Toxins plus climate harms likely cause of reduced fertility, study finds

Simultaneous exposure to toxic chemicals and climate change’s impacts likely generates an additive or synergistic effect that increases reproductive harm, and may contribute to the broad global drop in fertility, new peer-reviewed research finds.

The review of scientific literature considers how endocrine-disrupting chemicals, often found in plastic, coupled with climate change’s effects, such as heat stress, are each linked to reductions in fertility and fecundity across global species – including in humans, wildlife and invertebrates.

Though the reproductive harms of each of these issues in isolation are well-studied, there is little research on what happens when living organisms are subjected to both. Together, the two issues likely pose a greater threat to fertility, and the additive effect is “alarming”, said Susanne Brander, a study lead author and courtesy faculty at Oregon State University.

“You’re not just getting exposed to one – but two – stressors at the same time that both may affect your fertility, and in turn the overall impact is going to be a bit worse,” Brander said. The paper looked at 177 studies.

Shanna Swan, a co-author on the new paper, co-produced a groundbreaking 2017 study that found sperm levels among men in western countries had plummeted by more than 50% over four decades. Human fertility has been diminishing at a similar rate, other research has shown.

The University of Washington’s Institute for Health Metrics and Evaluation previously found the world was approaching a “low-fertility future”, with more than three quarters of countries below replacement rate by 2050.

The new paper’s authors zeroed in on the effects of endocrine-disrupting chemicals and substances, including microplastics, bisphenol, phthalates, and Pfas. These are thought to cause a range of serious reproductive issues, disrupt hormones, and be a potential driver of the fertility drop.

Brander noted how these chemicals’ harms are often the same across organisms, from invertebrates to humans. Phthalates, for example, have been linked to altered sperm shape in invertebrates, spermatogenesis in rodents, and reduced sperm counts in humans. Similarly, Pfas are thought to impact sperm quality, and both are linked to hormone disruption. The chemicals are ubiquitous in consumer goods, so humans are often regularly exposed.