Fifty years ago, there were no sperm banks.
There were no over-the-counter fertility tests, no proprietary zinc supplements for virility, and men pretty much took for granted that when the time came, their "swimmers" would do their job.
Fast forward five decades, and the average man in his 20s and 30s lives in a state that might be aptly described as sperm count paranoia.
"There has been scientific evidence that sperm counts have been dropping worldwide over the past 50 years," said Cynthia Daniels, associate professor of political science at Rutgers University and author of "Exposing Men: the Science and Politics of Male Reproduction."
"This evidence has been met with two extremes—either profound skepticism or a reaction that verges on public panic."
Thus far, solid scientific proof to completely back these fears has been elusive. But to paraphrase an old saying, just because you're paranoid doesn't mean environmental factors aren't killing off your sperm.
Some research studies do suggest that male sperm counts are falling across the globe, and a number of scientists are working to determine the real-world influences that might be causing a reduction in "swimmers."
Many researchers report there are a number of fertility-damaging culprits that may lurk within our workplaces, reside in the heat at the bottom of our laptops, float in our drinking glasses -- and possibly even rest on the dinner plates of mothers pregnant with male children.
"I think the evidence is growing that chemicals in the environment do affect a man's sperm count," said Shanna Swan, director of the Center for Reproductive Epidemiology at the University of Rochester School of Medicine. "It's probably not universal, but it is pretty good evidence for a decline in Western countries."
Daniels said these findings have been met with equal measures of fear and defensiveness, as they strike at the heart of social norms regarding masculinity.
"Others strongly contest these findings and say that the evidence is the result of social hysteria -- just one more example of men (and manliness) under attack in the 21st century," she added. "One thing is clear -- this question is socially and politically loaded because it involves not just questions of male health, but of how we view men in the world today."
When 19 Million Just Isn't Enough
Twenty million of anything may seem like quite a bit to most people. But if it's a milliliter of semen you're talking about, this number of sperm just barely cuts it.
"Semen typically contains 70 million sperm per milliliter," Swan said. "That's a lot. But if you get to the low end of the concentration spectrum -- anywhere below 20 million sperm per milliliter -- your fertility could be affected."
The simple reason for this, Swan explained, is because you need a lot of sperm in order to have a reasonable chance of one making it to the egg of your partner, as the odds of any one sperm actually fertilizing an egg are infinitesimal.
"In a lot of studies, if the count falls below 40 million, a man's chance of conception in a given month is decreased," Swan said.
None of this would be a worry, of course, if all men were able to retain a naturally large complement of sperm. But as current research pegs as much as 40 percent of reproductive problems to the male partner, it becomes evident that male infertility is a problem for many.
Swan's work has shown that certain chemicals in the environment -- such as those associated with plastics and pesticides -- seem to be linked to a lower sperm count in men who have been exposed to those chemicals.
"I think we are looking at a problem that has just recently been identified," Swan said.
The findings aren't just on paper. Swan said that in her study of men living in rural areas of mid-Missouri, the data suggested that pesticides may be responsible for cutting the usable sperms levels of these men in half when compared with their urban counterparts in Minneapolis or New York City.
In the Womb?
While some of these factors can be avoided (smoking and heavy alcohol use, for example, are known for their sperm-slaying potential) other fertility hazards may attack when males are most vulnerable -- before they have been born.
According to John McCarrey, professor of cellular and molecular biology at the University of Texas at San Antonio, a host of environmental influences can affect a man's future sperm count even while he is still in the womb.
During fetal development, McCarrey said, "There is a massive reprogramming of many genome functions. There is a lot that's happening during development."
The heart of the matter lies with what he calls the epigenome -- the way in which the body's cells interpret the genetic blueprints laid out by the DNA. Tinker with this at the wrong time, and the results could last a lifetime.
"We're really at the point where we're figuring out what kinds of things have adverse effects," McCarrey said. "At the very least, all of these recent findings have made us much more aware that this is a very sensitive period."
But sensitive to what? Most pregnant women don't go about eating bowls of pesticide, after all.
There could be a number of dietary influences at play. Red meat, for example.
Earlier this year, Swan and her colleagues published a study that suggested the beef that a woman eats while pregnant just might affect the future fertility of her male babies.
"The hypothesis is that hormones put in beef have an effect on sperm count," she said. "If a pregnant woman ate beef more than once a day, her son's sperm count was about 25 percent lower."
And though the effects from a lot of the chemicals in the environment today that men are exposed to are not considered to be persistent, exposures in the womb could have much more lasting effects.
"If the exposure is through the mother when she is pregnant with a male baby, then those changes are permanent," Swan said.
Keeping Your Swimmers in the Gene Pool
While much of the research on the possible decline of male fertility is still unclear, Swan said there are certain steps men can that may help safeguard their sperm.
"The first caveat is that all of these things have to be tested further, so at no point can we make firm health recommendations," Swan said. "However, if people want to change their behaviors, there are several things that they can do that will probably help and won't hurt."
One of the tips Swan listed is eating organic foods whenever possible. Organic foods, she said, mean less pesticide -- and, in turn, may lead to more viable sperm.
Her second tip: Pregnant women who fear for their future fetus' fertility should avoid heavily using plastic products known to contain phthalates -- softening agents that are suspected to have an effect on sperm count.
"There's also the question of water," she added. "Using reverse osmosis, charcoal filtered or distilled water is probably a good thing, and again there's no harm in doing this."
And then there are the no-brainers.
"Of course, by the way, smoking is not good for sperm count," she said. "Neither is excess alcohol, though I don't think men who are trying to conceive are going to go out and get blasted every night."
But while adherence to these tips may solve part of the problem, researchers say the true solution to safeguarding men's sperm counts lies in finding and eliminating hidden culprits in the environment.
"Most of these products are silent -- they are introduced to our environment without us knowing, and we have no control over it. So it is very hard to avoid them," Swan said.
"I'm hoping we can reverse this trend."