Fluctuations of occupational exposure indices to mixtures

In workplaces, two or more hazardous substances are often used simultaneously. Daily average exposure to each can vary considerably from day to day, and thus indices (Emix) combining exposures to all substances used must vary in a more complex manner. In this study, we examined the between-days distributions of Emix using occupational data for five workers exposed to two or more organic solvents, and found Emix to be log-normally distributed. To describe the between-days fluctuation of Emix, we propose a new model in which the causes of fluctuation were classified as a Specific Factor and a Common Factor. We also present a new method for estimating the distribution of Emix. The usefulness of our new model and new method is shown by their application to actual data.