Written by PhD student Prince Antwi-Agyei for the SHARE Consortium.
Have you ever wondered why people continue to use wastewater for vegetable farming and other purposes?
Wastewater can pose health risks to consumers and farmers of irrigated produce, such as diarrhoeal diseases and helminth infections. While we know there are health risks associated with wastewater use, we are unclear about how these risks differ at various stages of the food chain.
I conducted a study that involved interviewing about 700 farmers, vendors, chefs, and consumers on their hygiene behaviours and practices in Accra, Ghana, as well as testing 500 produce samples for E. coli contamination.
Surprisingly street salad was the most contaminated (4.1 Log E. coli/g or >12,000 E. coli/g) among all food samples, even more than raw produce directly irrigated with wastewater such as drain water. Despite this, about 80% of all produce collected from farms, markets, street vending sites and restaurants were also contaminated with E. coli.
The main causes of contamination included the use of irrigation water, contaminated soil, and use of poultry manure at the farms. At the street vending sites, poor sanitation and hygiene practices could influence the contamination levels, while the cut nature of salad facilitated the growth of microorganisms. Another unexpected observation was the fact that some street vendors who bought their produce directly from the farms actually wash their produce directly with the wastewater (dug-outs). Other risk factors for street salad could be the time between salad preparation and consumption, and not covering salad. In fact, vendors were observed to leave salad uncovered for almost 100 minutes every 3 hours.
In Ghana, the Food and Drug Authority recommends that ready-to-eat foods including salad that are consumed uncooked should only be considered satisfactory for consumption if the levels of E. coli in the food does not exceed 100 cfu/g. Based on this standard, only 10% of the prepared salad collected from street food vendors and 40% of those from restaurants could be considered safe and satisfactory for consumption.
How can we reduce health risks?
There are things we can all do to reduce the health risk arising from food contamination. For consumers, eating from hotels and restaurants could pose some health risks, but this could be reduced if the Food and Drug Authority enforces hygiene certification. Vendors should not use the same working surface for multiple purposes, such as cutting meat. Street food vendors should also prepare salad based on customer demand to prevent contamination. Consumers can also remove the outer parts of vegetables before preparing salads at home to reduce potential pathogen risks.
There is a clear need to put in control measures to reduce health risk at all domains – farms, markets and kitchens. More attention should, however, be given to risk reduction interventions at kitchens due to the high contamination levels and the fact that most consumers (about 300,000 consumers per day in Accra alone) buy produce directly from this domain.
Further details of the study findings are presented in this Farm-to-fork study.