Climate change and kidney disease
Greenhouse gas emissions cause rapid global heating resulting in a human health crisis. Climate change is causing droughts, floods, more powerful tropical storms, heat waves, wildfires, sea level rise, spread of infectious diseases, and blooms of microorganisms in oceans and lakes. Climate change is probably the most important event in the lives of younger people today. Reducing greenhouse gas emissions to zero gives them a chance for a longer, healthier, and happier life.
In the last 40 years, a new heat-related kidney disease (called Chronic Kidney Disease of unknown origin, Chronic Kidney Disease nontraditional, or Mesoamerican Nephropathy) has emerged among outdoor laborers in tropical countries. Chronic kidney disease means kidney damage or dysfunction lasting three months or longer. Chronic kidney disease of unknown origin (CKDu) is associated with working and living in a hot, humid environment, poverty, and poor working conditions. Patients have been identified in Egypt, El Salvador, Panama, Nicaragua, Costa Rica, Honduras, Mexico, Sri Lanka, Bangladesh, and India.
There are high rates of chronic kidney disease among laborers along the Pacific Coast of Central America. This condition develops in farm workers, miners, and construction workers. Workers at higher elevations associated with cooler temperatures (coffee workers) tend to be spared.
CKDu has been identified in northern Sri Lanka. The disease, described in the 1990s, affects persons working in rice paddies. Men are more commonly affected than women, with an average age at presentation of 40 to 50 years. Prolonged sun exposure and low fluid intake seem to be risk factors for developing CKDu. In a health survey in 2014 in northern Sri Lanka, 13,764 CKDu cases were identified in a screening sample of 96,521, a prevalence of 14.3%. Numerous cases of chronic kidney disease have been reported among farmers in the hottest areas in India. CKDu appears to be driven by occupational heat stress.
The cause of CKDu is unknown, but it is related to heat exposure, dehydration, physically demanding labor, poor access to health services, less education, and poverty. It is possible that this disease is caused by an infection or toxic exposure that has not yet been identified. For example, lead or tuberculosis may cause chronic kidney disease. Kidney injury is then accelerated by heat. Alternatively, repeated exposure to extreme heat, dehydration, and long work hours may cause damage to renal tubules which over gradually progresses to chronic kidney disease. CKDu is not associated with hypertension, diabetes, obesity, or advanced age (frequent causes of kidney disease in temperate countries). Although patients are initially asymptomatic, signs and symptoms of end-stage kidney disease such as anemia, anorexia, nausea, edema, hypertension, and uremia (retention in the blood of chemicals normally excreted in urine) develop over a period of several years.
CKDu has not been detected in the U.S. However a study of 192 Florida agricultural workers revealed that dehydration and acute kidney injury often follow a day of working in the hot sun. One-third of immigrant workers experienced acute kidney injury on at least one work day during the study and heat index (the local temperature and humidity) was significantly related to the incidence of acute injury. Immigrant workers in the US may also work in unhealthy conditions, endure toxic exposures from pesticides and herbicides, and have limited access to medical care.
As of 2012, an estimated 20,000 deaths were related to CKDu globally. In El Salvador the death rate from chronic kidney disease is approximately tenfold higher than in the United States. WHO data for 2012 suggest kidney disease is the seventh most common cause of death in Sri Lanka.
Chronic kidney disease of unknown origin is a newly-described disease related to ambient heat exposure, although the cause is not understood. As global temperatures increase, more cases of CKDu may occur and CKDu may appear among U.S. laborers. CKDu appears to be an example of a climate change health effect that is new and unexpected. Public health physicians warn that climate change is the greatest health problem of this century. Already, global warming is one of the most harmful drivers of worsening hunger and starvation, migration, poverty, and inequality all over the world. Reducing climate change helps everyone. A future with less CKDu and less climate change is a better future.
References:
Johnson RJ, Wesseling C, Newman LS. Chronic Kidney Disease of Unknown Cause in Agricultural Communities. N Engl J Med 2019; 380:1843-1852. DOI: 10.1056/NEJMra1813869
Ordunez P et al. The epidemic of chronic kidney disease in Central America. https://www.thelancet.com/