Sperm Count Zero
Men are doomed. Everybody knows this. We’re obviously all doomed, the women too, everybody in general, just a waiting game until one or another of the stupid things our stupid species is up to finally gets us.
The male of the species dies younger than the female—about five years on average. Divide a population into groups by birth year, and by the time each cohort reaches 85, there are two women left for every man alive. In fact, the male wins every age class: Baby boys die more often than baby girls; little boys die more often than little girls; teenage boys; young men; middle-aged men. Death champions across the board.
Researchers from Hebrew University and Mount Sinai medical school published a study showing that sperm counts in the U.S., Europe, Australia, and New Zealand have fallen by more than 50 percent over the past four decades. (They judged data from the rest of the world to be insufficient to draw conclusions from, but there are studies suggesting that the trend could be worldwide.) That is to say: We are producing half the sperm our grandfathers did. We are half as fertile.
The Hebrew University/Mount Sinai paper was a meta-analysis by a team of epidemiologists, clinicians, and researchers that culled data from 185 studies, which examined semen from almost 43,000 men. It showed that the human race is apparently on a trend line toward becoming unable to reproduce itself. Sperm counts went from 99 million sperm per milliliter of semen in 1973 to 47 million per milliliter in 2011, and the decline has been accelerating. Would 40 more years—or fewer—bring us all the way to zero?
And though lower sperm counts probably have led to a small decrease in the number of children being conceived, that decline has been masked by sociological changes driving birth rates down even faster: People in the developed world are choosing to have fewer children, and they are having them later.
Almost all the scientists I talked to stressed that not only were low sperm counts alarming for what they said about the reproductive future of the species—they were also a warning of a much larger set of health problems facing men. In this view, sperm production is a canary in the coal mine of male bodies: We know, for instance, that men with poor semen quality have a higher mortality rate and are more likely to have diabetes, cancer, and cardiovascular disease than fertile men.
Testosterone levels have also dropped precipitously, with effects beginning in uterus and extending into adulthood. One of the most significant markers of an organism’s sex is something called anogenital distance (AGD)—the measurement between the anus and the genitals. Male AGD is typically twice the length of female, a much more dramatic difference than height or weight or musculature. Lower testosterone leads to a shorter AGD, and a measurement lower than the median correlates to a man being seven times as likely to be subfertile and gives him a greater likelihood of having undescended testicles, testicular tumors, and a smaller penis. “What you are seeing in a number of systems, other developmental systems, is that the sex differences are shrinking,” Swan told me. Men are producing less sperm. They’re also becoming less male.
“Here in Denmark, there is an epidemic of infertility,” he said. “More than 20 percent of Danish men do not father children.”
So what was causing this disruption? To say there is only a single answer might be an overstatement—stress, smoking, and obesity, for example, all depress sperm counts—but there are fewer and fewer critics of the following theory: The industrial revolution happened. And the oil industry happened. And 20th-century chemistry happened. In short, humans started ingesting a whole host of compounds that affected our hormones—including, most crucially, estrogen and testosterone.
Anna-Maria Andersson, a biologist whose research has focused on declining testosterone levels. “There has been a chemical revolution going on starting from the beginning of the 19th century, maybe even a bit before and upwards and exploding after the Second World War, when hundreds of new chemicals came onto the market within a very short time frame.” Suddenly a vast array of chemicals were entering our bloodstream, ones that no human body had ever had to deal with. The chemical revolution gave us some wonderful things: new medicines, new food sources, faster and cheaper mass production of all sorts of necessary products.
When a chemical affects your hormones, it’s called an endocrine disruptor. And it turns out that many of the compounds used to make plastic soft and flexible (like phthalates) or to make them harder and stronger (like Bisphenol A, or BPA) are consummate endocrine disruptors. Phthalates and BPA, for example, mimic estrogen in the bloodstream. If you’re a man with a lot of phthalates in his system, you’ll produce less testosterone and fewer sperm. If exposed to phthalates in uterus, a male fetus’s reproductive system itself will be altered: He will develop to be less male.
Women with raised levels of phthalates in their urine during pregnancy were significantly more likely to have sons with shorter anogenital distance as well as shorter penis length and smaller testes. “When the [fetus’s] testicles start making testosterone, which is about week eight of pregnancy, they make a little less,that’s the nub of this whole story. So phthalates decrease testosterone. The testicles then do not produce proper testosterone, and the anogenital distance is shorter.”
The problem is that these chemicals are everywhere. BPA can be found in water bottles and food containers and sales receipts. Phthalates are even more common: They are in the coatings of pills and nutritional supplements; they’re used in gelling agents, lubricants, binders, emulsifying agents, and suspending agents. Not to mention medical devices, detergents and packaging, paint and modeling clay, pharmaceuticals and textiles and sex toys and nail polish and liquid soap and hair spray. They are used in tubing that processes food, so you’ll find them in milk, yogurt, sauces, soups, and even, in small amounts, in eggs, fruits, vegetables, pasta, noodles, rice, and water. The CDC determined that just about everyone in the United States has measurable levels of phthalates in his or her body—they’re unavoidable.
What’s more, there is evidence that the effect of these endocrine disruptors increases over generations, due to something called epigenetic inheritance. Normally, acquired traits—like, say, a sperm count lowered by obesity—aren’t passed down from father to son. But some chemicals, including phthalates and BPA, can change the way genes are expressed without altering the underlying genetic code, and that change is inheritable. Your father passes along his low sperm count to you, and your sperm count goes even lower after you’re exposed to endocrine disruptors. That’s part of the reason there’s been no leveling off even after 40 years of declining sperm counts—the baseline keeps dropping.
Can anything be done? Over the past 20 years, there have been occasional attempts to limit the number of endocrine disruptors in circulation, but inevitably the fixes are insubstantial: one chemical removed in favor of another, which eventually turns out to have its own dangers. That was the case with BPA, which was partly replaced by Bisphenol S, which might be even worse for you. The chemical industry, unsurprisingly, has been resistant to the notion that the billions of dollars of revenue these products represent might also represent terrible damage to the human body, and have often followed the model of Big Tobacco and Big Oil—fighting regulation with lobbyists and funding their own studies that suggest their products are harmless.