Temporal trends in ambient fine particulate matter and the impacts of COVID-19 on this pollutant in Grenada, West Indies.

Most Caribbean islands do not have air pollution surveillance programs. Those who live in these countries are exposed to ambient air pollution from a variety of sources including motor vehicles, ocean-going vessels, and Saharan dust. We conducted an air sampling exposure study in Grenada to describe daily changes in fine particulate matter (PM 2.5 ) pollution, and during Saharan dust episodes. Further, we assessed the impacts of COVID-19 public health interventions on PM 2.5 concentrations in 2020. Four fixed-site PurpleAir monitors were installed throughout Grenada, and one on the neighboring island of Carriacou. PM 2.5 was measured between January 6 and December 31, 2020. We classified each of these days based on whether COVID-19 public health mitigation measures were in place or not. Descriptive analyses were performed to characterize fluctuations in PM 2.5 , and we assessed the impacts of public health restrictions on PM 2.5 using multivariate regression. The mean daily PM 2.5 concentration in 2020 was 4.4 μg/m 3 . During the study period, the minimum daily PM 2.5 concentration was 0.7 μg/m 3 , and the maximum was 20.4 μg/m 3 . Daily mean PM 2.5 concentrations more than doubled on Saharan dust days (8.5 vs 3.6 μg/m 3 ; p  < 0.05). The daily mean PM 2.5 concentrations were estimated to be 1.2 μg/m 3 lower when COVID-19 restrictions were in effect. Ambient PM 2.5 concentrations in Grenada are relatively low compared to other countries; however, Saharan dust episodes represent an important source of exposure. Low-cost sensors provide an opportunity to increase surveillance of air pollution in the Caribbean, however their value could be enhanced with the development of correction algorithms that more closely approximate values from reference-grade monitors. Implications : This study describes daily fluctuations in ambient PM 2.5 concentrations in Grenada in 2020. Overall, concentrations of PM 2.5 were low; however, we found that Saharan dust events cause daily exceedances in PM 2.5 above the current 24-hr limits of the World Health Organization. Moreover, the constructed models suggest that public health interventions to reduce the spread of COVID-19 reduced PM 2.5 concentrations by 27%.