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A mysterious form of kidney disease has killed tens of thousands of people in Central America. Many of them are relatively young farmworkers in their 30s and 40s. Kidney failure is now the second leading cause of death in Nicaragua and El Salvador. The new disease has also turned up in hot, humid agricultural communities in India and Sri Lanka. Some researchers now say it may be linked to global warming.
NPR's Jason Beaubien reports.
JASON BEAUBIEN, BYLINE: In an editorial in the current issue of the New England Journal of Medicine, Dr. Cecilia Sorensen calls this new mysterious form of kidney failure a sentinel disease in the era of climate change.
CECILIA SORENSEN: This disease probably wouldn't have occurred if it weren't for the extreme global temperatures that we're seeing.
BEAUBIEN: Sorensen, from the University of Colorado, has been studying chronic kidney disease of unknown origin, also known as CKDu, for the last three years. The disease was first flagged by doctors in Central America in the 1990s. Farmworkers from sugar cane plantations in Nicaragua, El Salvador and Guatemala were turning up at clinics with end-stage kidney disease, yet they didn't have diabetes or hypertension or some other traditional factor that might explain why their kidneys were failing.
Among the early cases, almost all worked in agriculture, but it's also been found among miners, fishermen and workers in hot industrial plants. Then, farmworkers in Sri Lanka and tropical parts of southern India started coming down with a similar condition.
SORENSEN: It's very difficult to prove direct attribution, to say, this person is sick because of climate change, right? That link is very difficult. But what we can say is that this disease is occurring in parts of the world that are experiencing unprecedented warming, which we can directly attribute to climate change.
BEAUBIEN: There are many theories about what's causing CKDu. Most focus on heat stress and dehydration. Others are looking at heavy metals and chemicals in the drinking water. Sri Lanka banned the herbicide glyphosate sold under the brand name Roundup over concerns that it was causing CKDu. Early on, some health officials blamed the epidemic on home-brewed alcohol.
Neil Pearce at the London School of Hygiene and Tropical Medicine is also studying CKDu in Central America and southern Asia. He's skeptical of the link to climate change.
NEIL PEARCE: It's a very unusual phenomenon. You know, I've done work in this general area for 40 years, and it's very unusual to come across something like this.
BEAUBIEN: The disease destroys people's kidneys incredibly quickly. Pearce has tracked some sugar cane workers who over a two-year period lost a third of their kidney function.
PEARCE: It may well be due to heat stress and the extremely bad working conditions in Central America, but adding on the link to climate change is a bit tenuous.
BEAUBIEN: He doesn't think that the relatively small rise in global temperatures over the last few decades would cause such a significant epidemic. Also, Pearce has looked for CKDu in other places with similar climatic conditions to Central America's Pacific coastal plains and hasn't found it.
PEARCE: If you go to south India, there's villages that are very close to each other, and some of them are getting CKDu and some of them are not, you know? And they're both equally hot, and they're not the hottest parts of India. Yeah, there's something very strange going on. It's really interesting scientifically and obviously tragic in terms of the deaths and illness that it's caused.
BEAUBIEN: Sorensen in her editorial doesn't claim that she has the exact answer to what's causing this strange kidney disease, but she and just about everyone else studying it agrees that the disease is heat-related. And as global temperatures rise, she warns that health professionals should think about how climate change may be driving what seem to be mysterious new ailments.
Jason Beaubien, NPR News.
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