You really should read the article. You'll find that the researchers are attempting to figure out why it's confined to certain areas. They are also seeing the high rates of kidney disease as far north as southern Mexico.
They are finding that a key chemical that is supposed to be filtered out by healthy kidneys is higher in coastal workers than people in the same country at higher altitudes, where it is presumably cooler. Everything else is the same: work habits and exposure to pesticides.
There is nothing in the article but speculation, I just noted that dehydration and heat stress are daily occurrences in places where there is no major issues.
Grasp of the obvious, different elevations dictate different water source contaminants, be it chemical, mineral, or biological.
In reading about this affliction, the first thing that came to mind was poisoning by industrial chemicals.
I recently read the book, The Poisoners Handbook. It is about chemistry and the development of forensic medecine in New York City during the Prohibition years. Very interesting read.