What Are Toxic Chemicals Doing to Our Genitals? Scientists Are Finding Out.

One potential effect of our world of plastic? Smaller penises.
What Are Toxic Chemicals Doing to Our Genitals? Scientists Are Finding Out.
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ABSTRACT breaks down mind-bending scientific research, future tech, new discoveries, and major breakthroughs.

Maybe we’ll save the planet from climate change over the next quarter century—right in time, some scientists say, for most heterosexual intercourse to culminate in little pools of sad, spermless jizz, thanks to endocrine-disrupting chemicals like phthalates. 

These chemicals, coined “endocrine disruptors,” are used to produce beloved everyday items like toilet paper, personal care products, cosmetics, food packaging, and detergents. Since their introduction into modern manufacturing practices in the 1950s, endocrine disruptors have become ubiquitous in our environments and bodies. Some of these disruptors are known as “forever chemicals” due to how difficult they are to break down. They’ve weaseled their way into tap water, food, and even into 97 percent of Americans' blood. As you might imagine, that’s not a good thing.


Reproductive and environmental epidemiologists like phthalate expert Dr. Shanna Swan, a professor at the Icahn School of Medicine at Mount Sinai, say these chemicals do significant damage to our health, primarily by inhibiting hormone function

Swan’s research, comprised of over 200 peer-reviewed studies that she has co-authored, demonstrates that endocrine disruptors may be bulldozing several aspects of hormonal health and fertility. Their effects may be grave if pregnant women are exposed; studies have shown that some of the chemicals can cross the placental barrier, affecting the fetus’s health and reproductive organ development.

In her 2021 book on the subject, Swan argues that the chemicals’ ability to impede proper reproductive organ development in utero likely contributes to our plummeting fertility rates. Her research found that sperm count dropped by a whopping 50-60 percent in Western men between 1973 and 2011. Along with it went sperm quality and testosterone levels. The latter is declining by about 1 percent per year. Testicular cancer, erectile dysfunction, miscarriage, and polycystic ovarian syndrome rates are increasing at concerning paces, too, she says. 


Despite the gravity of her statements on our reproductive health, the public seems to be especially entranced by her findings on penis size and anogenital distance (AKA, the “taint”). In her book, she writes, “my colleagues and I published our study that showed that an expectant mother with higher DEHP levels [an endocrine disrupting chemical] in early pregnancy was more likely to have a son with less ‘male-typical’ genitals—for example, a shorter anogenital distance (AGD) and a smaller penis.”

But an interesting caveat to this conversation arose last month: a meta-analysis study by researchers from Stanford, Emory, and several universities in Italy found that erect penis length increased by 24 percent over the last 29 years. 

The penis size statistics were not self-reported. Instead, the authors reviewed past studies where penis length was measured by clinicians. They looked at measurements in flaccid, stretched, and erect penises (both spontaneously and after an injection), and reported a trend in erect penis lengths. The trend for stretched or flaccid measurements was not clear, they wrote, likely because these methods are inherently less standardized than measuring when erect.


“We were surprised that things were not getting shorter,” said Dr. Michael Eisenberg, a co-author of the study, in an interview with Motherboard. “With some of the work that Shanna [Swan] has done… and declining reproductive health, more of these chemical exposures, [we thought] likely things would decrease in size. And if nothing else, the obesity epidemic is also very prevalent, and so, you know, functional length can decline as a result of there being more tissue there. So we were surprised that there was potentially an increase.”

While this finding might appear to contradict Swan’s research, she clarified in an interview with Motherboard that penile “width is what is reduced in infants when their mother is exposed to phthalates,” the endocrine disruptor she focuses much of her work on. 

“We didn’t look at length because length is very hard to measure… what is fully erect?” she said. She went on to assert that penis length “is not a precise measurement. Width is precise.”

Eisenberg said that he doesn’t think his team’s work casts down Swan’s findings about the effects of endocrine disruptors on fertility. There is literature that shows obesity and increased chemical exposures may be contributing to earlier puberty in boys, he explained, which could be one reason for the findings.


“We went back to the literature to look at, you know, how lengths are sort of developed and defined. There is data that puberty is happening earlier, and when puberty occurs earlier, it tends to lead to longer [penis] lengths,” he said.

