Epistemological Contributions to Environmental Health Risk Assessment Methodology in Sub-Saharan African Contexts: A Nigerian Case Analysis

Environmental health risk assessment as currently practiced in Nigeria predominantly imports methodological frameworks developed in Western high-income settings, raising fundamental epistemological questions about the validity of exposure parameters, dose-response relationships, and risk characterization approaches in the Nigerian context. This dissertation critically examines the epistemological assumptions embedded in standard risk assessment methodology and proposes adaptations grounded in Nigerian epidemiological, demographic, and environmental realities. A critical realism philosophical framework guided the research, which combined systematic review of fifty-six published environmental health risk assessments conducted in Nigeria between 2015 and 2024, in-depth expert interviews with thirty-two environmental health scientists and risk assessors, and original empirical case studies from Kano, Lagos, Enugu, and Bayelsa states. The dissertation identifies five systematic biases in imported risk assessment methodology: use of non-representative body weight and inhalation rate defaults, absence of multipathway exposure models for subsistence farming populations, underestimation of indigenous dietary exposure patterns, culturally inappropriate behavioral exposure parameters, and inadequate uncertainty characterization for African-specific dose-response relationships. Original locally calibrated exposure factors are developed and validated through empirical field measurement. A revised risk assessment protocol incorporating Nigerian-specific parameters is proposed and demonstrated through three case applications. The dissertation makes a foundational theoretical and methodological contribution to environmental health science in sub-Saharan Africa. Keywords: risk assessment methodology, epistemology, Nigeria, exposure factors, sub-Saharan Africa.