Redox-active metals impact the highest oxidative potential values in the urban and roadside locations in London

Abstract

The OP of ambient PM has been associated with adverse respiratory outcomes using acellular models, such that the measured activity is the sum of the pro-oxidants associated with the particle surface. PM10 OP was measured using daily filters collected consecutively during summer and winter periods (3-5 weeks) at 4 sites in Southern England, based on their capacity to deplete glutathione (OPGSH) from a synthetic RTLF. The four sites represented roadside (Marylebone) and urban background (North Kensington) locations in London; plus rural sites to the West (Harwell) and East (Detling) of the city. PM metal concentrations were determined by ICP-MS. All data are expressed per m3 of ambient air. In the winter period equivalent OPGSH values were observed in the rural sites west (7.57±10.06%/m3) and east of London (7.98±7.18%/m3), representing approximately 20% of the urban background value (38.65±13.05%/m3). In contrast, during the summer the measured OPGSH was similar across the rural and urban background sites: 13.01±12.86 (Harwell), 12.25±12.68 (North Kensington) and 18.77±5.61 (Detling) %/m3, with a significant increment only apparent at the roadside location (31.77±10.10%/m3). When the contribution of PM metals to the measured OPGSH was assessed, inconsistent associations were apparent across the site types and seasons with no significant associations with metals during the summer at Detling. In our study we found that OPGSH within London during the winter is dominated by diffuse urban sources, whilst in the summer regional contributions dominated. The contribution of metals related to mechanical abrasion to this metric varied by season and location.