In the early 1990s, Scandinavian researchers published a meta-analysis of sperm count studies in which they concluded that the number of sperm men were producing had fallen by half since the 1930s. The decline was allegedly the result of men being exposed to trace amounts of synthetic chemicals in plastics and pesticides that mimic estrogen. Greenpeace launched an anti-chemical campaign with the clever slogan, "You're Not Half the Man Your Father Was" and also claimed that the chemicals were shrinking average penis size as well.
The claim of sperm decline was just recycled by andrology researcher Niels Jorgensen at the European Society of Human Reproduction and Embryology's annual meeting in Lisbon last week. Jorgensen provoked a spate of anxious news articles when he asserted that exposure to cosmetics, sunscreen, and varoius plastics was reducing human sperm production. In fact, Jorgensen was merely reporting the findings of a study that he had published back in 2012.In that 15-year study involving nearly 5,000 Danish men he supposedly found that only 25 percent had good sperm quality. That figure is evidently the source of the claims being made in the media.
What's really interesting is that Jorgensen's 2012 study had actually reported:
"Fifteen years monitoring of semen quality in men of the general population indicated a slight increase in both median sperm concentration and total sperm count."
That's right sperm counts among Danish men are not declining, but actually increasing from 45 million to 48 miliion per milliliter between 1996 and 2010. The World Health Organization's latest sperm quality reference limits were set by measuring the amount of sperm produced by recent fathers in six different countries. The lower limit (5 percentile) for sperm count is 15 milion per milliter. The Mayo Clinic also uses the WHO reference limits noting:
Normal sperm densities range from 15 million to greater than 200 million sperm per milliliter of semen. You are considered to have a low sperm count if you have fewer than 15 million sperm per milliliter or less than 39 million sperm total per ejaculate.
Eyeballing Jorgensen's data, it looks as though more three quarters of his subjects produced sperm in amounts higher than that.
A 2013 meta-analysis of 35 major studies found no overall decline in sperm quality. From the abstract:
Allegations for a worldwide decline in semen parameter values have not withstood scientific scrutiny. Methodological flaws in an influential 1992 paper are summarized here, and studies that have been published since 1992 are reviewed. Of the 35 major studies of time trends in semen quality reviewed here, eight (a total of 18 109 men) suggest a decline in semen quality; 21 (112 386 men) show either no change or an increase in semen quality; and six (26 007 men) show ambiguous or conflicting results.
So no sperm apocalypse, after all.
Bonus Monty Python song "Every Sperm Is Sacred" from The Meaning of Life below.