Donor sperm frozen in liquid nitrogen Ted Soqui/Corbis via Getty Images
An 16-year study of US donors of sperm shows that sperm quality has steadily declined over the years, possibly due to increasing chemical exposure or lifestyle changes.
Chelsea Canon, Reproductive Medicine Associates in New York, a fertility clinic looked at over 170,000 semen analysis results for healthy 19- to 38-year olds from nine US regions. Researchers claim the data is from a variety of men, but it is not clear how representative it is.
