Unveiling environmental and economic drivers of pollution-related mortality in sub-Saharan Africa: evidence from Panel QARDL and LightGBM analyses

This study investigates the environmental and economic factors driving pollution-related mortality in 37 Sub-Saharan African countries from 1990 to 2022. The analysis combines two complementary approaches. The first is a Panel Panel Quantile Autoregressive Distributed Lag (QARDL) model, which captures both short- and long-run relationships across different levels of the mortality distribution. The second is a Light Gradient Boosting Machine (LightGBM) model, a machine-learning method that detects nonlinear patterns and reveals interactions that may be missed by traditional statistical models. Together, these methods integrate structured econometric inference with flexible pattern recognition, offering a clearer and more reliable picture of how environmental and economic forces jointly shape mortality outcomes. The LightGBM partial dependence plots further confirm the Panel QARDL results, showing consistent directional effects across all variables. Fine particulate matter and consumer price index display the strongest nonlinear responses, while methane, health expenditures and Gross Domestic Product exhibit moderate but coherent patterns that reinforce the robustness of the findings. The results show that higher levels of fine particulate matter are consistently linked to increased mortality across all quantiles. Economic growth reduces mortality at higher quantiles of the distribution, where health burdens are most severe, indicating that stronger economies are better able to mitigate pollution-related deaths. Inflation exhibits a positive relationship with mortality, particularly at higher quantiles, indicating that rising prices can limit access to essential health services and increase vulnerability. Health spending, in contrast, reduces mortality, though its impact varies by both time horizon and income level. Overall, the findings highlight the importance of cleaner air, stable prices and stronger healthcare systems for reducing pollution-related mortality in Sub-Saharan Africa. The study provides policy-relevant insights for promoting health resilience under economic and environmental stress.