Climate Change Is Quietly Rewriting Human Health and How Our Medicines Work

Climate change has long been framed as a crisis of melting ice sheets, rising seas, and vanishing species. But a growing body of evidence points to a quieter, more intimate threat: the way a warming world is reshaping the human body itself and the medicines we rely on to treat it. A new review published in PLOS Climate by Pono Pono and Alan M. Jones synthesises research on how climate change and air pollution affect every major organ system, altering both the burden of disease and the way patients respond to pharmaceutical treatments. The central finding is stark: the drugs sitting in pharmacy cabinets and medicine chests around the world may not work the same way in the climate of the coming decades as they did in the climate of the past.

The review begins with the most direct pathway between a warming planet and human physiology: heat. Extreme heat events are already among the deadliest consequences of climate change, and the evidence compiled by Pono and Jones shows they contribute to increased morbidity and mortality across an alarming range of organ systems. Cardiovascular disease sits at the top of the list. When ambient temperatures climb, the heart must pump harder to shuttle blood toward the skin for cooling, increasing cardiac workload precisely in people whose hearts are already compromised. Heat waves are consistently associated with spikes in heart attacks, arrhythmias, and heart failure admissions, and the effect is amplified in urban environments where the heat island effect keeps nighttime temperatures elevated, denying the body its usual window for recovery.

The damage does not stop at the heart. The review documents exacerbation of cerebrovascular disease, including stroke, as dehydration thickens the blood and heat stress disrupts vascular regulation. The gastrointestinal system is vulnerable through both direct heat effects and the expansion of foodborne and waterborne pathogens into new regions as temperatures warm. Renal disease emerges as a particular concern: repeated dehydration episodes, especially in outdoor workers and agricultural laborers, have been linked to chronic kidney disease of non-traditional origin, an epidemic that has already devastated young workers in Central America and South Asia. Respiratory illness completes the picture, driven by the interaction of heat with air pollution, ground-level ozone formation, and longer, more intense pollen seasons that worsen asthma and allergic disease. In effect, climate change operates not as a single disease agent but as a multiplier that stresses nearly every physiological system simultaneously.

Certain populations bear a disproportionate share of this burden. Older adults are repeatedly identified as the most vulnerable group, owing to diminished thermoregulatory capacity, reduced thirst perception, higher prevalence of chronic disease, and social isolation that can leave people unaware of dangerous indoor temperatures during heat waves. Patients with chronic conditions such as diabetes, heart disease, and kidney disease face compounded risks, as their organs have less reserve to absorb the physiological stress of extreme heat. But the review highlights a third, less obvious category of vulnerability: people taking medications that impair the thermoregulatory system itself. This includes widely used drug classes such as anticholinergics, tricyclic antidepressants, antipsychotics, beta-blockers, and diuretics, each of which can interfere with sweating, vasodilation, or fluid balance. For millions of patients, the very prescription that manages their chronic illness may quietly erode their ability to survive a heat wave.

This intersection of pharmacology and climate is where the review makes its most original contribution. High temperature and humidity do not merely make patients sicker; they can physically alter the medicines themselves. Active pharmaceutical ingredients are chemical compounds with defined stability profiles, and elevated temperatures accelerate degradation reactions that break those compounds down. Many formulations are engineered and tested under the climatic assumptions of temperate zones, with stability data gathered at standard storage conditions of roughly 25 degrees Celsius. In regions where ambient temperatures routinely exceed those thresholds, and where cold-chain infrastructure is unreliable, drugs may degrade on the shelf before they ever reach a patient. Humidity adds a second mechanism of damage, promoting hydrolysis of active ingredients, softening tablets, dissolving coated formulations, and compromising blister packaging that is supposed to protect the contents.

