Spirometric impairments in long-term insulators. Relationships to duration of exposure, smoking, and radiographic abnormalities.

A study of 2,611 long-term asbestos insulators was well suited to provide information on (1) the prevalence of spirometric impairments in a large, well-defined population and (2) the effects of cigarette smoking, radiographic abnormalities, and duration from onset of exposure on pulmonary function. Prevalences are reported by a mutually exclusive classification of impairments (normal, restrictive, obstructive, small airways, and combined) as well as by abnormality of specific spirometric tests (FVC, FEV1/FVC, and midexpiratory time). Only 3 percent of nonsmokers (NS) had obstruction and 6 percent a decreased FEV1/FVC. Frequency of restriction did not vary by smoking history; it was 31 percent in NS and current smokers (CS) and 34 percent in ex-smokers (XS). Obstruction (present in 17 percent) and combined impairment (in 18 percent) were most common in CS. The FEV1/FVC was decreased in 35 percent of CS and 18 percent of XS. The FVC was decreased in 49 percent of CS, 44 percent of XS, and 33 percent of NS. Normal spirometry was most common when the radiograph was normal (almost half the workers with normal radiographs had normal spirometry). Nevertheless, FVC was reduced in 27 percent of those with normal radiographs and a normal radiograph was seen in 11 percent of workers with restriction. Restrictive and combined impairments were most frequent when both parenchyma and pleura were abnormal. Restriction was more frequent in isolated pleural disease (seen in 34 percent such subjects) than in isolated parenchymal disease (22 percent). The contribution of pleural fibrosis to reduced FVC and of asbestos exposure and smoking both to reduced FVC and to reduced FEV1/FVC was confirmed by regression analysis. That reduced FVC and reduced FEV1/FVC are both more frequent in insulators who have smoked (compared with NS insulators or smokers in the general population) suggests an interaction between asbestos and smoking in producing both these physiologic abnormalities.

Lung cancer in the Schneeberg mines: a reappraisal of the data reported by Harting and Hesse in 1879.

The first description of occupational lung cancer, by Harting and Hesse in 1879, unfortunately is not readily accessible. Its account of the vicissitudes of the Schneeberg miners merits study and is therefore presented in summary and set in a historical and geological context. The authors attempted to discover the cause of the disease and made recommendations for improving the health of miners. In the course of their programme of investigations, they developed methods for measuring airborne dust and inhaled dust by personal monitoring. It was left to subsequent discovery for radon and its daughter products to be identified as the causal agents. Later generations were to discover the impact of radioactive spoils from mines situated in the mountain range in which Schneeberg was located.

Survival of asbestos insulation workers with mesothelioma.

Malignant mesothelioma is a lethal disease. It is rare in the general population; however, workers exposed to asbestos suffer significant burdens of the neoplasm. The survival time of 457 consecutive fatal cases of pleural and peritoneal mesothelioma that occurred among 17,800 asbestos insulation workers observed prospectively from 1 January 1967 to 1 January 1987 was studied. Mean survival time from initial presentation of the disease to death was 11.4 months for the pleural mesothelioma patients compared with 7.4 months for the peritoneal group. This difference was statistically significant. Mean survival time from diagnosis to death was shorter for both groups of patients: 8.4 months for pleural mesothelioma v 5.8 months for the peritoneal cases. In conclusion, survival time in mesothelioma patients is short; most die within a year from the onset of the initial symptoms. No effective therapy is yet available.

Changes in PCB serum concentrations among capacitor manufacturing workers.

To assess the elimination of PCBs in humans, PCB concentrations in serum from 165 capacitor manufacturing workers were measured twice within a 46-month interval (March 1976-December 1979). Use of PCBs at the facility was entirely eliminated in 1977. PCB congeners with lower chlorination (LPCBs--mainly tri- and tetrachlorobiphenyls) had decreased in concentration, with six of the LPCB 7 peaks observed by packed column GC showing average reductions of 25-90%. Higher chlorinated PCBs did not decrease significantly as a whole, although three of the six constituent congener peaks showed some decline (15-25%). As expected, decreases in PCB congener concentrations were associated with chlorine substitution configurations known to be amenable to metabolism.

