Editor's Note: This story was reported as part of a joint investigation with the Center for Public Integrity. Read more reports in the series Mystery in the Fields. See more photos from this project at TheWorld.org.

Thousands of people in the Asian island nation of Sri Lanka have been struck by a mysterious and deadly form of kidney disease.

A new study points to a likely cause: pesticides and fertilizers.

Tucked away in Sri Lanka’s North Central Province is the village of Halmillawetiya. A pebbled path connects small houses of brick and mud set among coconut palms and other tropical trees.

Sampath Kumarasinghe, 21, lives here with his widowed mother and extended family.

As Kumarasinghe sits on his porch, his mother, P. Dingirimenike, sits close by, talking and cutting areca nuts, which people chew like tobacco. The sounds of a radio waft from the house.

Kumarasinghe tells visitors he's doing fine.

But you can tell he isn’t fine.

Despite the brutal heat, he’s wearing a wool hat. He speaks softly, and his movements are slow for someone his age.

Like most people here, Kumarasinghe is a rice farmer, but recently he hasn’t had the strength to work on his farm.

Kumarasinghe’s kidneys are failing. They are no longer filtering waste from his bloodstream.

“My body is weak,” he said.

He is being kept alive by dialysis, a procedure he receives twice a week at a regional hospital. He is hoping to get a kidney transplant.

A Disease of “Unknown Etiology”

Kumarasinghe is one of thousands of people in the North Central Province suffering from chronic kidney disease. According to the Sri Lankan Ministry of Health, 15 percent of the population here is affected.

The public hospital in the provincial capital of Anuradhapura treats at least 2,000 chronic kidney disease patients every month.

No one knows the exact death toll, but health officials say that in Anuradhapura district alone, about 150 people die from the disease every year.

The disease first came to the attention of physicians at the hospital about 20 years ago, says Dr. Rajeewa Dassanayake, the hospital’s kidney specialist.

“They started noticing that there (were) a number of deaths due to kidney disease,” he said. “And the physicians at the time noticed that this was not happening in the rest of the country.”

Dassanayake says these patients didn’t fit the typical profile. They didn’t have diabetes or high blood pressure, the common causes of chronic kidney disease worldwide.

To distinguish this illness from the more common form of chronic kidney disease, the Sri Lankan government labeled it CKDu — chronic kidney disease of unknown etiology (i.e. of unknown cause).

“Unfortunately, for CKDu, there’s still no specific treatment,” Dassanayake said.

And there has been no known way to prevent it.

The Search for Answers

Four years ago, the World Health Organization (WHO) and the government of Sri Lanka launched a joint investigation into the causes of the disease.

Scientists looked for clues by testing people and the environment. They took blood, urine and tissue samples. They tested the region’s food, water and air.

The results of those analyses were released this summer, in a one-page press release.

The culprits appeared to be two toxic metals, cadmium and arsenic, which previous studies suggest can harm the kidney.

Palitha Mahipala, an official with the Sri Lankan Ministry of Health, says that people in the North Central Province showed relatively high levels of the metals in their blood and urine.

Although the levels were generally within what is considered the safe range, Mahipala says that continuous exposure to those levels may have damaged kidneys.

“Probably the chronic exposure would have been the reason for this,” he said.

But if arsenic and cadmium are to blame, where are they coming from?

The new study blames farm chemicals, which may be slowly poisoning the population by contaminating food and air.

Cadmium is found in some fertilizers. Arsenic is an active ingredient in some pesticides, although it is illegal to use arsenic-based pesticides in Sri Lanka.

Farm chemicals are so cheap here, thanks to government subsidies, that farmers tend to put far too much on their fields, thereby increasing the amounts of contaminants in the environment.

Companies that import and sell pesticides and herbicides contest the government’s conclusion. They point out that the government and WHO have not yet released their full study.

