Scientists tested 23 human testicles as well as 47 from pet dogs. They found microplastic pollution in every sample, The Guardian reports.

The study demonstrates a correlation, but further research is needed to prove that microplastics cause a decrease in sperm count.

Male sperm count has been declining for decades, with chemical pollution, such as pesticides, being associated with this by many studies.

Microplastics have recently been discovered in human blood, placentas and breast milk, indicating widespread contamination of the human body.

The health impact is still unknown, but it has been shown that microplastics cause damage to human cells in the laboratory.

Huge amounts of plastic waste are being dumped into the environment, and microplastics have polluted the entire planet, from the peak of Mount Everest to the deepest oceans.

It is known that humans consume these tiny particles through food and water, as well as through air.

Particles can accumulate in tissue and cause inflammation, as air pollution particles do, or chemicals from plastic materials.

In March, doctors warned of life-threatening effects after finding a substantially increased risk of stroke, heart attack and premature death in people whose blood vessels were contaminated with microscopic plastic materials.

"At first, I doubted that microplastics could penetrate the reproductive system", said professor Xiaozhong Yu of the University of New Mexico in the USA.

"When we first received the results for dogs, I was surprised. I was even more surprised when we received the results for humans".

The analyzed testicles were obtained from autopsies in 2016, with the men ranging in age from 16 to 88 at the time of death.

"The impact on the younger generation could be more worrying now that there is more plastic than ever in the environment", said professor Yu.

The study, published in the journal Toxicological Sciences, involved dissolving tissue samples and then analyzing the remaining plastic. The dog testicles were obtained from veterinary clinics that performed sterilization surgeries.