Endocrine disruptors are chemicals that interrupt the processes of natural hormones and have been previously implicated in affecting human reproduction. Now, these chemicals - which can be found in household and personal care products - have been shown to affect sperm function, potentially impacting fertilization.
The research team, from the Center of Advanced European Studies and Research in Germany and the University Department of Growth and Reproduction in Denmark, published the results in the journal EMBO reports.
Medical News Today recently reported on several findings regarding endocrine-disrupting chemicals (EDCs). One study questioned the safety threshold for such chemicals, while another detected EDCs in commercialized bottled water.
The researchers from this latest study note that EDCs are present in everything from food and textiles to drugs and household products, including plastic bottles, toys and cosmetics.
Currently, the European Commission is reviewing its policy on EDCs, and their plans from last year sparked a debate between endocrinologists and toxicologists on how to regulate such chemicals.
Though proving adverse effects of EDCs on humans has been difficult with a lack of acceptable experimental systems, lead study author Timo Strünker, from the Center of Advanced European Studies and Research in Germany, says their study "provides scientific evidence to assist forming international rules and practices."
With a new bioassay developed by the researchers, they were able to rapidly test hundreds to thousands of chemicals for potential interference with function of human sperm.
EDCs prompt changes in sperm swimming behavior
They explain that for their study, they tested about 100 chemicals and found significant results that suggest endocrine disruptors may lead to widespread fertility issues in the Western world in a way that has not been identified until now.
The team's findings reveal that about one third of these chemicals showed adverse reactions.
Some of these chemicals include ultraviolet filters such as 4-methylbenzylidene camphor (4-MBC), which is used in some sunscreens, and Triclosan, an anti-bacterial agent used in toothpaste.
"For the first time," says Prof. Niels E. Skakkebaek, leader of the Danish team, "we have shown a direct link between exposure to endocrine disrupting chemicals from industrial products and adverse effects on human sperm function."
They looked specifically at how these chemicals affected the CatSper ion channel, which they explain is a calcium channel that controls sperm motility.
Applied at concentrations they measured in bodily fluids, the team says EDCs directly open the CatSper channel, increasing calcium levels in sperm and changing their swimming behavior. The investigators say this also triggers the release of digestive enzymes that help the sperm to break through the egg.
Additionally, EDCs make sperm less sensitive to progesterone and prostaglandins, which are two hormones released by cells around the egg.
The team says their findings illustrate how EDCs disturb the mechanisms underlying fertilization by prompting changes in swimming behavior, hampering sperm navigation and interfering with penetration into the egg's protective coat.
The authors conclude their study by writing:
"Here, we provide a direct link between exposure to EDCs and potential adverse effects on fertilization in humans. About 800 omnipresent man-made chemicals are suspected to interfere with the endocrine system. To this day, the majority of these potential EDCs have not been evaluated for their action in humans."