Abstract
Suspected detrimental health effects associated with ultrafine particles (UFPs) are impressive. However, epidemiological evidence is still limited. This is potentially due to challenges related to UFP exposure assessment and the lack of consensus on a standard methodology for UFPs. It is imperative to focus future health studies on those UFP metrics more likely to represent health effects. This is the purpose of this paper, where we extend the results obtained during the CARE (“Carbonaceous Aerosol in Rome and Environs”) experiment started in 2017 in Rome. The major purpose is to investigate features of airborne UFPs associated with pro-inflammatory and oxidative responses. Aerosol chemical, microphysical, and optical properties were measured, together with the oxidative potential, at temporal scales relevant for UFPs (minutes to hours). The biological responses were obtained using both in-vivo and in-vitro tests carried out directly under environmental conditions. Findings indicate that caution should be taken when assessing health-relevant exposure to UFPs through the conventional metrics like total particle number concentration and PM2.5 and Black Carbon (BC) mass concentration. Conversely, we recommend adding to these, a UFP source apportionment analysis and indicators for both ultrafine black carbon and the size of particles providing most of the total surface area to available toxic molecules.
Highlights
Half of all people in the world live in cities, air quality is increasingly polluted.Urban air pollution associated with fine particulate matter is considered the leading environmental health risk factor globally, causing several million deaths per year [1,2,3,4]
We show limitations of both the mass-based regulatory standards for PM2.5 and the conventionally used metrics for ultrafine particles (UFPs) in indicating the pro-inflammatory and oxidative responses observed during the CARE experiment, and we propose alternative approaches
We analyse how the commonly used aerosol metrics for fine and ultrafine particles weigh the biological responses observed during the CARE experiment under conditions dominated by combustion aerosols
Summary
Half of all people in the world live in cities, air quality is increasingly polluted. UFPs and assess their relationship with health outcomes As these measurement campaigns are often based on daily data and are limited to one UFP metric (mostly Ntot ) and one city, the few existing epidemiological studies on effects of short-term exposure to UFPs from these sites may lack adequate statistical power [35,36,37,38]. We aim at identifying metric(s) that can be considered as predictor(s) only for the pro-inflammatory and oxidative responses observed during the CARE experiment It is clearly limited, the approach relies on the oxidative stress paradigm, a well-recognized and accepted hypothesis for several air pollution-related health diseases
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