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 quantitativ e relationship between respirable particulates and inhalable particula tes in various dust workplaces. Methods: Both respirable particulate a nd inhalable particulate concentrations were measured in 1644 dust wor kplaces by means of elutriation, and the ratio of respirable particula te 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 ra tio was highest in welding workplaces (mean +/- SD: 53 +/- 19%) and lo west in foundries (23 +/- 16%); the former value suggests that respira ble 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 comp liance with the limit for inhalable particulates is not sufficient, an d the limit for respirable particulates should also be simultaneously cleared.