Perhaps both could be true—maybe endocrine disruptor exposure decreases penile width in utero but causes puberty to occur earlier in childhood, leading to longer penises in adolescence and, later, in adulthood. But both Swan and Eisenberg mentioned that the data is too preliminary to come to this conclusion. 

“This is a single study,” said Eisenberg. “I think that you know, this is the first study of its kind that looked at this… one of our conclusions was that it needs to be replicated.”

“It’s interesting, but it’s limited,” Swan said of the study. “If you look at Table One and look for measurement methods, most of them are not listed,” she said. 

When asked about it, Eisenberg acknowledged that “any time you’re doing a meta-analysis over decades, I think things may change, also [research] center to center… I certainly acknowledge that there could be some variation.” He went on to explain that they chose to look at erect penile length over stretched length because “with erect length… you can’t pull any harder, it is what it is. We thought that may be more reliable.

This laser-focus on penis size seems to leave something out: what about vaginas, ovaries, and uteruses? More specifically, what about vagina and uterus development in relation to endocrine disruptor exposure in utero? 


Less is known about that. Swan explains in her book that “for one thing, there are more studies on men’s reproductive functionality, partly because, well, more medical studies are conducted on men—period.” 

Additionally, “there may be an element of practicality at work here: men’s genitals are on full display, and a sperm sample can be obtained… without too much effort or trouble,” Swan said. “With women, by contrast, no fluid offering can reveal her reproductive potential or limitations… there’s no easy way to count the number of eggs a woman has in reserve.”

Though significant, changes in genital sizes seem like a side note in comparison to the gargantuan weight of other ominous questions native to this conversation—one of which being how we will overcome this.

“It’s not only that sperm counts have plummeted by 50 percent in the last forty years; it’s also that this alarming rate of decline could mean the human race will be unable to reproduce itself if the trend continues,” Swan explained. 

She warns that by 2045, most heterosexual couples will struggle to conceive through intercourse alone. “It seems hard to fathom, but an argument could be made that Homo sapiens already fit the standard for an endangered species, based on the US Fish and Wildlife Service’s (FWS) requirements,” she wrote.


Aside from fertility issues, these chemicals pose several other nightmarish health risks, including cancer. The Endocrine Society estimates that “two-thirds of all cancer is environmentally linked in some way.” Some research has also linked exposure to these chemicals to mental health conditions, obesity, liver damage, thyroid conditions, and several other villainous health conditions. 

So what’s being done about the ubiquity of these chemicals? The European Union has gotten started with regulation. So far, they’ve limited or banned 1300 chemicals in cosmetic products, which are absorbed through the skin. The United States, on the other hand, has addressed an arguably measly 11


“In Europe, they have a precautionary principle, where they have to prove [the chemical is] safe before they start using it,” Dr. Matt Simcik, an environmental chemist at the University of Minnesota, explained. Indeed, the EU’s REACH program requires manufacturers to prove the chemicals they put in products are not harmful before using them. The United States is not as proactive. Instead, they regulate chemicals after they’ve been shown to cause harm, according to Simcik.

However, a statement from the White House earlier this month may offer a ray of sunshine. The Biden-Harris administration proposed regulation of a particularly gnarly and dangerous set of endocrine-disrupting “forever” chemicals, PFAS, in the water supply. As of now, they are abundant in American tap water.

While we wait impatiently for more rigorous policies to be passed, there are ways to reduce our exposure to endocrine disruptors. That is, if you can muster the willpower and the cash. 

Swan’s book lists several objectively unfun but powerful ways to proactively limit your contact with these chemicals. In short, the most impactful actions you can take are filtering your tap water, using hygiene and cosmetic products that are low in known endocrine disruptors, and refraining from heating plastics—that means no microwavable meals unless you put the contents in a separate dish.

Luckily, Simcik feels optimistic about the prospect of regulation. “I’m heartened that we’re starting to realize that these things can be issues,” he said. “I think we’re getting smarter…by making these chemicals and seeing what we’re doing to our environment, hopefully, we learn from it, and the next chemicals won’t do that and yet still operate in the way we need them to for industry and consumers, residential products and all these other things that make our lives so great.”