• Research is ongoing into the health effects of the world’s roughly 350,000 synthetic chemicals, but what we know so far is cause for concern. Plastics, PFAS and other synthetic chemicals are linked to numerous health risks, and emerging research even suggests rising atmospheric CO2 levels may harm health.
• Specifically, there is growing evidence that plastics and their chemical additives pose threats to human health at every life stage. Five major classes of plastic additives have been linked with harm to the brain, kidneys and immune system; microplastics in the human body can affect fertility, development and ageing.
• Atmospheric CO2 is natural, but not at the levels to which humanity is pushing them — levels higher than any human ancestor ever experienced. Initial research finds elevated CO2 can cause changes to the lungs and alter growth patterns in mice. The effects of long-term exposure in humans are unknown.
• Emerging evidence for these and other novel entity health risks highlights the need to establish safe limits and monitor global and local exposures, experts say. A ‘planetary health framework’ could become a valuable tool for scientists and policymakers, but developing such a framework would be a Herculean task.

See All Key Ideas

Over the past century, humanity has invented a dizzying array of novel chemicals for industrial, commercial and domestic use. These synthetic chemicals have been manufactured and released into the world with little caution for the harm they might cause to human health or to ecosystems that we depend on for life as we know it.

An estimated 350,000 synthetic chemicals had been registered for production as of 2020, and for the vast majority, we know next to nothing about their health effects. Even their chemical compositions are often hidden as proprietary trade secrets.

“The world today is full of manufactured chemicals,” says Philip Landrigan, public health physician and director of the Program for Global Public Health and the Common Good at Boston College in the U.S., who spoke to Mongabay via video call. But “we have really good data on the health effects for only 30 or 40 of these chemicals,” he warns. Only a handful of chemicals have been banned or restricted in U.S. markets in the last 50 years.

The evidence base for some classes of chemicals is more developed than others, but what we know so far gives serious cause for concern, experts say. From thalidomide-induced birth defects to the pesticide DDT’s ecological impacts and cancers linked to polychlorinated biphenyls, the chemical industry has a long history of rushing new synthetics to market while largely asking questions about toxicity later.

“I would think of it as an iceberg — there’s a little bit of ice visible above the water, and we just don’t know how much is underneath,” Landrigan says.

Given the scale and potential severity of chemical health risks, some experts are calling for the creation of a global planetary health framework to assess potential impacts.

There is growing evidence that plastics and their chemical additives pose risks to human health. Data from more than 6,000 meta-analyses showed evidence of harm to the brain, thyroid, cardiovascular system, kidneys, bones, immune system and fertility, as well as elevated risk of type 2 diabetes, cancer and obesity across five classes of chemicals commonly associated with plastics. Image by Samuel Love via Flickr (CC BY-NC-ND 2.0).

Plastics and their additives: Causing harm at every life stage

One of the most pervasive classes of synthetic chemicals are plastics. Ubiquitous in our daily lives, there is growing evidence that plastics pose human health risks. Some arise from the chemical and physical properties of the plastics themselves, particularly when they fragment into tiny particles called micro- and nano-plastics. Other risks stem from the toxic chemical additives they contain.

“For a long time, people looked at plastics as only an environmental issue, and now we’re realizing belatedly that they also affect human health,” Landrigan says.

More than 16,000 different chemicals are routinely added to plastics, around a quarter of which are potentially hazardous. When they leach out of plastics into the environment or the human body, they can cause harm.

“The many thousands of chemicals that are in plastics, don’t stay in plastics. They get into people and [can] cause disease,” he explains.

Landrigan recently participated in an international project to collate evidence on the health effects of plastics, called PlasticHealthAware. As of the latest update in July 2026, the project dashboard presented results from 6,841 meta-analyses of published data on the health effects of five classes of chemicals associated with plastics: Bisphenols, phthalates, polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers, and per- and polyfluoroalkyl substances (PFAS).

The data show that across these five chemical classes there is consistent evidence for human harm to the brain, thyroid, cardiovascular system, kidneys, bones, immune system and fertility, as well as elevated risk of type 2 diabetes, cancer and obesity.

Research suggests that micro- and nano-plastics can negatively affect human fertility, development and ageing. Their small size allows them to pass through the intestinal wall, cross the blood-brain barrier and even enter the placenta during pregnancy. Image by Oregon State University via Flickr (CC BY-SA 2.0).

