Interdisciplinary approach to environmental health research related to wastewater and excreta use in agriculture in Vietnam
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
IntroductionAdvantages• In Vietnam, the use of wastewater & excreta in agriculture has a long history• Many benefits: reliable nutrients and water source; reduce chemical fertilizerRisks• Wastewater & excreta contain variety of pathogens (viruses, bacteria, protozoa & parasites)• Enteric pathogens is a fundamental consideration of public health (diarrhoea, parasitic diseases)
Analysis of interrelations between environmental sanitation systems, health status and well-being Health status (Water and Sanitation) Exposure to pathogens (viruses, bacteria, protozoa, helminths) Health related and help seeking behavior QMRA EPI Health risks-impacts, Affected population Dynamic interactions Physical environment Social, cultural and between systems and economic environment interventions Food chain Structure of society Excreta, Wastewater, Water Empowerment Nutrients: N, P Economic status Chemical pollutants SSA MFA Ecological risks and use Vulnerability, resilience of resources and equity patterns Critical control points: comprehensive biomedical, epidemiological, ecological, social, cultural and economic assessment Interventions (biomedical, systems, engineering, behavioral or in combination):Nguyen-Viet et al. 2009. EcoHealth Efficacy, effectiveness and equity studies measured in relation to risks
Study aim & objectivesAim: 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)Vietnam: Area: 331,000 km2 Population: 87 million (MOH, 2011) Rural population: 74% Population below poverty line: 29% Hoang Tay & Nhat Tan communes
Situation of the study sites Raise animals: 84% Households: 4,300 Single vault latrine: 56% Inhabitants: 16,200 Use of excreta as fertilizer: 51% Local ponds: 10% Use of Nhue River water: 93%
The environmental sanitation and agricultural systems Water Household (wastes) source Excreta/ Solid Landfill Waste water Manures wastes Sanitation Composting Food (5) Sewages (2) Livestock Pond (3) Irrigation system Crop (4) Pumping stations Nhue River (1) 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 Literature Review Development of model Define a preliminary MFA system with main processes and mass flows Conduct field survey to collect primary, secondary data Calibration of model Adapt MFA model Conduct uncertainty analysis (sensitivity, plausibility assessments) Yes Model validated successfully Develop scenario of target site and Development of scenario propose mitigation measure
III. Social aspects• In-depth interviews, participatory observations, focus group discussions• Protection Motivation Theory (Roger, 1983) Threat appraisal - Vulnerability - Fear - Severity Motivation - Response efficacy - Self efficacy Intention Habit Coping appraisal Action
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)
Results – Environmental impactsNitrogen and Phosphorus fluxes in wastewater in different scenarios 199 200 180 160 140 Year 2008 Tonnes per year 115 120 109 Year 2020 100 100 Year 2020 with improved on-site 80 71 sanitation Year 2020 with reuse wastewater 60 35 32 35 40 20 0 Nitrogen Phosphorus Wastewater to drainage system
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 0.35 Fear of disease Hygiene 0.11 practice 0.32 Self-efficacy 0.30 Motivation Response-efficacy Hygiene 0.30 0.19 practice in Severity relation to wastewater use Vulnerability 0.18
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.