I became interested in this issue after speaking to people in Colombia. One woman told me she was working in the fields with her family when aeroplanes came down and started spraying.
The spray killed their small patch of coca, but also their food crops. She said that the spray was sticky, like cooking oil.
The spray is supposed to be Roundup — the ordinary herbicide that people use in their gardens — and I knew Roundup is not sticky.
I heard stories about skin and eye infections, and diarrhoea after spraying took place.
Coca fumigation began on a really large scale with Plan Colombia. This plan was announced by Bill Clinton in 2000 and turned Colombia into the third biggest recipient of US aid.
At that time it was difficult for the US to be seen as being involved in a military conflict in the region.
Plan Colombia was a counterinsurgency programme — aimed at the Farc guerilla movement — disguised as a counter-narcotics programme.
The plan didn’t make any sense as a counter-narcotics programme. Last year a record area was fumigated but there was a small increase in coca production.
And although the plan paid lip-service to countering large-scale trafficking, which everyone knows is mainly controlled by the right wing paramilitaries, in practice this was largely ignored.
We investigated the impact of the spraying on Colombian families.
Hugh O’Shaughnessy, who co-wrote the book, travelled to Ecuador and spoke to doctors there. They were carrying out a controlled examination of families who had undergone spraying.
Large amounts of pesticides blow over into Ecuador. It was much easier to investigate in this country because there are more democratic rights there.
The doctors looked at groups of women, who were less likely to use chemicals in farming.
Some were from Colombia and came across the border, some were Ecuadorian and there was a control group of women who lived a long way from the spraying.
This team found evidence of long term genetic damage to the women in areas sprayed with fumigant.
It is very reminiscent of Vietnam — we were told that Agent Orange was just a defoliant, but we see today tens of thousands of Vietnamese suffer long term effects.
There have been few investigations into fumigation. The major UN study was largely funded by Monsanto, the multinational that produces the herbicide.
Other investigations were done in laboratories with the herbicide that they claim they are using.
A few scientists are trying to discover what they are actually using. One scientist we spoke to explained that extra ingredients are added to Roundup to make it more effective.
She found that the mix of chemicals used, in the conditions it was used, was 104 times more toxic than ordinary Roundup.
Chemical Warfare in Colombia: the Costs of Coca Fumigation, by Hugh O’Shaughnessy and Sue Branford (£8.99). Phone Bookmarks on 020 7637 1848 to order copies.