Lead and Cadmium Bioaccumulation in Amaranthus cruentus L. and its Health Implication.

Abstract

Lead and Cadmium are among the major toxic heavy metal contaminants found in anthropogenic soil. However, there has been a growing concern on human health risk from these metals bioaccumulation in vegetables grown on such contaminated soils. This study investigated lead and cadmium bioaccumulation in Amaranthus cruentus and the implications on human health. Pot culture experiments were carried out in which A. cruentus plants were grown in soil contaminated with varying concentrations of lead and cadmium salts (100 mgPb/kg+10 mgCd/kg, 200 mgPb/kg+20 mgCd/kg, and 400 mgPb/kg+40 mgCd/kg). Plants in the control soil were grown without the heavy metals salts. Plant growth was observed under greenhouse conditions and plants were harvested after five and ten weeks. The concentrations of lead and cadmium in the plant tissues were determined using Atomic Absorption Spectrophotometry. Throughout the experiment, no visible symptom of metal toxicity was observed on any plant. The concentrations of lead measured in plant shoot across the groups ranged from 11.5 to 135.7 and 30.5 to 200.5 mg/kg while that of cadmium ranged from 0.1 to 133.1 and 0.5 to 166.7 mg/kg at five and ten weeks, respectively. Lead and cadmium bioaccumulation in the plant increased significantly with increasing levels of soil contamination, and the values were far above FAO/WHO recommended safe limits of 0.3 and 0.2 mg/kg for lead and cadmium, respectively. The high capacity for lead and cadmium bioaccumulation in the edible parts of A. cruentus coupled with the absence of visible phytotoxic symptoms implies a potential danger for humans.