The Climate-Health Connection: From Bacterial Infections to Geriatric Depression, The Diverse Health Impacts of Environmental Hazards

On February 3rd, close to 50 cars of a Norfolk Southern train were derailed near East Palestine, Ohio, causing long-lasting fires and releasing numerous hazardous chemicals in the area. Among them were vinyl chloride and benzene, both known carcinogens, as well as the highly flammable isobutylene, paint thinner additive ethylene glycol monobutyl ether, and the possible carcinogen ethylhexyl acrylate.

Since the derailment, subsequent public evacuation, and a “controlled” release of the chemicals followed by a lifting of the evacuation order, the town has seen an uptick in reports of concerning symptoms and animal illnesses. As a significant body of evidence proves, both short and long-term exposure to noxious chemicals can have significant health consequences. With symptoms ranging from headaches and nausea to dizziness and loss of consciousness, the list of patient cases associated with the derailment continues to grow – despite the purported dissipation of toxic fumes. And the long-term population health risk assessment remains to be determined.

This is just one recent example of toxin-related illness with far-reaching and wide-ranging implications. Albeit more acute in impact than most recently studied environmental health risks, the East Palestine train derailment contributes to the investigative work that reveals the hidden costs of the air we breathe and the elements we are inevitably exposed to. Recent research findings unveil even more health risks tied to climate change and pollution that pose an immeasurable threat, largely due to the scale of their reach and their inescapable nature.

How Climate Change Could Lead to Rise in C. Difficile Cases

As flooding becomes a more common occurrence with rising temperatures across the globe, so does the incidence of Clostridioides difficile (C. diff) infections, according to a recently published review. While circulating levels of the bacterium have declined in recent years due to a more conservative approach to antibiotic treatment, experts forecast an increase in infections tied to extreme weather events.

This potentially fatal bacterial infection of the colon results in nearly half a million cases per year and is the most common cause of healthcare-associated infectious diarrhea.

Patients at increased risk for C. diff are those undergoing chemotherapy, antibiotic treatment, people living in rural areas near animal feeding operations, and those who experience flooding conditions. A 2015 study reported a significantly higher number of C. diff infections in working-age adults seven to 13 days after flood events in Massachusetts between 2003 and 2007. Consequently, emergency department and outpatient visits also rose during that period.

Further, extreme weather events such as Hurricanes Matthew and Florence caused widespread contamination in affected areas, in which flooding resulted in an 11% increase in acute gastrointestinal illness and emergency department visits.

The increasingly frequent erratic meteorological activity witnessed worldwide and its devastation also contributes to mental distress, leading to heightened anxiety and a growing number of anxiety diagnoses. Meanwhile, those who are prescribed antidepressant medications experience a greater risk for C. diff infection. Both fluoxetine and mirtazapine were tied to nearly doubled odds of C. diff infection.

Meanwhile, Air Pollution Raises Risk of Later-Life Depression 

Further perpetuating a vicious cycle is the relationship between air pollution and numerous health conditions, including depression. Prior research has connected air pollutant exposure to the development of neurodegenerative diseases among older adults. However, emerging findings suggest a heightened risk for late-life mental disorders, such as geriatric depression as well.

Depression in older adults is a growing concern, with a socioeconomic burden rivaling that of dementia. Per current estimates, the excess annual adjusted healthcare costs of geriatric depression have surpassed $27 million per 1 million older adults.

2022 cohort study published in JAMA Network Open evaluated the association between long-term exposure to air pollution and the risk of late-onset depression among older adults in the United States. The investigation analyzed data from millions of U.S. Medicare enrollees and found statistically significant harmful associations between long-term exposure to standard air pollution levels and an increased risk of late-onset (after the age of 64) depression diagnoses.

The results remained consistent when accounting for climate co-exposures, neighborhood greenness, socioeconomic conditions, healthcare access, and other relevant factors.

But Wait, There’s More 

The latest research from the University of British Columbia has even more dire news for population health. In a first-of-its-kind study, UBC researchers proved that standard levels of traffic pollution could impair human brain function – in only a matter of hours.

As part of their investigation, the authors analyzed brain activity before and after exposure to diesel exhaust and filtered air using functional magnetic resonance imaging (fMRI). They measured changes in the brain’s default mode network (DMN), a set of inter-connected brain regions that play an important role in memory and internal thought. Their findings revealed that exposure to diesel exhaust disrupts interaction and communication between brain regions, causing decreased functional connectivity in just two hours.

“While more research is needed to fully understand the functional impacts of these changes, it’s possible that they may impair people’s thinking or ability to work,” Dr. Jodie Gawryluk, a psychology professor at the University of Victoria and the study’s first author told ScienceDaily in a press release.

Senior author of the study Dr. Chris Carlsten, a professor and head of respiratory medicine at UBC, stressed the importance of the climate-health connection in his comments: “Air pollution is now recognized as the largest environmental threat to human health, and we are increasingly seeing the impacts across all major organ systems.” Dr. Carlsten suggests similar results are likely to emerge in studies of other air pollutants, such as forest fire smoke. “With the increasing incidence of neurocognitive disorders, it’s an important consideration for public health officials and policymakers.”

Recent events and the latest scientific evidence underscore the clear connection between environmental risk factors and a rising prevalence of adverse health effects in the population. Although significant research advancements are being made, our understanding of the relationship remains limited, and our ability to protect ourselves against the health risks of noxious environmental exposures is even more so. Much of the capacity for change lies in the hands of policymakers, federal government officials, and other distant to us parties.

Ultimately, addressing the complex interplay between environmental factors and human health requires a collaborative effort from individuals, communities, and decision-makers. Now more than ever, research is a critical tool for driving change based on understanding the profound health implications of environmental factors and progressing toward a healthier, more sustainable future.