Developing Probabilistic Environmental Health Risk Assessment Methods for Artisanal Mining Communities in Northern Nigeria Under Data Scarcity

This dissertation develops original probabilistic environmental health risk assessment methods adapted for artisanal and small-scale mining communities in Northern Nigeria under the data scarcity and measurement uncertainty conditions that characterise this assessment context. Conventional environmental health risk assessment methodologies assume data richness, spatial comprehensiveness, and well-characterised exposure pathways that are rarely achievable in artisanal mining assessments in low-resource settings, resulting in either paralysis of assessment activity or use of point-estimate methods that ignore uncertainty in ways that mislead risk management decisions. The theoretical contribution is a Bayesian hierarchical risk assessment framework that formally represents multiple layers of uncertainty including measurement error, spatial variability in contamination, population exposure behaviour heterogeneity, and toxicokinetic parameter uncertainty using informative priors informed by the Northern Nigerian environmental and epidemiological literature where available and uninformative priors where data are absent. The framework is applied to quantify children's blood lead exposure risk in three artisanal gold mining communities in Zamfara State, integrating environmental sampling, biomonitoring data from blood lead level measurements in 320 children, exposure pathway analysis, and toxicokinetic modelling. Validation is conducted by posterior predictive checking against independent blood lead datasets. The dissertation also develops a minimum viable risk assessment data collection protocol specifically designed for resource-constrained artisanal mining assessment contexts. Original contributions include the Bayesian hierarchical risk framework, the minimum viable data protocol, and the first calibrated probabilistic blood lead risk model for Zamfara State mining communities. Keywords: environmental health risk assessment, Bayesian methods, artisanal mining, lead exposure, Northern Nigeria.