Air pollution and cardio-respiratory mortality in Limpopo, South Africa (2011–2020): evidence on population and seasonal vulnerability

Abstract Ambient air pollution is a growing public health concern in South Africa. However, the health impacts of ambient air pollution in the country remain largely unquantified, a gap that is consistently reflected in global systematic reviews. This study investigates the association between ambient air pollution and cause-specific mortality, cardiovascular (CVD), and respiratory disease (RD), in Limpopo province, South Africa, over a decade from 2011 to 2020, with the aim of unravelling population and seasonal vulnerability. Daily mortality data were sourced from Statistics South Africa, while ambient air pollutant concentrations (PM₁₀, PM₂.₅, SO₂, NO₂, and O₃) were retrieved from the South African Air Quality Information System. Time-series and quasi-Poisson regression models within a generalized additive model framework were employed to estimate relative risks (RRs) per interquartile range (IQR) increase in pollutant concentrations, adjusting for seasonality and meteorological covariates. A total of 73,167 CVD and 62,248 RD deaths were recorded during the study period. PM and O₃ emerged as the strongest predictors of excess mortality, with O₃ particularly linked to CVD mortality and PM to RD mortality. An interquartile range increase in O₃ was associated with a 0.3–7.5% increase in CVD and RD mortality across subgroups, while PM₂.₅ showed smaller but significant increases, ranging from 0.3 to 1.2% across subgroups for CVD and RD mortality. Notably, SO₂ and NO₂ exhibited weaker and more variable effects, often manifesting at delayed lags. Vulnerable populations, particularly women, older adults (65+), and certain outdoor-exposed workers, experienced greater mortality risks, highlighting the differential susceptibility of specific subgroups. Seasonal analysis revealed elevated mortality and pollutant concentrations during the cold compared to the warm period. Short-term exposure to ambient air pollution is associated with increased cardio-respiratory mortality in Limpopo Province, with stronger effects for ozone and particulate matter and heightened vulnerability during the cold season, highlighting the need for targeted public health and regulatory interventions.