Handbook of Occupational Safety and Health, 3rd Edition

CHAPTER 5STATISTICAL METHODS FOR OCCUPATIONAL EXPOSURE ASSESSMENT

DAVID L. JOHNSON

Department of Occupational and Environmental Health, College of Public Health, University of Oklahoma, Health Sciences Center, P.O. Box 26901, Oklahoma City, OK, 73126‐0901

5.1 INTRODUCTION

Exposure assessment is a primary function of the occupational safety and health professional. Airborne gas and vapor concentrations, aerosol concentrations and particle size distributions, sound pressure levels, radiation levels, and other potential hazards are measured to assess exposures as to their ranges, maxima, averages, and frequency distribution. Exposure guidelines and standards may then be consulted to make decisions about the adequacy of workplace exposure controls. The likelihood of overexposure and regulatory noncompliance can be explored by modeling the exposure frequency distribution to determine how often unacceptably high exposure might occur.

Measurements might be made to address specific questions such as:

• At what levels are workers being exposed?
• Are exposures different for different worker groups?
• Are exposures in compliance with occupational exposure limits?
• Has an intervention changed worker exposures?
• How likely is it that workers will be overexposed?
• How much uncertainty is there in the measures and the values calculated from them?

In this chapter, statistical techniques useful in answering such questions will be reviewed. Both parametric and nonparametric techniques are discussed, ...