Variation in the ratio of respirable particulates over inhalable particulates by type of dust workplace

Objective: The aim of the present study was to clarify the quantitative relationship between respirable particulates and inhalable particulates in various dust workplaces. Methods: Both respirable particulate and inhalable particulate concentrations were measured in 1644 dust workplaces by means of elutriation, and the ratio of respirable particulate mass over that of inhalable particulate (R/I ratio) was calculated for each workplace. Results: Statistical analyses showed that the R/I ratio varied substantially, depending on the type of dust work. The ratio was highest in welding workplaces (mean ± SD: 53 ± 19%) and lowest in foundries (23 ± 16%); the former value suggests that respirable particulate exposure may be underestimated in substantial parts of welding work when only the occupational exposure limit for inhalable particulates is taken for compliance testing. Conclusions: Simple compliance with the limit for inhalable particulates is not sufficient, and the limit for respirable particulates should also be simultaneously cleared. Received: 21 February 1997 / Accepted: 17 July 1997