Assessment of Heavy Metals in Airborne Particulates from Industrial Areas of Kaduna Metropolis, Nigeria: Emphasis on Concentrations and Toxicity Potential

Abstract

Industrialization contributes significantly to the release of toxic pollutants, particularly heavy metals, into the environment. Unlike organic contaminants, heavy metals are non-biodegradable and persist in air, soil, and water, posing long-term health and ecological risks. This study assessed the concentrations of selected heavy metals (Ni, Co, Cu, Pb, Cd, Cr, Mn, Zn) in airborne particulates collected from five major industrial locations in Kaduna Metropolis, Nigeria: Kaduna Refinery (10.4896° N, 7.4119° E), Indomie Factory (10.5015° N, 7.4408° E), Hikman Gas Plant (10.6446° N, 7.5439° E), PZ Cussons Factory (10.5864° N, 7.4658° E), and A.A. Rano Diesel Plant (10.5516° N, 7.4547° E). Air samples were collected using high-volume samplers fitted with membrane filters, and the captured particulates were digested and analyzed for heavy metal content using Atomic Absorption Spectrophotometry (AAS). Results revealed the consistent presence of zinc and copper across all sites, with zinc recording the highest concentrations (1.97–2.44 mg/m³), followed by copper (0.79–0.97 mg/m³), while cobalt and cadmium showed the lowest concentrations (0.0002–0.0018 mg/m³). Comparisons with WHO/EU limits indicated that all detected heavy metals remained within permissible safety thresholds. Toxicity Potential Values (TPVs) ranged from 0.18 to 1 across the study sites, signifying low toxicity potential. Copper exhibited the highest TPVs (0.79–0.97), while cadmium recorded the lowest (0.28–0.36). Although the measured concentrations fall within international safety limits, the findings highlight potential long-term risks of continuous exposure, especially for factory workers and nearby residents. Preventive measures such as the consistent use of protective gear (e.g., facemasks), stricter enforcement of emission control policies, and continuous environmental monitoring are strongly recommended. This study provides baseline data on airborne heavy metal pollution in Kaduna industrial zones and underscores the need for sustainable industrial practices to safeguard public health and the environment.