Post on 31-May-2015
Susmita Dasgupta, Craig Meisner, David Wheeler, Nhan Thi Lam, Khuc Xuyen
The World Bank and The National Institute of Occupational and Environmental Health, Vietnam
Pesticide Poisoning of Farm Workers: Implications of Blood Test Results from
Vietnam
Pesticide consumption (metric tons)in Vietnam
Source: FAO, 2004
Pesticide consumption has more than doubled in the past decade
In 2000, a nation-wide survey by PPD found:– 2,500 kg of banned pesticides (Methamidophos, DDT and others).– 4,753 litres and 5,645 kg of illegally imported/ counterfeit pesticides.
In 2000, another survey in the South found:– 96.6% of the farmers over-use pesticides– 95% of the farmers pour residual spray into canals/ ditches/ re-apply it on other plants/ over-apply it to the same crop to get rid of it.
Alarming Composition/Application of Pesticides
Vietnam has limited secondary data on Health Effects of pesticides
1. Survey of Rice Farmers (pesticide applicators) in Mekong delta.
2. Clinical Exam
3. Blood Test
Methodology:
Questions of Interest:
1. What is the incidence of pesticide intoxication?
2. Are self-reported data good indicators of actual intoxication?
3. What are the determinants of pesticide intoxication?
Application of pesticides: survey evidence
Class No. of
applications Pesticide amount
(kg a.i.) Intensity
(kg a.i./appl.)
Summer- Autumn
Autumn- Winter
Summer- Autumn
Autumn- Winter
Summer- Autumn
Autumn- Winter
2-dimethylaminopropane-1,3-dithiol 106 37 78.36 10.91 0.74 0.29
Chloroacetamide 52 36 29.55 10.08 0.57 0.28
Dithiolane 49 33 31.25 7.51 0.64 0.23
DMI: triazole 208 92 22.19 5.93 0.11 0.06 Carbamate 27 10 24.63 1.63 0.91 0.16
Organophosphate 20 16 12.76 8.68 0.64 0.54
MBI: reductase 57 9 19.99 1.16 0.35 0.13
Multi-site: inorganic 3 2 3.97 12.80 1.32 6.40 Phenoxycarboxylic acid 18 16 8.77 4.22 0.49 0.26
Benzimidazole 14 10 7.23 4.82 0.52 0.48
Dicarboximide 16 11 6.56 0.64 0.41 0.06
Pyrethroid 71 51 3.50 2.21 0.05 0.04 Phosphorothiolate 6 4 3.20 0.88 0.53 0.22
Antibiotic 31 34 2.90 1.17 0.09 0.03
Multi-site: alkylenebis (dithiocarbamate) 1 4 1.36 1.79 1.36 0.45
Neonicotinoid 22 7 2.43 0.04 0.11 0.01 Glycine derivative 1 0 1.85 0.00 1.85 -
Fiprole 34 22 1.03 0.71 0.03 0.03
Unknown 8 2 1.32 0.05 0.16 0.03
Pyrimidinyloxybenzoic 35 3 1.12 0.06 0.03 0.02 Aryloxyphenoxypropionate 25 8 0.68 0.26 0.03 0.03
Cyclodiene 0 2 0.00 0.88 - 0.44
Quinolinecarboxylic acid 3 4 0.27 0.45 0.09 0.11
Sulfonylurea 15 9 0.41 0.14 0.03 0.02 Multi-site: phthalimide 0 1 0.00 0.39 - 0.39
Non-ester pyrethroid 1 2 0.05 0.15 0.05 0.07
Benzimidazole precursor 1 0 0.07 0.00 0.07 -
Hexopyranosyl antibiotic 2 1 0.01 0.02 0.01 0.02
Total 826 426 265.46 77.58
* A total number of 1252 applications by 190 farmers. Chemical class was derived from the British Crop Protection Council e-Pesticide Manual, Thirteenth Edition (BCPC, 2003).
Health Effects of Organophosphates and Carbamates cited in Medical Literature
Acute:
• Mild headaches
• Flu-like symptoms
• Skin rashes
• Blurred vision
• Other neurological disorders
Chronic:
• Cardiopulmonary problems
• Neurological and hematological symptoms
• Adverse dermal effects
Blood Test for the Detection of Acute and Chronic Pesticide Poisoning
Cholinesterase Enzyme (AchE)Test: (poisoning from organophosphates and carbamates)
• Low Acute Poisoning: Reduction of numerical value of AchE in red cells and in plasma >25%
• High Acute Poisoning: Reduction of numerical value of AchE in red cells and in plasma >33%
• Chronic Poisoning: Reduction of numerical value of AchE in red cells >66%
Specific Health Effects found in the Survey
0
10
20
30
40
50
60
70
Skinirritation
Headache Otherproblems
Eyeirritation
Dizziness Shortness ofbreath
Vomiting Fever Diarrhea Convulsions
Per
cent
age
% responding 'Yes'
• 98% of the farmers in the survey reported health problems
• 88% of the respondents experienced multiple health effects, with the maximum number of ailments as nine
Blood (Cholinesterase Enzyme) Test Results
Low acute
poisoning1
9%
High acute
posioning2
5%
Chronic
poisoning3
21%
Poisoning35%
Normal65%
(Correlation between each individual symptom and blood test results were conducted. The
highest correlation found was 0.17)
Self-reported symptoms are not reliable indicators of actual pesticide poisoning
Determinants of Cholinesterase Enzyme Inhibition: Regression Analysis
Model 1 Model 2 Variable Coefficient Coefficient PESTAMT -0.098**
(-2.09) -0.105** (-2.24)
PWHOIab 0.039*** (2.51)
0.030** (2.08)
PWHOII 0.003 (0.46)
PWHOIII 0.008 (1.19)
PWHOU 0.006 (0.90)
PTRAIN 0.262 (1.22)
NPROTECT -0.443* (-1.86)
-0.440* (-1.91)
IPMD 0.043 (0.19)
An Giang -0.118 (-0.33)
Can Tho -0.821** (-2.49)
-0.628** (-2.39)
Long An -0.449 (-1.36)
Tien Giang -0.841*** (-2.58)
-0.605** (-2.41)
Observations 187 187
* - significant at the 1% level; ** - significant at the 5% level; *** - significant at the 10% level
Determinants of Cholinesterase Enzyme Inhibition: Regression Results
• Farmers applying more hazardous pesticides (WHO Ia & Ib) are more likely to suffer
• Incidence of pesticide poisoning can be significantly reduced by suitable averting behavior
• Pesticide poisoning in Vietnam revealed strong provincial pattern. This raises the concern that the environment in certain regions may have been contaminated from prolonged exposure to toxic pesticides
Summary and Conclusions
• Health effects of organophosphates and carbamates is serious in Mekong Delta, Vietnam
• Self-reported symptoms have very weak associations with actual poisoning
• Suitable averting behavior while handling pesticides should be advocated
• Significant provincial differences in poisoning incidence implies that pesticide contamination may be pervasive in certain areas
• Tests of pesticide residues in surface/ground water and soil is necessary