Effects of a provincial ban of two toxic organophosphorus insecticides on pesticide poisoning hospital admissions

Abstract

Background: Pesticide self-poisoning causes one third of global suicides. Sri Lanka halved its suicide rate by banning WHO Class I organophosphorus (OP) insecticides and then endosulfan. However, poisoning with Class II toxicity OPs, particularly dimethoate and fenthion, remains a problem. We aimed to determine the effect and feasibility of a ban of the two insecticides in one Sri Lankan district.

Methods: Sale was banned in June 2003 in most of Polonnaruwa District, but not Anuradhapura District. Admissions with pesticide poisoning to the district general hospitals was prospectively recorded from 2002.

Results: Hospital admissions for dimethoate and fenthion poisoning fell by 43% after the ban in Polonnaruwa, while increasing by 23% in Anuradhapura. The pesticide case fatality fell from 14.4% to 9.0% in Polonnaruwa (odds ratio [OR] 0.59, 95% confidence interval [CI] 0.41-0.84) and 11.3% to 10.6% in Anuradhapura (OR 0.93, 95%CI 0.70-1.25; p = 0.051). This reduction was not sustained, with case fatality in Polonnaruwa rising to 12.1% in 2006-2007. Further data analysis indicated that the fall in case fatality had actually been due to a coincidental reduction in case fatality for pesticide poisoning overall, in particular for paraquat poisoning.

Conclusions: We found that the insecticides could be effectively banned from agricultural practice, as shown by the fall in hospital admissions, with few negative consequences. However, the ban had only a minor effect on pesticide poisoning deaths because it was too narrow. A study assessing the agricultural and health effects of a more comprehensive ban of highly toxic pesticides is necessary to determine the balance between increased costs of agriculture and reduced health care costs and fewer deaths.

Fig. 1.

(A) Map showing study districts (Anu: Anuradhapura, Polo: Polonnaruwa; source: Wikimedia Commons, http://en.wikipedia.org/wiki/File:Sri_Lanka_North_Central_ Province_locator_map.svg); (B) One of the public meetings with pesticide sellers showing staff from both Provincial Department of Agriculture and Provincial Ministry of Health; (C) Study doctor and agriculture instructor visiting a pesticide shop; (D) Schema of study design. (See colour version of this figure online).

Fig. 2.

Polonnaruwa District showing the seven administrative divisions, district health care facilities, and pesticide shops in January 2005. Shops are marked in black where neither dimethoate nor fenthion was stocked, green or red where fenthion or dimethoate were stocked, respectively, and grey where access to the shop could not be obtained. Agriculture in the poorly populated Mahaweli B area (Welikanda and Dimbulagala divisions) was not under the jurisdiction of the Dept of Agriculture and continued to use the insecticides. The Mahaweli river national park, where agriculture is banned, is marked in dark green. Abbreviations: DH, district hospital; GH, general hospital; PU, peripheral unit; RH rural hospital. (See colour version of this figure online).

Fig. 3.

Admissions to hospital with dimethoate or fenthion poisoning (A) or case fatality for pesticide poisoning (B) by quarter in Anuradhapura (red circles) and Polonnaruwa (blue squares) district general hospitals. (See colour version of this figure online).

Fig. 4.

Admissions to hospital (A, B) and case fatality for poisoning (C, D) with insecticide (green), herbicide (blue), unknown pesticide (purple), and any pesticide (red squares) in Polonnaruwa (A, C) and Anuradhapura (B, D) district general hospitals from June 2002 until June 2008. (See colour version of this figure online).