relative toxicity of pesticides in the developing world
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Relative toxicity of pesticides in the developing world. A Dawson, M Fahim, I Gawarammana, N Buckley, M Eddleston, G Manuweera South Asian Clinical Toxicology Research Collaboration, Faculty of Medicine, University of Peradeniya. Pesticide Poisoning Problem. Asia 300,000 deaths /year - PowerPoint PPT PresentationTRANSCRIPT
South Asian Clinical Toxicology Research Collaboration
Relative toxicity of pesticides Relative toxicity of pesticides in the developing world in the developing world
A Dawson, M Fahim, I Gawarammana, N Buckley, M Eddleston, G Manuweera
South Asian Clinical Toxicology Research Collaboration, Faculty of Medicine, University of Peradeniya
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South Asian Clinical Toxicology Research Collaboration
PesticidePesticide PoisoningPoisoning ProblemProblem
Asia 300,000 deaths /year
– Underestimate Sri Lanka
– 17000 admissions
– 35% ICU
– 10% Die
– (20% if symptomatic)
South Asian Clinical Toxicology Research Collaboration
SACTRC: OverviewSACTRC: Overview Observational Cohort of
19,000 patients– Nested clinical trials
Community studies
15 postgraduate students
International Partners:– UK, USA, Denmark,
Germany, Portugal
Chilaw.
South Asian Clinical Toxicology Research Collaboration
Anuradhapura District 2006Anuradhapura District 2006
Peripheral Hospitals1942 admissions
Peripheral Hospitals1942 admissions
11071107
Anuradhapura General Hospital1908 admissions
Anuradhapura General Hospital1908 admissions
South Asian Clinical Toxicology Research Collaboration
BackgroundBackground Clinical impact of pesticide poisoning is a function of both:
– the intrinsic toxicity of the pesticide
– and availabilty of treatment resources Effective pesticide regulation
– can be threatened by illegal importation
– considers agricultural and economic outcomes. Effective regulation in Sri Lanka with targeted pesticide
restrictions
– reduced pesticide deaths
– maintained agricultural production. Do targeted bans of insecticides to prevent deaths from self-poisoning
result in reduced agricultural output? (Manuweera G )
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South Asian Clinical Toxicology Research Collaboration
Pesticide RestrictionPesticide Restriction
•Gunnell D, Fernando R, Heganawathna N et al Journal of Epidemiology 2007;1–8
South Asian Clinical Toxicology Research Collaboration
AimAim To provide information about the relative toxicity
of pesticides that:
– could inform regulatory policy
– and may assist in the development of a minimum pesticide list
Eddleston,M. et al. Pesticide poisoning in the developing world--a minimum pesticides list. Lancet 360[9340], 1163-1167. 2002.
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South Asian Clinical Toxicology Research Collaboration
MethodsMethods Data was prospectively collected from a cohort
of consecutive patients from April 2002 to April 2007.
Identification of pesticides was based on– history or positive identification of the
container– and plasma assays in some cases.
Case fatality calculated.
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South Asian Clinical Toxicology Research Collaboration
ResultsResults 6449 patients who ingested a pesticide and were
analysed.
Plasma assayed for pesticides– 60% of all patients– 90% of organophosphate admissions– Confirmed the history in over 90% patients.
. Overall mortality 11.2%
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The case fatality for commonly ingested pesticides The case fatality for commonly ingested pesticides
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South Asian Clinical Toxicology Research Collaboration
Dying is too easy for death to be a “Hard Dying is too easy for death to be a “Hard Outcome” in the developing world.Outcome” in the developing world.
South Asian Clinical Toxicology Research Collaboration
South Asian Clinical Toxicology Research Collaboration
Primary Rural HospitalsPrimary Rural HospitalsLalith Senarathna: Master’s Thesis 2007 www.sactrc.orgLalith Senarathna: Master’s Thesis 2007 www.sactrc.org
Poor antidote stocking Poor antidote utilisation A gap between actual practice and perceived
practice
“We are like frogs in a well”
Clustered RCT Antidote Stocking & Academic Detailing
South Asian Clinical Toxicology Research Collaboration
3 compounds: 60% of 3 compounds: 60% of mortalitymortality
South Asian Clinical Toxicology Research Collaboration
South Asian Clinical Toxicology Research Collaboration
Results: Pesticide WithdrawalResults: Pesticide Withdrawal Assuming paraquat and dimethoate were removed from
the market – and that people substituted the next most toxic compound in that
class
Paraquat removal could lead to a 30% reduction in deaths Dimethoate removal could lead to a 12% reduction.
Extrapolation of this data to the national figures of 3000 deaths per year from pesticides suggests a reduction in deaths of about 1200 per year.
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South Asian Clinical Toxicology Research Collaboration
Pesticide Restriction in Sri LankaPesticide Restriction in Sri Lanka
•Gunnell D, Fernando R, Heganawathna N et al Journal of Epidemiology 2007;1–8
Bans 2008•Paraquat•Dimethoate•Fenthion
South Asian Clinical Toxicology Research Collaboration
Results (2)Results (2) Pesticide Withdrawal November 2007
– Paraquat 6.5% Concentration Model a 10 % reduction
– Dimethoate & Fenthion to be withdrawn over 3 years from 2008
– Paraquat withdrawn from 2009 Modeled Substitutions
– Worst CFR within the class– Median CFR within the class
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South Asian Clinical Toxicology Research Collaboration
Projected CFR 95% CIProjected CFR 95% CI
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South Asian Clinical Toxicology Research Collaboration
DiscussionDiscussion Benefit of dimethoate restriction may be an
underestimation– clinical research units has been shown to reduce
mortality
Mortality from paraquat is likely to be a robust estimate as there is no treatment which clearly alters outcome.
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South Asian Clinical Toxicology Research Collaboration
When can we decide ?When can we decide ?
South Asian Clinical Toxicology Research Collaboration
South Asian Clinical Toxicology Research Collaboration
DiscussionDiscussion within a pesticide class there is a significant
range of mortality. The usefulness of point estimates of zero
fatalities which have wide confidence intervals could be enhanced by
– including other more sensitive clinical markers of toxicity
– based on animal toxicity data
– and known mechanisms of action.
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South Asian Clinical Toxicology Research Collaboration
Discussion (2)Discussion (2) This data can inform a restricted pesticide
policy that operates within the constraints of local health systems.
A cost-minimization approach could be explored, using models similar to those developed for drug regulation and subsidy.
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South Asian Clinical Toxicology Research Collaboration
ConclusionConclusion
There is sufficient information to iteratively develop a minimum pesticide list.
Such implementation will require continuous sentinel monitoring of usage and clinical presentations.
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