Exposure to asbestiform minerals and radiographic chest abnormalities in a talc mining region of upstate New York
Edward F. Fitzgerald
THE NEW YORK STATE DEPARTMENT OF HEALTH conducted a case history study of radiographic chest abnormalities that occurred in St. Lawrence and Jefferson counties. This project was stimulated by the report of a local radiologist who, as a result of his review of routine chest radiographs of “general” hospital patients, identified a cluster of parenchymal fibroses and pleural changes suggestive of exposure to asbestiform minerals. His concerns were precipitated by the fact that for several years, milling and mining of talc have been major local industries, especially in the area surrounding Gouverneur. The talc contains the amphibole minerals, tremolite and anthophyllite.  Representatives of the mining and milling industry argue that from a mineralogical point of view, the talc does not exhibit asbestiform properties.  Epidemiologic studies of local miners and millers, however, have demonstrated excesses of pneumoconioses, respiratory symptoms, pleural thickening and plaques, and pulmonary function impairment. [3,4,5,6] Elevated mortality from cancers of the lung and pleura have also been reported, [7,8,9] but the possibility exists that some deaths resulted from exposures that occurred prior to employment in the talc industry. [10,11]
Because the observations of the local radiologist raised the possibility that ambient exposures to talc may cause health problems in the general population, we expanded the focus of inquiry beyond employees of the mining and milling industries to include, for the first time, other inhabitants of the areas near the mines. The authors sought to ascertain the prevalence of radiographic chest abnormalities among general hospital patients and to assess frequency of occupational exposures and chest conditions or injuries reported by the confirmed cases. The purpose of this study was to determine if the radiologist’s report merited further investigation, which, if needed, would ultimately require a large-scale commitment of resources for an analytic study.
Case ascertainment. Cases were identified from radiologic records of the five hospitals in St. Lawrence County and of the one hospital in Jefferson County that was used most frequently by county residents. If inpatients, outpatients, and emergency room patients met all of the following criteria, their chest films were included in the study; (a) date of radiograph: between April 1, 1982, and March 31, 1983; (b) age: at least 40 y; and (c) residence: St. Lawrence or Jefferson County.
Each chest film was screened for parenchymal fibrosis or pleural changes by the local board-certified radiologist whose observations prompted this study. Radiographs he deemed positive were forwarded to an experienced and internationally recognized B-reader who rated all films with the International Labor Office 1980 classification system. 
Interview data. Only cases, i.e., persons whose radiographs were confirmed positive by the B-reader, or their next-of-kin were eligible for interview. Because occupation is a major risk factor in the development of asbestiform mineral-related lung diseases, much of the interview was focused on the person’s job. A detailed history was obtained, and a checklist of 13 occupations or industries known to utilize materials containing asbestiform minerals was reviewed for each case.
Census data. Occupational distribution of the cases was compared to that for men in St. Lawrence and Jefferson counties, the latter being determined according to the 1960 U.S. Census.  (Women were excluded inasmuch as most cases were male.) Because most cases were at the mid-point of their careers during the 1960 U.S. Census, data from that year provided for a more valid comparison than data from more recent censuses.
Prevalence. A total of 9 442 patients met the inclusion criteria. The radiologist reviewed their chest films, and he screened 500 as positive. The B-reader confirmed that 355 (71%) of the 500 patients had a radiographic chest abnormality consistent with dust exposure; therefore, the prevalence rate of confirmed abnormalities was 3.8% (355/9 442). The B-reader found pleural thickening or calcification without parenchymal involvement in 246 cases (prevalence rate of 2.6%) and diagnosed 109 persons (1.2%) as having parenchymal disorders with or without pleural findings. Only 8 of the 109 cases with parenchymal abnormalities had large opacities; the remainder had small opacities that were predominantly irregular in shape and were mostly find and of profusion grade 1/2 or less.
Men were 12 times more likely to exhibit parenchymal abnormalities and 5 times more likely to show pleural changes than were women (p < .001) (Table 1). The prevalence of abnormalities increased with age, but the test for linear trend was only statistically significant for parenchymal disorders (p = .005).
Occupational and medical histories. Interviews were conducted with 306 (86.2%) cases or their next-of-kin, of whom two-thirds were at least 60 y of age, and 86.5% were men. Approximately 70% had smoked cigarettes at some time during their lives.
A total of 182 (59.5%) reported that they had ever been employed for 1 y or more in at least one occupation or industry known to entail exposure to asbestiform minerals (Table 2). More than one-third of the cases had worked in talc mining and milling industries, and one-quarter had been employed in construction trades. When we analyzed usual occupation or industry, talc mining/milling and construction also were the trades that most frequently included high-risk individuals (15.5% and 13.4%, respectively). In contrast, the U.S. Census indicated that only 2.4% and 6.5%, respectively, of men in St. Lawrence and Jefferson counties were engaged in such employment in 1960.
