Simultaneous exposure to toxic chemicals and climate-related heat may be worsening fertility harms across humans and wildlife, research suggests.

The review of scientific literature looks at how endocrine-disrupting chemicals, often found in plastic, together with climate-related effects such as heat stress, are each linked to lower fertility and fecundity, meaning the ability to reproduce, across species including humans, wildlife and invertebrates.

Though the reproductive harms of each issue in isolation are well studied, there is little research on what happens when living organisms are exposed to both.

“Together, the two issues are likely to 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 2017 study that found sperm levels among men in western countries had fallen by more than 50 per cent over four decades. Other research has suggested human fertility has been declining at a similar rate.

The University of Washington’s Institute for Health Metrics and Evaluation has previously said 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 focused 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 problems, disrupt hormones and be a potential driver of falling fertility.

Brander said the harms linked to these chemicals are often similar across organisms, from invertebrates to humans.

Phthalates, for example, have been linked to altered sperm shape in invertebrates, spermatogenesis in rodents, meaning sperm production, and reduced sperm counts in humans.

PFAS are also thought to affect sperm quality, and both have been linked to hormone disruption.

The chemicals are widespread in consumer goods, so people are often regularly exposed.

Meanwhile, previous research has shown how rising temperatures, lower oxygen levels and heat stress, among other effects linked to climate change, may also worsen infertility.

Heat stress has been found to affect human hormones, and is linked to spermatogenesis in rodents and bulls.

Research shows temperature also plays a role in sex determination in fish, reptiles and amphibians.

The species has evolved to choose which sex it produces in part based on temperature, and the heating planet can “push it too far in one direction or the other, which overrides that evolutionary benefit”, Brander said.

Similarly, many endocrine disruptors may alter environmental sex determination.

The study set out some of the overlapping effects of chemical exposure and climate change across taxonomic groups, from invertebrates to humans.

In birds, for example, exposure to increased temperature, PFAS, organochlorines and pyrethroids may each individually cause abnormal sperm, increased fledgling mortality, abnormal testes and population decline.

“What happens if they’re exposed to more than one of those stressors at the same time? There has been little exploration of that question.

“Even if there have not been a lot of studies looking at these simultaneously, if you have two different factors that both cause the same adverse effect, then there’s a likelihood that they are going to be additive,” Brander said.

Katie Pelch, a senior scientist with the Natural Resources Defense Council nonprofit, who was not part of the study, said the authors had reviewed high-quality science.

She said she wanted to see more examples of the overlap in impacts, but agreed with the overall premise.

“It is likely [multiple stressors] would have an additive effect, at very least, even if they have different mechanisms of harm,” Pelch added.

The solution to the systemic problems would involve tackling climate change and reducing the use of toxic chemicals.

The study cites the global reduction in the use of DDT and PCBs achieved under the Stockholm Convention as an example of an effective measure, but Brander said much more is needed.

“There is enough evidence in both areas to act to reduce our impact on the planet,” she said.

Future Fertility Inc. has announced the closing of a US$4.1 million Series A financing round.

The round was led by M Ventures (the corporate venture capital arm of Merck KGaA, Darmstadt, Germany) and Whitecap Venture Partners, with participation from new investors Sandpiper Ventures, Gaingels, and Jolt VC.

The financing will accelerate Future Fertility’s commercial expansion into Asia-Pacific and support its entry into the United States, including planned FDA 510(k) clearance for additional products as part of a broader U.S. market entry strategy.

Proceeds will also advance the development of a broader AI platform, from egg assessment through to embryo transfer, designed to support clinicians, embryologists, and patients across the full IVF journey.

M Ventures and Whitecap have supported Future Fertility’s mission to translate AI innovation into meaningful clinical outcomes since the company’s earliest stages.

Oliver Hardick, investment director, M Ventures, said: “Future Fertility is addressing a critical unmet need in reproductive medicine with a differentiated AI platform grounded in clinical data and real-world workflow integration.

“We are excited to continue supporting the company and team because we believe its technology has the potential to improve decision-making for clinicians, bring greater clarity to patients, and help advance a more personalised standard of care in fertility treatment.”

Future Fertility’s AI platform addresses a long-standing gap in fertility care: historically, there has been no objective, clinically validated method for assessing egg quality (Gardner et al., 2025), despite it being one of the most important drivers of reproductive success.

The company’s suite of deep learning tools includes VIOLET™, MAGENTA™, and ROSE™, purpose-built for egg freezing, IVF, and egg donation respectively.

The tools are based on AI models trained and validated on more than 650,000 oocyte images and are deployed in over 300 clinics across 35 countries.

Rhiannon Davies, founding and managing partner, Sandpiper Ventures, said:  “The best outcomes in fertility care globally come from better data and smarter tools. Future Fertility understands that, and they’ve built a platform that delivers on it.

“Sandpiper is proud to back a team turning rigorous science into real results for patients and clinicians alike.”

Partnerships with the world’s leading fertility networks – including IVI RMA and Eugin Group across Latin America and Europe, FertGroup Medicina Reproductiva in Brazil, and most recently announced Kato Ladies Clinic in Japan –  reflect growing demand for objective, AI-powered oocyte assessment in fertility care. In the United States, ROSE™ is newly available under an FDA 513(g) determination.

Research shows that approximately 50 per cent of IVF patients do not understand their likelihood of success, and many discontinue treatment prematurely, even though cumulative success rates improve significantly with multiple cycles (McMahon et al., 2024).

By delivering earlier clarity on egg quality, Future Fertility’s tools support more informed conversations between clinicians and patients, helping set realistic expectations and guide decisions about next steps.

Future Fertility’s growing evidence base spans seven peer-reviewed publications in Human Reproduction, Reproductive BioMedicine Online, Fertility & Sterility, and Nature’s Scientific Reports, and more than 70 scientific abstracts accepted and presented with partner clinics at conferences worldwide.

Christine Prada, CEO, Future Fertility, said: “Fertility treatment is one of the most emotionally and physically demanding experiences a person can go through.

“Every patient deserves objective data, not just a best guess, to support better decisions at critical moments in their care.

“This funding means we can bring that clarity to more patients, in more countries, at a moment when it matters most.”

Find out more about Future Fertility at futurefertility.com