Toxic chemicals are increasing infertility in humans, fish, birds, and insects: ‘A whisper that is powerful enough to redirect a hurricane’

(SeaPRwire) –   Earlier this month, the Centers for Disease Control and Prevention (CDC) reported that fertility rates—defined as the average number of children a woman is expected to have during her lifetime—dropped to an all-time low in the previous year. This demographic shift could have far-reaching implications for the nation’s economy and political landscape.

Numerous factors contribute to this trend, including voluntary choices women make as their career opportunities and earning potential have expanded. However, not all causes of declining birth rates are tied to daily personal decisions.

Profound, long-term environmental changes mean that individuals in the U.S. and across the globe who wish to have children may face increasingly unfavorable odds these days.

Why toxic chemicals impact reproduction

Successful reproduction depends on hormones—vital biological regulators that coordinate everything from puberty and sperm production to fertilization and pregnancy. This holds true for humans just as it does for most animals, including other mammals, fish, and birds.

Yet a growing volume of man-made chemicals and pollutants have infiltrated the environment and the biological systems of nearly all animal life. When combined with rising temperatures, these changes are starting to severely disrupt the reproductive processes of humans and other species, according to a review of existing research in the field published last week in the journal npj Emerging Contaminants.

The review found that substances like microplastics and harmful forever chemicals—a class of compounds used in items from food packaging to some nonstick cookware that do not break down naturally—can either mimic or block hormonal activity critical to sexual health and successful reproduction. Even small amounts of these contaminants are enough to impair normal biological processes.

“This can occur at effective concentrations so low they are analogous to a whisper that is powerful enough to redirect a hurricane,” the authors wrote.

Ubiquitous disruptors in everyday life

The review highlighted several toxins and chemicals that have become pervasive in daily life, though relatively few have been deeply studied for their potential harm to humans.

The authors note that among the 140,000 registered synthetic chemicals, only 1,000 are known to affect the endocrine system—the biological processes governing hormones. But this is likely a “gross underestimate,” per the review, given that just 1% of these chemicals have been sufficiently researched and around 2,000 new chemicals are produced and released each year.

These substances are invasive disruptors of animals’ endocrine and reproductive systems. For example, the review included multiple studies documenting the effect of microplastics—plastic particles smaller than 0.2 inches in diameter—on semen production, collectively finding that exposure leads to reduced sperm counts and motility in multiple species, including humans.

Pollutants aren’t the only environmental factor harming fertility. The review also analyzed climate change’s role in declining birth rates, finding that higher temperatures take a heavy toll on the reproductive prospects of most animal life.

A prominent example cited is turtle reproduction. Like some other reptiles, turtles rely on external temperatures to determine an individual’s sex before hatching. But rising temperatures have caused most turtles to be born female, skewing sex ratios and making populations harder to self-sustain.

Climate change also affects humans’ ability to procreate. The review references a 2018 study that found hotter weather was associated with declining conception levels over 80 years of birth rate data. Higher temperatures have also been shown to impact human fertility similarly to chemicals, specifically by reducing sperm health and motility in males.

Population concerns

To be clear, environmental factors aren’t the only reason birth rates are declining in the U.S. and globally. Reduced gender discrimination in education has been a key driver, as more women in developed economies opt to pursue schooling and careers over starting a family.

The drop in U.S. fertility also has positive explanations. A large factor in last year’s record low was a sharp decline in teen pregnancy rates, according to the CDC, which found the fertility rate for 15- to 19-year-olds fell 7% in 2025—part of a decades-long trend of progress. Since 1991, the U.S. teen birth rate has plummeted 81%.

But with pollution and warming taking their toll on fertility, the choice to avoid having children may be taken out of some people’s hands.

The review’s authors linked declining fertility rates to the historic crash in global biodiversity. Over the past 50 years, the average size of wildlife populations has collapsed by 73% due to nature loss and climate change. Together, environmental pollutants and climate change-fueled temperature rise form another powerful demographic threat for all animal species, the review states.

“We must recognize that chemicals, once released, don’t simply disappear,” the authors wrote. “Instead, they contribute to the larger issue of driving humanity towards the exceedance of planetary boundaries when considered in combination with climate change and other planetary-level impacts.”