Air quality in the Canary Islands: A geographical, climatic, and health-based approach

Abstract

This study analyses air quality in the Canary Islands between 2009 and 2024, being the first to simultaneously examine five pollutants: PM₁₀, PM_2.5, SO₂, NO₂, and O₃. The research focus is justified by the archipelago's proximity to the Sahara Desert, its high vehicle density, and the recent decommissioning of major industrial sources, including an oil refinery and a thermal power plant in Tenerife. Hourly data from 76 stations of the Canary Islands Air Quality Control and Monitoring Network were combined with daily meteorological observations from 22 stations and ECMWF satellite reanalysis, including temperature, humidity, wind, and the altitude of the characteristic subsidence thermal inversion. Correlations, multivariate models, and an XGBoost machine learning model were applied to evaluate the influence of meteorological conditions on pollutant concentrations. Results show a marked increase in PM₁₀ and PM_2.5 during Saharan dust intrusions, particularly in winter, when dust is transported at low altitudes, significantly deteriorating air quality. In contrast, SO₂ and NO₂ concentrations have decreased substantially since 2009 (−51% and −27%, respectively), reflecting reduced industrial emissions and moderate improvements in urban mobility, although peak traffic episodes still cause localized pollution in Santa Cruz de Tenerife and Las Palmas de Gran Canaria. O₃ levels remain low and are primarily modulated by meteorological factors, including the altitude of the subsidence inversion and the dispersive effect of trade winds. The subsidence thermal inversion is confirmed as the main predictor of particle and primary pollutant accumulation, while periods of high temperatures and low humidity amplify simultaneous exposure to multiple pollutants, posing elevated public health risks.