Systematic bias in real-time dust monitoring: a meta-analysis of measurement discrepancy and its implications for occupational exposure assessment

Abstract

Real-time dust monitors (RTMs), particularly light-scattering photometers, are increasingly used in occupational exposure assessment, yet their measurement agreement with gravimetric sampling (GS)—the regulatory reference method—has not been systematically quantified across the occupational hygiene literature. This meta-analysis qualitatively synthesised 112 occupational studies and quantitatively analysed 96 independent comparison pairs identified through systematic searches of Scopus, Web of Science, and PubMed (2010 to 2025) following PRISMA 2020 guidelines. Using a three-level random-effects model with log response ratios (lnR) of geometric mean concentrations as the effect size, we found that professional-grade optical RTMs reported concentrations on average 36% higher than GS (pooled lnR = 0.31; 95% CI: 0.25, 0.37; I2 = 78.4%; 95% prediction interval: 0.11, 0.63). In subgroup analysis, factory-calibrated instruments showed 43% higher concentrations, whereas site-specifically calibrated instruments showed only 13% higher concentrations. Mixed-effects meta-regression identified site-specific calibration as the strongest moderator (β = −0.24; P < 0.001). Additional moderators included particle size distribution (log GSD: β = 0.15; P = 0.012) and relative humidity (β = 0.002; P = 0.046). The included studies employed professional-grade instruments (eg, TSI DustTrak™, SidePak™, Thermo pDR™); no eligible occupational study reported concurrent low-cost sensor (<$500) versus gravimetric comparisons meeting our inclusion criteria, highlighting a critical evidence gap as these sensors enter occupational use. These findings provide the first pooled quantitative evidence base supporting site-specific calibration as a prerequisite for valid quantitative exposure assessment with optical dust monitors in occupational settings.