Lung cancer and hydrogen chloride exposure: results from a nested case-control study of chemical workers.

There are few epidemiologic data available to address the question of potential carcinogenic effects of hydrogen chloride (HCl) exposure on humans. An opportunity arose to augment a nominal HCl exposure classification that had been done earlier for a nested case-control study of lung cancer among a cohort of chemical manufacturing employees. Working from first-hand knowledge of the relevant chemical processes and limited HCl monitoring data, a certified industrial hygienist estimated average exposures for each of the job assignments of 308 lung cancer cases and 616 comparison workers. The risk of lung cancer was then analyzed in relation to several measures of HCl exposure, including duration, a cumulative exposure score, highest average exposure, and latency. None showed evidence of an association between HCl exposure and lung cancer. This is consistent with the limited rodent bioassay data, which also failed to find a tumorigenic response from HCl. Thus, even at high level occupational exposures (up to 3000 micrograms/m3 for several years) there is no evidence that HCl is a human carcinogen.

An epidemiologic investigation of forced expiratory volume at 1 second and respiratory symptoms among employees of a toluene diisocyanate production plant.

Pulmonary function tests were done and compared to current and past potential exposure levels of toluene diisocyanate (TDI) for 57 TDI manufacturing workers and 89 workers not exposed to TDI or other known respiratory hazards. The average TDI plant experience was 4.1 years (standard deviation = 2.8). Routine industrial hygiene measurements have shown TDI exposure below a time-weighted average of 0.005 parts per million and a short-term exposure level of 0.02 parts per million. A certified industrial hygienist ranked department and job classification by level of potential exposure to TDI (none, low, moderate, and high). A questionnaire was administered to determine the prevalence of respiratory symptoms and smoking habits. Using backward regression analysis, cumulative pack-years of cigarette smoking and prevalence of lower respiratory symptoms were statistically significant predictors of a standardized forced expiratory volume at 1 second observed v expected difference; however, TDI exposure, whether classified as current, highest career level, cumulative, or cumulative highest-to-date, was not associated with a decline in forced expiratory volume.

Validation of work histories obtained from interviews.

There have been few attempts to assess the validity of occupational histories obtained from interviews. A nested case-control study of lung cancer conducted in 1985 among a cohort of 19,608 male workers at a Texas chemical production facility provided such an opportunity. Telephone interviews were attempted with 308 lung cancer patients and 588 matched controls or their next of kin in order to gather information on tobacco use, diet, places of residence, and occupations. Interview data from 734 respondents (143 subjects and 591 next of kin) were then compared with the records of work area assignments maintained by the company and with exposure profiles developed by an industrial hygienist. Respondents recalled 48.4 per cent of all documented work area assignments, but only 2.6 per cent of the chemical agents judged as likely exposures. Recall of usual work area assignment was 70.8 per cent. Among the factors found to have most influenced recall were the number and durations of assignments, a subjective assessment of the quality of the interview, and the relationship of the interview respondent to the subject. The elapsed time from job assignment to interview was also found to affect recall of the longest assignment of the subject.

Nested case-control study of lung cancer among chemical workers.

A recent cohort mortality study of 19,608 male employees of a major Texas chemical production facility had suggested that they might be at higher risk of lung cancer compared with the male population of the United States or Texas but not with the male population of the five-county area in which they reside. An occupational exposure was a possible explanation for this pattern, and a nested case-control study was undertaken of the 308 lung cancer deaths observed between 1940 and 1981. Two control groups, one a decedent and the other a "living" series, were individually matched to cases one-for-one. Interviews were conducted with subjects or their next of kin to collect information on smoking and other potential confounders. These data were combined with employee work history records and industrial hygiene data to form the basis of the analyses. Traditional stratification methods and conditional logistic regression were employed to examine for effect modification and to control confounding. Statistically significant, positive and negative associations were found for assignment to several work areas within the facility. Suggestive associations were observed for exposure to sulfur dioxide and heat. These and additional associations are discussed relative to evidence from other studies.

A case-control study of renal cancer mortality at a Texas chemical plant.

An in-plant case-control study of 26 renal cancer deaths was conducted to determine whether an occupational exposure may be related to an apparent increase in mortality from this disease observed among a sample of employees at a multiple process chemical production facility. None was found that explained the excess. Elevated odds ratios were identified for employment in the cell maintenance area of chlorine production and with those presumptive exposures considered to occur in this job, asbestos and caustic, but not chlorine. While an association between renal cancer and asbestos has been previously reported, an association with caustic, per se, is not consistent with prior observations made by others. Diminished risk estimates were observed for employment in magnesium production and for exposures in this process to sulfur dioxide and heat. Both the increased and decreased risks, while statistically significant, are based on small numbers of exposed subjects and may be spurious owing to the problem of multiple comparisons.

A case-control study of brain tumor mortality at a Texas Chemical plant.

A plant-based case-control study was undertaken to investigate a possible excess of brain tumor mortality identified at a Texas Chemical plant from a sample-based cohort study. Work histories and presumptive exposures of 28 former employees who had died of primary intracranial neoplasms were contrasted with those of two matched comparison groups in an effort to identify a possible etiologic agent. Because the sample-based cohort study suggested they might be at increased risk, those employees hired prior to 1945, those employed from one to four years and those employed for 20 or more years were studied separately. No statistically significant associations were found, although an elevated risk was suggested for employment in the machine shop prior to 1945 based on three exposed cases.