Micro- and nano-plastics — and the chemical additives they contain — can find their way into the body via the food we eat and air we breathe, resulting in lifelong exposure that can impact fertility, development and ageing. Because of their size, micro- and nano-plastics can travel throughout the body, passing through the intestinal wall, crossing the blood-brain barrier and even entering the placenta during pregnancy, meaning they can potentially affect every bodily system and possibly cause harm at every life stage. Research into their myriad health effects is ongoing.

Forever chemicals: Linked to lifelong health effects

In addition to use as plastic additives, PFAS or “forever chemicals,” are widely found in consumer products, including food packaging, cookware and paint. PFAS have been linked to inflammatory bowel disease, and recent research indicates that early life exposure could have long-lasting health effects.

For example, a 2026 study led by Manasi Agrawal, associate professor of medicine at the Icahn School of Medicine at Mount Sinai and a gastroenterologist at Mount Sinai Hospital in the U.S. state of New York, detected PFAS chemicals in blood samples from pregnant women and their newborn babies living in New York City and Mexico City.

This study shows that “there is internalization of PFAS chemicals by mothers and babies,” explains Agrawal, who spoke to Mongabay via a video call.

The researchers found that children who had been exposed to higher levels of PFAS in the womb and during the first few days of life tended to have higher levels of calprotectin — a protein associated with intestinal inflammation — later in childhood. Although the study didn’t track participants’ health into adulthood, previous research has linked elevated calprotectin in children to a greater risk of inflammatory bowel disease later in life.

PFAS or “forever chemicals,” are widely used in consumer products, such as plastics, paint, food packaging and cookware. Among other health concerns, PFAS have been linked to inflammatory bowel disease, and recent research indicates that early life exposure could have long-lasting health effects. Image by Mark Ordonez via Flickr (CC BY-SA 2.0).

Though much more research is needed, the study adds to a growing body of evidence that environmental pollutants can impact gastrointestinal health, and that fetuses, infants and children are particularly vulnerable.

The early life period, which extends from pregnancy through the first few years of life, “is a period of high vulnerability to all kinds of environmental exposures and toxicants, and these inform later health and disease,” Agrawal says. That’s when the immune system and microbiome are developing — both key elements of gastrointestinal health.

Emerging research: Potential health risks of record CO2 levels

Pollution from plastics, PFAS and other synthetic chemicals is tracked within the novel entities planetary boundary framework. But novel entities are just one of nine boundaries that mark the ‘safe zone’ for a habitable planet. In 2023, scientists concluded that humanity has crossed the safe threshold for six of the nine planetary boundaries, including novel entities — which encompasses all synthetic chemicals — and climate change.

Climate change is having many indirect effects on health, including heat stress, undernutrition and increased susceptibility to infection. But elevated atmospheric CO2 levels may have another, unexpected, health impact that scientists are just beginning to understand.

Atmospheric carbon dioxide is natural, but the levels at which we are now breathing it are not. CO2 has soared upwards from roughly 280 ppm in the pre-industrial period to 429 ppm in 2026.

That means we’re all now continuously breathing higher concentrations of CO2 than any human before us. This trend looks set to escalate, and atmospheric CO2 could exceed 860 ppm by century’s end based on a medium-to-high greenhouse gas emissions scenario and depending on humanity’s path forward.

Carbon dioxide has been “studied intensively for a century as a greenhouse gas and barely at all as something we inhale continuously at levels no human ancestor experienced,” says Alexander Larcombe, a senior research fellow at the Kids Research Institute Australia, who spoke to Mongabay via email.

But that doesn’t mean no human impacts are occurring. For example, when CO2 accumulates in the body, it’s known to make the blood more acidic, and the body tries to neutralize that acidity by circulating more bicarbonate. This solution evolved to deal with temporary bodily increases in CO2 levels. But early evidence is suggesting that long-term exposure could have negative impacts on human physiology.

Larcombe and colleagues’ preliminary research found that mice exposed to 890 ppm CO2 during early life showed changes to lung structure and function and altered growth patterns.

These results, however, didn’t reveal whether elevated atmospheric CO2 is negatively impacting human physiology, or might do so in the near future. To shed light on these questions, the researchers analyzed human blood samples collected as part of the U.S. National Health and Nutrition Examination Survey. They found that bicarbonate levels increased steadily in the human body between 1999 and 2020, tracking increases in atmospheric CO2.

