Prince Antwi-Agyei

Prince joined SHARE in 2012 to commence his SHARE-funded PhD on wastewater use in agriculture. An engineer with over seven years experience in the WASH sector, he also holds an MSc in Water Supply and Environmental Sanitation from the Kwame Nkrumah University of Science and Technology (KNUST) in Ghana, and a degree in Civil Engineering. Prior to joining LSHTM, Prince worked for TREND and KNUST.

Wastewater Use in Urban Agriculture in Ghana: An Exposure and Risk Assessment in Accra, Ghana.

Urban agriculture has become more important in Ghana. Urban farmers gain economic benefits as a result of the use wastewater in agriculture, but besides benefits, wastewater use in agriculture holds clear risks to human health and the environment. What remains unknown is: how important is disease transmission with the occupational domain (wastewater irrigation) compared to the transmission of human pathogens within the household (domestic) and neighbourhood (public) domains.

This study aimed to test the appropriateness of the current QMRA model and the multiple-barrier approach advocated by WHO guidelines to protect human health. The study followed various at-risk populations (farm workers, market vendors, street food vendors, and consumers of salad produce) along the farm-to-fork pathway. The risk of infection attributable to E. coli, adenovirus, and norovirus was analysed using a combination of HACCP and QRMA assessment. 

The objectives of the study were:

1. To identify and quantify key exposures and behaviours associated with the transmission of faecal pathogens in farmers using wastewater for irrigation.
2. To describe how produce quality changes from farm to fork, and to identify key risks factors and possible control points for faecal contamination of salad crops in urban agriculture in Accra, Ghana.
3. To assess how farmer, crop handler and consumer knowledge and awareness of wastewater irrigated produce related health risks influence their buying, consumption and food hygiene practices.
4. To estimate the norovirus pathogen infection risk among consumers of wastewater irrigated produce by QMRA using field-based data collected from Accra, Ghana.

The results of the study showed that irrigation water was significantly more contaminated than farm soil, though exposure to soil was found to pose the key risk to farmers due to hand-to-mouth events. Over 80% of produce samples were found contaminated with E. coli, with street food salad being the most contaminated, and that consumption of salads did not meet health standards. Risk factors identified for produce contamination included farm soil contamination, wastewater use for irrigation, poor hygiene, and operating with a hygiene permit. Awareness of the source of irrigation water was low, but despite the high awareness of health risk, consumers did not prioritise health indicators when buying produce from vendors. Similarly, farmers’ awareness of health risk did not influence their adoption of safer farm practices. The study recommends the promotion of interventions that would result in more direct benefits to producers and vendors, together with hygiene education and inspection, hygiene certification and enforcement of food safety byelaws in order to increase the uptake of the multi-barrier approach.

Further information on the study in Ghana can be accessed by following the links below.