Something is destroying the kidneys of farm workers along the Pacific coast of Central America. Over the past two decades, more than 20,000 people in western Nicaragua and El Salvador — mostly men and many of them in their 20s and 30s — have died of a mysterious form of kidney failure. Researchers have been able to say definitively that it's not diabetes or other common causes of kidney failure. Theories have blamed everyone from the victims themselves (maybe they drink too much, maybe it's genetic) to rats (peeing on stored grain and spreading a nasty bacterial infection) to Monsanto (whose chemicals are used extensively in the cane fields) to the World Bank (for financing expansion of the sugar plantations).
Now a new study from Boston University finds a clear connection between the disease and the work these men are doing.
"The decline in kidney function during the harvest and the differences [in kidney function] by job category and employment duration provide evidence that one or more risk factors of CKD (chronic kidney disease) are occupational," the report says.
In 2011 the study followed 500 sugar cane workers at one plantation, El Ingenio San Antonio in Nicaragua. The researchers found that the kidney function of field workers declined over the course of the six-month harvest. Sugar cane cutters and planters saw the sharpest drop.
"Finding that one or more risk factors are occupational is important," says Rebecca Laws, a doctoral student at the Boston University School of Public Health and lead author of the paper. "Before this, it was still sort of unknown whether the major risk factors were occupational or nonoccupational."
The sugar cane workers themselves have previously come up with their own theories. In the Nicaraguan town of Chichigalpa, many men who are now sick with the condition blame their kidney failure on agricultural chemicals.
Last spring, Manuel Antonio Tejarino told NPR, "It's the chemicals, the chemicals." He died two months later.
A growing suspicion that pesticides or herbicides are the culprit prompted the Salvadoran National Assembly to ban 53 agrichemicals late in 2013.
But this new study casts doubt on that theory. It found that field workers whose primary jobs were spraying for weeds and pests (and who thus had the most contact with agricultural chemicals) had the least decline in kidney function over the course of the harvest.
The researchers also found that dehydration among workers with the most physically demanding job — cutting cane — could contribute to the illness.
Cutters who drank more of a generic energy drink while on the job had less of a drop in kidney function than co-workers who drank less of the beverage.
The sugar plantation tests workers' kidney function at the beginning of each year's harvest. Anyone who's starting to show kidney failure isn't hired back.
"Treatment for the disease is limited in the region," says Laws, "so it's usually fatal."
She hopes this study will help researchers better understand the disease and find a way to prevent it.
The funding of the study is a story in itself. The BU research was partially funded by the Nicaraguan sugar industry, El Comite Nacional de Productores de Azucar, as part of the settlement of a complaint filed by ASOCHIVIDA, a group of some 2,000 former sugar cane workers suffering from kidney failure and their widows.
Financial arrangements like this are not uncommon in industrial and environmental damage disputes. The money for the study was controlled by an arbitrator at the World Bank.
Laws puts it this way:"Even though we were partially funded by the sugar industry, they were not able to influence our findings or view our publication. We had complete independence with designing, conducting and publishing the study."