First forensic quantification, source-identification and health risk estimation of volatile organic carbons in the anthropogenically impacted Omi-Asoro Stream in Ilesa, Nigeria

This study quantified the volatile organic compounds (VOCs) in the Omi-Asoro Stream located in Ilesa town, Nigeria, to understand their sources and health risks to humans. The VOCs were measured in 2023 according to the US EPA equilibrium headspace method using a gas chromatograph (GC) and detected by a flame ionization detector (FID). Their human health risk assessments via ingestion and dermal contact were also estimated. The results showed that dissolved oxygen (DO) ranged 0.5–4.8 mg/L. Chemical oxygen demand (COD) was exceptionally high (March: 181.3 ± 45.5 mg/L; July: 180.7 ± 25.7 mg/L) in the industrial waste discharge area. Twenty-two and eighteen sets of VOCs were detected in March and July, respectively. 1,2-dibromo-3-chloropropane (DBCP) was the predominant VOC in the stream accounting for 18% (March) and 19% (July). DBCP, 1,2-dichlorobenzene+nbutylbenzene (oDCB+bBZ) and hexachlorobutadiene+1,2,4-trichlorobenzene (HCBD+TCB) were ubiquitous in the stream with 100% detection frequency. Disinfectants/fumigants, cleaning agents, industrial solvents, agrochemicals and plastic materials were the main sources of the VOCs. No individual VOC posed a non-carcinogenic risk (HI) in both months of the study. However, the total HI via ingestion route in March posed a non-carcinogenic health risk to children (HI_sum = 1.03). BDCM, TeCA, TCP and pDCB posed a high carcinogenic risk to humans via ingestion with values in the range of (0.00219–5.07) × 10⁻² for both months. TCP also posed a high carcinogenic risk (range of 10⁻⁴) via dermal contact to humans. The highly impaired water quality of the stream was due to industrial, agricultural and other anthropogenic activities.