Calibration Approach of Indoor PM2.5 Concentrations with the PurpleAir for Epidemiological Studies [PurpleAir 실내 초미세먼지 측정농도 보정 방법 개발: 건강영향 평가를 목적으로]

초록

Given the well-established evidence regarding the adverse health effect of PM2.5, one of the intrinsic limitations of many epidemiological studies is their reliance on ambient exposure. The recent technical developments in low-cost sensors (LCS) have reduced the logistical and financial burdens associated indoor and/or personal PM2.5 monitoring. However, LCS PM2.5 measurements obtained by optical methods are highly sensitive to meteorological conditions and require appropriate calibration approaches before application. This study aimed to develop a calibration equation for hourly indoor LCS PM2.5 measurements using PurpleAir, one of the most widely applied LCS worldwide, in South Korea. Our indoor monitoring campaign collected 2-minute PM2.5 concentrations in the homes of 65 older adults living in urban areas of South Korea for five days during each of four seasons in 2023. In addition to PurpleAir, we used MicroPEM, as the reference instrument, that provides gravimetrically corrected PM2.5 concentrations. Using 11,999 hourly-averaged PM2.5 concentrations, we applied 16 calibration models incorporating different combination of meteorological conditions and compared the evaluation statistics using cross-validation. During the monitoring period, the mean of hourly PM2.5 concentration measured by PurpleAir was 23.88 μg/m3 (standard deviation [SD]=10.18). The overestimation by PurpleAir was consistently observed across hours, days, and seasons, although the seasonal and diurnal patterns were similar to those measured by MicroPEM. Among the 16 calibration models, the model including the dew point as a predictor yielded the lowest root mean square error (RMSE) among the single-predictor models and achieved an RMSE nearly identical to that of the most complex model. These findings suggest an optimal calibration approach for indoor PM2.5 measurements obtained using LCS devices and support the application of LCS technology in large-scale indoor and personal exposure assessment studies investigating the health effects of the PM2.5. Copyright © 2026 Korean Society for Atmospheric Environment This is an Open Access article distributed under the terms of the Creative Commons Attribution-NoDerivatives 4.0 International (CC BY-ND 4.0) License, which permits copying and redistribution in any medium or format, provided the original work is properly cited. The License does not permit modification, adaptation, translation, transformation, or the creation of derivative works.

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