Are Xenoestrogens Causing a Global Fertility Crisis?
A strange, invisible environmental and hormonal crisis
Fertility is collapsing in much of the world. Most humans on Earth now live in a country with a below-replacement fertility rate. It is surprising how ubiquitous the drop is—North and South America, Europe, East Asia, and even once procreative Islamic regions are filled with countries that will soon be shrinking. Take China—a recent article containing leaked data showed that there were more deaths than births in 2022 and 2023. The number of births has reportedly plummeted 40% in the last 5 years. The 1.4 billion strong nation of China is shrinking.
To many, shifting preferences is the simplest explanation for the decline in fertility. But this is unconvincing since culture would have needed to change very rapidly in virtually all nations simultaneously. There are extremely few global exceptions. Another potential answer is rising incomes or wealth. It is true that rising incomes are associated with lower fertility, and incomes have risen in most countries. But birth rates have collapsed very quickly over the past decade, often in regions that are still very poor. According to the World Bank, the entirety of Latin America and the Caribbean has a fertility rate of 1.9 children per woman, below replacement. GDP per capita, adjusted for purchasing power, was about $16,000 in Latin America and the Caribbean in 2022. This is equivalent on average to the per capita wealth level of the United States in the 1950s. At the same level of income as below-replacement Latin America, fertility in the USA was nearly 4 children per woman. Indeed, at 1.9 children per woman, the fertility rate in Latin America and the Caribbean is equivalent to that of the United States just 10 years ago. India, meanwhile, fell below replacement in 2020, and its GDP per capita is still well below $3,000—it remains an extremely poor country! All this suggests that there could be more at work besides just culture or income in explaining collapsing fertility worldwide.
Are Endocrine Disruptors to Blame?
The ubiquity and suddenness of the drop in fertility imply a recent cause that affects all regions of the world, and is rising in potency quickly and simultaneously. This raises a disturbing possibility—what if environmental pollution is interfering with our bodies and reducing human fertility? In fact, there is abundant evidence that an accumulation of man-made chemicals in our environment is detrimentally affecting the hormonal systems of humans and other animals.
Something is happening to male hormones
Male testosterone levels have sharply declined over the past few decades. Researchers from the Yale University School of Medicine found that bioavailable testosterone declined by about 25% in American males from 2000 to 2016. This was after controlling for age, race, BMI, comorbidity status, alcohol use, smoking use, and level of physical activity—in other words, none of those factors explain the drop. Today, about 20% of adolescent and young adult men suffer from testosterone deficiency.
This study confirms the results from an earlier study of 1,700 Massachusetts males, indicating that bioavailable testosterone levels declined 45% from 1987 to 2005.
Sperm counts, for their part, are also on the decline. A recent meta-analysis found sperm counts among men in North America, Europe, Australia (and New Zealand) have roughly halved between 1973 and 2011. A 2023 study estimated that the age-standardized rate of global male infertility rose about 19% from 1990 to 2019.
Something is Happening to Animals
“They’re turning the freaking frogs gay!” It’s an absurd joke and conspiracy theory… but it has a point. It turns out that frogs, reptiles, and fish are changing from male to female, and a broader range of animals are suffering from hormonal disturbances caused by a range of pollutants. A 2004 report from the UK’s Environment Agency wrote: “Since the 1980s […] the apparent widespread feminization of male fish in rivers has received particular attention.” It writes, “scientific investigations in the UK, Europe, USA and Japan have demonstrated the occurrence of the intersex condition […] in fish in freshwater environments.” It continues: “The UK and European epidemiological datasets have clearly demonstrated that […] incidence and severity directly [of intersex condition] related to the proportion of treated sewage effluent in rivers.” The pollutants in question were likely hormones released in urine by women using contraceptive birth control.
But hormones from birth control in the water are not the only thing affecting animal hormones. In 2010, a study out of UC Berkeley found that Atrazine, one of the world’s most widely used herbicides, wreaks havoc with the sex lives of adult male frogs, emasculating three-quarters of them and turning one in 10 into females. Some 80 million pounds of atrazine are applied annually in the United States on corn and sorghum to control weeds and increase crop yield. Atrazine interferes with endocrine hormones, such as estrogen and testosterone, in fish, amphibians, birds, reptiles, laboratory rodents, and even human cells.
