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J Occup Health year 2000 volume 42 number 6 page 281 - 283
Classification Original
Title Log-Normality of Air Contaminants and Its Hidden Characteristics Useful for
Industrial Hygiene Technology
Author Akio KOIZUMI1, Masayuki KATAHIRA2, Takeshi SEKIGUCHI3 and Yasunobu SHIOTA3
Organization 1Department of Health and Environmental Sciences, School of Public Health, Kyoto University,
2Department of Medical Information Center, School of Medicine, Akita University and
3Information Science, Liberal Arts, Tohoku Gakuin University
Keywords Air contaminants, Stochastic nature, Log-normal distribution, Ito-process, Industrial hygiene technology, Split source theorem
Correspondence A. Koizumi, Department of Health and Environmental Sciences, School of Public Health, Kyoto University, Kyoto 606-8501, Japan
Abstract Log-Normality of Air Contaminants and Its Hidden Characteristics Useful for Industrial Hygiene Technology: Akio KOIZUMI, et al. Department of Health and Environmental Sciences, School of Public Health, Kyoto University-It is well known that concentrations of contaminants in the air fluctuate log-normally, but there has been no mathematical model that can describe the stochastic nature of this. In the present study we constructed a stochastic model that can describe log-normal distribution of the air contaminantion in workplaces. The so-called Ito-process can describe the log-normality of the stochastic nature of the air contaminants by using two parameters: ventilation performance and random release of contaminants from the source. We also derived a theorem from the model. It indicates that splitting the source into small independent compartments decreases randomness and thereby reduces exposure intensity. The reduction of randomness of contaminant release is considered to be as effective as improvement of ventilation performance in reducing workers' exposure.