Exposure to o-Toluidine, Aniline, and Nitrobenzene in a Rubber Chemical Manufacturing Plant: A Retrospective Exposure Assessment Update

Abstract

The National Institute for Occupational Safety and Health previously conducted a retrospective cancer incidence and mortality study of workers employed at a rubber chemical manufacturing plant. Compared with New York State incidence, the bladder cancer risk was 6.5 times higher for workers considered to have definite exposure to ortho-toluidine and aniline, and 4 times higher for workers with possible exposure. Exposure characterization in the original study utilized a surrogate measure based only on departments in which each worker was ever employed. As part of an update of that study, some departments in the three original exposure groups were reclassified based on a follow-up site visit; interviews with employees, management, and union representatives; and review of records including exposure data. An additional evaluation of department-job combinations, rather than only departments, was used to stratify exposure into four categories. An approximate rank of “relative” exposure level for each department-job-year combination was also assigned using a ranking scale of 0 to 10. The ranks were supported by quantitative exposure levels and by professional judgment. The numerical ranking scale was applied to each worker by multiplying the exposure rank by duration for each job held based on comprehensive individual work histories. The cumulative rank scores for this cohort ranged from 0 to 300 unit-years. The medians of the cumulative rank scores for the exposure categories showed very good agreement with increasing exposure classifications (e.g., 0.72, 4.6, 11, 14 unit-years for the four exposure categories). Workers’ breathing zone air sampling data collected at this plant from 1976–2004 were well below published occupational exposure limits for these chemicals, but additional cases of bladder cancer have been reported. The exposure assessment revisions and rank estimates will be used to analyze the updated bladder cancer incidence data.

Keywords:

• aniline
• bladder cancer
• job-exposure matrix
• nitrobenzene
• occupational epidemiology
• ortho-toluidine
• retrospective exposure assessment

ACKNOWLEDGMENTS

The authors wish to acknowledge the company workers, management, and union staff who provided valuable input into the exposure reassessment activities. The authors also wish to thank Scott Henn for quality inspection of air monitoring data; Lian Luo and Pi-hsueh Chen for programming support; and Kim Jenkins, Jean Geiman, and Denise Giglio for assistance with work histories and data coding.

The findings and conclusions in this report are those of the authors and do not necessarily represent the views of the National Institute for Occupational Safety and Health (NIOSH), nor that of Westat, Inc. Mention of company names does not constitute an endorsement by either NIOSH or Westat, Inc.