a new study points to the impact of everyday pollutants on the decline in sperm quality

The rapid decline in human fertility is, in itself, an indication of the close links between the health of populations and the quality of their environment in the broad sense. British and Danish researchers highlight it again in a study published Thursday, June 9 by the journal Environment International. Led by Andreas Kortenkamp (Brunel University, London) and Hanne Frederiksen (Rigshospitalet, University of Copenhagen), the authors present the first risk assessment, with respect to male fertility, of mixtures of everyday pollutants.

They have thus managed to prioritize, among the substances most suspected of harming the quality of human sperm, the most decisive in the current decline. Plastics hold the upper hand by far. Bisphenol A (BPA) and its substitutes (BPS, BPF) are the substances that weigh the most. They are followed by polychlorinated dioxins and other plasticizers (phthalates), certain parabens and paracetamol. According to the researchers’ estimates, the median level of combined exposure of the general population to these products is approximately twenty times higher than the risk threshold.

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The fall in male fertility has been a phenomenon identified for about thirty years. A variety of factors – diet, smoking, stress, exposure to some common chemicals, etc. – is suspected to be involved. “For thirty years, numerous studies have been carried out around the world to measure the characteristics of human sperm.explains Pierre Jouannet, professor emeritus at the University of Paris-Descartes, one of the great pioneers in this field of research. The most serious of them show a decline in sperm quality, especially in the most economically developed countries. »

A fall of 50% to 60% in less than forty years

The numbers are striking. The most exhaustive synthesis published to date dates back to 2017. Conducted by Shanna Swan’s team (New York University) and published in the journal Human Reproduction Updateit indicates that the average concentration of spermatozoa in Western men fell from 99 million to 47 million spermatozoa per milliliter between 1973 and 2011. A drop of 50% to 60% in less than forty years.

Other, more recent data indicate that the problem is far from a thing of the past. In 2019, Ashley Tiegs’ team (Thomas Jefferson University, Philadelphia) published in Urology a study of 120,000 American and Spanish men of couples who consulted a center for assisted procreation. Among this sample, the proportion of men with less than 15 million motile spermatozoa per milliliter increased from 12.4% to 21.3% between 2002 and 2017. An increase of nearly 10 percentage points in fifteen years. , within this population subgroup.

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