What's Driving the Spike in Kidney Disease in the Tropics?

Chronic kidney disease is a fact of life among the rice farmers of north-central Sri Lanka, the teardrop-shaped island dangling off the Indian subcontinent, 7 degrees north of the Equator.

“It’s a common, well-known fact of life among the community,” said Nishad Jayasundara, an assistant professor of environmental toxicology at Duke University’s Nicholas School of the Environment and the Duke Global Health Institute who is studying the trend. “Anyone you speak to in these villages would say, ‘oh yeah, so and so died from kidney disease, and so and so just got it.’”

While there is a known association with kidney disease and physical work and dehydration in hot regions like Sri Lanka, there seems to be more to this story than that. Kidney damage in Sri Lanka is more prevalent in some areas than others, peaking in particularly dry, low-lying regions.

“In Sri Lanka, and generally around the world where this mysterious kidney disease is emerging, there are two hypotheses,” Jayasundara said. “One is that it's directly caused by exposure to agrochemicals -- among farmers who use the chemical, or among family members who drink well water or water that's contaminated with these agrochemicals.”

Many of the drinking water wells in the region – open-topped reservoirs, sometimes lined with brick, sometimes just a hole in the earth – stand in or near the rice paddies where agrochemicals are used.

“No one really knows what the chemical is or if it is multiple chemicals,” Jayasundara said.

He has teamed up with Prof. Lee Ferguson, an analytical chemist in Duke’s Department of Civil and Environmental Engineering, to assess samples taken from hundreds of wells in Sri Lanka.

“Really cutting edge analytical chemistry work by the Ferguson lab is finding that drinking water in these regions carries a heavy chemical burden, contaminated with a multitude of kidney-toxic compounds,” Jayasundara said. “Our ongoing work is teasing apart the culprit based on toxicity assays in the lab as well as looking into why chemicals tend to stay longer than they should in the drinking water in these regions.” The natural hardness of the local water likely plays a role in the formation of longer-lasting compounds.

“The other hypothesis is that it's nothing to do with agrochemicals,” he said. “It's these farmers that work in really hot, humid conditions. They’re dehydrated, and that's damaging the nephrons, and accumulated damage over time is what's causing kidney damage. There's no clear evidence yet on either hypothesis to say it's one or the other.”

But the evidence is building that there’s more to this pattern than just a warm climate, and it may be that both hypotheses are valid.

“It’s very possible that these farmers in Sri Lanka are working in the hot, dry conditions, and their kidneys are damaged,” Jayasundara said. “And then they also get a nice dose of one or a few nephrotoxic chemicals.”

In partnership with Professor Mangla De Silva and colleagues at the University of Ruhuna, Sri Lanka, and with funding support from The World Bank and Duke University, Jayasundara’s team has sampled more than 200 rural wells while also comparing the differences in the mix of proteins found in samples of urine from healthy Sri Lankans and kidney patients. “The goal is to be able to identify biomarkers that can help us identify the disease early.”

“We’re also seeing a rise in kidney damage markers in kids between the ages of 10 to 17, which tells us that it’s not just the stress of being a farmer,” Jayasundara said, referring to a paper that appeared in Nature Scientific Reports in May, 2022. “The main source we can think of is drinking water contamination.”

The researchers have taken what they’ve learned so far from their sampling into the lab and are experimenting now with zebrafish, a widely used toxicology model, to see whether they can replicate these disorders with exposures to glyphosate and other agrochemicals. One thing they’ve already seen is that kidney development is stunted by the chemical exposures, according to a paper which is currently in review.

The Sri Lankan farmers also say their seasons are changing, and that different planting times and different conditions are leading them to use even more agrochemicals. So the changing global climate is also a driving force.

“Environmental change can have negative health outcomes on some of the most poor and disadvantaged communities around the world,” Jayasundara said.

"We should be mindful across the world now about how these factors are playing out,” he said. “Sri Lanka is one of the hotspots around the world. India has three regions that are currently considered hotspots for this. I've been contacted by folks in Ghana, Kenya and Egypt, indicating that they're seeing this rise in kidney disease. In South America, it's a big problem -- Guatemala, El Salvador, Nicaragua. So it's emerging on this tropical belt, and our work in Sri Lanka is giving us a framework to study this type of complex environmental health problem.”

While they’re waiting for the answers in Sri Lanka, the team has already built a water purification system for one school in the affected area that provides 1000 liters of water per day to children.

Karl Leif Bates is the executive director of research communications at Duke University in Durham