Seasonal variation in chemical composition of size-segregated urban air particles and the inflammatory activity in the mouse lung

Abstract

We investigated the seasonal variations in the chemical composition and in vivo inflammatory activity of urban air particulate samples in four size ranges (PM_10–2.5, PM_2.5–1, PM_1–0.2, and PM_0.2). The samples were collected in Helsinki using a high-volume cascade impactor (HVCI). Healthy C57BL/6J mice were intratracheally instilled with a single dose (10 mg/kg) of the particulate samples. The lungs were lavaged and the bronchoalveolar lavage fluid (BALF) was assayed for indicators of inflammation and tissue damage: cytokines (tumor necrosis factor [TNF]-α, interleukin [IL]-6, and keratinocyte-derived chemokine [KC]) at 4 h, and total cell number and total protein concentration at 12 h. The PM_10–2.5 and PM_2.5–1 samples had much higher inflammatory potency than the PM_1–0.2 and PM_0.2 samples. The relative inflammatory activities of the autumn samples were the highest on an equal mass basis, but when estimated for the particulate mass per cubic meter of air, the springtime samples had the highest inflammatory potential. Resuspended soil material and other non-exhaust particulate material from traffic were associated with a high inflammatory activity of the PM_10–2.5 and PM_2.5–1 samples. Secondary inorganic ions in the PM_1–0.2 and PM_0.2 samples had inconsistent negative or positive correlations with the inflammatory activity. There were no systematic seasonal variations in the tracers of incomplete combustion and atmospherically oxidized organics in the PM_1–0.2 and PM_0.2 samples, which probably explains their low correlations with the inflammatory activity. In conclusion, in a relatively clean Nordic city, the resuspension of road dust and other non-exhaust particulate material from traffic were the major sources of inflammatory activity of urban air inhalable particles.

Keywords::

• Inflammation
• particulate matter
• road dust
• sources
• traffic

Acknowledgements

This study was conducted within the framework of the project ‘Chemical and biological characterization of ambient air coarse, fine, and ultrafine particles for human health risk assessment in Europe’ (PAMCHAR) co-ordinated by the National Public Health Institute of Finland (http://www.pamchar.org/) and the Graduate School of Environmental Health (SYTYKE). The authors are grateful to MSc Anna Frey, MSc Sanna Saarikoski, and MSc Ulla Makkonen (Finnish Meteorological Institute), TechLic Tarja Koskentalo and Jouni Kettunen (Helsinki Metropolitan Area Council YTV), MSc Erik Sandell and Sirpa Himberg (Technical Research Centre of Finland, VTT Processes, Espoo, FI), and PhD Sirpa Pennanen and Virpi Turunen (Finnish Institute of Occupational Health) for collaboration in the field work or performing chemical analyses. The laboratory assistance in the toxicological experiments by Heli Martikainen, Arja Rönkkö, and Reetta Tiihonen and the statistical guidance by MSc Pekka Tiittanen (National Institute for Health and Welfare, Kuopio, FI) are highly appreciated.

Declaration of interest: The authors highly appreciate funding by the EC-FP5 Quality of Life and Management of Living Resources Programme (contract QLK4-CT-2001-00423), the Academy of Finland (FINE, contract 201701), and the Centre of Excellence Programme 2002–2007 of the Academy of Finland (contracts 53307 and 77298) and the Finnish Funding Agency for Technology and Innovation (Tekes, contracts 40715/01 and 40550/04). The PAMCHAR project belongs to the COST Action 633 on Particulate matter: Properties related to health effects (http://cost633.dmu.dk). The authors alone are responsible for the content and writing of the paper.