The International Agency for Research on Cancer, an arm of the World Health Organization (WHO), on March 24 officially reclassified the herbicide glyphosate as a cancer threat—citing what it called convincing evidence the chemical produces cancer in lab animals and more limited findings that it may cause a form of lymphoma in humans. Monsanto markets glyphosate as Roundup for use in agriculture worldwide, but the reclassification is especially big news in Colombia—where the government has sprayed more than 4 million acres of land in the past two decades to eradicate coca plantations.

The fumigation program, which is financed by the US State Department and carried out by US contractors in conjunction with the National Police, has long been opposed by Colombia’s left opposition, which likens it to the Pentagon’s use of the Agent Orange during the Vietnam war. Ending the spraying has been a key demand of the FARC guerillas in peace talks now underway with the government.

Even the new WHO findings may not mean an end to the spraying. "Without a doubt this reopens the debate on fumigation and causes us to worry," Colombia's Health Minister Alejandro Gaviria told the Associated Press. "But these are interests here that transcend" science, he added.

Aerial spraying in Colombia last year reached some 55,000 hectares (136,000 acres), down from a peak of 172,000 hectares (425,000 acres) in 2006. In 2013, Colombia agreed to pay Ecuador $15 million to settle a lawsuit over economic and health damage linked to spraying along the countries' border.

General Ricardo Restrepo, head of the Anti-narcotics Directorate of Colombia's National Police, said that he had not yet seen WHO's new warning and that the spraying program is operating as usual. "My job is to carry out the strategy," he told AP.

Cross-post to Global Ganja Report