If you geek out about male fertility like I do, you’ll remember how your newsfeed blew up on December 15, 2021 with a study out of Denmark that was published in the journal Nature Reviews Endocrinology. This study was one of only a few that have found a possible link between lower fertility rates and the prevalence of fossil fuels in modern society.
What’s that you say? You don’t read scientific journals and you have absolutely no clue what I’m talking about? Well, don’t worry your pretty little head, because I’ll fill you in on everything you need to know.
Industrialization: A Quick History Lesson
Fossil fuels refer to any fuel that’s found naturally in the earth such as coal or gas that was formed from the remains of living organisms. Even though the sources of these fuels are ancient, the way we burn them for almost all of our energy needs is astoundingly modern. Fossil fuels only began to be the primary source of energy during the Industrial Revolution, which began in the mid-18th century.
Industrialization marked the transition from an agrarian society to an industrial society, and it really picked up steam (pun intended) in the mid-19th century with the proliferation of the steam engine, the invention of the internal combustion engine and the widespread utilization of electricity. We entered into an age of machines and technology that continues to evolve to this very day.
If you’re a human, you’ve been part of an almost 200-year experiment to find out what burning ridiculous amounts of fossil fuels does to our earth, our air, our bodies and our health. Although these chemicals affect all of our organs and body systems, for the sake of this article, we’re going to stick with the effects on our sperm. Spoiler alert: it’s not good.
Over the last 50 years, the global fertility rate has fallen by half. Women use to have 4.5 to 7 children during their lifetime. That number is now below 2.5. Much of that can be attributed to the changing roles of women in society, birth control, evolution of societal norms and cost of raising children. All of that stuff is fine and good. The part that’s not so good is that many couples who want to have children these days are struggling with infertility and must resort to costly and stressful fertility interventions.
So, what’s that got to do with my offspring sauce? Well, it turns out – a lot (maybe). The Denmark study that dropped in mid-December looked to see if the rise in poor semen quality, testicular cancers and falling birth rates were linked at all to the increasing exposures that humans have to the toxic chemicals that directly or indirectly come from burning fossil fuels.
According to the study’s authors, fossil fuels serve as the raw material for more than 100,000 synthetic chemicals that are now ubiquitous in our modern lifestyles. These chemicals can be found in virtually every living creature. What the study found is that as our dependence on fossil fuels increased, thereby increasing the prevalence of these toxic chemical byproducts, our fertility and birth rates decreased.
These harmful chemicals are found in all parts of our bodies, including our reproductive systems. The rise of these pollutants not only mirrors a decline in fertility in general, but it also mirrors the decline in sperm counts specifically. A study in 1992 found a 50% decrease in sperm counts has occurred in men globally over the last 60 years. According to Statista, a study done in 2017 found that the average sperm count of a Western man in 1973 was 337.5 million. In 2011, it had fallen to 137.5 million.
Studies in animals have shown that when exposed to chemicals that disrupt the endocrine system, rats and mice suffer changes to their DNA that affect their reproduction. Niels Erik Skakkebæk, the lead author of the Denmark study, put it this way, “We know from numerous experimental animal studies that plastics, chemicals, and so forth can cause problems in animal reproduction. We cannot do such exposure studies in humans, that would not be ethical, but we know enough from animal studies to be concerned.”
Where Do We Go from Here?
Male fertility is incredibly complex. There are biological, environmental, societal, economic, genetic and geographical factors at play. What the authors of the Denmark study hope is that their findings will encourage more scientific research into the possible link between fossil fuels and infertility.
Toward the end of the study, Skakkebæk sums it up this way, “In support of a biological hypothesis, the trends in testicular cancer that can be seen as the ‘canary in the coal mine’ for other spermatogenic disorders, are clearly increasing. … Also in favour of a biological hypothesis is the fact that reproductive toxicants are ubiquitously present in our diet, drinking water and the air we breathe. It is well established that these chemicals have become part of our tissues and fluids. But do they contribute to the current epidemic of infertility? We know that they can be a threat to wildlife. Unfortunately, too little has been done to uncover their role in humans.”
With so many unknowns about fossil fuels and fertility, there’s one thing that’s certain. I and the other fertility geeks out there will be paying close attention to this field of study so that we can bring the very best advice and recommendations back to our patients who are suffering from fertility issues like low semen quality and low sperm count. So, stay tuned – we’ll be sure to keep you posted.