Combined Threat of Toxic Chemicals and Climate Change to Global Fertility

A peer-reviewed synthesis of 177 studies finds that simultaneous exposure to endocrine-disrupting chemicals (EDCs) such as microplastics, bisphenol, phthalates and PFAS, together with climate-change stressors like heat stress, likely produces additive or synergistic reproductive harm across species, leading to greater fertility declines than exposure to either factor alone.

The Guardian

Phthalates cause altered sperm morphology in invertebrates, disrupted spermatogenesis in rodents and reduced sperm counts in humans; PFAS are linked to poorer sperm quality. Heat stress impairs hormone regulation and spermatogenesis in rodents and bulls and can shift sex ratios. Shanna Swan’s 2017 analysis documented a >50 % drop in sperm counts among Western men, and the University of Washington’s IHME projects that over three-quarters of nations will fall below replacement fertility by 2050. The review combines these data to evaluate joint effects.

The Guardian

The additive reproductive risk spans humans, wildlife and invertebrates, potentially accelerating the global fertility decline projected in demographic forecasts. Biodiversity loss linked to reproductive failure could worsen ecosystem instability, while human health concerns raise urgent policy questions about chemical regulation and climate mitigation.

The Guardian

Lead author Susanne Brander (Oregon State University) says “the evidence is enough … to act to reduce our impact on the planet,” urging stricter chemical controls and citing the Stockholm Convention’s DDT and PCBs phase-out. NRDC senior scientist Katie Pelch agrees that “multiple stressors would have an additive effect, at very least,” and calls for more research on overlapping impacts.

The Guardian

The authors note a paucity of direct studies on combined exposures, calling the question of simultaneous stressor effects “little explored.” Pelch highlights the need for more examples of overlap, noting a research gap that limits precise risk quantification.

The Guardian

• “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.” — Susanne Brander, Study Lead Author

The Guardian

• “What happens if they’re exposed to more than one of those stressors at the same time? … there’s a likelihood that they are going to be additive.” — Susanne Brander, Study Lead Author

The Guardian

• “It is likely [multiple stressors] would have an additive effect, at very least, even if they have different mechanisms of harm.” — Katie Pelch, Senior Scientist, NRDC

The Guardian

• “There is enough evidence in both areas to act to reduce our impact on the planet.” — Susanne Brander, Study Lead Author

The Guardian

The authors propose extending regulatory frameworks to cover additional endocrine disruptors and aligning chemical-policy actions with climate mitigation targets, using the Stockholm Convention as a template for broader action.

The Guardian