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

Abstract

To identify interventions which reduce health risks of consumers where highly polluted irrigation water is used to irrigate vegetables in West Africa, scientists worked over 5 years with farmers, market traders and street food vendors in Ghana. The most promising low-cost interventions with high adoption potential were analyzed for their ability to reduce common levels of pathogens (counts of fecal coliforms and helminth eggs). The analysis showed the combination potential of various interventions, especially on-farm and during vegetable washing in line with the World Health Organization (WHO) guidelines. The tested market-based interventions were important to prevent new or additional contamination

Microbiological quality of lettuce (Lactuca sativa) irrigated with wastewater in Addis Ababa, Ethiopia and effect of green salads washing methods

“…The reason can be several: a) the Akaki river offers more dilution than the smaller streams e.g. in Kumasi, b) furrow and flood irrigation reduce leaf contact (Ghana: overhead irrigation with watering cans), and c) irrigation frequency in Addis (1-2 times per week) is much lower than in hot Ghana where lettuce is irrigated twice a day which also allows more natural die-off (Keraita et al 2002;Amoah et al 2011). Unfortunately, on some farming sites vegetables including lettuce are washed by farmers and traders with the water used for irrigation to remove soil residues and keep it fresh until selling.…”

On-farm treatment options for wastewater, greywater and fecal sludge with special reference to West Africa

“…As these highly polluted waters are used for irrigation in and around four of five cities across low-income countries, the likelihood of the transmission of excreta-related diseases to farmers and, for example, vegetable consumers is very high (RaschidSally and Jayakody 2008). The same applies to West Africa, where high levels of fecal contamination of water sources and vegetables in urban farming sites have been reported across the region (Amoah et al 2011;Okafo et al 2003;Niang 1999). …”

“…Van Donsel and Geldreich (1971), for example, stated that 100-1,000 times more fecal coliforms were recovered from sediments than in the overlying water. To avoid this situation, different options can be applied as further illustrated by Keraita et al (2010) and Amoah et al (2011). These include the use of self-made stairs or a wooden log across the pond (Figure 4(a)) to prevent a farmer from stepping into the pond or touching the ground with their cans.…”

“…Complementary options for safeguarding public health are needed until better alternatives are available. These options can range from safer irrigation practices to crop restrictions or post-harvest handling, and should ideally be combined to form multiple barriers for cumulative risk reduction (Amoah et al 2011;Bos et al 2010). Where industrial development and chemical contamination remain localized, these barriers should focus on reducing pathogen loads in irrigation water and on crops eaten raw…”

UN World Water Development Report 2017: "Wastewater: The untapped resource"

“…Where wastewater treatment is insufficient and wastewater irrigation common, safety measures can be implemented at critical control points along the food chain (from 'farm to fork') as described by the World Health Organization (WHO, 2006a) and illustrated by Amoah et al (2011), among others. Care has to be taken about gender roles which can change from the farm level to wholesale, and to retail .…”