Comparison between different traffic-related particle indicators: Elemental carbon (EC), PM2.5 mass, and absorbance

Abstract

Here we compare PM 2.5 (particles with aerodynamic diameter less than 2.5 mm) mass and filter absorbance measurements with elemental carbon (EC) concentrations measured in parallel at the same site as well as collocated PM 2.5 and PM 10 (particles with aerodynamic diameter less than 10 mm) mass and absorbance measurements. The data were collected within the Traffic-Related Air Pollution on Childhood Asthma (TRAPCA) study in Germany, The Netherlands and Sweden. The study was designed to assess the health impact of spatial contrasts in long-term average concentrations. The measurement sites were distributed between background and traffic locations. Annual EC and PM 2.5 absorbance measurements were at traffic sites on average 43-84% and 26-76% higher, respectively, compared to urban background sites. The contrast for PM 2.5 mass measurements was lower (8-35%). The smaller contrast observed for PM 2.5 mass in comparison with PM 2.5 absorbance and EC documents that PM 2.5 mass underestimates exposure contrasts related to motorized traffic emissions. The correlation between PM 10 and PM 2.5 was high, documenting that most of the spatial variation of PM 10 was because of PM 2.5 . The measurement of PM 2.5 absorbance was highly correlated with EC measurements and suggests that absorbance can be used as a simple, inexpensive and non-destructive method to estimate motorized traffic-related particulate air pollution. The EC/absorbance relation differed between countries and site type (background/traffic), supporting the need for site-specific calibrations of the simple absorbance method. While the ratio between PM 2.5 and PM 10 mass ranged from 0.54 to 0.68, the ratio of PM 2.5 absorbance and PM 10 absorbance was 0.96-0.97, indicating that PM 2.5 absorbance captures nearly all of the particle absorbance.

Personal exposures and indoor, residential outdoor, and urban background levels of fine particle trace elements in the general population

“…Because EC is the dominant light-absorbing substance in the atmosphere (Hoek et al, 1997;Horvath et al, 1996;Seinfeld and Pandis, 1998), an alternative way to estimate EC concentrations in the atmosphere as BS is to measure light absorption or reflectance of PM, collected on filter media. Several studies have reported that BS, derived from absorbance coefficients, is well correlated with the concentration of EC or soot and can be recommended as a valid and cheap indicator in studies on combustion-related air pollution and health (Cyrys et al, 2003;Götschi et al, 2002;Janssen et al, 2001;Kinney et al, 2000).…”

“…In Paper IV the areas studied were the same as those studied in the impact of TrafficRelated Air Pollution on Childhood Asthma (TRAPCA) study (Cyrys et al, 2003;Emenius et al, 2003). They were Norrmalm in Stockholm's city centre, the municipalities of Solna and Sundbyberg located about 10 km NW of the city centre, and the municipality of Järfälla which lies about 25 km NW of the city centre.…”

“…They were Norrmalm in Stockholm's city centre, the municipalities of Solna and Sundbyberg located about 10 km NW of the city centre, and the municipality of Järfälla which lies about 25 km NW of the city centre. These areas are affected differently by local sources such as traffic, as presented by Emenius et al (2003) for the traffic marker NO 2 and by Cyrys et al (2003) for EC, BS and PM 2.5 .…”

Relationship between indoor and outdoor levels of fine particle mass, particle number concentrations and black smoke under different ventilation conditions

“…Thus, in addition to the measurements of particle number and/or mass concentration the characterization of the chemical composition of particles may also be important for assessment of health effects. Several studies have documented that black smoke (BS), derived from absorbance coefficients, is well correlated with the concentration of elemental carbon (EC) or soot and can be recommended as a valid and cheap indicator in studies on combustion-related air pollution and health (Kinney et al, 2000;Janssen et al, 2001;Gotschi et al, 2002;Cyrys et al, 2003).…”

On exposure and response relationships for health effects associated with exposure to vehicular traffic

“…In the United States, the recent emphasis on fine particles (PM 2.5 ) has resulted in attempts to characterize its relationship with traffic. However, comparative studies have shown that the elemental carbon content of PM is a better indicator of traffic than PM mass (Cyrys et al, 2003;Smargiassi et al, 2005), even when measured indoors . There are many other elements and compounds that may also be associated with vehicular traffic (Schauer et al, 2006;Cadle et al, personal communication), most of which are not routinely monitored:…”