Global warming.
Credit: iStock Photo
Global warming refers to the long-term increase in a planet’s overall temperature, primarily driven by the rising concentration of greenhouse gases such as carbon dioxide, methane, and ozone in the atmosphere. Over the past century, there has been a significant increase in global temperatures, with the average rising by 1.8 degrees Fahrenheit. This phenomenon has had a major impact on human health, particularly evident in the occurrence of heat waves. Heat waves are characterised by temperatures exceeding the daily mean by at least 5 degrees and persisting for 3-5 consecutive days.
Notable instances include the 1945 Chicago heat wave, where over 50% of cases presented with heatstroke and acute kidney injury, as well as the 2014-15 heat wave in Andhra Pradesh, India.
Adverse impact of rise in temperature
Global warming poses significant threats to human health, including its impact on kidney function. The kidneys play a crucial role in protecting the body from heat and dehydration, while also serving as a vital site for heat-related diseases. They perform a multitude of functions, including the excretion of waste products, regulation of blood pressure, maintenance of hormonal balance, and preservation of bone health. Moreover, kidneys maintain urine concentration to minimise fluid loss while excreting nitrogenous wastes — a function often overlooked by many.
During extreme heat waves, the kidneys face significant challenges in maintaining these functions. The high temperatures and extreme weather events lead to increased dehydration as the body loses water through sweat, compounded by insufficient water intake. Consequently, the concentration of solutes in the body rises, potentially reaching levels where molecules precipitate within the kidneys. This phenomenon reduces the efficiency of the kidneys in flushing out toxins from the body. In essence, the decreased water content in the body during high temperatures compromises the kidneys’ ability to adequately perform their essential detoxification role.
Additionally, kidneys with high metabolism are particularly vulnerable to injury due to the body’s additional demand for oxygen to perform regular kidney functions resulting in a spectrum of renal disorders such as acute kidney injury (temporary), chronic kidney disease (permanent), kidney stones, and urinary tract infections (UTIs).
Extreme heatstroke, defined by a temperature exceeding 40.6 degrees Celsius, can also lead to hyperthermia, an altered mental state, seizures, coma and multiple organ failure. The decreased circulation of blood to vital organs such as the kidney due to this chain of events could consequently result in acute kidney failure. This acute kidney injury can also occur due to increased muscle breakdown (rhabdomyolysis) or allergic reactions (interstitial nephritis — blood in the urine).
Additionally, environmental conditions as highlighted above can contribute to electrolyte abnormalities, leading to low levels of sodium, potassium, and calcium etc., further impacting kidney dysfunction.
Populations at increased risk include marathon runners, military personnel, miners, agricultural workers — especially those in sugarcane fields — elderly individuals, diabetics, obese individuals, and those with pre-existing heart or respiratory conditions.
Furthermore, heat stress and environmental pollutants can exacerbate kidney-related illnesses. Heat-stress kidney dysfunction can induce irreversible kidney disease (chronic kidney disease). This is coming to be known as CKDu observed in parts of the world like Latin America, Sri Lanka, India etc., which have a tropical climate. Especially, agriculture-heavy communities like Uddanam etc., are impacted due to the nature of their work and constant exposure to the heat with limited access to clean drinking water.
Lastly, the more commonly known kidney disorder, i.e., kidney stone formation caused due to increased acidification of urine is also one of the consequences of environmental conditions as well as broader lifestyle choices. To address these challenges, it is essential to raise awareness about the connection between global warming and kidney health and to implement measures to mitigate the impact.
Contributing factors
Contrary to popular belief, consuming soft drinks or fizzy drinks does not alleviate thirst or reduce dehydration; instead, the fructose content (a form of sugar) can stress the kidneys, leading to inflammation and potential temporary or irreversible kidney injury over time. Furthermore, in today’s world, people are increasingly exposed to man-made toxins such as agrichemicals, heavy metals, and the habit of consuming over-the-counter painkillers, as well as tobacco. These factors can adversely affect kidney health when combined with the escalating temperatures caused by global warming and climate change.
As global warming continues to impact humanity, it is imperative to promote adequate hydration, identify vulnerable populations, and advocate for measures to mitigate, halt, and reduce the health effects of global warming, particularly its impact on kidneys.
(The author is a consultant nephrologist & transplant physician.)