Specific man-made chemicals found in common household items can cause damaging effects to male fertility in both humans and domestic dogs.
A study conducted by researchers of the University of Nottingham in the United Kingdom found that chemicals identified as plasticizer DEHP and polychlorinated biphenyl 153 or PCB153 may have contributed to the declining human male reproductive health and the decreasing sperm motility of dogs.
Declining Male Reproductive Health
In the past 80 years, the quality of the human male sperm count declined by 50 percent worldwide. A similar trend was observed in household dogs that indicated a 30 percent decrease in sperm motility.
Scientists are pointing to long-term exposure to chemicals and pollutants as the possible culprit to this "shocking" reality.
"This new study supports our theory that the domestic dog is indeed a 'sentinel' or mirror for human male reproductive decline," said Richard Lea, a reproductive biologist at the University of Nottingham School of Veterinary Medicine and Science and the study's lead author.
Environmental Pollutants Affecting Sperm
The common plasticizer DEHP, a type of phthalate used to soften plastics, can be found in common household items such as carpets, flooring, upholstery, clothes, wires, and plastic toys. It is already banned in Europe and considered as one of the leading chemical threats to humans.
Exposure to DEHP can cause damage to internal organs, including the liver, kidneys, lungs, and reproductive system in animals.
PCB153 belongs to a group of industrial chemicals identified as persistent organic pollutants. It is commonly found in lubricants, coolants, and electrical equipment like capacitors and transformers.
It is regarded as an endocrine disruptor or chemicals that interfere with hormones or endocrines and can cause tumors, birth defects, and developmental disorders.
Both chemicals have already been banned globally, but they remain widely detectable in the home, working environment, and even in food.
The researchers first conducted the sperm study in domestic dogs in 2016 and later on tested if it is the same case for human males.
Using identical experiments and the same concentrations of a specimen, they studied sperm from 11 donor males and nine dogs living in the same region. The results showed poor motility and DNA fragmentation in the sperms of both human and canine that are exposed to the same household contaminants.
"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," said Dr. Rebecca Sumner who carried out the laboratory tests on both dog and human sperm.
The study is published in the journal Scientific Reports.