For years, the two emergencies have traveled on parallel tracks: on the one hand , the climate crisis, with its heat waves, droughts and rising sea levels; on the other, chemical pollution, with the widespread spread of microplastics and synthetic substances now found everywhere, from the ocean depths and Himalayan peaks to human blood. Science has dealt with them separately, as if they were separate phenomena. But a new study, published in late April 2026 and based on an analysis of 177 previous research papers, suggests that this conceptual separation is a mistake.
The research, led by Susanne Brander, a professor at Oregon State University, focuses on what happens when a living organism – human, animal or invertebrate – faces both factors together. The answer is alarming: the combined effect is not simply a summation, but an amplification of each individual effect. The two threats enhance each other: it is a synergistic effect, and in this case the synergy works against life.
Chemical culprits: microplastics, phthalates, PFAS and bisphenol
The study focuses in particular on one class of substances: so-called endocrine disruptors, i.e., chemical compounds capable of mimicking or blocking the body’s natural hormones, altering their regulation. These include phthalates, PFAS (perfluoroalkyl substances), bisphenol A, and microplastics more broadly.
What these substances – phthalates, PFAS, bisphenol A, microplastics – have in common is their ability to infiltrate the hormone system without the body being aware of it. They do not act as acute poisons but as interferents: they mimic natural hormones, block their receptors, and alter the chemical signals that regulate reproduction. The problem is not occasional exposure but chronic exposure, because these substances are now incorporated into the materiality of daily life — in packaging, textiles, nonstick surfaces, food containers — and the body can never get rid of them completely.
Heat as a damage multiplier
Then the second factor, climate crisis, comes into play. Heat stress, that is, prolonged exposure to high temperatures, is already known for its negative effects on reproduction. But another element emerges from the meta-analysis: heat does not simply act in parallel with chemical interferents. The two factors amplify their effects in interaction. An organism already stressed by exposure to PFAS or phthalates is less able to tolerate heat stress. Its biological defenses are already compromised, its metabolic reserves already committed to coping with the chemical disruption.
Not just humans: a crisis spanning the realms of the living
One of the most significant aspects of the research is its taxonomic breadth. The study is not limited to humans, but embraces vertebrates, aquatic and terrestrial invertebrates, fish, reptiles, birds and mammals. The depressive effect on fertility crosses species boundaries: these are not vulnerabilities specific to individual organisms, but fundamental biological mechanisms shared by much of the living world.
This finding has implications beyond human health. If fertility collapses also affect populations of pollinating insects, freshwater fish, amphibians and birds, we face a threat to the very structure of ecosystems. Many of these species perform essential functions: pollination, pest control, water purification, decomposition of organic matter. A reduction in them would represent a concrete loss of services on which agriculture also depends.
The declining birth rate seen from a new perspective
In turn, this research interacts with other research in different fields. And even here the sum of the two strands of analysis amplifies the concerns. Declining birth rates are almost always explained by analyzing social and economic factors: access to female education, cost of living, job instability, changing family patterns, postponement of reproductive choices. All are legitimate and documented explanations. But this research adds a biological variable hitherto kept at the margins of the debate: physiological impairment of reproductive capacity.
It is not a matter of choosing between social explanation and biological explanation. The two dimensions are intertwined. A couple that decides to have children but encounters fertility difficulties is experiencing a problem that may be rooted in both cultural behaviors and chronic exposure to chemicals and climatic conditions in their environment. Clearly separating the two spheres is not only reductive: it is misleading.
What can be done: the double lever
The conclusions of the research do not stop at diagnosis. The authors also indicate the direction of intervention, which must act simultaneously on two fronts. The first is reducing the use of toxic chemicals in production processes, consumer materials and packaging. The second is combating climate change.
On the chemical front, the European Union has made progress with the REACH regulation and, more recently, with proposals to restrict PFASs, but implementation is slow and manufacturers are resisting. On the climate front, global emissions are not yet showing the downward trajectory that would be needed. Meanwhile, billions of living things continue to be exposed every day to a cocktail of stressors whose effects science is just beginning to understand.
There is a certain irony in the fact that Europe is hotly debating empty cradles and birthrate incentives while its environmental policies struggle to keep up with the spread of endocrine disruptors. The problem is not just convincing couples to have more children: it is also ensuring that those who want children still have the biological capacity to have them.
