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

Date Published: October 26, 2010

Publisher: Public Library of Science

Author(s): Andrew H. Dawson, Michael Eddleston, Lalith Senarathna, Fahim Mohamed, Indika Gawarammana, Steven J. Bowe, Gamini Manuweera, Nicholas A. Buckley, Mervyn Singer

Abstract: In a prospective cohort study of patients presenting with pesticide self-poisoning, Andrew Dawson and colleagues investigate the relative human toxicity of agricultural pesticides and contrast it with WHO toxicity classifications, which are based on toxicity in rats.

Partial Text: Suicide and deliberate self-harm using pesticides is a major but under-recognised public health problem in the developing world. Each year 250,000–370,000 thousand people die from deliberate ingestion of pesticides [1],[2]. These deaths are responsible for about a third of suicides globally [1]; the World Health Organization (WHO) now recognizes pesticide poisoning to be the single most important means of suicide worldwide [3].

During the study period, 9,302 patients were admitted following deliberate ingestion of a single pesticide. The pesticide ingested could be identified by history in 7,461 patients; a further 1,841 had ingested an unknown pesticide. Within the unknown group, 497 were considered to have taken a cholinesterase inhibitor (either an OP or carbamate insecticide) on the basis of a typical anticholinesterase clinical syndrome, significant atropine requirement, and/or measured cholinesterase inhibition. A total of 808 patients, whose ingested pesticide was identified by history, had admission samples assayed for other nested studies; history correctly identified the ingested poison in 94.7% of these patients, the other 5.3% were not necessarily misclassifications (more likely to be simply below the level of assay detection). In a subset of the cohort we have also previously shown that analytical assay confirmed history in 92% of symptomatic patients with organophosphate poisoning [16].

This study demonstrates major differences in human case fatality between pesticides that are used for similar agricultural indications. These are the first systematically collected prospective human data, to our knowledge, that allow estimates of relative toxicity for pesticides. The data are much more directly relevant to human risk assessment than the existing animal data from which the WHO/EPA classifications of toxicity used in regulation are derived. Moreover, it provides evidence of very large differences in acute human toxicity within these widely used classifications. These data provide a basis for refining further public health, regulatory, and clinical responses to the problem of acute pesticide poisoning.



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