Interdisciplinary approach to environmental

health research related to wastewater and

excreta use in agriculture in Vietnam

Pham Duc P, Nguyen-Viet H, Tu Vu-Van, Khuong Nguyen-

Cong, Nga Do-Thu and Zinsstag J. Hanoi School of Public Health (HSPH)

Contents

• Introduction

• Aim & objectives

• Study sites

• Health impacts: Epidemiology and Microbial risk assessment

• Environmental impacts: Material Flow Analysis

• Social aspects

• Conclusions

Introduction

Advantages

• In Vietnam, the use of wastewater & excreta in

agriculture has a long history

• Many benefits: reliable nutrients and water

source; reduce chemical fertilizer

Risks

• Wastewater & excreta contain variety of

pathogens (viruses, bacteria, protozoa &

parasites)

• Enteric pathogens is a fundamental consideration

of public health (diarrhoea, parasitic diseases)

Interventions (biomedical, systems, engineering, behavioral or in combination): Efficacy, effectiveness and equity studies measured in relation to risks

Critical control points: comprehensive biomedical, epidemiological, ecological, social, cultural and economic assessment

Analysis of interrelations between environmental sanitation systems, health status and well-being

Health status

Exposure to pathogens (viruses, bacteria, protozoa, helminths)

Health related and help seeking behavior

Food chain

Excreta, Wastewater, Water

Nutrients: N, P

Chemical pollutants

Ecological risks and use of resources

MFA

Health risks-impacts, Affected population

QM

RA

Vulnerability, resilience and equity patterns

SSA

Structure of society

Empowerment

Economic status

EPI

Physical environment Social, cultural and economic environment between systems and

interventions

Dynamic interactions

(Water and Sanitation)

Nguyen-Viet et al. 2009. EcoHealth

Study aim & objectives

Aim: To enhance our understanding on health & environmental impacts & social aspects of wastewater and excreta use in agriculture by combining health & environmental & social assessment approaches.

Objectives:

1. To assess health risks for helminth infections and diarrhoea among people working and living in agricultural settings, where wastewater and excreta are intensively used.

2. To analyse nutrient fluxes of nitrogen and phosphorus in an environmental sanitation and agricultural system, by using material flow analysis (MFA).

3. To understand the people’s awareness & motivations of hygiene as a risk to human health related to excreta and wastewater management.

Study sites (2008-2010)

Hoang Tay & Nhat Tan communes

Vietnam: Area: 331,000 km2

Population: 87 million (MOH, 2011)

Rural population: 74%

Population below poverty line: 29%

Situation of the study sites

Use of excreta as fertilizer: 51%

Households: 4,300

Inhabitants: 16,200

Single vault latrine: 56% Raise animals: 84%

Use of Nhue River water: 93% Local ponds: 10%

The environmental sanitation and agricultural systems

Landfill

Composting

(5)

Water

source Household (wastes)

Solid

wastes

Excreta/

Manures

Food

Waste

water

Sewages (2)

Sanitation

Irrigation system

(4) Pond (3) Crop

Livestock

Nhue River (1)

Pumping stations

Wastewater from Hanoi City (households, industries, hospitals,..)

I. Health risk assessment

• Epidemiological studies (EPI)

– Cross-sectional study (Prevalence and risk factors for helminth

infections)

– Cohort and nested case-control studies (Incidence rates & risk factors

of diarhoea)

• Quantitative microbial risk assessment (QMRA)

– Hazard identification, dose-response analysis, exposure assessment

and risk characterization

– Estimated risk of diarrhoea caused by E. coli, Giardia and

Cryptosporidium at the specific exposure points

II. Material flow analysis

Develop scenario of target site and

propose mitigation measure

Literature Review

Define a preliminary MFA system

with main processes and mass flows

Conduct field survey to collect primary,

secondary data

Adapt MFA model

Conduct uncertainty analysis (sensitivity,

plausibility assessments)

Model validated successfully

Yes

Calibration of model

Development of model

Development of scenario

III. Social aspects

• In-depth interviews, participatory observations, focus

group discussions

• Protection Motivation Theory (Roger, 1983)

Threat appraisal

- Vulnerability

- Severity

Coping appraisal

- Response efficacy

- Self efficacy

Motivation

Action

Intention

- Fear

Habit

Results – Health risks • Prevalence: any helminths (47%), A. lumbricoides (24%), T. trichiura

(40%), hookworm (2%).

• Incidence rate of diarrhoea: 0.25-0.32 episodes per person-year (pppy)

• Estimated annual risks of diarrhoea:

– Giardia: 0.13 - 0.50 pppy

– Cryptosporidium: 0 - 0.15 pppy

– E.coli: 0 - 0.24 pppy

• Risk factors for helminth infections and diarrhoea

– Direct contact with water from Nhue river (OR: 2.4; 95% CI: 1.2 – 4.7)

– Handling human excreta in field work (OR: 5.4; 95% CI: 1.4 – 21.1)

– Not use of protective measures at work (OR: 6.9; 95% CI: 3.5 – 13.9)

– Never handwashing with soap (OR: 3.3; 95% CI: 1.8 – 6.3)

– Drinking rainwater (OR: 5.4; 95% CI: 2.4 – 12.1)

Nitrogen and Phosphorus fluxes in wastewater in different scenarios

Results – Environmental impacts

109

35

199

71

115

32

100

35

0

20

40

60

80

100

120

140

160

180

200

Nitrogen Phosphorus

Wastewater to drainage system

To

nn

es p

er

year

Year 2008

Year 2020

Year 2020 with improved on-site

sanitation

Year 2020 with reuse wastewater

Results – Social aspects • People perceive wastewater as smelly and black in colour, whose

contact can cause skin problems & diarrhoea.

• Correlation between motivation and hygiene practice

Self-efficacy

Response-efficacy

Vulnerability

Fear of disease

Severity

Motivation

Hygiene

practice

Hygiene

practice in

relation to

wastewater use

0.35

0.30

0.30

0.18

0.11

0.19

0.32

Conclusions • Health risk assessment

– Exposed to wastewater and excreta increase risks for helminth infections and diarrhoea

– Basic personal hygiene measures and food hygiene increase to protect against diarrhoea

– Annual risks of diarrhoea exceeded the acceptable risk levels set by the WHO (at least 3 times)

• Environmental impacts – Uncontrolled on-site sanitation system discharge large amount of nutrients into the

environment (drainage system & surface water)

– If nutrient management not improved, levels of nutrients due to wastewater, faecal sludge, and organic solid waste will double until 2020.

• Social aspects – Raising farmers’ awareness of health risks associated with wastewater reuse and

ability to cope with these risks enhance safe handling and health improvement practices.

• QMRA, MFA and PMT methods could use the same platform, which is an environmental and agriculture system, to introduce a combined environmental, health risk & social aspects.

Acknowledgements

Thank you for your attention!!!