Comparative quantitative evaluation of pleural fibrosis and its effects on pulmonary function in two large asbestos-exposed occupational groups--insulators and sheet metal workers.

Two large (N = 1584 and N = 1330) population groups of workers exposed to asbestos as insulators (I) or sheet metal workers (SM) were compared. Prevalence rates of radiographic changes including pleural fibrosis (circumscribed and diffuse) were found to be much higher in I than SM. An integrative index of pleural fibrosis (INDEX) showed similar distribution patterns in the two groups; the effect of INDEX on FVC% predicted was more marked in insulators. Factors that could contribute to this difference are thought to be the higher prevalence of interstitial pulmonary fibrosis (probably including that which is not yet radiologically detectable) in I than in SM, the possibility of more extensive pleural fibrosis in areas not accessible to the standard chest X ray (and thus not affecting INDEX) and a higher proportion of diffuse pleural fibrosis in the I group.

Long term radiological effects of short term exposure to amosite asbestos among factory workers.

Chest radiographs were read from a sub-cohort of 386 factory workers with short term exposure to amosite asbestos (median exposure six months) and long follow up (median 25 years). Prevalence of abnormality was determined independently by two readers from the first film available after 20 years from first employment. Serial films were obtainable for 238 men (median interval from first to last film: nine years). Progression was classified with a direct progression scoring scale. Individual dust exposure estimates were derived from dust counts from two similar plants. With as little as one month or less of employment, about 20% of the films showed parenchymal abnormality and about a third showed pleural abnormality. Those in the lowest cumulative exposure stratum (less than 5 fibre-years/ml) were similarly found to have high rates of abnormality. Dose-response relations were present in the data of both readers. Smokers had higher rates of parenchymal abnormality. On multivariate analysis, cumulative exposure was the exposure variable most closely related to parenchymal abnormality, and time from first employment was the variable most closely related to pleural abnormality. Progression (including first attacks) 20 or more years after ceasing employment occurred and was more common for pleural than for parenchymal abnormality. It is concluded that with exposure to high concentrations to amosite such as existed in this factory and with follow up for at least 20 years, (1) exposure for as little as a month was sufficient to produce radiological signs of parenchymal and pleural fibrosis, (2) no cumulative exposure threshold for parenchymal and pleural fibrosis was detectable, and (3) parenchymal and pleural progression were still detectable >/= 20 years after the end of exposure.

Relationship of pulmonary function to radiographic interstitial fibrosis in 2,611 long-term asbestos insulators. An assessment of the International Labour Office profusion score.

Radiographic evidence of interstitial fibrosis (IF) secondary to asbestos inhalation (using the International Labour Office [ILO] profusion of small irregular opacities) was compared with FVC as an independent indicator of IF. In addition, spirometric indices of airflow (FEV1/FVC and FET25-75%) were correlated with the radiographic profusion score. A study of 2,611 long-term insulators was well designed for these analyses since all subjects were from the same trade, there were sufficient (n = 515) nonsmokers to assess the effects of asbestos exposure in the absence of smoking, most (60%, n = 1,557) of the workers had parenchymal abnormalities (scores greater than or equal to 1/0), and there was a greater prevalence of high scores than in other published series (347 workers or 13.3% had scores greater than or equal to 2/1). Looking at all subjects, the FVC decreased as profusion score increased. The FVC was abnormal (88.0% of predicted) even when the profusion score was clearly normal (0/0). The FVC was lower at any score in smokers and in workers with pleural thickening (more so with diffuse thickening). There was, however, no difference in FVC between intermediate scores 0/1 versus 1/0 and 1/2 versus 2/1. Airflow increased with greater profusion, tending to overcome a decrease seen at lesser profusion scores. These results provide a greater understanding of the relationships among profusion scores, smoking, pleural diseases, and pulmonary function.

Use of death certificates in epidemiological studies, including occupational hazards: discordance with clinical and autopsy findings.

There has long been evidence of frequent inaccuracy of death certificates, with significant discordance between such designations and clinical and autopsy data. This exists for occupational diseases as well. The use of statistical rates based on death certificates has been seriously questioned despite their utility for total mortality. Programs to supplement death certificate data, particularly in occupational disease studies, may be helpful, and are reviewed.

