Are humans going extinct? Chemical threats to the future of human reproduction

The Handmaid’s Tale has become a modern classic, keeping readers and viewers hooked through the story of a dystopian society where a decline in human fertility has led to cruel and rigid gender roles, and where fertile women are forced to bear children against their will to ensure the survival of the species. While The Handmaid’s Tale remains an extremist fiction, there are truths in the horrors of this imagined world that may already be in motion in real life.

The numbers are clear: in the Western world, fertility has dropped more than 50% over the past 50 years, a man today has only half the number of sperm that his grandfather had at the same age, and women in their twenties are less fertile today than their grandmothers were at 35. In just three generations human reproductive capacities have changed drastically, and the situation is expected to worsen in the coming years. Advances in technology and medicine mean that changes in commonly used markers for fertility are unlikely to represent the imminent extinction of the human race. Additionally, this field requires further study in order to properly assess the validity of these alarming numbers. But based on what we currently know, we can predict that how we approach reproduction as a species is subject to change going forward.

Getting a desired positive result might require many more doctor’s appointments, and a lot more money, that it has in the past.

So, what’s to blame? Notably, pollution. Other factors are involved- many people are choosing to have children later in life, when fertility is naturally reduced- but synthetic chemicals present in our daily lives play a prominent role by diminishing sperm count, decreasing libido, causing early ovarian failure, miscarriages, or premature births. Unfortunately, the chemical industry is largely unregulated, meaning many products that we use and assume to be safe may be causing serious harm. They accumulate in the environment as well as in our bodies, leading to many known and unknown consequences. Regarding reproductive health, the most worrying chemicals are those that interfere with our natural hormonal systems, known as endocrine disruptors. When exposed to these chemicals our bodies may be tricked into producing less of our necessary sex hormones and a loss of fertility (or disruption of common markers of fertility) ensues.

Many different types of endocrine disruptors exist. Xenoestrogens are likely the most well-known and include compounds known as alkylphenols and bisphenols. The most notorious of these is BPA (bisphenol-A), which has begun to be phased out of products over the past decade. Xenoestrogens, as the name would suggest, have structures similar to that of oestrogen and particularly affect people with a female reproductive system. While bisphenols are often direct ingredients in many of the man-made materials we use, used to add durability to plastics, alkylphenols are most commonly used as precursors for detergents, fragrances, and elastic and fire-retardant materials. Although used in different ways, both of these xenoestrogens are linked to a decline in female reproductive capacities, as well as impaired development of the nervous and immune systems of young children and fetuses. These impacts extend to all mammals and many forms of aquatic life.

Next come phthalates, a large group of chemicals added to many types of products used on a daily basis. As phthalates can take on a large variety of roles, they can be found in cosmetics, soaps, non-prescription drugs, natural health products, fabrics and textiles, electrical items and electronics, children’s toys, food packaging, and construction and renovation products. Although they allow many items to have the properties we desire as consumers, in the human body they mimic testosterone and are primarily linked to negative effects on male reproductive systems. Only one type of phthalate has yet to be banned (DEHP, or di-(2-ethylhexyl)phthalate), but there is a growing body of evidence suggesting that phthalates in general could be contributing to declining testosterone levels and a consequent decrease in male reproductive capacities. The impacts of phthalate exposure can be measured from birth, with greater levels of phthalates in the human body correlating to smaller penis size and reduced urogenital distance (size of the perineum). These markers, in turn, predict reduced reproductive capacities as an adult.

Other endocrine disruptors that affect the reproductive systems include DDT, PCBs, and PFOA. DDT (dichlorodiphenyltrichloroethane) is a pesticide that was once widely used to protect crops and to prevent the spread of diseases such as malaria, typhus, and dysentery. It has been largely banned worldwide since the 70s but is still used in limited quantities in Africa and parts of Southeast Asia. DDT has many adverse side effects in humans, including being linked to cancers, inhibition of the development of female reproductive organs, and decreased fertility in adult men. Similar reasons led to the ban of PCBs (polychlorinated biphenyls), which were used as industrial coolants and lubricants, around the same time. PFOA (perfluorooctanoic acid) is also associated to greater infertility with effects on male and female reproductive systems. It has been used in the production of a variety of textiles including garments, upholstery, and carpeting, but has largely been phased out of production in recent years. However, just like xenoestrogens and phthalates, these molecules persist in the environment and have lasting effects on humans and other animals.

The four Fs of evolution (fighting, fleeing, feeding, and mating) might have taken humans from caves to cities, but they are no match for environmental pollution

Dr. Shanna Swan, a prominent environmental epidemiologist and author of the book Count Down: How Our Modern World Is Threatening Sperm Counts, Altering Male and Female Reproductive Development, and Imperiling the Future of the Human Race, is leading the research on the links between human reproductive capacities and certain chemical compounds. She specifically warns against the use of phthalates and bisphenols which, despite their ties to a decrease in reproductive health, are still widely used. In other cases, certain flagged compounds are simply being replaced with other potentially damaging molecules. For example, although it’s become fairly common to see “BPA-free” stickers on items such as water bottles or sandwich bags, in many instances BPA has been substituted for BPF (bisphenol-F) or BPS (bisphenol-S), chemical cousins that do not come without their own levels of risk. In this way, consumers are duped into purchasing products that they believe to be safe, only to still end up suffering the consequences of a poorly regulated industry.

“Known endocrine disruptors must be kept out of homes and bodies completely,” says Dr. Swan. “Before a chemical enters the marketplace, it should pass stringent requirements to ensure that it is not capable of interfering with our hormones, that it is free of low-dose adverse effects, and that it is minimally environmentally persistent.” When humans suffer from declining reproductive capacities, this is an indicator that our general health is suffering, and that other animals and our planet as a whole are suffering too. It may be too late to improve the odds for those who are currently looking to get pregnant, but we can help avoid future generations having to suffer a similar fate by being aware of the substances we are exposed to and calling for better regulations in the chemical industry. With the will to enact change, we can always turn things around.

Advice for consumers :

  • Avoid plastic packaging or containers for food and beverages as they commonly contain bisphenols. Especially do not heat these containers, as this can cause greater quantities of these chemicals to leach out
  • When shopping for cosmetics and personal hygiene products, look for those that are phthalate free
  • If you are pregnant or looking to become pregnant, be especially mindful of the chemicals you may be exposed to, as these chemicals have the greatest impact on unborn children
  • If in a position to do so, encourage local policy-makers to push for greater regulations regarding bisphenols and phthalates, and greater regulations for the chemical industry as a whole

Note: studies regarding sperm count have a Eurocentric focus, which its own authors admit have led to biased results. Better studies need to be done take into account a wider range of locations, as well as through identifying and including other data that can contribute to these results. Also, higher sperm count does not necessarily indicate better fertility by itself, and needs to be considered alongside other factors, such as sperm motility.

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