Assessment of personal exposure and spatial concentration variability in a small-scale chemical laboratory

Exposure assessment in chemical laboratories is often conducted using area-based measurements; however, the extent to which such measurements represent actual personal exposure remains uncertain. In Japan, chemical risk management has traditionally relied on the regulatory working environment measurement system, in which area concentrations are evaluated using fixed-point sampling. As part of recent regulatory changes, personal exposure measurements will become mandatory from October 2026, highlighting the need to clarify the adequacy and limitations of conventional area-based measurements in laboratory environments. In this study, the relationship between area concentrations obtained by area measurements and personal exposure levels during student experiments conducted in a small-scale chemical laboratory was investigated. Field measurements were conducted during the same experiments in 2024 and 2025. Area concentrations were measured at fixed locations, whereas personal exposure levels were evaluated for students using passive samplers. The results showed that personal exposure concentrations were consistently higher than area concentrations, with mean values approximately one order of magnitude greater in both years. In addition, computational fluid dynamics simulations were conducted to analyze the concentration distributions within the laboratory. The numerical analysis demonstrated height-dependent concentration variability that cannot be captured by fixed-point measurements at a single height. These findings suggest that area-based measurements alone may be insufficient for accurately evaluating personal exposure in small-scale chemical laboratories.