Military use of herbicides

The military use of chemical herbicides first rose to prominence during the Vietnam War. The presence of the environmentally persistent dioxin TCDD in the herbicide formulations used by the US in the conflict continues to be linked to health problems in military personnel and Vietnamese civilians. States have different interpretations over whether the widespread spraying of chemical herbicides is prohibited under the Environmental Modification Convention (ENMOD), the UK and US argue that it is not.


Case study: Coca eradication in Colombia
A young boy looks over a farm damaged by aerial herbicide spraying in Putumayo, Colombia. Credit: Kyle E Johnson.

A young boy looks over a farm damaged by aerial herbicide spraying in Putumayo, Colombia, 2007. Credit: Kyle E Johnson.

Since the 1980s, and with funding from the US under its Plan Colombia programme, which aimed to combat left wing guerrillas in Colombia’s civil war, aerial spraying of herbicides has taken place to destroy coca fields. It is thought that up to 8% of Colombia’s agricultural land has been sprayed with the herbicide Glyphosate, which is manufactured by Monsanto. The precise formulation of its commercial Glyphosate formulations Roundup and Roundup Ultra are commercially sensitive.

Critics have argued that the strategy has been ineffective in combating coca production and there is widespread concern over the health and environmental impact of the spraying, some of which has taken place in recognised biodiversity hotspots. The potential health effects of Glyphosate, one of the world’s most commonly used herbicides, are still being studied but in recent years research has demonstrated that it is an endocrine disruptor.

In 2013, a case brought by Ecuador against the Colombian government at the International Court of Justice was dropped after agreement was reached between the two parties over ‘no spray zones’ along the border to prevent transboundary contamination. Ecuador had argued that the spraying put the health of communities and the environment at risk and damaged the livelihoods of farmers.

In March 2015, the World Health Organisation’s specialist cancer research arm the International Agency for Research on Cancer (IARC) classified Glyphosate as a possible human carcinogen. Six weeks later the Colombian government stopped the use of aerial coca spraying over concerns about its public health risks. A previous ruling by Colombia’s constitutional court that invoked the precautionary principle required an end to the practice if evidence of health risks emerged.

Key issues
  • Aerial spraying of herbicides can affect huge areas and the lessons from both Vietnam and Colombia suggest that it is often ineffective.
  • The health risks from chemical herbicides may take many years to be properly understood, by which time vast quantities may have been dispersed into the environment.
  • Disagreement over the interpretation of international law on environmental modification techniques and chemical weapons has allowed the practice to continue, in spite of the risks it poses to public and environmental health.
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