Estimating Error in Using Ambient PM2.5 Concentrations as Proxies for Personal Exposures: A Review

Abstract

Background Several methods have been used to account for measurement error inherent in using ambient concentration of particulate matter < 2.5 μm/m3 (PM2.5) as a proxy for personal exposure. Such methods usually rely on the estimated correlation between ambient and personal PM2.5 concentrations (r). These studies have not been systematically and quantitatively assessed for publication bias or heterogeneity. Methods We searched seven electronic reference databases for studies of the within-participant correlation between ambient and personal PM2.5. Results We identified 567 candidate studies, eighteen (3%) of which met inclusion criteria and were abstracted. The studies were published between 1999 and 2008, representing 619 non-smoking participants aged 6–93 years in seventeen European and North American cities. Correlation coefficients (median 0.54; range 0.09–0.83) were based on a median of eight ambient-personal PM2.5 pairs per participant (range 5 to 20) collected over 27 to 547 days. Overall, there was little evidence for publication bias (funnel plot symmetry tests: Begg’s log rank test, P=0.9; Egger’s regression asymmetry test, P=0.2). However, strong evidence for heterogeneity was noted (Cochran’s Q test for heterogeneity, P < 0.001). European locales, eastern longitudes in North America, higher ambient PM2.5 concentrations, higher relative humidity, and lower between-participant variation in r were associated with increased r. Conclusions Characteristics of participants, studies, and the environments in which they are conducted may affect the accuracy of ambient PM2.5 as a proxy for personal exposure.

Validity of using annual mean particulate matter concentrations as measured at fixed site in assessing personal exposure: An exposure assessment study in Japan

“…Our findings suggest that the concentrations measured at fixed sites are likely to correspond with the concentrations measured outside homes within a 5-km radius. However, people spend approximately 85% of their time indoors (Avery et al, 2010), and our findings were in accordance with the earlier report: the average proportion of each day our participants undergoing personal monitoring spent indoors during summer and autumn was 84%. Therefore, it is clear that a significant portion of total personal exposure to PM occurs in the indoor environment.…”

“…Although many studies have investigated the correlations between fixed-site and personal PM and NO 2 concentrations (Avery et al, 2010;Lai et al, 2004;Sarnat et al, 2000), they focused on short-term PM and NO 2 exposure. Similar investigations of long-term exposure to pollutants, particularly to PM, are sparse, so the results of the present study are valuable in clarifying any bias caused by the use of fixed-site measurements as proxies for individual exposure in studies of the effects of long-term PM and NO 2 exposure on health outcomes.…”

An Exposure-Mortality Relationship for Residential Indoor PM2.5 Exposure from Outdoor Sources

“…The change in mortality risk in relation to changes in personal exposure is appreciably greater (30-50%) than the original ACS coefficient indicates, but the fact that indoor PM 2.5 is only a partial determinant of overall PM 2.5 exposure tends to reduce the overall relative "correction" for residential indoor exposure to approximately unity. A modification to the ACS coefficient of around 30% to 50% for total personal exposure is broadly consistent with previously published evidence suggesting increased coefficients for personal exposure in time-series studies [37,38]. Similarly, studies adjusting coefficients for exposure measurement error using regression calibration techniques have tended to suggest that central monitoring sites generally provide a reasonable representation of overall personal exposures [39][40][41].…”

A measurement of summertime dry deposition of ambient air particulates and associated metallic pollutants in Central Taiwan

“…For many epidemiologic air pollution time series studies, a central monitoring site is used to determine the exposure of study subjects. Previous studies have shown that the ambient concentrations of PM 2.5 at a fixed site can be a good predictor of personal exposure, but the accuracy is dependent on the characteristics of the participants, studies, and environments in which they are conducted (Avery et al 2010). Additionally, the highest PM 10 and PM 2.5 concentrations in European cities occur at roadsides.…”