Heavy Metals and Polycyclic Aromatic Hydrocarbons Levels in Selected Occupational and Environmental Settings in Liberia: A Systematic Review

Abstract

Environmental degradation in Liberia has reached critical levels due to years of unregulated artisanal mining, poor waste management, and rapid urbanization have severely compromised the quality of its water and soil resources. This review critically evaluates the extent, sources, and implications of physicochemical and heavy metal contamination in Liberia’s aquatic and terrestrial environments. From an initial pool of 38 studies, 9 met the inclusion criteria based on relevance from 2020, quantitative data quality, and geographic coverage. The methodology combined descriptive statistics, correlation analysis, and multivariate statistics to trace pollution patterns and their geochemical drivers. Findings reveal severe contamination: water turbidity reached 320.00 NTU (mean: 42.85 NTU) against the WHO guideline of 5 NTU, while electrical conductivity peaked at 3000.00 µS/cm. Total dissolved solids averaged 267.92 mg/L, exceeding permissible levels near estuarine zones. Heavy metal concentrations surpassed WHO limits in numerous cases—Fe (up to 23.69 mg/L), Mn (9.12 mg/L), and Cd (0.40 mg/L) in water, and Fe (115,781.00 mg/kg), Ni, and Cd in soil. Strong correlations (eg, EC-TDS: r = .997; NO 3 − -PO 4 3− : r = .923; Zn-Mn: r = .90) suggest shared contamination pathways linked to mining runoff and agrochemical inputs. This review provides critical baseline data, identifies high-risk hotspots, and highlights the geochemical mechanisms driving pollution. It establishes the novelty of synthesizing Liberia-specific contamination trends with quantitative rigor, which had not been comprehensively undertaken. The study highlights the urgent need for environmental policy reform, site-specific remediation, and public health interventions to align national development with SDGs 3, 6, and 15.