Plastics and microplastics can also disrupt the endocrine system of animals and humans by leaching chemicals like BPA and phthalates, which mimic hormones such as estrogen. Even animals that are very isolated from humanity and its pollutants are found to be contaminated with microplastics. For example, the Andean Condor, whose habitat is in the remote Patagonian mountains, is commonly found by researchers to have plastic in its droppings. As Condors are at the top of the food chain, this implies that the links below the condor are also contaminated. These plastics are found to disrupt the hormonal systems of these birds. The hormones of polar bears and belugas are also found to be affected by Polychlorinated biphenyls, a man-made chemical used in a range of products.
Whew! Glad to be a human living in a safe, clean city, not a condor in the remote Patagonian mountains, right? Well… if these hormones, plastics, and pollutants are known to affect hormonal systems in animals, sometimes in extreme ways, including causing intersex conditions, could they have the same effects in humans?
Rising Human Prevalence of Intersex Conditions
A 2016 academic paper found that “an increasing number of children are born with intersex variation” including ambiguous genitalia and hermaphroditism. The authors point to “endocrine-disrupting chemicals (EDCs) in the environment” as the cause of the increase. To support this, they point to evidence from animal studies, the theoretical mechanisms by which these chemicals interfere with the endocrine system, and the fact that there is a higher prevalence of offspring with intersex variation in male and female workers exposed to EDCs. A study examining the incidence of genital malformations in French newborn male infants found a direct association between parental pesticide exposure and abnormal male external genital development, including an increase in cryptorchidism (the absence of testicles), hypospadias (incorrect location of the urethra), micropenis (0.35%), and disorders of sex development. Disturbingly, EDCs are widespread in consumer products and pesticides. Another study examined a large industrial chemical spill in Italy in 1976. The offspring of the people who lived in the affected town of Seveso were found to have a skewed sex ratio, with more females born than males. Fathers exposed when they were younger than 19 years of age sired significantly more girls than boys (38 boys for every 100 girls).
Another clue is the observed changes in anatomical features in humans which correlate with hormonal exposure in utero. Anogenital distance refers to the length of the gap between the anus and the genitals of males and females. A longer distance correlates with greater exposure to androgens (male hormones) as a fetus. It also correlates with genital size in males and testosterone levels in both men and women. Recent research shows that anogenital distance is negatively correlated to phthalate levels in mothers. It turns out that the level of phthalate exposure required to have substantial effects on babies is present in about one-quarter of American females. Phthalates are commonly used in consumer plastics to make them more durable.
The final and most controversial piece of evidence may be the rise in human self-identification as LGBT. If the intersex condition is linked to endocrine-disrupting chemicals in the environment, is it possible that exposure to EDCs is playing a part in the increasing prevalence of transgender individuals? According to GALLUP, 21% of Generation Z now identify as gay, lesbian, bisexual, or transgender, with about 1 in 50 identifying as transgendered. This rate is twice as high as millennials, 10 times higher than baby boomers, and 100 times higher than those of the silent generation.
The relative roles of nature and nurture in LGBT identification remains controversial and unknown. But we know that biology plays more than zero part. One clue is the “digit ratio,” the ratio of the index finger to the ring finger. It turns out that men tend to have a longer ring finger relative to their index finger, and women are the opposite. This is because the length of these fingers is related to the level of androgenic hormones a person was exposed to as a fetus. This digit ratio corresponds to a wide range of psychological traits and behaviors, including the likelihood of being gay, lesbian, or transgendered. Women and gay men tend to have a higher digit ratio, while lesbians and straight men tend to have a lower ratio. This is highly suggestive that biology and hormones play a substantial role in whether humans turn out to be gay or straight.
Conclusion
Diving into the world of xenoestrogens and their role in the fertility collapse is a bewildering detective adventure, where the clues are esoteric and microscopic, and suspects are everywhere. But the stakes are high—our bodies are stewing in a historically unprecedented brew of novel industrial chemicals that masquerade as hormones within our bodies. This science is complex and controversial, but it demands our attention amid an existentially relevant drop in global fertility. The consumer products of modernity may be changing who we are on a very intimate level… not just metaphorically but also in alarmingly literal ways. The research isn’t settled, but it may be strange new coalitions of pro-natalists and environmentalists will be required to solve this problem.
It’s the plastics. Follow link. https://medium.com/read-or-die/were-facing-a-collapse-in-global-fertility-c211bc05f373?sk=84e815295034c91301aef8914400d3d1
Interesting read. This is worth further study.