Facing political opposition and questions about its scientific evidence, Sri Lanka’s government has placed on hold its decision to ban the top-selling Monsanto herbicide glyphosate based on the weed killer’s alleged role in a deadly epidemic of kidney disease.
The delay represents a setback to efforts by some scientists and health officials, primarily in Sri Lanka and El Salvador, to remove the herbicide for its potential link to the mysterious kidney disease that has killed tens of thousands of agricultural workers.
Monsanto, other agrochemical producers and Sri Lankan officials, including Registrar of Pesticides Anura Wijesekara, have pushed back, noting that the ban rests on a theory that has not been proven.
“It is an interesting hypothesis, but we don’t have any evidence for it,” said Dr. Wijesekara, a consistent skeptic of curbs on agrichemicals. Banning glyphosate, he said, “will affect the tea plantations and also the [rice] paddy cultivation drastically.”
For more than two years, the International Consortium of Investigative Journalists has examined a rare form of kidney disease devastating agricultural workers in Central America, Sri Lanka and India. Scientists suspect the malady is caused by a combination of factors including chronic dehydration from hard labor in tropical heat, and exposure to toxins such as pesticides.
As death tolls mount, the disease’s origins have yet to be fully uncovered. Now, the search for a cause has triggered a scientific back-and-forth spanning continents, with potential international repercussions.
On March 12, a Sri Lankan minister announced that President Mahinda Rajapaksa, after receiving a scientific report that “revealed that kidney disease was mainly caused by glyphosate,” was banning the herbicide. The decision followed publication of a scientific paper that laid out a new theory attributing widespread kidney failure among farmers to the popular herbicide. The study did not include new scientific data; its authors say they have original data supporting their conclusion, and are working to publish that information.
Since the announcement, Sri Lanka’ government-sponsored Pesticide Technical Committee, Monsanto and agrochemical industry groups have objected — and the ban has been placed on hold. Officials opposing the ban are seeking further meetings with the president, according to a report in the Sri Lankan daily The Island.
The office of Sri Lankan President Mahinda Rajapaksa has not responded to interview requests.
The glyphosate theory
Sri Lanka is not the first country to target glyphosate for its alleged role in chronic kidney disease. El Salvador’s Legislative Assembly approved a ban on 53 agrichemicals including glyphosate last year, but it was not signed into law by the country’s president.
Recently Sri Lanka has drawn international attention for singling out glyphosate as a cause of the epidemic, based largely on a theory presented by the scientist Channa Jayasumana.
Under Dr. Jayasumana’s hypothesis, glyphosate bonds with toxic heavy metals in the environment such as cadmium and arsenic, forming stable compounds that are consumed in food and water and do not break down until reaching victims’ kidneys. A study in Sri Lanka by the World Health Organization detected both cadmium and glyphosate, as well as other pesticides and heavy metals, in the environment of endemic areas, and in kidney patients’ urine.
The missing step, contends Jayasumana, is the compound formed by glyphosate and one or more heavy metals. He notes that glyphosate was initially patented as a chelating agent, a substance useful in industrial processes for its ability to form strong chemical bonds with metals.
“Glyphosate acts as a carrier or a vector of these heavy metals to the kidney,” Jayasumana told ICIJ in March.
Monsanto disputes the idea that glyphosate is uniquely suited to bond with heavy metals. “There is no evidence that glyphosate complexes effectively with arsenic, cadmium, or other nephrotoxic metals,” said Monsanto’s Director of Corporate Affairs Thomas Helscher. “Glyphosate is actually a relatively poor chelator for heavy metals when compared to pharmacological chelation agents.”
Yet glyphosate does form strong bonds with heavy metals, according to scientists and academic studies consulted by ICIJ.
Glyphosate is a highly versatile chelator because its molecule includes three different chemical groups capable of bonding with metals. Studiesindicate that it forms strong bonds with heavy metals including calcium, manganese and iron. A study by Monsanto using computer modeling found that glyphosate is a less potent chelator for these metals than certain compounds found within plants, but it is unclear how this applies to glyphosate’s interactions with the broader environment.
Paul Capel, a hydrologist with the U.S. Geological Survey, said glyphosate formed stronger bonds with metals than those formed by other herbicides. “As far as I know, there are no other common herbicides that would have this same sort of strength of interactions with metals,” Capel said.
There is less scientific data regarding glyphosate’s capacity to bond with cadmium or arsenic. One study indicated that glyphosate does form strong bonds with cadmium, and Capel said that based on glyphosate’s chemical structure, it was likely to bond with cadmium and its strength if binding to arsenic is unknown.
Disputed evidence
An even more fundamental issue is raised by Jayasumana’s research: Proving the existence of the glyphosate-heavy metal compounds said to be at fault.
Jayasumana’s paper proposes a possible structure for such a compound, and says his team’s preliminary tests of well water used by kidney patients in Sri Lanka found glyphosate with high levels of calcium and other metals. The paper does not describe finding a compound containing cadmium or arsenic, the metals thought to be at fault, and data from the tests has yet to be published.
Jayasumana said his team has found the key compound in its lab tests, and plans to publish its findings. “We experimentally detected [the compound] in drinking water samples, some food items and in urine samples of CKDu patients,” Jayasumana said.
Sri Lanka pesticide official Wijesekara points to another flaw in the glyphosate theory, in his assessment: He maintains that glyphosate did not become popular in Sri Lanka until the late 1990s, after the onset of the epidemic, and that it was not until 2003 or 2004 that it became the leading herbicide in the affected regions.
“At the beginning of the disease, glyphosate was not there in the [rice] paddy fields,” Wijesekara said. “All the paddy farmers used paraquat at that time.”
Jayasumana disputes this point, saying glyphosate has been available in the affected areas of Sri Lanka since the 1980s.
His results — and Sri Lanka’s decision of whether to go forward with banning the world’s top-selling herbicide — will have repercussions beyond the island’s borders.
El Salvador recently elected a new president, Salvador Sánchez-Cerén, and proponents of the pesticide ban passed by El Salvador’s legislature last year hope the former guerilla commander will sign a prohibition into law. President-elect Sánchez-Cerén’s office did not respond to ICIJ’s inquiries.
In Brazil, a prosecutor recently requested a ban on glyphosate and other agrichemicals because he said the government had not fully reviewed their health and safety effects. Prosecutor Anselmo Lopes of Brazil’s Federal District told ICIJ that his request was unrelated to chronic kidney disease among agricultural workers, which has not been reported in Brazil.
The U.S. Environmental Protection Agency said it is now engaged in a registration review process for glyphosate, but has “not seen any pattern of kidney health effects” in its study of scientific literature. The U.S., like Brazil, has not had reports of unexplained kidney failure among agricultural workers. The EPA said it would act promptly if urgent public health risks emerged.