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