This is a good question, but difficult to nail down exactly. Testosterone levels have been declining in men for 70 years, the minority are testicular failures and pituitary tumors, the other 70% are unknown.
It’s multifaceted, processed foods, pesticides, pollution, working night shifts, swing shifts are disruptive to sleep patterns and the list goes on.
Every creature on earth is passing micro plastics in the stools. Fertility is also on the decline, we may soon be infertile, some say as soon as 2040 if the trend continues.