Urban farming as a possible source of trace metals in human diets

Abstract

HOW TO CITE:Olowoyo JO, Lion GN. Urban farming as a possible source of trace metals in human diets. S Afr J Sci. 2016;112(1/2), Art. #2014-0444, 6 pages. http://dx.doi.org/10. 17159/ sajs.2016/20140444 Rapid industrialisation and urbanisation have greatly increased the concentrations of trace metals as pollutants in the urban environment. These pollutants (trace metals) are more likely to have an adverse effect on peri-urban agriculture which is now becoming a permanent feature of the landscape of many urban cities in the world. This review reports on the concentrations of trace metals in crops, including leafy vegetables harvested from different urban areas, thus highlighting the presence of trace metals in leafy vegetables. Various pathways of uptake of trace metals by leafy vegetables, such as the foliar and roots, and possible health risks associated with urban faming are discussed and various morphological and physiological impacts of trace metals in leafy vegetables are described. Defensive mechanisms and positive aspects of trace metals in plants are also highlighted. IntroductionUrban farming can be defined as the act of cultivating food crops, mostly vegetables, wherever land is available around or in the immediate vicinity of a major city.1,2 Farming activities around urban areas have become a prominent feature of some urban city landscapes, especially in developing countries. 3 There are several reasons for farming activities around peri-urban areas and these include easy access to markets and transportation of goods. In some countries, poor urban households use urban farming to increase their household income by selling the yield or surplus to reduce part of daily expenses. 4 The other probable reason for the increase in urban farming is the shortage of land. This involves farming areas previously used for either household or industrial waste, 5 supported by the notion that the soil will be very fertile. Urban farming also supports the campaign for organic farming. Consumers, in most cases, evaluate quality of leafy vegetables on their dark green colour and on size of the leaves as opposed to where farming activities have taken place. 6 However, in urban city centres where farming activities are carried out around industrial areas, safety around the consumption of these vegetables cannot be guaranteed because various disposal practices often cause the accumulation of potentially toxic trace elements in the soil. 7,8 Anthropogenic activities such as mining, emissions from vehicles, wrong agricultural practices and improper waste disposal are major sources of trace metal pollution in the urban environment. 5,9 It was recently discovered that a large percentage of toxic trace metals find their way into the human diet through consumption of vegetables and agricultural products. 5-14In acceptable limits, trace metals play an important role in the health and physiological activities of plants, animals and humans.15 They are required in minute quantities as natural components of the environment. For exa...

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“…Also, there is a need for more studies on other river catchments where there is lack of information in the Limpopo province. Other studies by Sibanda et al [25], Shibambu [32], Gumbo et al [68], and Olowoyo and Lion [69] have shown that the wastewater is rich in nutrients and essential traces such that the wastewater is usable for irrigation of crops, fruit trees, and vegetables. Limpopo province is a dry and arid region and the use of wastewater for irrigation is a welcome idea but there should be safeguards in place to protect the food consumers and irrigators from the negative impacts of wastewater reuse [68,69].…”

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