Oral Bioaccessibility of Polycyclic Aromatic Hydrocarbons in Fly Ash Derived from Incineration of Petroleum Products and Waste Motor Tyres

Aim: The aim of this study is to generate and investigate oral bioaccessibility based on the health risk of polycyclic aromatic hydrocarbon (PAHs) in fly ash from waste tyres and petroleum products in Rivers State, Nigeria.

Study Design: Crude oil, crude oil asphalt, artisanal diesel, refined diesel, waste engine oil and waste tyres samples were collected and incinerated. The different fly ash samples were analyzed with GC-MS.

Place and Duration of Study: Rivers State is a state that is rich in oil in the Niger Delta area of Nigeria. The State has been experiencing the release of soot into the environment for more than five (5) years now. This soot is noticeable to all residents of Port Harcourt and its environment with soot covering both indoor and outdoor objects such as clothes, cars, houses, floors, soil, water body, etc. The five (5) petroleum products and waste tyres samples were collected and incinerated for six (6) weeks (22nd of June to 7th of August 2021).

Methodology: The petroleum products and waste tyres samples were collected and incinerated. The different fly ash samples were collected after combustion daily. The total and oral bioaccessible PAH concentrations were determined using GC-MS. The oral bioaccessibility of PAHs in the fly ash was evaluated using the physiologically-based extraction test method (PBET) to determine the bioaccessible concentrations of 16 priority US Environmental Protection Agency (USEPA) PAHs in fly ash samples. The results obtained for PAHs were used for health risk assessment.

Results: A wider range of total PAH concentrations were observed in the six (6) fly ash samples from 49.71 to 926.62 mg/kg. The PAHs concentrations were significantly higher in higher molecular weight PAHs (with benzene of 4-5-6 rings) than lower molecular weight PAHs (benzene of 2-3 rings). Naphthalene, acenaphthylene, acenaphthene, and fluorene with 2-3 ring structures had the highest bioaccessible concentrations in both gastric and gastrointestinal phases of all the six fly ash samples studied. Flourene had the maximum percentage bioaccessibility of 91.30 % in the gastric phase from locally refined diesel fly ash whilst acenaphthene had a maximum percentage bioaccessibility of 98.75% in the gastrointestinal phase from crude oil asphalt fly ash.

Conclusion: Data obtained from this study indicated that crude oil fly ash is a potential point source of toxic polycyclic aromatic hydrocarbons with significant levels of health risk to humans.