One-seventh of the cases did not report a relevant occupation or industry. They did, however, provide a[TABULAR DATA OMITTED]
Table 2.–Number and Percentage of Cases Who Were Ever Employed in Potentially High-Risk Occupations for 1 y or More: St. Lawrence and Jefferson Counties, New York (April 1, 1982-March 31, 1983)
Occupation (*1) n Percentage
A. Based on occupational checklist
Mining and milling 111 36.3
Paper 50 16.3
Pipe and furnace insulation 19 6.2
Sheet rock taping compound 16 5.2
Brake and clutch 8 2.6
Shipyard 6 2.0
Electric wire insulation 5 1.6
Asbestos tile or shingle 4 1.3
Plastic 3 1.0
Spray-on fireproofing 2 0.7
Asbestos filter 1 0.3
Asbestos cement 1 0.3
Asbestos textile 1 0.3
B. Based on occupational history
Construction 76 24.8
Aluminum foundry worker 12 3.9
Heating and plumbing 10 13.3
Cases who ever worked with at least 59.5
one of the above
(*1) Occupations are not mutually exclusive.
history of a chest condition or injury, e.g., emphysema (6.2%), broken ribs (4.2%), and pleurisy (3.6%), which could have accounted for their abnormal radiograph. The remaining one-quarter of cases reported neither occupational exposure nor history of chest disease.
This study was designed to determine if the report of a local radiologist merited further investigation. Our case history approach has limitations. All radiographs were initially screened by the local radiologist; only those he deemed positive were forwarded to the B-reader. Therefore, it was not possible to estimate the frequency of false negative or false positive errors, both of which may have influenced prevalence rates. Also, interviews were not conducted for persons whose radiographs were considered normal. Consequently, comparison of the reported frequencies of occupational exposures among the cases and internal controls was not done. These concerns were addressed, in part, by the use of an experienced and internationally recognized B-reader and by the use of external comparisons, i.e., occupational data from the U.S. Census. Nonetheless, the results should be interpreted cautiously.
Despite their limitations, the data support several conclusions. One is that radiographic chest abnormalities exist in residents of areas where Gouverneur talc is mined. There are limited prevalence data from other studies with which comparisons can be made. The most similar methodologically by Epstein et al., [14,15] who reviewed the routine chest radiographs of men and women who were admitted to an urban medical center. Epstein et al. determined that 18.0% had small parenchymal opacities at a profusion level 1/0 or greater and that 6.2% had pleural thickening. Our estimates were 1.2% and 2.6%, respectively. The urban versus rural settings of the two investigations may have contributed to the observed differences, but the results of both studies are consistent with the belief that radiographic chest abnormalities are not uncommon among general hospital patients.
The results also indicate that some abnormalities were associated with occupational exposures. In fact, almost 60% of the cases reported that they were employed for at least 1 y at a job (most frequently talc mining or milling) that entailed at least potential exposure to asbestiform minerals. Prior to the date of their radiograph, at least 90% of the cases worked in these potentially high-risk occupations or industries for 20 y or more, which is probably the minimum latency period for the abnormalities under study.  In addition, the overall prevalence rate for men &7.1%) was seven times greater than that for women (1.0%). There was a seven-fold difference in the reported frequency of talc mining or milling as the usual cases (15.5%) in our study compared with that of the 1960 U.S. Census (2.4%) for men in the two counties. These findings further support the conclusion that occupation played a major etiological role.
Another 15% of the cases did not recall employment in a high-risk occupation or industry, but reported a chest condition or injury that could have been responsible for the abnormal radiograph. Neither risk factor was reported by the remaining one-quarter of cases. Secondary exposure may have been involved because more than one-half of the women with unexplained abnormalities had a spouse or other relative who lived with them and who worked in the talc mines or another high-risk industry. [17,18] Perhaps cigarette smoking is involved; studies suggest that it causes small irregular opacities visible with low profusion. [19,20]
In conclusion, this study is the first to investigate the health status of residents in the area wher Gouverneur talc is mined. Causality can not be imputed from the results of this descriptive study, but the data are relevant to the controversy that surrounds the pulmonary toxicity of Gouverneur talc. [21,22] The data do not generally support the contention that environmental exposures to asbestiform minerals in the region are resulting in widespread radiographic chest abnormalities. This conclusion is consistent with the results of a limited environmental assessment, which failed to detect elevated levels of asbestiform mineral fibers in local samples of various media. The findings, however, support earlier studies that indicate that occupational exposures to Gouverneur talc are associated with parenchymal fibroses and pleural changes. [3-6] Findings also suggest that workers in the paper industry and construction trades may be at risk. Analytical studies are necessary to quantify these risks.
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