Unusually High Incidence of Malignant Pleural Mesothelioma in a Town of Eastern Sicily: An Epidemiological and Environmental Study

Archives of Environmental Health, Nov, 2000 by Luigi Paoletti, Domenico Batisti, Caterina Bruno, Maurizio Di Paola, Antonio Gianfagna, Marino Mastrantonio, Massimo Nesti, Pietro Comba

THE CAUSAL ASSOCIATION between malignant mesothelioma and exposure to asbestos fibers dates back to the early 1960s. This specific neoplastic form, generally localized in the pleura, is a rare tumor, the incidence of which is estimated at 1-2/million persons [multiplied by] y in the general population.[1] Pleural mesothelioma can be caused by occupational, domestic, or residential asbestos exposure; the etiologic role of other factors is negligible.[2]

In a recent epidemiological study on mortality for malignant pleural neoplasms in Italy, Di Paola et al.[3] detected some geographic clusters of cases. For some of the cases, previous asbestos exposure was easily identifiable, whereas for others an occupational exposure could not be suggested.

Given the preceding facts, we found Biancavilla, a town in eastern Sicily located in a volcanic area, to be of special interest. Industrial activities involving asbestos have never occurred in Biancavilla. The subjects who resided in this town--and for whom a diagnosis of pleural mesothelioma had been made--never had any relevant exposure to asbestos during their professional lives.

The results of an environmental survey, which was conducted by the Istituto Superiore di Sanita in collaboration with the local health authorities, suggested that a possible cause of the asbestos exposure of Biancavilla's population was the stone quarries located in Monte Calvario. Monte Calvario is located on the southwest side of the Etnean volcanic complex, northeast of Biancavilla. The materials extracted from the quarries contain large quantities of fibrous amphiboles; these materials are used widely in the local building industry. In consideration of the available data and in view of some analogies with other situations observed in various areas of the Mediterranean basin,[4-8] we undertook an in-depth study of the potential connection between the increased occurrence of pleural mesothelioma and the presence of mineral fibers in the building materials that originated in the stone quarries.

I. Mortality and Morbidity among Residents

I. Material and Method

We studied cause-specific mortality among residents in Biancavilla from 1980 (i.e., the first year for which such figures were available at the municipality level) through 1993 (i.e., the most recent year for which mortality data were provided by the National Institute for Statistics. We selected causes of death for which a causal association with asbestos has been ascertained (e.g., malignant neoplasms of the pleura, peritoneum, and lung) or suspected (e.g., malignant neoplasms of the ovary).

We are aware that the relationship between ovarian cancer and asbestos exposure is controversial. The results of epidemiological and experimental studies indicate a possible association between, ovarian cancer and materials of the talc-asbestos group.[9] Findings relative to gas-mask assemblers in the United Kingdom support this hypothesis,[10 11] and, recently, in two Italian studies researchers reported an increased risk of ovarian cancer in female workers exposed to asbestos.[12 13] In our view, the aforementioned evidence justified the inclusion of ovarian cancer in the mortality study.

For each cause of death, we confronted the observed morality with the corresponding expected value on the basis of cause-sex-age-calendar year-specific morality rates of Sicily's population. To this end, we used the epidemiological databank of the National Board for Energy, New Technology and Environment. Standardized mortality ratios (SMRs) were computed, and we estimated their 95% confidence intervals (CIs) in accordance with Poisson distribution.

Cases of pleural mesothelioma were searched thoroughly via the files of Biancavilla Registrar Office and hospital discharge cards. Patients or their close relatives were interviewed about previous fiber exposure, and we used guidelines of the National Registry of Mesotheliomas[14] to assign them to exposure categories.

I. Results

Mortality. A significant increase in mortality from malignant pleural neoplasms occurred in Biancavilla during the study period (Table 1). The increase was relatively stronger (a) among women, (b) in subjects 65 y of age or less, and (c) during the most recent years. No comparable finding could be detected in any of the neighboring municipalities.

Table 1.--Mortality from Malignant Pleural Neoplasms in Biancavilla, 1980-1993: Analysis by Age, Class, and Calendar Year

Men

Year and age Obs. Exp. SMR 95% CI

1980-1993:
all ages 4 1.57 255 69, 652
1980-1987:
all ages 2 0.74 270 33, 976
1988-1993:
all ages 2 0.82 244 30, 881
1980-1993:
< 65 y of age 2 0.62 323 39, 1,165
1980-1993:
[is greater than or
equal to] 65 y of age 2 0.95 211 26, 761

Women

Year and age Obs. Exp. SMR 95% CI

198.0-1993:
all ages 5 0.74 676 219, 1,577
1980-1987:
all ages 2 0.40 500 61, 1,806
1988-1993:
all ages 3 0.33 909 188, 2,657
1980-1993:
< 65 y of age 3 0.27 1,111 229, 3,247
1980-1993:
[is greater than or
equal to] 65 y of age 2 0.48 417 51, 1,505

Total

Year and age Obs. Exp. SMR 95% CI

198.0-1993:
all ages 9 2.31 390 178, 740
1980-1987:
all ages 4 1.14 351 96, 898
1988-1993:
all ages 5 1.15 435 141, 1,015
1980-1993:
< 65 y of age 5 0.89 562 182, 1,311
1980-1993:
[is greater than or
equal to] 65 y of age 4 1.43 280 76, 716