BBC News - French sperm count 'falls by a third'
One of the paper's authors, Dr Joelle Le Moal, an environmental health epidemiologist, said: "To our knowledge, this is the first study concluding a severe and general decrease in sperm concentration and morphology at the scale of a whole country over a substantial period.
"This constitutes a serious public health warning."
But Dr Allan Pacey, senior lecturer in andrology at the University of Sheffield, said: "The change in sperm concentration described, 73.6 to 49.9 million per millilitre [on average for a 35-year-old], is still well within the normal range and above the lower threshold of concern used by doctors which is suggestive of male infertility, 15 million per millilitre."
As the study took place over a period of years, it is important that methods remained the same for comparison- but critics have questioned this.
Dr Pacey said: "In the paper, the authors claim that the methods for measurement of sperm concentration and motility 'have not changed noticeably during the study period', yet to me this is an odd thing to say as in my experience they have changed remarkably everywhere else in the world.
"I would argue that the 'jury is still out' on this issue."