“We believe the evidence is not scientific enough to say that the pesticide is the main reason for this chronic kidney disease,” said Senarath Kiriwaththuduwage, research and development manager at Crop Life Sri Lanka, an industry trade association. “These findings are not published in reputed scientific journals.”

Some doctors and scientists familiar with the study agree that more research needs to be done, but many believe that farm chemicals are at least partly to blame for CKDu.

Vested Interests

In its press release about the study, the government writes that farmers can protect their kidneys by stopping the “indiscriminate use of fertilizers and certain pesticides.”

Yet little has been done to spread that message to the people who should hear it. Farmers in the North Central Province said they don’t even know about the study.

J.A. Jayarathne, 46, lives in Mihintale, a small village near the regional capital. He too has chronic kidney disease.

“They haven’t told me (about) the cause of the disease,” he said.

Jayarathne shows off his stock of fertilizers. A few sacks are piled in one corner of a shed behind his house. He says he has no plans to change the way he uses farm chemicals.

“I’ll use these fertilizers for my next crop,” he said.

It’s not just farmers who are in the dark about the government findings. Consumers too have not been told what foods are most likely to be contaminated, and therefore which foods they might do well to avoid. The government says it will release that information after it has conducted more detailed studies.

The fact that the WHO and the Sri Lankan government have not yet publicized their findings to the affected population frustrates doctors.

Dr. Palitha Bandara, the top health official in the North Central Province, says it is critical that the public’s exposure to the contaminants be reduced immediately “because day by day (they) will accumulate (in) the skin, blood and other peripheral organs, including kidneys.”

Bandara says since farm chemicals are the suspected source of the toxic metals, the government should improve measures to test fertilizers and pesticides imported into the country — to make sure they are safe.

Many fertilizers, he says, come from China.

“We don’t know what types of chemical ingredients, elements, are there in the fertilizers,” he said.

As for pesticides, last year customs officials did test some imports and found four kinds of pesticides contained small amounts of arsenic. Those pesticides were initially seized by the authorities but were later released.

The head of the pesticide regulatory agency assured the public that the arsenic levels were too low to cause any harm.

Aniruddha Padaniya, president of the Government Medical Officers’ Association, sees the incident as evidence that regulators are reluctant to strictly police the agrochemicals industry. He believes there are “certain vested interests” involved.

The Ministry of Health says the government is looking more closely at agrochemicals imported into the country, but Padaniya believes that his country has been too slow to address chronic kidney disease.

He says the illness should be a national priority.

“We are losing the very productive crowd. They are farmers. They feed us,” Padaniya said. “We have to save them because they don’t have the ability to save themselves.”

Remaining Mysteries

Still, there are many unanswered questions.

Are the levels of cadmium and arsenic that have been found in people’s bodies high enough to cause harm?

If the metals are to blame, is the main culprit cadmium? Arsenic? Or are the metals acting in combination?

Are the metals coming mostly from pesticides, or fertilizers?

And if farm chemicals are the root cause of CKDu, why aren’t farmers elsewhere in the country affected?

Back in the North Central Province, in the area that is affected, it's surprising how little anger and frustration locals express. But what they lack in anger they make up for in resignation.

The mother of the 21-year-old kidney disease patient, Sampath Kumarasinghe, chokes up as she recalls the time doctors first told her about her son’s illness.

“I felt sad,” said P. Dingirimenike as she begins to cry. “I’m still sad.”

And yet, she says she’s grateful for the role government has played.

“The government has helped us,” she said.

Government hospitals provide her son’s medical care, including dialysis, for free.

Other countries that have been struck by a similarly mysterious form of chronic kidney disease — most notably, in Central America — offer dialysis to only a small fraction of patients who need it. Kidney dialysis is an expensive procedure.

In Sri Lanka, the government is trying to help larger numbers of patients. It is expanding access to dialysis and to kidney transplants. These efforts are keeping many patients alive.

But doctors and public health officials remain frustrated. They say more should be done to prevent people from getting sick in the first place.