Temporal trends in ambient fine particulate matter in Grenada between 2009 and 2022

Despite its association with significant morbidity and mortality, ambient fine particulate matter (PM_2.5) is not robustly monitored in the Caribbean region. To estimate historical PM_2.5 concentration trends in Grenada, an island often impacted by Saharan dust storms, a daily time series analysis was conducted using PM_2.5 reanalysis data from the Modern-Era Retrospective Analysis for Research and Applications (MERRA-2) as a proxy, due to the absence of reference ground monitoring stations. A multivariate linear regression model was used to evaluate the interactions between MERRA-2 PM_2.5 concentrations and meteorological correlates. Finally, MERRA-2 PM_2.5 concentrations were compared to low-cost ground monitoring data obtained from PurpleAir laser particle counters. Although mean PM_2.5 concentrations remained relatively stable over the study period (14.50 μg m^-3), significant variability was noted with a standard deviation of 8.07 μg m^-3. PM_2.5 concentrations were consistently and significantly higher during the months typically associated with Saharan dust events, with pronounced peaks linked to recorded dust storms and other natural phenomena. Given that PM_2.5 exposure is linked to various adverse health effects, the findings from this study can serve as a basis for establishing more comprehensive monitoring networks. Additionally, these findings can help inform air quality management decisions that are better tailored to the region. Finally, the lessons learned from this evaluation of temporal trends in PM_2.5 can serve to enhance research capabilities and support the implementation of air quality management initiatives in Grenada and other small island developing states in the region.