Comparative Assessment of Polycyclic Aromatic Hydrocarbon Levels in Indoor and Outdoor Air and Associated Inhalation Health Risks in Akpajo, Alesa and Aleto Communities, Eleme, Rivers State, Nigeria

Abstract

Polycyclic aromatic hydrocarbons (PAHs) are persistent semi-volatile organic contaminants generated mainly during the incomplete combustion of organic materials and petroleum-derived fuels. This study assessed PAH levels in indoor and outdoor air and estimated the associated inhalation health risks in Akpajo, Alesa and Aleto communities of Eleme Local Government Area, Rivers State, Nigeria, an industrially and traffic-influenced area of the Niger Delta. Twelve 24-hour integrated air-sampling conditions were evaluated across three communities, two seasons (dry and wet) and two microenvironments (indoor and outdoor). Airborne particulate-bound PAHs were collected using a high-volume air-sampling approach, solvent-extracted with dichloromethane:n-hexane (1:1, v/v), concentrated and quantified by gas chromatography-mass spectrometry. Method quality control included internal-standard calibration, field and method blanks, duplicate checks, surrogate recovery assessment, blank correction, and limits of detection and quantification. Statistical analysis was based on descriptive statistics, including range, arithmetic mean, pooled congener totals, community means, seasonal means and indoor-outdoor means. Total PAH concentrations ranged from 7.40 µg/m³ in Alesa wet-season indoor air to 30.55 µg/m³ in Aleto dry-season outdoor air. The mean total PAH concentration was highest in Aleto (21.41 µg/m³), followed by Akpajo (11.80 µg/m³) and Alesa (10.39 µg/m³). Dry-season air had a higher mean total PAH concentration (18.18 µg/m³) than wet-season air (10.88 µg/m³), while outdoor air (15.75 µg/m³) exceeded indoor air (13.32 µg/m³). Anthracene, pyrene, benzo(k)fluoranthene, naphthalene, fluorene and phenanthrene were the dominant contributors to the pooled PAH burden. Non-detected high-molecular-weight PAHs were reported as below the method detection limit rather than as true zero values. Screening-level risk assessment showed that children had higher estimated lifetime average daily dose and incremental lifetime carcinogenic risk than adults under the same sampling conditions. The highest child ILCR occurred in Aleto dry-season outdoor air (4.12E-04), while several child-risk estimates exceeded 1.00E-04, indicating potential concern under the assumptions used. The findings indicate measurable PAH contamination, higher dry-season burden and greater screening-level risk estimates for children. Routine monitoring, emission reduction, dust control and targeted public-health communication are recommended.