(CNN) - A new study found the sperm count of men in France fell by a third from 1989 to 2005. But while it's a dramatic decline, the count is still within the range of fertility.
The study also found there was a "significant" decrease in normally shaped sperm over that time, although it couldn't be quantified.
In the study, published online in the journal Human Reproduction, researchers looked at data from more than 26,000 men between the ages of 18 and 70.
The authors say the findings are a "serious public health warning" and want to know if there is an environmental link.