Ambient site, home outdoor and home indoor particulate concentrations as proxies of personal exposures

Abstract

Despite strong longitudinal associations between particle personal exposures and ambient concentrations, previous studies have found considerable inter-personal variability in these associations. Factors contributing to this inter-personal variability are important to identify in order to improve our ability to assess particulate exposures for individuals. This paper examines whether ambient, home outdoor and home indoor particle concentrations can be used as proxies of corresponding personal exposures. We explore the strength of the associations between personal, home indoor, home outdoor and ambient concentrations of sulfate, fine particle mass (PM2.5) and elemental carbon (EC) by season and subject for 25 individuals living in the Boston, MA, USA area. Ambient sulfate concentrations accounted for approximately 70 to 80% of the variability in personal and indoor sulfate levels. Correlations between ambient and personal sulfate, however, varied by subject (0.1 – 1.0), with associations between personal and outdoor sulfate concentrations generally mirroring personal-ambient associations (median subject-specific correlations of 0.8 to 0.9). Ambient sulfate concentrations are good indicators of personal exposures for individuals living in the Boston area, even though their levels may differ from actual personal exposures. The strong associations for sulfate indicate that ambient concentrations and housing characteristics are the driving factors determining personal sulfate exposures. Ambient PM2.5 and EC concentrations were more weakly associated with corresponding personal and indoor levels, as compared to sulfate. For EC and PM2.5, local traffic, indoor sources and/or personal activities can significantly weaken associations with ambient concentrations. Infiltration was shown to impact the ability of ambient concentrations to reflect exposures with higher exposures to particles from ambient sources during summer. In contrast in the winter, lower infiltration can result in a greater contribution of indoor sources to PM2.5 and EC exposures. Placing EC monitors closer to participants’ homes may reduce exposure error in epidemiological studies of traffic-related particles, but this reduction in exposure error may be greater in winter than summer. It should be noted that approximately 20% of the EC data were below the field limit of detection, making it difficult to determine if the weaker associations with the central site for EC were merely a result of methodological limitations.

Personal, Indoor, and Outdoor Concentrations of Fine and Ultrafine Particles Using Continuous Monitors in Multiple Residences

“…This finding is unusual; of eleven recent studies, most showed mean personal exposures that were higher than mean outdoor concentrations (personal/outdoor ratios ranging from 0.8 to 2.5, compared to our ratio of 0.6, the lowest of all the studies) (Jannsen et al 1999;Pellizzari et al 1999;2001;Rojas-Bracho et al 2000;Williams et al 2000;Weisel et al 2005;Turpin et al 2007;Brown et al 2008). The DEARS study in the neighboring city of Detroit took place in the same years and resulted in similar mean outdoor PM 2.5 concentrations of about 16 µg/m 3 (Williams et al 2008), which is nearly identical to the mean of 15.9 µg/m 3 in Windsor; yet the mean indoor concentrations in Detroit were 19 µg/m 3 compared with 8 µg/m 3 in Windsor.…”

Concentrations of PM2.5 mass and components in residential and non-residential indoor microenvironments: The Sources and Composition of Particulate Exposures study

“…Previous exposure studies focused on personal exposures and/or home indoor PM 2.5 mass concentrations, as most individuals spend a large fraction of time indoors at home. A number of these studies have also measured levels of PM 2.5 components, such as sulfate and EC (Sarnat et al, 2006;Brown et al, 2008). Furthermore, some exposure studies have shown that personal PM 2.5 mass exposures exceed corresponding outdoor or ambient particulate concentrations (Wallace et al, 2006).…”

Relationships between Outdoor and Personal Exposure of Carbonaceous Species and Polycyclic Aromatic Hydrocarbons (PAHs) in Fine Particulate Matter (PM2.5) at Hong Kong

“…The weak correlation (r s = 0.328, p = 0.055) between ambient and personal PM 2.5 and the intercept greater than zero from the regression analysis in Table 4 suggests that the non-ambient sources (e.g., indoor sources, personal activities) had a significant role in personal exposures. As reported in Brown et al (2008) and Rivas et al (2015), local traffic, indoor sources and/or personal activities can significantly affect the personal exposure to PM 2.5 and EC. Mohammadyan (2011) found that ambient PM and time spent in polluted microenvironments (e.g., buses) are the most important determinants of personal exposure to PM 2.5 .…”