Qatar has spent $300 billion in preparation for the most expensive World Cup ever. That construction boom is now revealing a concerning health cost to workers toiling in many of the hottest countries around the world.

Over the past decade, deaths of workers involved in World Cup-related construction in Qatar drew global attention to their working conditions. Yet researchers say there’s an even broader problem emerging among low-income migrants across hot regions from the Middle East to Central America — an epidemic of chronic kidney disease.

"Many workers returning from the Persian Gulf, and indeed those that worked to build the infrastructure required for the World Cup in Qatar, left their home countries healthy and returned with kidney disease after being exposed to extreme temperatures and brutal conditions while at work,” said Jason Glaser, CEO of the international climate and health research organization La Isla Network.