Use of death certificates in epidemiological studies, including occupational hazards: variations in discordance of different asbestos-associated diseases on best evidence ascertainment.

There is extensive information on discordance in general between accuracy of medical diagnoses on death certificate categorization of cause of death and available clinical and histopathological data. This is as true for occupational disease as for other conditions. But occupational illnesses bear a special problem. Discordance is not equal across the board--it may vary with each occupationally related disease, and no single formula can be applied. It may be high for angiosarcoma and low for acute hydrogen sulfide poisoning, low for bladder cancer, high for unsuspected methyl mercury poisoning. We have found that for one agent--asbestos--there were different rates of discordance for different asbestos-related diseases (e.g., lung cancer, mesothelioma, asbestosis, kidney cancer) among 4,951 deaths studied prospectively from 1967 to 1986. Caution is therefore required before accepting generalizations concerning (unstudied) discordance in occupational mortality studies, and in their use in risk assessment models.

Death certificates in epidemiological studies, including occupational hazards: inaccuracies in occupational categories.

We compared death certificates for asbestos-associated diseases (mesothelioma, lung cancer, asbestosis) in two asbestos workers' cohorts. One (insulation workers) had current or recent employment and a strong, continuing union support system which gave them much information about the effects of asbestos exposure. The second cohort, asbestos factory workers, had no such advantage. The factory had closed almost 30 years before, and its workers had dispersed into many areas of the state and nation. Accuracy of medical diagnosis was comparable in the two groups, but occupational listings were not. Three-quarters of the insulators' death certificates told of asbestos work, while virtually none of the factory workers' certificates provided such information, even for deaths of mesothelioma and asbestosis. The data indicate that disease categories, based on medical and pathological diagnoses, at least for asbestos-associated disease, tend to be accurate. Attempts to identify groups at risk by sorting occupational categories can give variable results, good for those with current exposures, much less satisfactory for those with long-past occupational exposures.

Radiological abnormalities and asbestos exposure among custodians of the New York City Board of Education.

Six hundred sixty custodians employed by the New York City Board of Education underwent examination from 1985 through 1987 for asbestos-related disease and other general medical conditions by the clinical staff of the Division of Environmental and Occupational Medicine of the Mount Sinai School of Medicine of the City University of New York. Two-thirds of the men (no women were examined) were 20 or more years from onset of any custodial work, with 44% having had at least 20 years of employment as custodial workers in New York City Board of Education schools. Twenty-four percent had begun custodial work in buildings 30 or more years earlier. Findings among them were of particular interest since asbestos-related disease might forecast what might be expected among school custodians with less seniority. Since the Board of Education, in selecting custodians for examination, had chosen only custodians currently employed, the study group comprised men still working in the school system. These, then, represented a "survivor population" (4% had retired between the time of enrollment in the study and the date of examination, and only one of the seventeen retirees had left work owing to disability). Although a considerable amount of clinical information was obtained, abnormalities on chest X-ray consistent with asbestos-induced scarring were used as the key index of disease resulting from exposure to asbestos. Since scarring of the lung tissue or lining of the lung or chest wall (pleura) may be present but undetectable on standard chest radiographs (a relatively insensitive diagnostic technique), the prevalence of abnormality on X-ray film represents a conservative estimate of the actual burden of scarring lung disease in the group. Such changes are indicative of previous asbestos exposure, however, and provide evidence of an increased risk of later asbestos-related malignancy. Overall, abnormalities on chest X-ray consistent with asbestos-related scarring were found in 28% of the men examined. The expected relationship of increasing prevalence of radiographic changes with increasing time since onset of exposure in buildings was demonstrated; among those with 35 or more years since beginning custodial work, 39% had abnormal films. This is evidence that custodial workers as a group have had asbestos exposure in the past, as reflected also in the work histories obtained at the time of examination. Eighty-four percent reported that they themselves removed asbestos-containing materials in the course of their work. Eighty-nine percent had been present in the work area during asbestos abatement projects in the schools in more recent years.(ABSTRACT TRUNCATED AT 400 WORDS)

A landmark case in asbestosis.