Although average blood bicarbonate levels are still within the healthy range, if current trends continue, those levels “could be at the limit of the accepted healthy range in half a century,” the authors report.

These findings aren’t conclusive proof atmospheric CO2 levels are driving changes in human physiology. For example, increased time spent indoors, where CO2 can often already exceed 1,000 ppm, may have also influenced study results. Nevertheless, it’s a worrying correlation that scientists say warrants further investigation.

“I’d much rather we watched carefully and found there was nothing to worry about than looked away and found out too late,” Larcombe says.

As atmospheric carbon dioxide levels rapidly rose over the past century, humans have been exposed to CO2 levels never experienced by our ancestors. Emerging research suggests that long-term continuous exposure to high CO2 levels could have negative impacts on physiology within this century. Image by Mariano Mantel via Flickr (CC BY-NC 2.0).

Studies in humans and animals have shown that short-term exposure to CO2 concentrations greater than 1,000 ppm can lead to changes in heart rate and brain function, inflammation and kidney calcification. But no studies have yet investigated the impact of lifetime exposure to elevated CO2 levels in humans, and only a few have investigated long-term exposure in animals.

“That’s a blind spot for a change we’re all subject to and none of us can opt out of,” Larcombe says. Addressing that knowledge gap requires research funding, Larcombe notes, which “has so far been almost non-existent for this question.”

A planetary boundaries framework for human health

Emerging evidence for harmful health effects of environmental pollutants — including manufactured chemicals and high levels of carbon dioxide — highlights the need to establish safe limits for these substances, if they exist, and justifies monitoring global and local exposures.

The planetary boundaries framework, first proposed in 2009, includes safe thresholds for novel entities and carbon dioxide, but “those boundaries are set by what keeps the Earth System stable, not by what keeps human bodies healthy,” Larcombe explains. “What’s missing is a framework asking which measurable things in the human body tell us we’ve moved outside the conditions we evolved for, and how far.”

As such, an additional ‘planetary health framework’ could become a valuable tool for tracking and evaluating environmental pollutants of high concern and communicating those risks to policymakers and the public.

However, with such a vast array of pollutants already in the environment, developing such a framework would be a Herculean task. Establishing safe limits for PFAS alone would require “carefully unravelling the impact of PFAS as a mixture and the distinct impacts of individual PFAS chemicals on their own,” Agrawal says.

And setting thresholds without sufficient scientific evidence could do more harm than good, Larcombe cautions: “A stated threshold gets read as a guarantee of safety below it, and if set on thin evidence it can give false reassurance.”

Existing untested and potentially harmful chemicals are routinely released into the environment, and new synthetic chemicals continue to be developed. Health experts are calling for new legislation and a major overhaul of the chemicals industry to prevent new chemicals from coming to market without thorough testing. Image by nezume_you via Flickr (CC BY-NC-ND 2.0).

Experts call for chemical industry overhaul

Thousands of untested, potentially harmful chemicals continue being released into the environment today, and new chemicals continue to be developed. To address this issue, health experts are calling for new legislation and a major overhaul of the chemicals industry to prevent new chemicals from coming to market without thorough testing.

Whereas pharmaceutical companies are required to complete extensive clinical trials, safety testing and long-term surveillance of new drugs, no such requirements are enforced for non-pharmaceutical chemicals.

In the European Union, hundreds of hazardous chemicals have recently been banned under the Registration, Evaluation, Authorisation, and Restriction of Chemicals (REACH) regulation, which came into force in 2007, with plans to ban thousands more by 2030. The Toxic Substances Control Act (TSCA) in the U.S. is intended to regulate the chemicals industry, but has proven unsuccessful, due to loopholes, underfunding and unwillingness to place the financial burden of testing on chemical manufacturers. Regulation is even weaker in the rest of the world.

“We’re exposing people to thousands of chemicals, knowing that some fraction of those chemicals are going to cause disease. It’s insane,” Landrigan says.

Even after chemicals proven to be harmful are banned in G7 countries, it’s common for them to continue to be exported, marketed and used in other countries, reinforcing existing health inequalities.

In 2023, the United Nations Environment Programme (UNEP) adopted the Global Framework on Chemicals — a comprehensive plan for managing and regulating synthetic chemicals. How effective this currently nonbinding initiative will be remains to be seen. In November, the first International Conference of the Global Framework on Chemicals will bring policymakers, industry experts and scientists to Geneva to identify priorities, challenges and solutions for the framework’s implementation.

