Women will struggle to get pregnant naturally in the next few decades without stronger regulation of chemicals. Rates of miscarriages, abnormalities in penis development and intersexuality are all increasing at alarming levels. Professors Alex Ford and Gary Hutchison report.
The sperm count of Western men has plunged by more than 50% in less than 40 years according to a raft of evidence detailed by epidemiologist Shanna Swan in her new book “Countdown”.
If the data is extrapolated to its logical conclusion, men could have little or no reproductive capacity from 2060 onwards. And one of the main causes of the declining sperm levels is the chemicals we’re surrounded by in our everyday lives.
These claims are backed by a growing body of evidence that’s finding reproductive abnormalities and declining fertility in humans and wildlife worldwide.
Declining sperm count
Studies revealing declining sperm counts in humans aren’t new. These issues first received global attention in the 1990s, though critics pointed to discrepancies in the way sperm counts were recorded to downplay the findings.
Then, in 2017, a more robust study that accounted for these discrepancies revealed that the sperm count of Western men had declined by 50%-60% between 1973 and 2011, dropping on average 1%-2% per year. This is the “countdown” to which Shanna Swan refers.
The lower a man’s sperm count, the lower their chance of conceiving a child through sexual intercourse. The 2017 study warns that our grandchildren could possess sperm counts below the level considered suitable for successful conception – likely to force “most couples” to use assisted reproduction methods by 2045, according to Swan.
Equally alarming is an increase in the rate of miscarriages and developmental abnormalities in humans, such as small penis development, intersexuality (displaying both male and female characteristics) and non-descended testes – all found to be linked to declining sperm count.
Why fertility is falling
Many factors could explain these trends. After all, lifestyles have changed dramatically since 1973, including changes in diet, exercise, obesity levels and alcohol intake – all of which we know can contribute to low sperm counts.
But in recent years, researchers have pinpointed the foetal stage of human development as a decisive moment for men’s reproductive health.
During the “programming window” for foetal masculinisation – when the foetus develops male characteristics – disruptions in hormone signalling have been shown to have a lasting impact on male reproductive capabilites into adulthood. This was originally proven in animal studies, but there’s now growing support from human studies.
This hormonal interference is caused by chemicals in our everyday products, which have the capacity to either act like our hormones, or to prevent them from functioning properly at key stages in our development.
We call these “endocrine-disrupting chemicals” (EDCs), and we’re exposed to them through what we eat and drink, the air we breathe, and the products we put on our skin. They’re sometimes called “everywhere chemicals”, because they’re very difficult to avoid in the modern world.
Exposure to EDCs
EDCs are passed to the foetus by the mother, whose exposure to the chemicals during her pregnancy will determine the degree to which the foetus experiences hormonal interference. That means that present-day sperm count data speaks not to the chemical environment today, but to the environment as it was when those men were still in the womb. That environment is undoubtedly becoming more polluted.
It’s not just one specific chemical causing the disruption. Different types of everyday chemical – found in everything from washing up liquids to pesticides, additives and plastics – can all disrupt the normal functioning of our hormones.
Some, like those in the contraceptive pill, or those used as growth promoters in animal farming, were specifically designed to affect hormones, but are now found throughout the environment.
Animals suffering too
If chemicals are to blame for declining sperm counts in humans, you’d expect animals that share our chemical environments to be affected too. And they are: a recent study found that pet dogs are suffering the same decline in sperm counts for the same reasons as we are.
Studies of farmed mink in Canada and Sweden, meanwhile, have also linked industrial and agricultural chemicals with the creatures’ lower sperm counts and abnormal testicular and penis development.
In the wider environment, the effect has been seen in alligators in Florida, in shrimp-like crustaceans in the UK, and in fish living downstream of wastewater treatment plants around the world.
Even species thought to roam far away from these sources of pollution are suffering from chemical contamination. A female killer whale that washed up on the shores of Scotland in 2017 was found to be one of the most contaminated biological specimens ever reported. Scientists say she never calved.
In some instances, the abnormalities observed in wildlife are linked with very different chemical compounds to those observed in humans. But they all share a capacity to disrupt the normal functioning of the hormones that dictate reproductive health.
Better regulation vital
In the UK, the Department for Environment, Food and Rural Affairs is currently building a chemicals strategy that could tackle these issues. The EU, meanwhile, is changing chemical regulations to prevent banned substances being replaced with other harmful ones.
Chemicals require better regulation to protect our reproductive capacities, and those of the creatures with which we share our environment. Ultimately, public pressure could demand stronger regulatory interventions, but as chemicals are invisible, this may prove difficult to achieve.
Alex Ford is Professor of Biology at University of Portsmouth; Gary Hutchison is Professor of Toxicology and Dean of Applied Sciences at Edinburgh Napier University. This article was republished from The Conversation.
Alex Ford is Professor of Biology at University of Portsmouth.
Alex Ford is Professor of Biology at University of Portsmouth.
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