Determination of Polycyclic Aromatic Hydrocarbon Exposure and Serum Biomarker Changes in Residents Close to Oil-Refinery Sites in Rivers State

Determination of Polycyclic Aromatic Hydrocarbon Exposure and Serum Biomarker Changes in Residents Close to Oil-Refinery Sites in Rivers State

Abstract

Oil refining releases toxic compounds, especially polycyclic aromatic hydrocarbons (PAHs), which can alter biochemical functions and promote oxidative stress. This study investigates PAH exposure and its effects on serum biochemical markers among residents living near oil-refinery sites in Rivers State. Blood samples were collected from residents within 5 km of the refinery and compared with samples from a control group living over 20 km away. Standard biochemical techniques were used to determine serum levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), urea, creatinine, and malondialdehyde (MDA). Gas chromatography–mass spectrometry (GC–MS) measured PAH concentrations. Results showed significantly higher (p < 0.05) levels of MDA, ALT, and AST in exposed residents, alongside reduced activities of antioxidant enzymes such as superoxide dismutase (SOD) and catalase (CAT). These findings indicate oxidative stress and possible liver and kidney dysfunction. Therefore, continuous monitoring and community health screening are strongly recommended to minimize long-term health risks.

CHAPTER ONE

1.0 Introduction

1.1 Background of the Study

Polycyclic aromatic hydrocarbons (PAHs) are organic pollutants produced by incomplete combustion of fossil fuels, biomass, and other carbon materials. In oil-producing regions like Rivers State, people face frequent PAH exposure through air, soil, and water contamination. Over time, this exposure can lead to oxidative stress, liver injury, and other metabolic disorders.

Communities near oil refineries experience constant pollution from gas flaring and crude oil leaks. These pollutants enter the human body through inhalation, ingestion, and dermal contact. Once absorbed, PAHs are metabolized by liver enzymes, generating reactive compounds that bind to DNA and proteins. Consequently, enzyme activity in the liver and kidneys can change, and biochemical markers such as ALT, AST, urea, and creatinine help reveal such changes.

1.2 Statement of the Problem

Refinery operations in Rivers State continue to release large amounts of PAHs into the environment. However, little is known about how chronic exposure affects biochemical health among nearby residents. Without data, public health responses remain limited. There is therefore a pressing need to examine how PAHs influence biochemical indicators of organ function in these communities.

1.3 Aim and Objectives of the Study

The main aim of this study is to determine the levels of PAH exposure and assess its effects on serum biochemical biomarkers among residents living near oil-refinery sites in Rivers State.

Specific objectives include:

1. Quantify concentrations of selected PAHs in serum samples of exposed and control residents.

2. Measure serum levels of biochemical markers (ALT, AST, urea, and creatinine).

3. Evaluate oxidative stress indicators such as MDA, SOD, and CAT.

4. Identify relationships between PAH exposure and biochemical marker alterations.

1.4 Research Questions

1. What are the PAH concentrations in the serum of residents near refinery sites?

2. How does PAH exposure influence biochemical markers of liver and kidney function?

3. What relationship exists between PAH exposure and oxidative stress levels?

1.5 Significance of the Study

This study highlights the biochemical and health consequences of exposure to PAHs from refinery operations. The results will guide health authorities in creating safer living conditions and in monitoring pollution more effectively. Additionally, the study contributes to environmental toxicology research and strengthens awareness of pollution’s hidden biochemical impacts.

1.6 Scope of the Study

The study focuses on residents within a 5 km radius of selected oil refineries in Rivers State. It covers the analysis of PAHs in serum and the evaluation of liver and kidney function biomarkers.

1.7 Operational Definitions

• PAHs: Organic pollutants with multiple aromatic rings produced by incomplete combustion.

• Oxidative Stress: An imbalance between free radical generation and antioxidant defense.

• Biochemical Markers: Blood indicators used to assess organ function or tissue damage.

CHAPTER TWO

2.0 Literature Review

2.1 Polycyclic Aromatic Hydrocarbons (PAHs)

PAHs are environmental contaminants composed of fused benzene rings. They arise from both natural and anthropogenic processes. Common sources include vehicle emissions, gas flaring, and crude oil refining. Because of their lipophilic nature, PAHs persist in the environment and accumulate in biological tissues, creating long-term health risks.

2.2 Environmental Sources of PAHs

In Rivers State, refinery operations, gas flaring, and oil spills are major PAH sources. The compounds contaminate soil, water, and vegetation. Eventually, humans are exposed through the food chain, inhalation of polluted air, and consumption of contaminated water. Consequently, people living in refinery zones face a higher risk of exposure than those in non-industrial regions.

2.3 Mechanism of PAH Toxicity

Once PAHs enter the body, the cytochrome P450 enzyme system metabolizes them into reactive intermediates. These metabolites can bind to DNA and proteins, producing reactive oxygen species (ROS). Over time, ROS accumulation causes oxidative stress, lipid peroxidation, and tissue injury. Thus, chronic exposure may impair liver and kidney functions.

2.4 Biochemical Markers of Exposure

Serum enzymes such as ALT and AST are sensitive indicators of liver cell damage, while urea and creatinine reflect kidney function. Oxidative stress biomarkers like MDA, SOD, and CAT provide additional evidence of PAH-induced toxicity. Increased MDA levels combined with decreased antioxidant enzyme activity indicate significant oxidative imbalance.

2.5 Health Effects of PAHs

Extensive research links PAHs to mutagenic, carcinogenic, and teratogenic effects. They disrupt cellular metabolism, weaken immune defense, and impair reproductive health. Continuous exposure can result in liver dysfunction, renal impairment, and respiratory illnesses. In humans, these effects often emerge after years of low-level but consistent exposure.

2.6 Studies on PAH Exposure in Nigeria

Several studies have investigated PAH contamination in the Niger Delta region. For example, Nwaichi et al. (2018) reported increased oxidative stress and enzyme alterations among individuals near gas-flaring areas. However, few studies directly examined serum biochemical responses to refinery exposure in Rivers State. This gap justifies the present investigation.

2.7 Theoretical Framework

The Oxidative Stress Theory underpins this research. It proposes that environmental pollutants like PAHs generate free radicals that surpass the body’s antioxidant capacity. As a result, oxidative damage accumulates in tissues, leading to functional disorders. This framework explains how PAH exposure disrupts biochemical homeostasis in humans.

2.8 Conceptual Framework

PAH exposure from refinery emissions → Metabolic activation by liver enzymes → Generation of reactive oxygen species → Oxidative stress → Altered biochemical markers (ALT, AST, urea, creatinine, MDA, SOD, CAT) → Health impacts such as liver and kidney dysfunction.