Global fertility rates are declining, and new research suggests the cause may be an "alarming" combination of factors rather than a single driver.

What's happening?

A review of 177 studies found that two major stressors — hormone-disrupting chemicals and rising temperatures — may have a compounded impact on fertility across species, according to The Guardian.

These chemicals, known as endocrine disruptors, are commonly found in plastics and everyday consumer products. They include substances such as microplastics, bisphenol, phthalates, and PFAS, all of which have been linked to hormone imbalances, reduced sperm counts, and reproductive issues in both humans and animals.

At the same time, rising global temperatures are adding another layer of stress. Heat exposure has been shown to affect hormone levels and reproductive systems, including sperm production in mammals.

"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," lead author Susanne Brander said, per The Guardian.

Why is this concerning?

Scientists have traditionally studied chemical exposure and heat stress separately. This research suggests the two may interact in ways that amplify harm, especially since they target similar biological systems.

For example, in wildlife, these effects may even interfere with sex determination, potentially leading to imbalanced populations over time.

For individuals, the findings highlight how everyday exposures, from the products we use to the environments we live in, can subtly shape long-term health.

What's being done about it?

On a broader scale, regulating hazardous chemicals has proved effective. The study points to the decline in use of substances such as DDT and PCBs following global restrictions under the Stockholm Convention on Persistent Organic Pollutants as evidence that coordinated policy action can reduce harm.

Reducing plastic use and supporting stronger chemical regulations are practical steps individuals and communities can take to lower exposure.

At the same time, accelerating the shift to clean energy can help address the climate-related stressors highlighted in the research.

"There is enough evidence in both areas to act to reduce our impact on the planet," Brander said.

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