Exposure assessment for a study of workers exposed to acrylonitrile. III. Evaluation of exposure assessment methods.
Stewart-PA; Zey-JN; Hornung-R; Herrick-RF; Dosemeci-M; Zaebst-D; Pottern-LM
Appl Occup Environ Hyg 1996 Nov; 11(11):1312-1321
Methods used to assess historical exposures for an epidemiologic study when current exposure data were not available were described. The exposure data were to be used in a cohort mortality study of workers exposed to acrylonitrile (107131) at eight facilities. Approximately 18,000 measurements from company personal monitoring data were available. The data covered only about 3,500 out of 6,700 jobs. Four methods were used to estimate cohort acrylonitrile exposures from the data: the ratio method; the homogeneous exposure group (HEG) method; the time weighted average (TWA) method; and the informed judgment (deterministic) method. Representative data obtained from a random sampling of one job from each of 51 sets of four jobs showed that the ratio method overestimated the exposure by 77%, 1.64 parts per million (ppm) versus 0.93ppm. The TWA method underestimated the exposure of another job in the set by 24%, 0.47pppm versus 0.62ppm. The HEG and deterministic methods performed best, their estimates differing from the known exposures by only 0.01ppm. When applied to specific types of operation, fiber, monomer, or resin production, the HEG method showed relative imprecision and accuracy of 220% or less. The ratio, TWA, and deterministic methods showed relative imprecision and accuracies of 140 to 393, 76 to 137, and 123 to 346%, respectively. The authors conclude that these techniques can be used to estimate exposures from historical data when no current exposure data exist. The HEG, TWA, and deterministic methods appear to be more accurate than the ratio method.
NIOSH-Author; Occupational-exposure; Nitriles; Work-analysis; Chemical-factory-workers; Industrial-hygiene; Mathematical-models; Epidemiology; Statistical-analysis
Patricia Ann Stewart, Environmental Epidemiology Branch, National Cancer Institute, Executive Plaza North, Room 418, Rockville, Maryland 20892
Applied Occupational and Environmental Hygiene