An assessment of heavy metal and pathogen levels in vegetables cultivated with water from specific urban areas of the Greater Accra Metropolis has unveiled potential health hazards associated with mercury and faecal coliforms.
Published in April 2024, the study titled ‘Analysis of Heavy Metals and Pathogen Levels in Vegetables Cultivated Using Selected Water Bodies in Urban Areas of the Greater Accra Metropolitan Area (GAMA)’ delves into the concentrations of heavy metals and faecal coliform in lettuce and bell pepper grown using open-surface wastewater from drains and constructed reservoirs across various locations within GAMA.
To conduct the study, researchers utilized a combination of methods, administering questionnaires to 67 vegetable farmers and collecting vegetable samples from three urban farm sites – Haatso, Dzorwulu, and the Weija Irrigation Scheme site (WISS) – for subsequent laboratory analysis.
The concentrations of lead (Pb), mercury (Hg), and cadmium (Cd) were determined through atomic absorption spectroscopy following microwave digestion of the vegetables. Additionally, the total faecal coliform was quantified using the MacConkey-Endo broth method.
Findings from all three sites indicated that the concentrations of Cd (≤0.001 μg/mg) and Pb (≤0.005 μg/mg) in lettuce complied with the permissible levels set by the World Health Organization (WHO). However, the levels of Hg (≥0.309 μg/mg) and faecal coliform (>5 count/100 ml) in the vegetables from all three sites exceeded the WHO permissible limits.
The study concludes that consumers of vegetables from such urban farms are at risk of health issues associated with mercury and faecal coliforms.
Upon contacting a team member of the study, Alan Gbeasor, he informed the B&FT that the phenomenon is a significant concern. The study underscores the urgency to intensify education regarding the health risks associated with consuming vegetables grown from open-surface water sources in the observed sites. Furthermore, it advocates for the enforcement of existing phytosanitary standards to bolster food safety and the quality of urban vegetables.
Conventional practice
Open-surface water sources have commonly been employed to irrigate vegetable farms in urban areas and cities.
However, these sources frequently harbor unchecked levels of hazardous contaminants, presenting health risks, particularly when utilized for growing vegetables intended for consumption.
Yet, data regarding the presence of heavy metals and faecal coliform bacteria in such vegetables at specific locations, notably within the Greater Accra Metropolitan Area (GAMA) of Ghana, remains limited.
Urbanisation causing water scarcity
The swift pace of urbanization, standing at 56.7 percent in the country, coupled with erratic rainfall patterns leading to freshwater scarcity, has forced numerous small-scale farmers to turn to polluted or contaminated wastewater sources for their urban vegetable cultivation.
This shift not only sparks concerns regarding the quality of agricultural yields but also gives rise to potential food safety and health hazards for urban families reliant on these vegetables in the Greater Accra Metropolitan Area.
As per the 2024 Mordor Intelligence Report, the country’s vegetable market share is valued at US$0.95 billion, with projections indicating a climb to US$1.2 billion by 2029.