Abstract:
Vegetable cultivation using river water, which may be polluted with heavy
metals, can cause health problems to consumers. A study to establish cadmium and
lead levels in water from Msasa, Manyame; Mukuvisi and Nyatsime Rivers was
conducted in 2019. A questionnaire survey involving 105 randomly selected urban
vegetable growers was conducted to examine farmer knowledge of the potential of
polluted water to contaminate produce through heavy metals. Water, soil and
vegetable samples were also collected and analysed for heavy metal presence
using atomic absorption spectrophotometry. Results showed that some farmers
(62%) were aware that wastewater could contain heavy metals. The majority of
farmers (67%) applied phosphate-based fertilisers, a potential source of cadmium.
Tested at P < 0.05, the results showed that sampled water from the four sites failed
to meet the Standards Association of Zimbabwe 5560 (1997) standards. Cadmium
tissue concentration from wastewater from Msasa and Manyame rivers was 1.3 and
1.17 mg g−1 respectively, which were 59 and 65 times higher than 0.02 mg g−1 from
the control. Water from Manyame and Nyatsime rivers contains levels of heavy metals which exceed the Environmental Management Agency (EMA) safety guidelines. Farmers need to be educated on health hazards from contaminated wastewater. Enforcing regulations on effluent disposal, licencing of vegetable vendors and
labelling of vegetables with information on source of water used to irrigate the crop
can help reduce exposure of unsuspecting vegetable consumers.