The first published account of disease attributed to occupational asbestos exposure was that of Nellie Kershaw, who died in 1924. The circumstances relating to that case are described and explanations are given for its not having a greater impact on policy at that time. This case, starting in 1898, is set in the context of missed opportunities for preventing a major public health hazard. The effects of this hazard are still being witnessed today.

Evaluation of selection bias in a cross-sectional survey.

Selection bias is inherent in all occupational cohorts. Selection bias at entry has long been known and is commonly referred to as a "healthy worker effect." Less well appreciated is selection during the life of a cohort resulting from life-style factors (e.g., cigarette smoking); aging with accompanying chronic diseases, economic and demographic circumstances; and diseases that might result from exposures suffered by the cohort being studied, that influence whether individuals remain in a trade. These factors weigh differently at different times. Thus, at any point in time, "surviving" members of a cohort reflect an amalgam of selection factors. When such groups are studied in cross-sectional surveys there can be uncertainty whether clinical, radiological and physiological findings are necessarily representative for the trade or occupation as a whole. We analyzed the results of a large clinical field survey of long-term asbestos insulation workers to investigate whether the non-participants differed substantially from those who were examined. Five thousand three hundred and fifty-five (5,355) men, of an initial cohort of 17,800 established January 1, 1967, had reached 30 or more years from onset of their work by July 1, 1981. All were invited to come for examination. Two thousand and seventy-seven (2,077) came, and 3,278 did not. We questioned a sample of 1,393 non-responders to see why they failed to appear. The answers did not give evidence of significant health-related selection influence. Sickness only infrequently kept them away. We then followed both groups--those examined and those not examined--to the end of 1987 for their mortality experience. There was no great difference. The non-responders had somewhat fewer deaths overall and proportionately fewer of asbestos-associated cancers, such as mesothelioma and lung cancer. The results indicated that, in this cohort, there did not seem to be health-related selection bias that determined whether or not cohort members responded to invitations for examinations.

Radiographic abnormalities in asbestos insulators: effects of duration from onset of exposure and smoking. Relationships of dyspnea with parenchymal and pleural fibrosis.

Chest radiographs and spirometry were evaluated in 2,907 active and retired asbestos insulators; most (86.8%) had greater than or equal to 30 years from onset of asbestos exposure. Testing was performed in 19 cities in the United States during 1981-1983. Complete demographic, smoking, clinical, and radiologic data were obtained for 2,790 workers. This is the largest single group of insulators that has been studied. Five hundred forty-eight (19.7%) had never smoked cigarettes, 942 (33.9%) were current cigarette smokers, and 1,300 (46.6%) were ex-smokers. Only 439 (15.7%) workers had no radiographic evidence of asbestos-related disease (normal chest X-ray); 668 (23.9%) had pleural fibrosis only, 325 (11.6%) had parenchymal fibrosis alone, and 1,358 (48.7%) had both parenchymal and pleural fibrosis. The prevalence of radiographic parenchymal changes increased significantly (p less than .001) from 38.6% (DURONSET less than 30 years) to 70% (greater than or equal to 40 years). For pleural changes the comparative prevalences were 55% and 82%. Those with no history of cigarette smoking were more likely to have normal films than those with a history of smoking (19.2% versus 14.4% for current smokers and 15.2% among ex-smokers), and were less likely to have parenchymal fibrosis (44.5% versus 69.7% for current smokers and 60.2% of ex-smokers). Dyspnea, MRC grade 3 and higher, was more prevalent when pleural fibrosis was associated with interstitial pulmonary fibrosis (at all profusion levels of small opacities) than when pleural fibrosis was absent. Logistic regression analysis of factors contributing to such dyspnea showed that the presence of combined parenchymal and pleural abnormalities was a significant explanatory variable, in addition to age, smoking, and body mass (Quetelet index); the presence of parenchymal changes only or of pleural changes only, as factors contributing to dyspnea, did not reach the level of statistical significance in the regression analysis. The results of these examinations show that pleural fibrosis is a frequent finding in asbestos-exposed groups with long-term follow-up and that its functional significance is not negligible. The contribution of cigarette smoking to prevalence and severity of interstitial fibrosis is an additional reason for smoking cessation among asbestos-exposed individuals.