Concentrations of PAHs from urban and rural areas in southern nigeria using polyurethane foams (PUF) passive samplers: Health impact and cancer risk assessment

Abstract

Nigeria loses thousands of its populace annually to cancer. Probable upsurge in the atmospheric concentrations of polycyclic aromatic hydrocarbons (PAHs) has been suggested as a contributor to this menace. This baseline study has evaluated the concentrations of the 16 priority PAHs in urban and rural communities, Southern Nigeria to establish a nexus. Air samples were collected monthly for a period of 12 months from 10 sampling locations using passive samplers (polyurethane foams (PUF) disk). Results obtained revealed an average ambient air concentrations (∑16PAH) of 0.817 ± 0.33 µg/m3for the urban, 0.087 ± 0.05 µg/m3 for the rural and 0.011 ± 0.01 µg/m3 for the control site. Remarkably, the obtained urban and rural benzo(a)pyrene (BaP) mean concentrations, mainly from incessant combustion of unsorted municipal solid wastes and bush burning were outrageous (63 ng/m3 and 9 ng/m3 respectively), indicative of a significant cancer health hazard and a possible overlooked source of the global BaP burden. The Total Toxicity Equivalent Concentration (TTEC) were found to vary from 0.000063 – 0.417 µg/m3 with BaP once more reporting the highest toxicity value of 0.314 µg/m3. However, the Incremental Lifetime Cancer Risk (ILCR) values obtained, ranged from 7.8 × 10−8 to 5 × 10−5 which were within the acceptable limits. The Health Impact Assessment (HIA) reported symptoms suggestive of exposure to PAHs, with neurological and respiratory symptoms being the most prevalent by 31.4 - 61.4 % of the respondents. Spatial and temporal variations in the obtained PAH data were found to be significant (p<0.05) with higher values reported in the densely populated urban locations and during the dry season months.. Source identication studies by principal component analysis (PCA) revealed petrol, diesel and solid wastes combustion as the dominant anthropogenic source of the recorded PAHs, while the diagnostic ratio analysis revealed pyrogenic sources as the predominant PAHs emission source.