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Most fine ambient particulate matter (PM_2.5)-based epidemiological models use globalized concentration-response (CR) functions assuming that the toxicity of PM_2.5is solely mass-dependent without considering its chemical composition. Although oxidative potential (OP) has emerged as an alternate metric of PM_2.5toxicity, the association between PM_2.5mass and OP on a large spatial extent has not been investigated. In this study, we evaluate this relationship using 385 PM_2.5samples collected from 14 different sites across 4 different continents and using 5 different OP (and cytotoxicity) endpoints. Our results show that the relationship between PM_2.5mass vs. OP (and cytotoxicity) is largely non-linear due to significant differences in the intrinsic toxicity, resulting from a spatially heterogeneous chemical composition of PM_2.5. These results emphasize the need to develop localized CR functions incorporating other measures of PM_2.5properties (e.g., OP) to better predict the PM_2.5-attributed health burdens.

 

The MGO symposium was held on February 18th with seven featured speakers from all over the globe. Drs. Bin Zhang and Alexey Onufriev chaired the session with Drs. Yamini Dalal and Anna Panchenko as the 2022 MGO co-chairs. The session and goals of the MGO subgroup were introduced by Dr. Panchenko, followed by talks from the invited speakers. The presentations showcased research at the forefront of the field and elicited high audience engagement. Here, we summarize the presentations of these invited speakers. 

The Harmattan, a dry, northeasterly trade wind, transports large quantities of Saharan dust over the Sahelian region during the dry season (December–March). Studies have shown that bacterial meningitis outbreaks in Sahelian regions show hyper‐endemic to endemic levels during high‐dust months. We examine the (a) seasonality and intraseasonal variability of dust, climate, and meningitis and the (b) quantitative relationships between various dust proxies with meningitis lags of 0–10 weeks in Senegal from 2012 to 2017. The results show that the onset of the meningitis season occurs in February, roughly 2 months after the dusty season has begun. The meningitis season peaks at the beginning of April, when northeasterly wind speeds and particulate matter (PM) are relatively high, and the meningitis season ends near the end of June, when temperature and humidity rise and northeasterly wind speeds decline. Furthermore, we find that Senegal's relatively high humidity year‐round may help slow the transmission of the infection, contributing to a lower disease incidence than landlocked countries in the meningitis belt. Lastly, our results suggest the desert dust may have a significant impact on the onset to the peak of the meningitis season in Senegal, particularly at the 0–2 and 10‐week lag, whether that be directly through biological processes or indirectly through changes in human behavior. PM and visibility, however, are not in phase with aerosol optical depth throughout the year and consequently show different relationships with meningitis. This study further exemplifies the critical need for more PM, meteorological, and meningitis measurements in West Africa to further resolve these relationships.