Bisphenol A and other common estrogen-mimicking chemicals may be wreaking havoc on sperm and stymying some couples' hopes of having children, warns new research.
"We're seeing more and more guys who have low and troubling sperm counts," said Pat Hunt, a molecular biologist at Washington State University and co-author of a small study published Thursday that investigates how certain industrial chemicals may affect sexual development in newborn male mice.
"There's a hypothesis now that this might be due to these estrogenic exposures to the male testes -- because it's not just sperm counts that seem to be changing," she added, noting the similarly rising rates of testicular cancer, undescended testes and other abnormalities in male genitalia throughout the developed world.
Hunt's research isn't the first to place infertility alongside attention deficit hyperactivity disorder, female reproductive problems, obesity and heart disease on the list of potential consequences of exposure to endocrine disruptors -- a class of chemicals that get their name because they alter proper hormone functioning. Federal researchers published a study last year showing that phthalates, a family of compounds used in plastics, piping and cosmetics, can interfere with the hormone testosterone, likely playing a role in the international drop in male fertility.
A range of chemicals present in products such as soap, toothpaste and plastic toys may be directly affecting sperm function in men, according to another 2014 study. Of the 96 chemicals the researchers tested, one in three significantly changed the swimming behavior of sperm.
"We have seen quite dramatic increases [in infertility] over one or two generations," Niels Skakkebaek, of Copenhagen University Hospital in Denmark and a co-author of the study on sperm function, told The Huffington Post in an email. "Such changes can only be explained by environmental influences."
Approximately 40 percent of young men in Denmark have low sperm counts, reducing their ability to father children. The U.S. has seen similar trends, noted Hunt. The usage of IVF treatments for male infertility has doubled over the past decade. The procedure, according to another study published on Thursday, may be ineffective.
In their new study, Hunt and her team found that brief exposures right after birth to tiny amounts of bisphenol A (BPA) or ethinyl estradiol, a synthetic estrogen common in birth control pills and now ubiquitous in the environment, increased the errors made by a male mouse's testis when it began to produce sperm. Those errors led to a lower sperm count, and the effect carried on throughout the animal's adult life.
"The changes are subtle, but have pretty big repercussions," said Hunt.
The American Chemistry Council offered a different view of the findings.
"This new study is of limited relevance to human health," Steven G. Hentges, of the industry association's Polycarbonate/BPA Global Group, told HuffPost in an email.
Pointing to previous large studies of mice and rats, Hentges suggested that this earlier research had found "no reproductive effects in males or females at any dose remotely close to the levels of BPA to which people are actually exposed, or even to the extremely high levels tested in the new study."
Hunt countered that it's actually not clear how often or to what extent humans are exposed to BPA in the real world. "We only know the levels that have been reported in human blood and urine," she said. "The levels we used produce very low levels in mice that are lower than those reported in humans."
Andrea Gore, a hormone disruptor expert at the University of Texas at Austin and editor-in-chief of the journal Endocrinology, agreed. She noted that some of the differences between study results may be explained by the different strains and species of mice used. In fact, certain strains of mice in Hunt's study appeared more sensitive to the synthetic hormones than others.
"While there are probably a number of explanations for infertility," said Gore, "I believe that environmental chemicals -- in both men and women -- play a role."
BPA, an already highly controversial chemical, has received renewed attention in the past week. A study published last Saturday highlighted the potential heart health risks in females exposed to BPA. Yet days later, the European Food Safety Authority (EFSA) released a report concluding that BPA poses "no health concern for any age group from dietary exposure or from aggregated exposure."
"The evidence is not sufficient to infer a causal link between BPA exposure and reproductive effects in humans," the EFSA said in its report, which acknowledged uncertainty regarding exposure via routes other than ingestion. Experts often say that a lack of proof of harm is not proof of no harm.
"There's compelling evidence that non-oral routes are extremely important," said Hunt. "Basically, since EFSA doesn't know how to deal with them, they have ignored them and focused on oral exposure. The European Union has rejected the EFSA risk-assessment approach as scientifically unsound."
Meanwhile, "it's not just a BPA problem," she added. "Any type of estrogenic exposure would probably induce similar effects."
Some of the new replacement chemicals for BPA, such as bisphenol S (BPS), may in fact have an even more potent effect on hormones. "If we keep tweaking this molecule, we'll be busy for life," said Hunt. "Sister chemicals are as bad, maybe even worse, than BPA."
The burgeoning issues of hormone-mimicking chemicals and male infertility have garnered the attention of global environmental health leaders. Experts from the United Nations and the World Health Organization declared in February 2013 that endocrine disruptors posed "a global threat." On January 1 of this year, Skakkebaek's team received a grant from the Danish government to establish the International Center for Research and Research Training in Endocrine Disruption of Male Reproduction and Child Health -- a facility whose importance the European Parliament has also emphasized.
"Much more research is needed to delineate the role of endocrine disrupters (including BPA)," said Skakkebaek, whose research in the early 1990s brought attention to the issue of declining semen quality among males in the developed world.
One of the most glaring gaps in the current research, according to experts, is how exposure to a cocktail of hormone-mimicking chemicals can affect the human body. We're not exposed to such chemicals one at a time -- rather, we eat, breathe and touch a host of them daily.
"We think about all these chemicals that make our lives so much easier," said Hunt. "But we need to be aware."