[BOGOTÁ] Colombia's practice of spraying herbicide from aircraft to destroy illegal crops does not harm human health or the environment, according to a study by the Organization of American States (OAS).
Colombia uses the herbicide glyphosate as part of its US-backed 'war on drugs' to target fields of the opium poppy and of coca, which is refined to produce cocaine.
Environmental and human rights organisations have claimed that spraying the herbicide from aircraft threatens the health of local people, ruins other crops, and pollutes rivers (see Colombian herbicide spraying under attack).
According to Mamacoca, a Colombian non-governmental organisation, more than 8,000 people in the regions of Guviare, Putumayo and Caquetá say they were affected by herbicide spraying between 1999 and 2003.
Short-term exposure to toxic levels of glyphosate has been linked to vomiting, head and stomach pain and diarrhoea, while campaigners claim that longer-term effects include an increased risk of cancer and birth defects.
However, the OAS study, released on 22 April, says that producing the illicit crops carries greater health risks than efforts to control them.
"In the entire cycle of coca and poppy production and eradication, human health risks associated with physical injury during clear-cutting and burning [of forests] and the use of pesticides for protection of illicit crops were judged to be more important than those from exposure to glyphosate."
The report was prepared for the Inter-American Drug Abuse Control Commission, an OAS agency, by an international team of specialists in human and environmental toxicology, epidemiology, agriculture and ecology.
They evaluated risks by reviewing scientific literature and governmental reports, and through research by Colombian scientists on water bodies in five regions of the country.
The report says that surface waters in Colombia had little, if any, significant contamination with glyphosate.
But Fernando de la Hoz, a Colombian researcher at the London School of Hygiene and Tropical Medicine, United Kingdom, has doubts about the study's validity and conclusions because it did not directly evaluate how exposure to the herbicide affects coca and poppy growers.
"The study considers only short-term effects of exposure," says de la Hoz, adding that the study's authors acknowledge the need for long-term research to establish the effects of the herbicide.
Two Colombian research groups, one from the National Institute of Health (INS) and one at the Bogotà-based University of the Andes, have recently studied the impacts of herbicide spraying.
According to Rafael Romero, director of the INS, the findings are similar: "The impact on human health, regarding acute effects, is minimal". Moreover, he says, the claim that glyphosate causes birth defects has been ruled out.
Andrés Moya, a researcher from the Centre for Economic Development Studies at the University of the Andes says that there are other important factors to consider in the debate about human and environmental effects of spraying glyphosate.
"Coca growers have started to create strategies to minimise the herbicide's effectiveness, such as hiding plants under banana trees or covering the leaves with petrol," Moya told SciDev.Net.
Moya believes that removing illegal plants manually or promoting alternative livelihoods would lead to more sustainable rural development than aerial spraying.
The OAS study recommends the continued spraying of herbicide to kill coca and poppy plants. But it adds that because aerial herbicides could be detrimental to the Andes' rich variety of plant life, this effect should be carefully monitored.
Critics of the study are worried that it could open the way for the Colombian government to authorise aerial spraying of glyphosate in national parks, where farmers have started planting coca and poppy plants.
Sources from the environment ministry said glyphosate is not currently sprayed in these areas. The National Council of Narcotics, the body that makes the final decision on this issue will convene in late May to discuss whether to begin spraying there.
Link to the full OAS report (in English)