Studies Yield Conflicting Signals About Environment’s Impact on Fertility

Pity the human sperm?

By one new assessment, male fertility is holding up nicely. As The New York Times reports, Danish researchers have conducted an updated study showing that, despite ever-present environmental hazards, sperm counts remain steady.

But that discovery has been clouded by a pair of worrisome reports about the widely used compound BPA, which many fear is a possible gender-bending chemical that disrupts hormones in the human body.

The more optimistic news comes from a 15-year study based on semen samples collected from 5,000 Danish men, all 18 years old. The study was conducted by same group of researchers who set off an enduring controversy in 1992 when they reported that sperm counts declined 50 percent worldwide from 1938 to 1991, and projected that the trend would continue.

As Time puts it, the initial Danish study “was scary enough to support theories that endocrine disruptors and other chemicals in the environment could threaten the future of the human race.”

The previous study also was widely attacked by other scientists. So the Danish researchers launched a follow-up study, whose methodology has garnered better reviews from the scientific community.

Some scientific bickering has continued, and the researcher who initiated the updated study has resisted discussing the results so far. But now an American journal, Epidemiology, has published the information, and it shows sperm counts among the Danes holding steady from 1996 to 2010. An accompanying commentary in the journal–titled “Trends in Sperm Counts: The Saga Continues”–said the study provides “the best longitudinal semen data yet available.”

Separately, however, scientists have raised fresh concerns about BPA, a compound widely used in food can linings, plastics and other consumer items.

A University of Missouri study, based on laboratory research on mice, suggests that human and animal absorption and accumulation of BPA is much higher than previously estimated. According to a university news release,  the study differed from most previous research in that, instead of exposing the lab animals to a single dose of BPA, they were given a steady diet–a situation that more closely mimics the way human are exposed.

“People are primarily and unknowingly exposed to BPA through the diet because of the various plastic and paper containers used to store our food are formulated with BPA,” said Cheryl Rosenfeld, the lead author of the study, which appeared in the journal Environmental Health Perspectives.

“We know that the active form of BPA binds to our steroid receptors, meaning it can affect estrogen, thyroid and testosterone function. It might also cause genetic mutations. Thus, this chemical can hinder our ability to reproduce and possibly cause behavioral abnormalities that we are just beginning to understand.”

In yet another recent BPA study, investigators from Banaras Hindu University in Varanasi, India, found lower sperm counts among male mice that received daily injections of the chemical for two months. As Medical News Today reports, Surya Singh, a biochemistry expert at the university and the principal author, said that “even short-term exposure to BPA could be dangerous to fertility.”

The findings were presented at the just-concluded annual meeting in Boston of The Endocrine Society.

Related Posts:
Supermarket Giant Kroger to Rid Cans and Receipts of BPA
Pediatricians Group Calls for Tougher Regulation of Chemicals

 

 

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Stuart Silverstein

About the author

Stuart Silverstein is assistant editor at FairWarning.

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