Concentrations and health risks of selected elements in leafy vegetables: a comparison between roadside open-air markets and large stores in Johannesburg, South Africa.

This study compared concentrations and health risks of selected elements (Al, As, Cd, Co, Cr, Cu, Hg, Ni, Pb, Zn) in leafy vegetables (coriander, lettuce, mint, spring onion, swiss chard) from roadside open-air markets (OM) and large stores (supermarkets: SM, vegetable markets: VM) in Johannesburg, South Africa. Along with washed leaves (OMW, SMW, VMW), unwashed OM leaves (OMUW) were assessed to investigate the contribution of deposition. The findings revealed that OMUW leaves had the highest concentrations of all elements. Furthermore, compared with washed leaves, OMUW leaves showed significantly higher (p < 0.05) mean concentrations of Cd, Hg, Ni and Pb, elements that typify the composition of polluted urban air. Bi- and multivariate analysis indicated anthropogenic origin of most elements in OM leaves and several in SMW and VMW leaves. Although only OMUW leaves exhibited hazard quotient above the safe threshold of 1 for Cd, Cr, As and Ni, hazard index exceeded this safe limit in all samples (OMUW (11.77) > OMW (1.83) > SMW (1.29) > VMW (1.01)). Determined cancer risk for Cd and As was greater than 1 × 10-6 in both washed and unwashed leaves, and the greatest cancer risk was estimated for OM leaves. Thorough washing of OM vegetables with water reduced non-carcinogenic risk (84%) and cancer risk (74‒87%) markedly. In conclusion, residents primarily relying on open-air markets for their regular leafy vegetable supplies might face far more severe lifelong health implications compared to customers of large stores in Johannesburg.

Anthropogenic Sources Dominate Foliar Chromium Dust Deposition in a Mining-Based Urban Region of South Africa.

Dust pollution can be severe in urban centers near mines and smelters. Identification of dust sources and assessing dust capturing plant morphological traits may help address the problem. A chromium (Cr) mining and ferrochrome smelting region in Sekhukhuneland, South Africa, was investigated to identify the sources of Cr in soil and plant leaf surfaces and to evaluate the association between Cr sources and plant morphology. Combinations of bi- and multivariate statistical analysis techniques were applied. Non-significant relation between Cr quantities in surface soil and on leaf surfaces suggested negligible Cr dust contribution from soil to leaves. Association among Cr, Fe, Mg, Al, and Si levels on leaf surfaces confirmed their shared origin, possibly from chromite containing dust dispersed by mines, smelters, roads, and tailings. Both plant morphology and Cr sources (number and proximity to mines and roads) conjointly determined Cr dust deposition on leaf surfaces. Air mass movement patterns further identified local polluters, i.e., mines, ferrochrome smelters, and roads, as dominant dust sources in the region. Common plant species showed Cr dust adhesion favouring traits (plant tallness, larger leaf area, dense epicuticular wax structures, and larger stomata) and projected dust mitigation prospects for Sekhukhuneland.