Low-cost options for reducing consumer health risks from farm to fork where crops are irrigated with polluted water in West Africa

TY - BOOK

T1 - Low-cost options for reducing consumer health risks from farm to fork where crops are irrigated with polluted water in West Africa

AU - Amoah, Philip

AU - Keraita, Bernard

AU - Akple, Maxwell

AU - Drechsel, Pay

AU - Abaidoo, Robert

AU - Konradsen, Flemming

PY - 2011

Y1 - 2011

N2 - This report is based on research carried out over the last 5 years in West Africa, particularly in Ghana. The research aimed at developing appropriate intervention measures to reduce health risks posed to consumers from pathogens in domestic wastewater used raw or diluted for irrigation in urban and peri-urban vegetable farming. A variety of methods for participatory action research were used, where various key stakeholders at different levels were actively involved in identifying, testing and assessing intervention measures. Some components of the study have been published in journals earlier, but it is only in this report that all components are included and discussed together in one comprehensive synthesis. At farm level, the studies showed that sedimentation ponds and filtration techniques like sand filters could reduce the number of helminth eggs to acceptable levels in both dry and wet seasons. However, these interventions could not reduce fecal coliforms to acceptable levels. Among various irrigation methods, low-head bucket drip kits achieved high removal levels of up to 6 log units of fecal coliforms on vegetables. Removal rates for fecal coliforms were usually higher during the dry season. Low sunshine intensities, and splashing of contaminated soils from the use of watering cans and rainfall reduced the effectiveness of interventions during the wet season. To avoid splashing induced by watering cans, simple modifications on their use like lowering the watering height and using a rose on the mouth of the watering can reduced contamination levels on vegetables showing how simple adjustments can lead to significant contamination reduction. Cessation of irrigation was effective on longer durations and in the dry season but withdrawing from irrigating affected the physical quality and yields of vegetables, leading to low acceptance of this possible intervention by farmers. Suggestions to reduce consumer health risks by growing different crops as well as to use mostly alternative safer water sources like groundwater at the existing farming sites were unsuccessful. The tested market-based interventions had generally less impact on the contamination carried over from the farm, like through the support of microbial die-off but they remain important to prevent new or additional contamination. At the consumer level, the removal of outer cabbage leaves and vegetable washing proved most successful. Washing lettuce, especially with recommended sanitizers and longer contact time, reduced bacterial contamination by around 3 log units, while most washing methods commonly used in Ghana proved to be of little efficacy. There are also alternative and more cost-effective sanitizers used in Francophone West Africa, which could be introduced in Ghana. To protect the consumer according to the health-based targets suggested by WHO, combining intervention measures at different levels appear most promising. Their actual impact will however depend on their adoption rate. Possible strategies to enhance adoption should be based on social marketing, education, market and nonmarket incentives, and inspections. In the context of a low-income country like Ghana where wastewater treatment has a low coverage and does not protect public health, these findings show that a range of alternative options exist that can significantly reduce the risks from contaminated vegetables in line with the WHO wastewater use guidelines (WHO 2006).

AB - This report is based on research carried out over the last 5 years in West Africa, particularly in Ghana. The research aimed at developing appropriate intervention measures to reduce health risks posed to consumers from pathogens in domestic wastewater used raw or diluted for irrigation in urban and peri-urban vegetable farming. A variety of methods for participatory action research were used, where various key stakeholders at different levels were actively involved in identifying, testing and assessing intervention measures. Some components of the study have been published in journals earlier, but it is only in this report that all components are included and discussed together in one comprehensive synthesis. At farm level, the studies showed that sedimentation ponds and filtration techniques like sand filters could reduce the number of helminth eggs to acceptable levels in both dry and wet seasons. However, these interventions could not reduce fecal coliforms to acceptable levels. Among various irrigation methods, low-head bucket drip kits achieved high removal levels of up to 6 log units of fecal coliforms on vegetables. Removal rates for fecal coliforms were usually higher during the dry season. Low sunshine intensities, and splashing of contaminated soils from the use of watering cans and rainfall reduced the effectiveness of interventions during the wet season. To avoid splashing induced by watering cans, simple modifications on their use like lowering the watering height and using a rose on the mouth of the watering can reduced contamination levels on vegetables showing how simple adjustments can lead to significant contamination reduction. Cessation of irrigation was effective on longer durations and in the dry season but withdrawing from irrigating affected the physical quality and yields of vegetables, leading to low acceptance of this possible intervention by farmers. Suggestions to reduce consumer health risks by growing different crops as well as to use mostly alternative safer water sources like groundwater at the existing farming sites were unsuccessful. The tested market-based interventions had generally less impact on the contamination carried over from the farm, like through the support of microbial die-off but they remain important to prevent new or additional contamination. At the consumer level, the removal of outer cabbage leaves and vegetable washing proved most successful. Washing lettuce, especially with recommended sanitizers and longer contact time, reduced bacterial contamination by around 3 log units, while most washing methods commonly used in Ghana proved to be of little efficacy. There are also alternative and more cost-effective sanitizers used in Francophone West Africa, which could be introduced in Ghana. To protect the consumer according to the health-based targets suggested by WHO, combining intervention measures at different levels appear most promising. Their actual impact will however depend on their adoption rate. Possible strategies to enhance adoption should be based on social marketing, education, market and nonmarket incentives, and inspections. In the context of a low-income country like Ghana where wastewater treatment has a low coverage and does not protect public health, these findings show that a range of alternative options exist that can significantly reduce the risks from contaminated vegetables in line with the WHO wastewater use guidelines (WHO 2006).

KW - Faculty of Health and Medical Sciences

KW - wastewater

KW - wastewater use

KW - food hygiene

U2 - 10.5337/2011.201

DO - 10.5337/2011.201

M3 - Book

T3 - IWMI Research Report

BT - Low-cost options for reducing consumer health risks from farm to fork where crops are irrigated with polluted water in West Africa

PB - International Water Management Institute

CY - Colombo Sri Lanka

ER -