Banner image: Over the past century, humanity has invented thousands of novel chemicals. These synthetics now pollute air, water, soils and the human body. The evidence for harmful health effects is more developed for some classes of chemicals than others, but what we know to date is worrying. Image by Boinink via Flickr (CC BY-NC 2.0).

Should potentially harmful chemicals be appraised by class, not one at a time?

Citations:

Wang, Z., Walker, G. W., Muir, D. C., … Nagatani-Yoshida, K. (2020). Toward a global understanding of chemical pollution: a first comprehensive analysis of national and regional chemical inventories. Environmental science & technology, 54(5), 2575-2584. doi:10.1021/acs.est.9b06379.s001

Monclús, L., Arp, H. P., Groh, K. J., Faltynkova, A., Løseth, M. E., Muncke, J., … Wagner, M. (2025). Mapping the chemical complexity of plastics. Nature, 643(8071), 349-355. doi:10.1038/s41586-025-09184-8

Mulders, Y., Cann, S., Carpenter, C., Chiles, T. C., Kabeya, H., Lyons, A., … Dunlop, S. (2026). PlasticHealthAware: Presenting the latest Meta‑Analytical findings on plastic chemicals and human health. Annals of Global Health, 92(1), 76-76. doi:10.5334/aogh.5195

Liu, G., Shi, T., Tang, S., Huang, X., … Liu, X. (2026). Microplastic exposure and human health risks across the life cycle: A focus on reproduction, development, and aging. Frontiers in Cell and Developmental Biology, 14, 1778576. doi:10.3389/fcell.2026.1778576

Midya, V., Maroli, A. S., Picker, M., Dolios, G., Valvi, D., Nguyen, I., … Agrawal, M. (2026). Per- and polyfluoroalkyl substances in early life are associated with childhood intestinal inflammation: Analyses of three birth cohorts. Clinical Gastroenterology and Hepatology. doi:10.1016/j.cgh.2026.07.001

Dai, C., Huang, Y., … Jiang, M. (2026). Preclinical stages of Crohn’s disease defined by faecal calprotectin in asymptomatic first-degree relatives. Gut. doi:10.1136/gutjnl-2026-338123

Agrawal, M., Allin, K. H., Petralia, F., Colombel, J., … Jess, T. (2022). Multiomics to elucidate inflammatory bowel disease risk factors and pathways. Nature Reviews Gastroenterology & Hepatology, 19(6), 399-409. doi:10.1038/s41575-022-00593-y

Larcombe, A. N., Papini, M. G., Chivers, E. K., Berry, L. J., Lucas, R. M., … Wyrwoll, C. S. (2021). Mouse lung structure and function after long-term exposure to an atmospheric carbon dioxide level predicted by climate change modeling. Environmental health perspectives, 129(1), 017001. doi:10.1289/ehp7305

Wyrwoll, C. S., Papini, M. G., Chivers, E. K., Yuan, J., Pavlos, N. J., Lucas, R. M., … Larcombe, A. N. (2021). Long‐term exposure of mice to 890 ppm atmospheric CO2 alters growth trajectories and elicits hyperactive behaviours in young adulthood. The Journal of Physiology, 600(6), 1439-1453. doi:10.1113/jp282179

Larcombe, A. N., … Bierwirth, P. N. (2026). Carbon dioxide overload, detected in human blood, suggests a potentially toxic atmosphere within 50 years. Air Quality, Atmosphere & Health, 19(3), 44. doi:10.1007/s11869-026-01918-5

Jacobson, T. A., Kler, J. S., Hernke, M. T., Braun, R. K., Meyer, K. C., … Funk, W. E. (2019). Direct human health risks of increased atmospheric carbon dioxide. Nature Sustainability, 2(8), 691-701. doi:10.1038/s41893-019-0323-1

Landrigan, P. J., and Wirth, D. A. (2025). Manufactured chemicals and children’s health—the need for new law. Boston College Law School Legal Studies Research Paper, (643). doi:10.1056/nejmms2409092

FEEDBACK: Use this form to send a message to the author of this post. If you want to post a public comment, you can do that at the bottom of the page.

Cite this article

Claire Asher (2026). Global framework urgently needed to assess emerging health risks of novel chemicals, experts say. Mongabay Conservation news. DOI: https://doi.org/10.66709/news-333552