Retrospective Occupational Exposure Assessment for Case-Control and Case-Series Epidemiology Studies Based in Shanghai China

Abstract

To provide exposure information for epidemiology studies conducted in Shanghai from 2001 to 2008, we completed retrospective exposure assessments (EA) of benzene and other hazards. Interviewers administered questionnaires to subjects from Shanghai area hospitals. An initial exposure screening by EA staff members, blinded as to case-control status, stratified jobs into exposed, unexposed, or uncertain categories prior to review by a separate expert panel (EP). Resources for the EA included job/industry-specific questionnaire responses by subjects, short-term benzene area concentration measurements from a Shanghai regulatory agency database, Chinese literature for qualitative and short-term quantitative measurements, on-site investigations, summaries of technology changes, and selected task simulations with concurrent benzene concentration measurements. An EP in Shanghai completed semi-quantitative benzene exposure assignments, with categories of 0 to 4 corresponding to intensity ranges of none, <1, 1 to 10, >10 to 100, and >100 mg/m³. For other hazards, sources included the EP's knowledge of the industries and Chinese and Western literature. For benzene, 20% of the EAs selected by a stratified random process were evaluated by two alternate methods. The study database of potential cases and controls included 18,857 jobs from the subjects’ work histories. From 818 individuals initially screened as probably benzene exposed, 964 jobs underwent further review. From subjects with final diagnoses, 755 jobs qualified for inclusion in the final database for any study. For other exposures, the EA considered 17,893 jobs from 7654 subjects for possible exposures and were in the final study database. Of these, 2565 individuals had exposures of study interest from their 4909 exposed jobs. The prevalent exposures included agricultural chemicals, petroleum products, and metals. The EA involved extensive information assembly and exposure assignment by an EP and periodic reviews. The methods described went beyond those typically applied in past general population studies and may have provided improved information for the epidemiologic analyses. However, sufficient, reliable measured historical data are lacking to evaluate this conclusion.

Keywords:

• acute myeloid leukemia
• non-Hodgkin's lymphatic neoplasms
• epidemiology
• general population case-control study
• risk factors
• occupational exposures
• China

ACKNOWLEDGMENTS

The Benzene Health Research Consortium funded this project. The consortium companies were BP, Chevron, ConocoPhillips, ExxonMobil, and Shell Chemical. We first need to acknowledge the participants in the study and their willingness to answer many questions to the best of their recollection, sometimes repeated questions, and often questions that required deep thought and recall from many years past. The EA project reported herein was possible due to the dedicated work of the whole science team, with the contributions to EA in Shanghai by Professors Xipeng Jin and Shixing Yang, and by the contributions of the many other diligent members of the Shanghai EA team. A few team members of special note include Lizhuang Miao, Xibiao Yi, Yonghua He, Jinbin Fang, Liping Nie, and Chi Zhang, Hong Liu, and Hongzhi Xu. This list does not cover all the contributors over the years of the study. We also greatly appreciate the broad support of the study Science Advisory Board, chaired by Jerry Rice, and the EA advice by Harvey Checkoway, Robert Herrick, and John Cherrie. We especially thank authors Cherrie and Herrick for their contributions to periodic reviews and their work to complete estimates by different approaches for a 20% random sample of the benzene exposure scores.

[Supplementary materials are available for this article. Go to the publisher's online edition of Journal of Occupational and Environmental Hygiene for the following supplemental resource: a PDF containing four tables on summary of information considered by the expert panel for prevalent industrial categories and tasks, list of secondary questionnaires for the project, English language translation of codes for the standard classification of Industries in China, English language translation of codes for the standard classification of jobs in China, text from the web page, and additional details on statistical analyses.]