Interpersonal and daily variability of personal exposures to nitrogen dioxide and sulfur dioxide

Abstract

Chronic exposure is often assessed using a single measurement per individual or group. However, daily levels of personal exposure can vary greatly. Chronic exposure classification by a single measurement could be significantly affected by the interpersonal and daily variations of exposures. The purpose of this study is to determine the effect of using a single personal exposure measurement on estimating long-term exposure. This study used measurements of consecutive 14 daily personal exposures to nitrogen dioxide (NO₂) and sulfur dioxide (SO₂) of 50 individuals in Yeochun, Korea. The daily personal exposures were measured by passive samplers. Personal exposure to NO₂ was associated with gas cooking, and personal exposure to SO₂ was associated with ambient air pollution. Mixed effects models indicated that daily variability was greater than interpersonal variability for both the pollutants. Effectiveness of using single-day personal measurements for long-term population mean exposure was supported by relatively consistent daily population averages, but multiple-day measurements might be warranted for characterizing individual exposures or high-end population exposures such as the 95th percentile. Although classification of high and low exposure groups by 1-day exposure and by 14-day exposure produced similar group totals, 20% of individual NO₂ exposures and 31% of individual SO₂ exposures were misclassified using 1-day exposures. Average values of 1-day exposure and 14-day exposure were significantly different, but the difference decreased by an increase in the number of measurements for the short-term exposure. The findings were similar for both NO₂ and SO₂, although the two air pollutants have different sources and behaviors.