Concentrations, Source Apportionment, and Non-Carcinogenic/Carcinogenic Health Risk Assessment of Heavy Metals in Classroom Settled Dust at Federal University Wukari, Taraba State, Nigeria

Abstract

The presence of heavy metals in our environment is a persistent threat to our health. These toxic substances can accumulate in our bodies and cause serious harm, especially when we're exposed to them over a long period. This study investigated the concentrations of lead (Pb), cadmium (Cd), and chromium (Cr) in settled dust from ten classrooms (lecture theatres, science laboratories, and multipurpose halls) at Federal University Wukari, Taraba State, Nigeria. Dust samples were collected from floors, desks, and windowsills, sieved to particles <100 µm, and analysed using flame atomic absorption spectrophotometry (FAAS). Health risk assessment was conducted for adult and child receptors via ingestion, inhalation, and dermal contact pathways, following USEPA (2001) guidelines. Mean concentrations were Pb = 0.331 ± 0.204 mg/kg, Cd = 0.0102 ± 0.0118 mg/kg, and Cr = 0.0013 ± 0.0005 mg/kg, with multipurpose halls recording the highest levels (Pb: 0.741 mg/kg; Cd: 0.0421 mg/kg). Ingestion was the dominant exposure pathway, contributing >85% of total exposure. Non-carcinogenic hazard quotients (HQ) for all metals and pathways were <<1 (mean HQ of_Pb = 8.38 × 10⁻⁵ for adults; 7.82 × 10⁻⁴ for children), indicating no significant non-carcinogenic health risks. Cancer risks were below the USEPA acceptable range (10⁻⁶–10⁻⁴), with total risks of 2.94 × 10⁻⁹ (adults) and 5.99 × 10⁻⁹ (children). Principal contamination sources include vehicular emissions, generator exhaust, deteriorating building materials, laboratory activities, soil resuspension, and atmospheric deposition. While risks are currently low, proactive management is recommended to prevent future accumulation.