Thursday, March 9, 2017

Sloppy science: the global burden of deaths from pesticides

My interest was piqued when I saw the heading: "UN experts denounce myth pesticides are necessary to feed the world", published in March in The Guardian. The report says pesticides have “catastrophic impacts on the environment, human health and society as a whole”, "including an estimated 200,000 deaths a year from acute poisoning."

This number puzzled me, so I decided to try to trace this to the root reference. The initial source was a UN document, published by the Special Rapporteur on the right to food (2017), which stated: "pesticides are responsible for an estimated 200,000 acute poisoning deaths each year (ref 2).

Reference 2 was published - though not in a peer reviewed journal - in 2013 by workers based at Lund University, Sweden. It was called "Migrant agricultural workers and their socio-economic, occupational and health conditions — a literature review." This report includes the sentence: "In general, studies indicate that at least three million cases of pesticide poisoning occur each year and result in over 200,000 deaths throughout the world (59)."

Reference 59 was by Lee, B.W. et al., published in 2003, called: Association between human paraoxonase gene polymorphism and chronic symptoms in pesticide‐exposed workers (J Occupat Envtl Med, 45, 118-122).

It states "At least three million pesticide poisonings occur each year and result in over 200,000 deaths throughout the world (1)."

Reference 1 is by the World Health Organization, published in 1990, called "Public Health Impact of Pesticides Used in Agriculture" (Geneva, Switzerland). This states: “of the more than 220,000 intentional and unintentional deaths from acute poisoning, suicides account for 91%, occupational 6% and other causes, including food contamination for 3% (Jeyaratnam, 1985). The title of Jeyaratnam’s article is mis-spelled, but was published in the Scandinavian Journal of Work, Environment and Health (Vol 11, 229-34). I haven’t tracked this down yet, but the following points can be made.


1. Scientists should be more thoughtful. I did not track down this error by chance: it immediately looked strange to me.

2. Even if the 1985 reference is based on good research, we do not know if the figure is still true today. The global population has increased by over 50% since 1985 - what about the number of deaths from pesticides?

3. The 1990 report says more than 90% of the deaths were deliberate. Blaming pesticides for suicide deaths is like blaming guns or high bridges from which some people jump.

4. The UN report is embarrassing - I am surprised this error was not detected by peer review. The error is so egregious it is likely to be used by UN opponents,as well as by pesticide promoters, to try to discredit the report.

I am currently searching for a more recent reference - so far without success, though I found one other paper (published 2011) which is also indirectly based on the 1990 WHO report. This paper claims that 100,000 deaths per annum die from pesticide poisoning in China; however no reference is provided and this article lacks a coherent discussion of suicide.

Note: I do believe pesticides are harmful, to vulnerable groups and in large doses to everyone. See, also my blog Agriculture, inequality and poverty in India - problems with the Green Revolution