Assessment of human consumption ofwild and cultivatedplants in Kanana, agold mining town in North West Province

[摘要] This study evaluated potential health risks associated with the consumption of commonly consumed leafy vegetables, Amaranthus hybridus (tepe), Brassica oleracea (cabbage) and Spinacia oleracea (spinach) in the gold mining town of Kanana in North West Province, where these three plants were the most commonly consumed. Structured interviews were conducted with 40 households to determine their socioeconomic status and the consumption patterns of vegetables (cultivated and wild plants). Along with interviews, plant samples were sampled in home gardens and at various harvesting locations in the wild for chemical analysis. Finally, analysis of mercury content in the sampled three leafy vegetable species was performed to ascertain the contributions of the vegetables to the dietary mercury intake among a predominantly young and poor subpopulation of Kanana, which was found to be largely dependent on state welfare grants and on the cultivation and gathering of wild plants for survival.The study found that all three leafy vegetable species under analysis had mercury concentrations that exceeded the maximum permitted by the World Health Organisation. The highest mean mercury concentrations were found in A. hybridus 0.287μg/g dry mass and the lowest in S. oleracea 0.128μg/g dry mass. Equally, mercury ingestion through the three leafy vegetables by adults in the surveyed subgroups of Kanana exceeded thresholds prescribed by the (2007). Based on consumption patterns, dietary mercury intake by adults exceeded the recommended limits by one order of magnitude, with yearly dose exceeding by as much as four and three orders of magnitude. Long term mercury exposure can cause damage to the central nervous system and chronic intoxication. The surveyed subpopulation is therefore exposed to health risks from mercury toxicity. To ensure food safety and to protect the residents from metal toxicity, awareness programmes are recommended to educate communities living in the vicinity of mines to avoid the areas of highest contamination, such as the artisanal mine dumps and (in this case) the Schoonspruit stream, and to control the artisanal use of mercury. Alternative vegetable gardening methods such as vegetable container gardening using unpolluted soil can also be implemented for the community. In addition, remediation of all the sites where local people cultivate vegetables and gather edible wild plants should be considered where feasible. The insights gained through the study should be used to inform local land use planning and create awareness among personnel from local regulators and development agencies. The insights can also be used to inform environmental management planning processes, risk mitigation and social impact assessment for industries in the region, in particular those involved in mining.Keywords: consumption patterns, gold mining, human health risk, leafy vegetables, mercury.

[发布机构] University of the Witwatersrand