Analysis of Heavy Metals in Soil and Medicinal Plants using Risk Assessment Indices

Abstract

Studying heavy metal contamination in soil and plants is critical due to its impact on ecosystem health and human well-being. Industrialization, agriculture, and urbanization have contributed significantly to the rise of heavy metal pollution. This study investigated heavy metal levels in soil and the medicinal plants Bryophyllum pinnatum (BPi) and Vernonia amygdalina (VA) using environmental and health risk assessments. Atomic Absorption Spectrophotometry was employed to measure concentrations of manganese (Mn), iron (Fe), copper (Cu), zinc (Zn), chromium (Cr), and lead (Pb) in soil and plant parts (leaves, stems, and roots). Data were analyzed using descriptive statistics and Pearson correlation. Soil manganese concentrations ranged from 15.82 to 217.33 mg/kg (BPi) and 366.38 to 513.60 mg/kg (VA), while iron ranged from 8541.78 to 9632.78 mg/kg (BPi) and 6500.23 to 16045.03 mg/kg (VA). Concentrations of Cu, Zn, Cr, and Pb also varied. Metal levels in medicinal plants were comparable, with Mn ranging from 3.08 to 109.13 mg/kg and Fe from 36.05 to 2546.34 mg/kg. Except for Fe in soil, most metals (Mn, Cu, Zn, Cr, Pb) were below WHO permissible limits. Strong positive correlations between soil and plant metal concentrations indicated effective metal uptake. Ecological risk assessment revealed substantial soil pollution near the medicinal plants; however, health risk assessments showed hazard indices below one for both adults and children, suggesting no significant non-carcinogenic risk. Carcinogenic risk values for Pb and Cr were below hazardous thresholds, indicating minimal cancer risk. These findings support the safe use of Bryophyllum pinnatum and Vernonia amygdalina in treating cancer and malaria, as their heavy metal content remains within safe limits.