When a large number of young agricultural workers in Central America started developing kidney failure without any known risk factors in the nineties, many kidney organizations around the world started sounding the alarm bells. Scientists have been looking for reasons for this in the past two decades. Initially the connection between climate change on kidney health wasn’t a factor taken into consideration.
It has been suggested that it could be due to agricultural chemicals, heavy metal exposure, silica inhalation, infectious diseases, genetic predisposition. Many of these workers regularly work in hot conditions for long hours. More recently, they identified repeated heat stress as a cause and a risk factor for kidney disease.
There is no doubt that the prevalence of kidney disease is rising in the United States (US) and throughout the world. In fact, one in seven people in the US has kidney disease. It is one of the fastest growing causes of death throughout the globe. An estimated 5–10 million people die annually from kidney disease worldwide. Unfortunately, due to poor data, lack of awareness, early detection and access to care these numbers could underestimate the exact burden of kidney disease in the world.
Chronic Kidney Disease of Unknown Origin (CKDu)
The type of chronic kidney disease that affected the agricultural workers in Central America is now called chronic kidney disease of unknown origin (or CKDu). Since the nineties, CKDu has been identified in studies of similar etiologies in Siri Lanka, India, Africa, South America and the Middle East. The common thread is the hot and humid climate.
CKDu does not follow the conventional risk factors for kidney disease and, therefore, it’s challenging to detect early and prevent. It disproportionately impacts areas with underprivileged communities and poor infrastructure. However, it would be a mistake to assume that this problem is limited to developing countries. Acute kidney injury has been reported in agricultural workers exposed to hot conditions in California and Florida.
Primary Impact: Global Temperature & Kidney Injury
It has been documented that global temperature have increased by about 1 degree centigrade (1.8 degrees Fahrenheit) in the past 50-100 years. Scientists agree that these changes have contributed with record heat waves, melting ice caps and rising sea levels, and extreme weather patterns. This pattern is posing significant health risks, some directly and some indirectly.
According to a United Nations report, climate change is expected to exacerbate health problems that already pose a major burden to vulnerable populations including children and the elderly. Climate change has been associated with a rise in many infectious diseases, especially water-borne illnesses like cholera, typhoid, and dysentery. It is also expected to contribute to the chronic disease burden and bring on new health epidemics. Not surprisingly, CKDu is one of these health issues.
Secondary Impact: Kidney Disease, Pollution, Water & Food Security
So how does rising temperature affect kidney health? The evidence points to heat stress and dehydration can result in chronic kidney disease as playing an important role in the epidemic of CKD worldwide. In fact, the progression of kidney injury has been found to worsen with rising core body temperature.
The mechanism seems to be linked with a decrease in adenosine triphosphate (ATP) levels and reduced mitochondria. These energy powerhouses are particularly abundant in the kidneys, and with reduced ATP and mitochondria, oxidative stress and cellular damage increases. Combine that with a diet with low nutrient-density and inadequate antioxidant content to neutralize oxidative stress, and risk of CKD significantly elevates. In laboratory studies, the supplementation of antioxidants prevented rats who were exposed to heat stress from developing kidney injury.
Furthermore, heat has been associated with increased risk of kidney stones and kidney stones are known risk factors for kidney disease. Since the kidneys are major site for the metabolism and elimination of toxins, exposure to toxins such as glyphosate contributes to kidney injury due to oxidative damage. Glyphosate in particular also impacts dysbiosis and gut health, which may be a confounding factor in the equation when we consider the gut-kidney connection.
As droughts become a more frequent occurrence as a consequence of climate change, dehydration from heat exposure and inadequate water consumption can lead to concentration of these toxins and, therefore, amplification of their negative effects.
Another factor to consider is the increase of pollution like heavy metal, plastics, and chemicals like pesticides and herbicides. Contamination of air and soil with pollutants increases inhalation and ingestion through food, including rise of mercury contamination in fish and arsenic in rice for example. These toxins have been associated with the rise in incidence of KDas well as other chronic diseases like diabetes and hypertension.
Last but not least, as climate change impacts food security and farming practices, access to fresh food and produce might be compromised. This may shift consumption to processed foods with less nutrient value, including less vitamins, minerals, phytonutrients, and antioxidants needed to promote healthy kidneys. Increased consumption of processed foods also leads to reduced fiber consumption, which impacts gut health and the microbiome which might be the most significant factor as we’ve discussed in our blog on the gut-kidney connection.
Other Considerations
It may sound like a cliché, but hydration is key. For those in labor industries or who work in agriculture or at increased risk of extended heat and chemical exposure, extra effort should be made to adequately hydrate. Broader public health measure and policy should be put in place to improve worker safety.
The risk increases for those taking medications that:
· Increases risk for dehydration, including diuretics (furosemide, hydrochlorothiazide, etc) or SGLT-2 inhibitors (canagliflozin, dapagliflozin, etc), or
· Decreases circulation to the kidneys, including ACE inhibitors (lisinopril, captopril, etc), angiotensin receptor antagonists (ARBS like losartan, Olmesartan, etc). However, as we mentioned earlier, heat lead to energy depletion in the kidneys and supplementing with antioxidants may further decrease the risk of kidney injury due to extreme heat.
Bottom Line
Rising global temperatures are posing increasing risk for kidney disease and contributing to a worldwide rise in chronic kidney disease. Extended exposure to heat and dehydration can lead to kidney injury and kidney stones. Improved hydration, improved nutrient-density diet, and use of antioxidants maybe be preventive. Other confounding factors cannot be ignored, including increased environmental pollution, factors that impact on gut health, and medications. Although individuals can take steps to reduce our carbon footprint, but broad public health measures must advocate for policy changes that reduce contributions to climate change and the resulting global health impacts.
