Increased Oxidative Burden Associated with Traffic Component of Ambient Particulate Matter at Roadside and Urban Background Schools Sites in London

Abstract

As the incidence of respiratory and allergic symptoms has been reported to be increased in children attending schools in close proximity to busy roads, it was hypothesised that PM from roadside schools would display enhanced oxidative potential (OP). Two consecutive one-week air quality monitoring campaigns were conducted at seven school sampling sites, reflecting roadside and urban background in London. Chemical characteristics of size fractionated particulate matter (PM) samples were related to the capacity to drive biological oxidation reactions in a synthetic respiratory tract lining fluid. Contrary to hypothesised contrasts in particulate OP between school site types, no robust size-fractionated differences in OP were identified due high temporal variability in concentrations of PM components over the one-week sampling campaigns. For OP assessed both by ascorbate (OPAA m−3) and glutathione (OPGSH m−3) depletion, the highest OP per cubic metre of air was in the largest size fraction, PM1.9–10.2. However, when expressed per unit mass of particles OPAA µg−1 showed no significant dependence upon particle size, while OPGSH µg−1 had a tendency to increase with increasing particle size, paralleling increased concentrations of Fe, Ba and Cu. The two OP metrics were not significantly correlated with one another, suggesting that the glutathione and ascorbate depletion assays respond to different components of the particles. Ascorbate depletion per unit mass did not show the same dependence as for GSH and it is possible that other trace metals (Zn, Ni, V) or organic components which are enriched in the finer particle fractions, or the greater surface area of smaller particles, counter-balance the redox activity of Fe, Ba and Cu in the coarse particles. Further work with longer-term sampling and a larger suite of analytes is advised in order to better elucidate the determinants of oxidative potential, and to fuller explore the contrasts between site types.

Comparison between five acellular oxidative potential measurement assays performed with detailed chemistry on PM<sub>10</sub> samples from the city of Chamonix (France)

“…The ESR assay employs the spin trap 5,5-dimethyl-1-pyrroline N-oxide (DMPO) and is specific for reactive radical species, which for example result from partial reduction of dioxygen catalyzed by transition metal (Boogaard et al, 2012;Shi et al, 2003). The AA assays would be more specific to the oxidative potential of transition metals (Godri et al, 2011;Yang et al, 2014), but ascorbic acid is known to react with organics such as quinones (Shang et al, 2012;Visentin et al, 2016). All of these assays have shown some correlations with health outcomes in epidemiological studies (Abrams et al, 2017;Bates et al, 2015;Fang et al, 2016;Strak et al, 2017;Weichenthal et al, 2016a, b;Yang et al, 2016).…”

Relationship between chemical composition and oxidative potential of secondary organic aerosol from polycyclic aromatic hydrocarbons

“…In vitro cellular assays were conducted by detecting biological endpoints of the exposure, including heme oxygenase-1 (HO-1) and other cytokines as well as macrophage-related biomarker expressions (Krapf et al, 2017;Li et al, 2003b). On the other hand, acellular assays use specific chemicals, such as dithiothreitol (DTT), ascorbate (AA), and glutathione (GSH), as surrogates of low molecular weight (MW) antioxidants (Fang et al, 2016;Godri et al, 2011;McWhinney et al, 2013). Among acellular assays, the DTT assay quantifies OP by measuring the DTT depletion rate over a fixed time interval, which mimics the physiological process of electron transfer from biological antioxidants to dissolved O 2 (Cho et al, 2005).…”

Characterization of Traffic-Related Particulate Matter Emissions in a Road Tunnel in Birmingham, UK: Trace Metals and Organic Molecular Markers

“…Health risk (in terms of toxicity) associated with air pollutants has been linked to concentrations of transition metals and polycyclic aromatic hydrocarbons (PAHs), both of which are present in high concentrations in traffic emissions (Ayres et al, 2008). PM and diesel engine emissions have been classified as carcinogens by the International Agency for Research on Cancer (IARC), and several recent studies have linked vehicular emissions to adverse health effects (de Kok et al, 2006;HEI, 2010;Godri et al, 2011;Slezakova et al, 2013).…”