“There have been studies by sperm banks looking at the average sperm counts of then and now, and they’ve noticed in some parts of the world, the sperm count of healthy donors has gotten lower than average,” says Dr. Philip Werthman, a urologist and director of the Center for Male Reproductive Medicine and Vasectomy Reversal.
The declining sperm count thing is pretty controversial, though. While that first study in the early '90s sounded the semen alarm, it was followed by an analysis pointing out its flaws... THAT was followed by a study confirming the ORIGINAL study.
It's almost impossible to account for confounding variables; for example, sperm donors aren’t necessarily representative of the whole population. (It takes a special sort of person to jizz in a cup for money, after all.) Or maybe doctors simply know more about sperm now. “Some of it is just that we are performing more semen analyses... and seeing more of these issues,” Dr. Hernandez-Rey says.