How is the rise in carbon dioxide affecting our health?

Greenhouse gases, including carbon dioxide emissions from a plant leading to increasing its concentration in the atmosphere, which eventually affects our health.

Planet Earth is going through a crucial phase of anomalous anthropogenic atmospheric carbon dioxide concentration. Due to the widespread use of fossil fuels like coal, oil, and natural gas, atmospheric carbon dioxide (CO₂) levels have increased significantly since the Industrial Revolution. Along with methane and other greenhouse gases, CO2 is the most important heat-trapping greenhouse gas and the main cause of global warming. In April 2023, atmospheric CO2 concentrations hit 420.54 ppm, or around 149% of pre-industrial levels. They are still rising by about 2.3 ppm annually. This surplus of CO2 in the atmosphere is the primary driver of global warming and climate change. When we think about the rise of CO2 in the atmosphere, we think of global warming and generally imagine melting glaciers, rising sea levels, record-breaking temperatures, and heat waves. Apart from these effects of rising CO2, there is a quieter, but more powerful negative impact that these rising concentrations of carbon dioxide are having on our health, especially its cognitive impact. Beyond just raising the planet’s temperature, carbon dioxide is affecting the biochemical balance of human health, which science is just beginning to fully understand. This short article will try to highlight the major health-related effects due to the rise in concentration of carbon dioxide by exploring recent research developments made by the scientific community. The present recognised significant health impacts of the CO2 rise that go beyond climate change and need significant attention are as follows.

Cognitive impairment

Recent studies have shown that elevated indoor carbon dioxide directly impacts human cognitive function. Elevated CO2 diffuses from the lungs into the circulation and passes through the blood-brain barrier when we inhale it. This lowers oxygen availability (hypoxemia) and raises CO2 in the brain (hypercapnia), both of which are essential for brain function. Additionally, CO2 is known to exacerbate anxiety and drowsiness, both of which worsen cognitive function. For studying the health impact of carbon dioxide, we take the indoor air quality index or CO2 level values. It is well established that indoor carbon dioxide levels are higher than in open outdoor spaces, so the concentration of CO2 in indoor spaces can be 2-3times higher. The study published in GeoHealth has quantified and examined the effects of indoor CO2 concentration and inhalation.  According to the study, people constantly exhale CO2 in enclosed rooms, and inadequate ventilation allows the gas to build up, which is why indoor CO2 concentrations are consistently greater than outdoor ones. Future climate scenarios, particularly the high-emission RCP 8.5 route, could cause atmospheric CO2 concentrations to climb to around 930 parts per million (ppm) by 2100, driving interior levels in offices, schools, and urban buildings well past 1,400 parts per million. The mitigation-focused RCP 4.5 scenario, on the other hand, predicts lower atmospheric concentrations of about 540 ppm, significantly lowering the dangers of interior exposure. The study suggests that unchecked fossil fuel emissions may directly harm human brain function and productivity in the future by linking elevated indoor CO2 to impaired cognitive performance, including decreased attention, memory, decision-making, strategic thinking, increased sleepiness, anxiety, and decreased mental alertness. In addition to the negative effects, prolonged exposure to high carbon dioxide levels can cause cardiovascular problems and renal calcification. A study published in the Royal Society of Chemistry discusses data from EEG and brain imaging studies showing decreased brain activity at elevated CO2 levels. The article warns that humans evolved under atmospheric CO₂ levels below 300 ppm, whereas current levels have already exceeded 420 ppm and continue to rise, potentially creating long-term physiological and neurological risks for future generations, particularly because modern humans spend most of their time indoors, where CO₂ concentrations are significantly higher than outdoor air.

Respiratory issues

It is clear that human health is impacted by climate change, but it is still difficult to determine the scope and significance of many climate-sensitive health hazards. CO₂ does not cause respiratory disease directly in the way that particulate matter or ozone does, but it is a powerful driver of the conditions that harm our lungs. A research article reviewing the various findings correlating respiratory issues influenced by elevated indoor carbon dioxide gives an insightful direct link between them. According to the review article, increasing CO2 levels impair normal breathing physiology, decrease oxygen availability, and change blood chemistry, all of which lead to respiratory health issues. Outside air typically has 400 parts per million of CO2, while poorly ventilated indoor rooms often have levels beyond 1,000 parts per million, which are already linked to headaches, drowsiness, poor air quality, difficulty concentrating, and respiratory discomfort. The research suggests that elevated CO2 diffuses into the bloodstream, reducing blood pH and raising arterial CO2 pressure (PaCO2), which causes respiratory acidosis, an acid-base imbalance that hinders lung gas exchange and oxygen delivery. According to scientific research, exposure to 10,000 ppm CO2 for longer than 30 minutes can produce respiratory acidosis and metabolic stress; concentrations exceeding 30,000 ppm lower exercise tolerance; and levels above 50,000 ppm can result in dyspnea, confusion, dizziness, and severe breathing distress.

Heat risks: Climate change is making extreme heat deadlier

According to the WHO research, human-caused climate change is responsible for 37% of heat-related deaths. Over the past 20 years, the number of heat-related deaths among people over 65 has increased by 70%. Compared to the average from 1981 to 2010, 98 million more people suffered food insecurity in 2020. By the 2030s, the WHO estimates that the effects of climate change on diseases like malaria and coastal floods will cause an additional 250,000 fatalities annually. Our cities are facing the double whammy of global warming due to the rise in carbon dioxide and the heat island effect, which is making heat-related health issues further deadly. Changes in extremes get bigger with each new degree of global warming. For instance, the intensity and frequency of temperature extremes, such as heatwave intensity, frequency, and duration, increase noticeably with each extra 0.5°C of global warming. Climate change will continue to increase the frequency and severity of heat waves and intense heat in the twenty-first century. The human body experiences cumulative stress from prolonged high daytime and nighttime temperatures, which raises the risk of heat-related illness and mortality. Heatwaves frequently result in public health issues and can have a severe effect on large populations for brief periods of time. Human health is impacted by extreme heat because it reduces the body's capacity to expel internal heat, particularly in situations with high temperatures, high humidity, little breeze, and intense thermal radiation. Heat exhaustion, heatstroke, dehydration, and acute kidney damage are all made more likely when the body is unable to control its internal temperature. Additionally, heat stress worsens chronic illnesses, including diabetes, respiratory, cardiovascular, and mental health disorders, by putting extra load on the heart, lungs, and kidneys. In addition to disrupting vital services, decreasing job productivity, hindering learning, and increasing exposure to dangerous air pollution, severe heat events can quickly increase hospitalisations and fatalities.

Future Pathways

Human health in the future will depend more and more on how quickly carbon dioxide emissions are cut worldwide and how societies adjust to a warmer environment. Rising indoor and atmospheric CO2 concentrations, particularly in densely populated metropolitan areas, may exacerbate heat-related illnesses, respiratory conditions, cardiovascular stress, and cognitive loss in the absence of effective mitigating measures. Cleaner energy systems, better indoor ventilation, climate-resilient communities, heat action plans, and more robust air-quality monitoring must thus be the main focus of future public health initiatives. To better comprehend the long-term biochemical and neurological effects of chronic CO2 exposure on future generations, however, more scientific research is necessary.