The consequences extend beyond chemical stability into pharmacokinetics, the branch of pharmacology that describes what the body does to a drug. Temperature influences absorption, distribution, metabolism, and elimination. Heat-induced vasodilation can alter how quickly a drug is absorbed from the gut or a transdermal patch, and increased skin perfusion can raise delivery rates from patches to potentially dangerous levels, a phenomenon documented with fentanyl and nitroglycerin. Dehydration and reduced blood volume change the distribution of drugs within body water compartments and can concentrate drugs or their metabolites to toxic levels. Sweating depletes sodium and potassium, electrolytes that are critical for the safe action of cardiac drugs and diuretics. In patients whose kidneys or livers are already stressed by heat and dehydration, the clearance of drugs slows, extending half-lives and increasing the risk of accumulation and adverse events. The review concludes that climate conditions can reduce drug efficacy while simultaneously increasing the risk of harm, a double penalty that falls hardest on those least equipped to absorb it.

There is also a logistical dimension that is easy to overlook until it fails. Extreme weather events, including hurricanes, floods, wildfires, and prolonged heat waves, can disrupt pharmaceutical supply chains at multiple points simultaneously. Manufacturing facilities may lose power or be damaged, transport networks can be severed, and cold-chain storage, which depends on continuous refrigeration, becomes fragile precisely when temperatures are most extreme. The result is the threat of shortages of essential medicines, from insulin, which requires refrigeration, to cardiovascular drugs needed in greater quantities during heat emergencies. Access to medicines, the review notes, is not a static achievement but a system that must remain resilient under conditions the system was never designed for. A supply chain optimized for cost efficiency, with minimal inventories and long international routes, is inherently vulnerable to the intensifying weather of a destabilized climate.

What emerges from this synthesis is a picture of fragmented knowledge in urgent need of integration. Health systems, patients, healthcare professionals, and governments each face decisions about how to prepare, yet the evidence they need is scattered across climatology, pharmacology, epidemiology, and logistics, with little cross-communication between fields. Clinicians receive little training on how to adjust prescribing in extreme heat. Drug labels rarely address storage in hot, humid climates beyond generic instructions. Public health heat-action plans seldom account for the population of patients whose medications increase their heat vulnerability. The authors argue that closing these gaps requires integrated research explicitly designed to explore the interplay between climate change, therapeutic response, and drug safety, generating the evidence base for what they call resilient, climate-ready healthcare systems.

Some of the necessary responses are already conceivable within existing practice. Stability testing could be expanded to reflect realistic storage conditions in hot climates. Electronic health records could flag patients on thermoregulation-impairing medications during heat advisories, enabling proactive counseling on hydration, cooling, and temporary dose adjustments under medical supervision. Supply chains could be hardened with distributed stockpiles, temperature-robust formulations, and contingency plans for the regions where climate impacts will be most severe. Pharmacists, positioned at the interface between patients and medicines, could play a central role in climate adaptation, monitoring storage conditions, educating patients, and identifying those at highest risk. None of these measures requires new science so much as the will to connect existing science across disciplinary lines.

The deeper message of the review is that climate change is not a distant environmental problem with indirect health consequences. It is a present-day clinical variable, one that changes who gets sick, how sick they become, and whether the treatments they receive will work as intended. Every major organ system is implicated, from the heart pumping harder in the heat to kidneys failing under repeated dehydration to airways constricting in polluted, pollen-laden air. Every stage of the pharmaceutical pathway, from the stability of a molecule in a warehouse to its pharmacokinetics in a dehydrated body, is subject to climatic influence. As extreme heat grows more frequent and weather more violent, the gap between a healthcare system designed for a stable climate and the reality of an unstable one will only widen. Pono and Jones make the case that recognizing this gap is the first step toward closing it, and that the time to build climate-ready healthcare is not after the crisis arrives, but now, while the evidence still gives medicine a chance to stay ahead of the thermometer.

Subject of Research: The effects of climate change on human health, drug efficacy, and pharmaceutical systems

Article Title: The impact of climate change on human health and pharmaceuticals

Article References: Pono, P., & Jones, A. M. (2026). The impact of climate change on human health and pharmaceuticals. PLOS Climate, 5(9), e0001068. https://doi.org/10.1371/journal.pclm.0001068

Image Credits: AI Generated

DOI: 10.1371/journal.pclm.0001068

Keywords: climate change, human health, pharmacology, extreme heat, drug stability, pharmacokinetics, adverse drug events, supply chains, vulnerable populations, thermoregulation, PLOS Climate, public health