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)
Dec 06, 2014
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!!!