Sexual revolution and sperm count

EDITOR, - Together with other discoveries, the findings of Carlsen et al that the quality of semen has been declining over the past 50 years1 have led to disturbing speculation about the world's environment. I think, however, that the relation of their findings to such speculation is scientifically untenable.

Given the criteria for semen quality used by Carlsen et al, the findings suggest merely a general dilution of semen caused by more frequent ejaculation of men today compared with 50 years ago. But their conclusion …