Modeling the Compounding Effects of Multiple Environmental Stressors on Population Health in North East Nigeria Using a Cumulative Impact Framework

Populations in North East Nigeria are simultaneously exposed to multiple environmental health stressors, including water insecurity, air pollution from biomass combustion, drought-driven food insecurity, conflict-induced displacement, and heavy metal contamination, whose combined health effects are rarely analyzed within a unified cumulative impact framework. This dissertation develops and applies a cumulative environmental impact framework to model the compounding health effects of multiple co-occurring environmental stressors on populations in Borno, Yobe, and Adamawa states. The framework draws upon cumulative risk assessment theory, social determinants of health models, and resilience theory to construct a stressor-pathway-health outcome network. Empirical data were generated through a prospective cohort study following 3,200 households across twenty communities over eighteen months. Environmental stressor profiling included assessment of water quality, indoor and ambient air quality, food security indicators, displacement experience, and biomarker-confirmed heavy metal exposure. Health outcomes tracked included child growth, maternal health status, respiratory morbidity, and mental health. Structural equation modeling and Bayesian network analysis were used to estimate direct and indirect effects and interaction terms among stressor domains. Results demonstrated substantial interaction effects between water insecurity and displacement on both child stunting and maternal depression outcomes, with combined effects exceeding the sum of independent stressor effects. The cumulative stressor index explained sixty-one percent of variance in the composite health outcome score. The dissertation provides original theoretical and methodological contributions to the nascent literature on cumulative environmental health impact modeling in conflict-affected African settings. Keywords: cumulative impact, multiple stressors, North East Nigeria, population health, Bayesian analysis.