Common chemicals challenge sperm

Chemicals known as endocrine disruptors, commonly found in our food and products such as makeup, sunscreen and toothpaste, have been shown to cause fertility problems. Now scientists have a better understanding of why.

Researchers found endocrine disruptors can interfere with human sperm's ability to move, navigate and/or penetrate an egg. Their study results were published Monday in EMBO reports.

Wait, what's an endocrine disruptor?

Endocrine disruptors are chemicals that interfere with your endocrine system - the system in your body that regulates hormones. These hormones control everything from your metabolism to your sleep cycle to your reproductive system, so messing with them can cause serious issues.

Scientists have a long list of potential endocrine disruptors, including bisphenol-A (BPA), phthalates, dioxin, mercury and perfluorinated chemicals (PFCs). They can be natural or man-made and are virtually "omnipresent," the study authors write, in our food and in common household and personal care products.

This isn't the first time scientists have linked these chemicals with fertility issues in humans.  For example, in 2010, a study of Chinese factory workers found exposure to BPA can reduce sperm counts. More recent studies have shown BPA and chemicals called phthalates can hinder a couple's ability to conceive and carry a healthy baby to full term.

The study

Scientists in Germany and Denmark tested 96 endocrine disrupting chemicals on human sperm - both individually and in various combinations.  Around one-third of the chemicals had a negative effect.

The researchers found these endocrine disruptors increased the amount of calcium found in sperm cells - although BPA was found to have no effect. Calcium ions control many of the essential functions of sperm, study author Dr. Timo Strunker explains, including the flagellum - the tail that propels sperm forward. So changing the calcium level in a sperm cell can impact its motility, or swimming ability.

The researchers also found that some endocrine disruptors make sperm less sensitive to two hormones, progesterone and prostaglandins, that help a sperm cell navigate toward a woman's egg.

"Compare it with your GPS receiving abnormal signals," study author Dr. Niels E. Skakkebaek told CNN in an e-mail. "This may result in a wrong destination - read: the sperm may not reach the egg and fertilization may not occur."

One other factor may prevent conception: The study authors concluded some endocrine disruptors can trigger the release of enzymes designed to help sperm break the protective coating on an egg. While this is a good thing if it happens near the egg, the chemicals often cause a premature reaction, wasting the enzymes, Strunker says.

The takeaway

Avoiding endocrine disruptors altogether could prove difficult, as "we become exposed without knowing it from food, clothes, cosmetics, air, water, dust..." said Skakkebaek. "In my opinion, the take-home message to readers is to elect politicians who will work for a cleaner environment in a broad sense."

Many countries around the world are taking a look at these chemicals and evaluating their safety. For the most recent news, check out the National Institute of Environmental Health Science's website.