Effect of Soil Contamination by Cadmium on Growth Factors of Spinach and Radish in Relation to Human Health

Soil contamination by heavy metals around big cities and intensive vegetable cropping in these soils may be a threat to human health. A factorial greenhouse-experiment was conducted to evaluate the effects of different levels of cadmium (Cd) (0, 5, 10, 20 and 40 mg/kg) and soil calcium carbonate (13.5, 44.5 and 67.5 percent) on some growth indices of two common vegetables, namely, radish (Raphanus sativus) and spinach (Spinacea oleracea)).  Leaf area and wet weight of spinach and radish and wet weight of radish root were used to assess their marketing properties. Cd concentration in both plants was increased by soil Cd levels and it had a dramatically decreasing effect on plant growth indices and marketing properties of both vegetables, especially those of spinach, but soil calcium carbonate had no significant effect in this regard. All measured plant growth factors i.e. wet weight, dry weight, chlorophyll A and B were dramatically changed and depressed by Cd toxicity. Applied Cd at 40 mg kg^-1 decreased leaf area and wet weight of spinach by 77% and 86 percent, respectively. In radish, these figures were about 36% and 32 percent.  Radish root wet weight was decreased to 49 percent when compared to no-Cd treatment. Spinach showed a lower marketing value than radish despite the fact that Cd concentration in radish leaf was higher than that of spinach. Soil Cd concentration had less effect on radish marketing property (root wet weight). Radish root marketing properties were less affected despite having higher Cd concentration. This means that, in comparison with spinach, there is more risk to human health of a high Cd radish entering into human food chain.