The tiny plastic particles were found in all 23 human testes in a new study, and all 47 testes from pet dogs.

Microplastics have crossed so many boundaries it is hard to keep track.

The ‘red flag’ of our consumptive lifestyles, they have reached the limits of the Earth - from the Mariana Trench to the tip of Mount Everest. These tiny particles of decomposed plastic have seeped into clouds, and been found buried in archaeological remains believed to be ‘pristine’.

They have challenged our ideas of bodily inviolability too, infiltrating every organ. What might have been considered the ‘purest’ parts of human life - placentas, babies, breast milk - contain microplastics.

So it comes as little surprise that human testicles have them too, as the most comprehensive study yet on microplastics and the scrotum confirms.

Less is known about what microplastics are doing to our bodies. But in the case of testicles, the new research suggests they could be lowering sperm count.