As cases of chronic kidney disease emerge in outdoor laborers around the world, scientists are finding that repeated damage from prolonged extreme heat seems to be a leading factor to kidney failure

People working in construction and agriculture don’t just get hot from being outside in the Sun — they also generate heat through physical labour. Sweating a lot can leave them dangerously dehydrated at the end of a workday, even if they drink water as usual, says Giudice.

Except in the most severe cases, researchers thought that the kidneys could quickly bounce back from heat stress with no long-term damage. The emergence of CKDu instead hints that small, repeated injuries — even those that don’t result in a hospital visit — can build up over time. Compounded and amplified by other exposures, these small insults can lead to end-stage kidney failure, says Giudice.

“You’re having this acute kidney injury day after day,” she says. “Then you progress to a state where the cells can’t recover fully.”