Reproductive Toxicology of Artisanal Petroleum Refining Emissions on Hypothalamic-Pituitary-Gonadal Axis Function in Males in Bayelsa State, South South Nigeria

Background: Artisanal crude oil refining, locally termed kpo-fire, is widespread in Bayelsa State and releases complex mixtures of polycyclic aromatic hydrocarbons, volatile organic compounds, and heavy metals with established endocrine-disrupting properties. Disruption of the hypothalamic-pituitary-gonadal axis by these emissions may underlie the elevated rates of reproductive dysfunction reported anecdotally in affected communities. No mechanistic study has characterised this physiological pathway in human or animal models using exposure conditions relevant to the Bayelsa setting. Objectives: This study aims to assess hypothalamic-pituitary-gonadal axis function through measurement of gonadotrophin-releasing hormone pulse frequency, luteinising hormone, follicle-stimulating hormone, testosterone, and semen quality parameters in male residents of kpo-fire-exposed communities compared with unexposed controls, and to model the pathway from hydrocarbon blood biomarkers to hormonal and reproductive endpoints. Methods: Sixty adult males from three artisanal refining communities and thirty controls from inland non-refining communities will be recruited. Blood polycyclic aromatic hydrocarbon adducts will be quantified as exposure biomarkers. Reproductive hormones will be measured by immunoassay. Semen analysis will follow WHO 2021 criteria. Structural equation modelling will decompose direct and indirect effects of exposure on reproductive physiology endpoints. Expected Outcomes: Exposed men are expected to exhibit dose-dependent suppression of testosterone and luteinising hormone with deteriorating semen parameters, mediated through polycyclic aromatic hydrocarbon-driven disruption of gonadotrophin pulsatility. Conclusion: This study will produce the first mechanistic reproductive physiology evidence from Nigeria's artisanal refining communities. Keywords: reproductive toxicology, artisanal refining, hypothalamic-pituitary-gonadal axis, polycyclic aromatic hydrocarbons, Bayelsa.