title: Comparison of ambient airborne PM₂.₅, PM₂.₅ absorbance and nitrogen dioxide ratios measured in 1999 and 2009 in three areas in Europe.
abstract: Epidemiological studies often use nitrogen dioxide (NO2) or proximity to roads to characterize exposure to more health-relevant pollutants (e.g., fine particles or black carbon aerosol) in vehicle exhaust. Due to the introduction of diesel-soot filters, particle-to-NO2 ratios may have decreased, but little information is available about these ratios over time. Our study aim was to evaluate the change in particle-to-NO2 ratios between 1999 and 2009. We compared data collected during measurement campaigns in 1999 and 2009 from Munich, the Netherlands, and Stockholm. Traffic-impacted and urban and regional background sites were studied during each campaign. The same pollutants were measured in each campaign (mass concentration of particles ≤ 2.5 microns in diameter (PM2.5), PM2.5 absorbance (a marker for black carbon), and NO2) using the same methods except for NO2: Palmes tubes were used in 1999 and Ogawa badges in 2009. Both NO2 methods were validated against side-by-side chemiluminescence measurements. The levels of PM2.5 absorbance and PM2.5 were significantly lower (p<0.05) in 2009 at traffic and urban background sites in Stockholm, but only slightly lower in Munich and the Netherlands. In contrast, NO2 levels were not significantly different in the three areas in 2009 compared to 1999. Statistically-significant decreases between 1999 and 2009 pollutant ratios in the Netherlands (PM2.5 absorbance/NO2 and PM2.5/NO2) and in Stockholm (PM2.5 absorbance/NO2 and PM2.5 absorbance/PM2.5) were observed. Smaller decreases in these ratios were observed in Munich. The contrast between traffic and urban background locations was larger in 2009 than 1999 for NO2, whereas it was smaller for PM2.5 absorbance and PM2.5. The lower PM2.5 absorbance/NO2 and PM2.5/NO2 ratios in 2009 is likely explained by the introduction of oxidative particle filters for diesel vehicles that reduce particles but produce NO2. The changed contrasts may affect estimates of health effects related to NO2 as a marker of proximity to roads.
authors.affiliation: Institute for Risk Assessment Sciences (IRAS), Division of Environmental Epidemiology, University of Utrecht, Utrecht, The Netherlands; Department of Civil & Environmental Engineering, Tufts University, Medford, MA, USA. Electronic address: jdurant@tufts.edu.
authors.forename: John L
authors.initials: JL
authors.lastname: Durant
authors.affiliation: Institute for Risk Assessment Sciences (IRAS), Division of Environmental Epidemiology, University of Utrecht, Utrecht, The Netherlands.
authors.forename: Rob
authors.initials: R
authors.lastname: Beelen
authors.affiliation: Institute for Risk Assessment Sciences (IRAS), Division of Environmental Epidemiology, University of Utrecht, Utrecht, The Netherlands; Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, Basel, Switzerland; University of Basel, Basel, Switzerland.
authors.forename: Marloes
authors.initials: M
authors.lastname: Eeftens
authors.affiliation: Institute for Risk Assessment Sciences (IRAS), Division of Environmental Epidemiology, University of Utrecht, Utrecht, The Netherlands.
authors.forename: Kees
authors.initials: K
authors.lastname: Meliefste
authors.affiliation: Environment Science Center, Universität Augsburg, Augsburg, Germany; Helmholtz Zentrum München, German Research Center for Environmental Health, Institute of Epidemiology II, Neuherberg, Germany.
authors.forename: Josef
authors.initials: J
authors.lastname: Cyrys
authors.affiliation: Helmholtz Zentrum München, German Research Center for Environmental Health, Institute of Epidemiology I, Neuherberg, Germany.
authors.forename: Joachim
authors.initials: J
authors.lastname: Heinrich
authors.affiliation: Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden; Department of Occupational and Environmental Health, Stockholm, Sweden.
authors.forename: Tom
authors.initials: T
authors.lastname: Bellander
authors.affiliation: Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden; Department of Occupational and Environmental Health, Stockholm, Sweden.
authors.forename: Marie
authors.initials: M
authors.lastname: Lewné
authors.affiliation: Institute for Risk Assessment Sciences (IRAS), Division of Environmental Epidemiology, University of Utrecht, Utrecht, The Netherlands; Julius Center for Health Sciences and Primary Care, University Medical Center, Utrecht, The Netherlands.
authors.forename: Bert
authors.initials: B
authors.lastname: Brunekreef
authors.affiliation: Institute for Risk Assessment Sciences (IRAS), Division of Environmental Epidemiology, University of Utrecht, Utrecht, The Netherlands.
authors.forename: Gerard
authors.initials: G
authors.lastname: Hoek
mesh_terms: D000393:Air Pollutants / Q000032:analysis*; D000397:Air Pollution / Q000706:statistics & numerical data*; D004784:Environmental Monitoring; D005060:Europe; D009585:Nitrogen Dioxide / Q000032:analysis*; D052638:Particulate Matter / Q000032:analysis*
chemical_list: D000393:Air Pollutants; D052638:Particulate Matter; D009585:Nitrogen Dioxide
keywords: Germany; NO(2); Pollutant ratios; Sweden; The Netherlands; Traffic-related air pollution