It’s official: sperm counts have halved over the past 40 years. We know that BPA and other endocrine-disrupting plastics are linked to infertility in both men and women, so has this got anything to do with it? Are BPA plastics to blame for falling sperm counts?
Falling sperm counts: the evidence
News media has gone crazy over recent claims that men’s sperm counts have halved in the past 40 years. Perhaps most worryingly, the BBC is reporting that if these trends continue the human race could go extinct.
The stories are based on a report, Temporal Trends in Sperm Count: a Systematic Review and Meta-regression analysis, which looked at research from over 2500 studies from the past four decades. Estimates of sperm counts were based on samples taken from 42,935 men during the years 1973-2011.
In other words, the sample size was huge and therefore more likely to be reliable.
The meta analysis controlled for a number of variables such as geographic group, age, fertility group, etc. And the results were pretty shocking:
Sperm counts dropped by an average of 1.4% every year between 1973 and 2011, causing an overall decline of 52.4% during this time.
The drop in sperm count (SC) was most significant in men from ‘Western’ regions: the USA, Europe, etc.:
“This comprehensive meta-regression analysis reports a significant decline in sperm counts (as measured by SC and TSC) between 1973 and 2011, driven by a 50-60% decline among men unselected by fertility from North America, Europe, Australia and New Zealand. Because of the significant public health implications of these results, research on the causes of this continuing decline is urgently needed.”
Other than a call for more research, the report didn’t comment on the potential cause of this drop in sperm count.
But we know that western lifestyles are very different to how they were 40 years ago. And with so many changes, it’s incredibly difficult to pinpoint the exact reasons behind this alarming trend. It’s also likely more than one factor has contributed to this decline, further confusing the issue.
One possible factor though is plastic food and drink packaging – specifically BPA. We’ve seen huge increases in the use of these materials over the last four decades. And there is a substantial body of evidence linking BPA with male infertility.
BPA mice studies
Bisphenol A (BPA) is a common plastic used to make a huge range of products.
It’s also a xenoestrogen. This means it behaves like the female hormone estrogen. It binds to receptors in just the same way and causes similar effects. In fact, it’s so similar that it was once considered as a potential drug to treat the symptoms of low estrogen in women.
Consuming a load of hormone-mimicking chemicals is every bit as unhealthy as it sounds. Environmental estrogens – specifically BPA – have been linked with a host of health conditions from heart disease to cancer.
And since hormones play such a crucial role in reproduction, it’s no surprise that BPA and other endocrine disruptors are linked with infertility – in both men and women.
First off, there are the studies of the effects of BPA on mice:
“Males having ingested 25 and 100 micro g kg(-1) [corrected] BPA showed a significant reduction in testicular sperm counts and in the efficiency of sperm production. Epididymal sperm counts were also significantly reduced in males that had ingested BPA. There were significant reductions in the absolute weights of the testes and seminal vesicles. These results suggest that male fertility and reproduction is impaired by bisphenol A.“
It gets worse, though. This study on rats found that the negative effects of BPA on male fertility get exaggerated with each generation of males, “leading to impairments in the fertility of F(1) male offspring and their subsequent F(2) and F(3) generations.”
The rats weren’t subjected to some unrealistic BPA megadose, either. The pregnant animals were fed between 1.2 and 2.4 µg of BPA per kilogram during pregnancy. This is much lower than the FDA’s supposedly safe limit of 5000 µg/kg.
This raises the question of whether these effects can be observed in humans as well.
BPA and male infertility
Given its estrogen-mimicking properties, it’s perhaps unsurprising that BPA is linked with infertility in humans too.
BPA use in food packaging has declined slightly in recent years as consumers become increasingly aware of the health risks associated with it. Nevertheless, you can still commonly find it in products used to store food and drink such as plastic sports bottles, food containers, and coatings in tin cans.
Evidence of the negative impact of BPA on male sperm counts is equally damning in humans as it is rats. Studies have demonstrated time and again a positive correlation between male fertility problems and BPA exposure.
“BPA has been found to produce several defects in the embryo, such as feminization of male fetuses, atrophy of the testes and epididymides, […] and alteration of adult sperm parameters (e.g.,sperm count, motility, and density). […] Epidemiological studies have also provided data indicating that BPA alters male reproductive function in humans. These investigations revealed that men occupationally exposed to BPA had high blood/urinary BPA levels, and abnormal semen parameters.”
Despite the comprehensive body of evidence, BPA use in food and drink packaging is still largely unregulated. In the USA, for example, there is no federal regulation of BPA in plastic bottles. In the EU and Canada, BPA regulation is confined exclusively to baby bottles. While such rules are welcome, they do nothing to prevent infant exposure to BPA in utero – the very stage at which future effects are most devastating.
And of course these regulations do nothing to protect adults, either. In safety reviews of BPA, the FDA points to evidence that BPA concentrations in humans are well below recommended limits. But as we saw in the rat study earlier, these limits appear to be anything but safe!
How to minimise BPA exposure
In the absence of any serious regulation, it is up to consumers to take responsibility for their exposure to the estrogenic effects of BPA.
Common sources of exposure to BPA are:
- Plastic food packaging
- Bottled water
- Sports bottles
- Tinned food
- Soda cans
In case you were wondering, BPA is used to coat the inside of the metal tins and cans. This is to stop the contents from getting contaminated by the metal. Instead, they get contaminated with BPA.
Unfortunately, avoiding these items completely is pretty much impossible. But substituting fresh produce (or if not, frozen) for packaged or tinned foods is a good place to start. If you store your food in plastic containers, consider investing in glass alternatives.
Fortunately, manufacturers are slowly moving away from BPA as consumers become increasingly aware of the health risks.
However, this is small comfort when the materials used instead are even more powerfully estrogenic. Remember, just because a product is BPA free does not mean it is estrogenic activity (EA) free.
BPA sperm count decline: correlation or causation?
BPA came into commercial use in 1957. But it would be about another decade before its use became widespread. Sperm counts have halved over the last 40 years – a timeframe that roughly correlates with increased BPA use.
“Our data suggest that exposure to BPA in the United States is widespread.”
– Environnmental Health Perspectives, Jan 2008
But despite all this it’s still difficult to say how much BPA is to blame for low sperm counts – if at all.
First off, there is no control group. Almost every single person on earth will have been exposed to BPA at some point. This makes it virtually impossible to compare the effects on fertility of BPA-exposed males with those who haven’t been exposed. The latter group just doesn’t exist.
It might be useful to investigate whether reduction in sperm counts by region corresponds to that region’s BPA consumption. We know that the reduction in sperm count was most noticeable in western countries. Might it be that there is a higher BPA consumption per capita here?
Secondly, there have been many other changes in western countries over the past 40 years. While western men have likely been exposed to more BPAs during this time, there have also been huge changes in dietary habits, exercise, and drug and alcohol consumption. All this makes it highly unlikely that BPA is solely responsible for male sperm count decline.
But given the multitude of studies linking BPA and male fertility problems, it’s difficult to believe it’s not partly responsible. We know that BPA negatively affects developing babies. We also know that this effect becomes exaggerated across generations (at least in rats). Finally, common sense would suggest a chemical that behaves exactly like estrogen – a female hormone – won’t be too great for male reproductive health!