Health risk of human excreta and wastewater reuse in agriculture in Hanam province, Vietnam: a combined approach of health and social research

The use of excreta in agriculture can help communities grow more food and make use of nutrient resource. However, it should be done safely to maximize public health gains and environmental benefits. The risks associated with the use of excreta are mostly from excreta-related pathogens. Health risks associated with excreta use are linked mainly to occupational exposure of those who handle the excreta and consumption of potentially contaminated products. In some places in developing world like in Vietnam, the use of excreta in agriculture and aquaculture is still common and the health risk related to this practice is a public health issue if excreta and wastewater are not properly managed. The general goal of this project was to further understand the health risks related to the use of wastewater and excreta among different groups of people in Hanam province, North Vietnam with a focus on helminth infections and diarrhoeal diseases using a combined approach of health and social social research. This project contributed to a larger framework on the combination of health, ecological, socio-economic and cultural assessments to efficiently and effectively address measures of improving health and environmental sanitation in developing countries.

The results showed that in both rainy and dry season, 95.8% and 92.3% of the surveyed household had a latrine respectively. Among those, 60% and 51.5% used of human excreta in agriculture in the rainy and dry season, respectively. Most of the households used domestic wastewater and water from Nhue river for rice and vegetable cultivation, and fish breeding (86.4% and 85.9%, respectively). Households keeping domestic animal at their house were most commonly observed in the area (78.9% and 62.8% in rainy and dry season, respectively). Cross-sectional studies showed that 47.6% of subjects in rainy season 46.3% in dry season were infected with at least one of the three helminth species Ascaris lumbricoides, Trichuris trichiura and hookworm. The use of human excreta was significantly associated with the risk of general helminth infection in both rainy and dry season with a prevalence rate of 57% and 58%, respectively in the group exposed to excreta. In addition, there was a significant difference in helminth infections between people who were exposed to wastewater (57%) in rainy season and in the dry season (52%) and those who were not.

The diarrhoeal infection risks for both single and yearly exposure revealed that G. lamblia caused higher infection risks than E. coli and C. parvum, particularly when exposed during transplanting rice seedlings (4.10-2). Infection risk is far greater when handling excreta. When exposed to Nhue river water during vegetable cultivation, annual infection risk by E. coli, G. lamblia and C. parvum amounted to 2.9x10-4, 3.9x10-2 and 2.7x10-2. All these calculated infection risks are higher than the acceptable risk from wastewater and excreta reuse recommended by WHO at 1x10-4. To put QMRA results into practice, a one-week training entitled “Environmental health risk assessment of microbiological hazards in water and foods in Vietnam“ was organized successfully with great interest and feedback from participant. The Department of Food Administration (Vietnam Ministry of Health) is being interested in the training and would like to make the training materials available for a larger use in the form of a brochure on guideline for QMRA to be published by the Vietnam Ministry of Health.

Finally, the social research showed that people perceive wastewater as smelly and black in colour, whose contact can cause skin problems (e.g. itching). Farmers feel that fish from the Nhue river and vegetables irrigated with wastewater are potential causes for diarrhoea. When working with wastewater, women use protective wear more often than men. This is attributed to the fact that women spend more time in the fields than men and pay more attention to their skin and beauty. The developed questionnaire focused on eight different aspects, was developed and validated. These aspects centred on: fear of disease, self-efficacy, response-efficacy, severity, vulnerability, motivation, hygiene practice, and hygiene practice in relation to wastewater use. The test results show that motivation can be improved by increasing fear of disease, self-efficacy, response-efficacy, and severity. However, the relation between motivation and hygiene practice was rather weak, then other aspects have to be considered.

In conclusion, this project showed the evidence on health risk associated with wastewater and excreta re-use in agriculture in Vietnam. Improving people’s awareness with regard to risks; using protective measures; and personal hygiene practices would be the most effective intervention measures to reduce the risk of infection. However, the safe handling and management of excreta, and treatment of wastewater at the household level also constitute effective and sustainable solution to protect health as well as the environment. The follow–up of this project is being done in the framework of a newly acquired project. The latter is focusing on the assessment of exposure to human excreta and wastewater in the same community and deepening our understanding on the pathogen behaviors (die-off, growth rate) in excreta to better estimate the health risk in the community. This project could help the postdoc establish his research partnership with local institution and develop further the collaboration in the future. The project also supported post-graduate students in Hanoi and seems to be on good track to have impact on policy in the country.

 

Address in Switzerland

Nguyen Viet Hung, PhD
Department of Public Health and Epidemiology
Swiss Tropical Institute
Socinstrasse 57, P.O Box
CH-4002 Basel, Switzerland
Tel: +41 61 284 83 15
Fax: +41 61 284 81 05
Email: hung.nguyen@unibas.ch

 

Research-partner / partner institution

Phung Dac Cam, MD, PhD, Professor
Chief of Division of Enteric Infections
Department of Microbiology
National Institute of Hygiene and Epidemiology
1, Yersin street, Hanoi, Vietnam
Tel:  +84 4 8219074
Fax: +84 4 971 9045
E-mail: cam@fpt.vn

Vegetable grown with wastewater from a discharge river in Kim Bang, Hanam Province

Typical complex of house, fish pond and livestock in Kim Bang, Hanam Province

Farmers exposed to wastewater and excreta in the field in Kim Bang, Hanam Province