Search

In a retrospective assessment of employee exposure to acrylonitrile (AN) for an epidemiological study, investigators from the National Cancer Institute (NCI) and the National Institute for Occupational Safety and Health (NIOSH) evaluated the feasibility of using historic acrylonitrile air samples without modification. The evaluation discussed here was to determine whether the air sampling results across plants were comparable. During site visits to each plant conducted between 1984 and 1986, study investigators collected personal air samples for four days on approximately ten jobs per day. During these visits, IHs at seven of the eight plants also collected personal samples to compare their sample values to the study-collected sample values. Each plant's IH collected these concurrent measurements for their own use and independent of the IHs at the other plants. The plant IHs had no common sampling protocol but, rather, used professional judgment in deciding sampling logistics for their concurrent measurement. In addition, each plant IH used a different laboratory to analyze samples (the study industrial hygienists used one laboratory). Three sampling methods were used by plant industrial hygienists to collect concurrent measurements: charcoal tubes, passive monitors, and porous polymer tubes. The study investigators only used charcoal tubes. Two hundred and sixty four (264) pairs of concurrent measurements were collected. To assess the +/- comparability of the data sets, paired-observation tests were used. The two sets of charcoal tubes were found to compare favorably with each other. The study's charcoal tubes were 1.2 times higher than results from plant passive monitors. No correlation was found between the study's charcoal tube results and plant porous polymer tube results, although the means for 34 pairs of samples were equivalent. As a result of this evaluation, the investigators decided that no adjustments would be made to the plant measurements. This type of evaluation should be considered when using measurement data in multisite epidemiological studies.

Although results from some epidemiologic studies indicate an association between silicosis and lung cancer, other investigations have not confirmed these findings. The discrepancies may be related to methodologic problems. These include the lack of autopsy confirmation for the presence of silicosis or of information on the histologic lung cancer type, and unavailable or uncertain estimates of exposures to silica and to known carcinogens that may interact with silica or silicosis. This study will be designed to avoid the above weaknesses and reconcile observations in humans with results from animal studies, which show a carcinogenic effect for silica. We have formulated a series of testable hypotheses based on plausible mechanisms of carcinogenesis. These hypotheses suggest that silica interacts with known carcinogens (e.g., radon or cigarette smoke), and that only specific types of lung cancer are associated with silica or silicosis: (1) if silica or silicosis of lung parenchyma causes proliferat...

Retrospective exposure assessment in epidemiologic studies is dependent on the availability of historical monitoring results, yet rarely are there sufficient results to rely upon them exclusively. An approach is described that has a formal structure for developing exposure estimates for an epidemiologic study using a variety of methods depending on the information available. The approach identifies criteria for determining what data are needed for each method and the hierarchy for using the methods. The estimation methods include: (1) calculating a mean from the monitoring results of a job; (2) identifying homogeneously exposed jobs and using the mean of the measurements for the jobs as the estimate; (3) applying a ratio of the measurement means of two jobs in one operation to a third job in another operation to estimate a fourth; (4) weighting by time various areas or personal (short or full-shift) measurements representing tasks or locations; (5) taking a deterministic approach that modifies a ...

The validity of exposure assessment in retrospective epidemiologic studies has often been questioned, in part because systematic methods have not been developed to estimate historical exposure levels when insufficient monitoring results are available. In addition, documentation as to how the exposure estimates are derived is often lacking. A previously published report described a data management system, called Job Exposure Profiles, that organized and maintained job-related information available on each job in a mortality study of workers exposed to acrylonitrile. This database, and a second one containing almost 19,000 acrylonitrile monitoring results with accompanying documentation (job, department, date, type of sample, etc.), were linked to a computerized, interactive exposure assessment program (EAP) to allow the user to develop historical exposure estimates. The EAP is the subject of this report. In this program, monitoring results were sorted into various subfiles based on their quantity ...

In industry-based epidemiologic studies, both air monitoring data and descriptive information are often used in the evaluation of workplace exposures. The format of the descriptive information may vary by plant, department, job title, and year; information on a particular job may often be scattered throughout many documents and may be repetitious. These problems make it difficult to efficiently and systematically assess exposures and document the basis for the assessment. This report describes a computerized data management system that provides a systematic organization of the exposure information collected from various sources at different plants. This computerized system was developed for an epidemiologic study of workers exposed to acrylonitrile to provide documentation of the information that was evaluated to assess exposures. The system was also developed to allow efficient reference as to where that information was found in the study documents and was maintained by unique job/department/pla...

To conduct a retrospective exposure assessment for a study of silica, silicosis, and lung cancer, current exposure measurements and techniques were compared with industrial hygiene data that had been systematically collected in Chinese industries over the past three decades. Historically, sampling was usually confined to total dust evaluation and bulk silica determinations. For comparison, from 1988 through 1989, several special surveys were conducted in Chinese iron and copper mines in the Huangshi region of Hubei Province. In addition to the total dust and silica measurements using the traditional Chinese sampling system, data were collected using standard National Institute for Occupational Safety and Health (NIOSH) sampling equipment for respirable dust, total dust, particle size distribution, selected trace elements, radon, and fibers. Overall, total dust measurement using NIOSH sampling and analytical procedures were correlated to the corresponding Chinese measurement, r2=0.77. No statistic...

Performing an exposure assessment in occupational epidemiology studies requires the collection of a wide variety of exposure data, because there are usually too few biological or air monitoring measurements over the time period of interest to allow retrospective assessment of exposures for individual study subjects. This article describes different types of exposure data that can be used to supplement monitoring results and provides a brief description of how they might be used. It also identifies sources from which these data may be obtained and the resources that may be needed to collect them.

In the absence of current and/or historical monitoring data, qualitative and semiquantitative methods have been used for estimating historical exposure to chemicals in retrospective occupational studies. Two semiquantitative exposure assessment methods—the Job Exposure Matrix (JEM) and the Interview-Based Evaluation (IBE)—were introduced in the early 1980s. Both methods have some advantages and disadvantages in terms of accuracy and feasibility. In order to overcome the disadvantages of these earlier methods, three semiquantitative methods are proposed as possible alternative methods to the JEM and the IBE methods for estimating historical exposures. Two of the proposed methods—the Exposure Source Evaluation (ESE) and the Job Function Evaluation (JFE) methods—are based on information of current and historical working conditions, which can be obtained from walk-through surveys and interviews with long-term employees. The third method—the Parallel Agent Evaluation (PAE) method—is based on the avail...

In most occupational case-control studies, assessment of exposures is based on occupation and industry due to the lack of any other exposure information. The traditional approach to assessing exposures to specific substances is to estimate exposure for each occupation/industry combination. A modified procedure that substantially reduces the effort necessary to complete such assessments is described. In this procedure, exposure levels (none, low, medium, and high) are estimated for each occupation and industry separately. Numeric weights are assigned to these exposures levels. Final estimates for each occupation/industry combination are derived using exposure weights for occupations and industries. This method was applied to a case-control data set to estimate levels of silica exposure for the work histories of subject. The traditional method required 13,445 individual evaluations while the new approach required only 2,000 estimates. Results from the new approach were compared with those from the ...