Acute Human Lethal Toxicity of Agricultural Pesticides: A Prospective Cohort Study

Andrew H Dawson,Michael Eddleston,Steven J Bowe,Nicholas A Buckley,Gamini Manuweera,Fahim Mohamed,Indika Gawarammana,Lalith Senarathna,Mervyn Singer

doi:10.1371/journal.pmed.1000357

Abstract

agricultural pesticide poisoning is a major public health problem in the developing world, killing at least 250,000-370,000 people each year. Targeted pesticide restrictions in Sri Lanka over the last 20 years have reduced pesticide deaths by 50% without decreasing agricultural output. However, regulatory decisions have thus far not been based on the human toxicity of formulated agricultural pesticides but on the surrogate of rat toxicity using pure unformulated pesticides. We aimed to determine the relative human toxicity of formulated agricultural pesticides to improve the effectiveness of regulatory policy. we examined the case fatality of different agricultural pesticides in a prospective cohort of patients presenting with pesticide self-poisoning to two clinical trial centers from April 2002 to November 2008. Identification of the pesticide ingested was based on history or positive identification of the container. A single pesticide was ingested by 9,302 patients. A specific pesticide was identified in 7,461 patients; 1,841 ingested an unknown pesticide. In a subset of 808 patients, the history of ingestion was confirmed by laboratory analysis in 95% of patients. There was a large variation in case fatality between pesticides-from 0% to 42%. This marked variation in lethality was observed for compounds within the same chemical and/or WHO toxicity classification of pesticides and for those used for similar agricultural indications. the human data provided toxicity rankings for some pesticides that contrasted strongly with the WHO toxicity classification based on rat toxicity. Basing regulation on human toxicity will make pesticide poisoning less hazardous, preventing hundreds of thousands of deaths globally without compromising agricultural needs. Ongoing monitoring of patterns of use and clinical toxicity for new pesticides is needed to identify highly toxic pesticides in a timely manner.

Highlights

Suicide and deliberate self-harm using pesticides is a major but under-recognised public health problem in the developing world
The human data provided toxicity rankings for some pesticides that contrasted strongly with the World Health Organization (WHO) toxicity classification based on rat toxicity
The pesticide ingested could be identified by history in 7,461 patients; a further 1,841 had ingested an unknown pesticide

Summary

Introduction

Suicide and deliberate self-harm using pesticides is a major but under-recognised public health problem in the developing world. Further efforts can range from educating farmers in the use of safer pesticides to imposing regulatory restrictions on the sale and distribution of the most toxic class II pesticides [7,8] These strategies would be aided if countries developed pesticide policies that balanced agricultural and economic needs against the public health impact of acute and chronic human toxicity [9]. Between 250,000 and 370,000 people die from deliberate ingestion of pesticides (chemicals that kill animal pests or unwanted plants) Most of these suicides occur in rural areas of the developing world where high levels of pesticide use in agriculture combined with pesticide storage at home facilitate this particular method of suicide

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