For decades, scientists have been struggling to determine what's cut the quality of human sperm in half since 1938. It turns out man's best friend—the dog—can help them find the answer.
Researchers from the University of Nottingham and Hartpury University found that adding environmental pollutants to both human and canine sperm produced similar effects, making canine sperm a useful proxy for further studies.
Endocrine disrupting environmental pollutants are linked to chemicals widely used in plastics.
Studies point to diet as the likely contamination source in both humans and animals.
The goal of the study is to build a “concentration range previously established in the dog as a ballpark estimate of chemical concentrations in the male reproductive tract,” the authors write. By doing so, scientists will be able to control and study the impacts different levels of environmental pollutants like PCBs have on male reproductive health.
The study will bring scientists closer to studying how environmental pollutants damage human sperm within a living organism, rather than in isolated sperm cells. The findings also make an argument for using different combinations of pollutants to try to understand how they interact, a process that still is not understood.
The study says exposure to mixtures of pollutants can have “synergistic” effects on sperm, making the impact worse or harder to predict.
“Human male infertility is associated with increased levels of sperm DNA damage,” according to the study. Higher levels of DNA fragmentation leaves only strands and pieces instead of chromosomes, decreasing sperm movement.
The chemicals used, DEHP and PCB153, write the authors, “are widely present in the environment and have been detected in tissues/fluids ranging from human breast milk to ovine liver.”
Scientists found concentrations of both chemicals in wet and dry dog food, and write that foods with higher fat content are likely to carry more contamination due a chemical attraction present in fatty foods.
PCBs and DEHP were first introduced in the middle of the 20th century. DEHP was first used in medical devices like blood bags. Now known to be toxic, DEHP is classified as a carcinogen in California. It is banned in the European Union and heavily regulated in Taiwan.
Some uses of PCBs were banned in the United States and the United Kingdom as long ago as 1976.
According to the U.S. Department of Health and Human Services, about 12 percent of couples in the U.S. have trouble conceiving a child, and roughly one-third of infertility problems are linked to men.