Cancer mortality in an Italian rubber factory

Exposure to high concentrations of nitrosamines and cancer mortality among a cohort of rubber workers

OBJECTIVES

To examine if the occurrence of different cancers was increased among rubber workers, as the highest known exposures of humans to nitrosamines have occurred in the rubber industry.

METHODS

A cohort of 8933 rubber workers (hired after 1 January 1950, still active or retired on 1 January 1981 and employed for at least 1 year in one of five study factories) was followed up for mortality from 1 January 1981 to 31 December 1991. Work histories were reconstructed with routinely documented cost centre codes, which allowed identification by employment in specific work areas. For each cost centre code time and factory specific, semi-quantitative exposures to nitrosamines (three levels: low, medium, high) and other compounds were estimated by industrial hygienists. Rate ratios for medium (RRm) and high (RRh) exposures and 95% confidence intervals (95% CIs) were calculated with Cox's proportional hazards models with the low exposure as reference.

RESULTS

Exposure to nitrosamines was significantly associated with an increased mortality from cancers of the oesophagus (13 deaths: RRm 1.7, 95% CI 0.3 to 10.3; RRh 7.3, 95% CI 1.9 to 27.8) and of the oral cavity and pharynx (17 deaths: RRm 0.8, 95% CI 0.2 to 4.1; RRh 3.9, 95% CI 1.4 to 11.1). A non-significant trend of increasing mortality with exposure to higher concentrations of nitrosamines was found for mortality from cancer of the prostate (26 deaths: RRm 1.4, 95% CI 0.5 to 3.8; RRh 2.2, 95% CI 0.9 to 5.6), and the brain (six deaths: RRm 3.9, 95% CI 0.3 to 42.6; RRh 6.0, 95% CI 0.6 to 57.6). No association was found between exposure to nitrosamines and cancer of the stomach (RRm 0.8, 95% CI 0.4 to 1.8; RRh 1.2, 95% CI 0.5 to 2.5) or lung (RRm 1.0, 95% CI 0.6 to 1.5; RRh 1.0, 95% CI 0.7 to 1.6).

CONCLUSIONS

Exposure to high concentrations of nitrosamines is associated with increased mortality from cancers of the oesophagus, oral cavity, and pharynx, but not with increased mortality from cancers of the stomach or lung.

Occupational cancer in Italy

This article is a discussion of occupational cancer in Italy. The introduction provides the necessary context of Italian industrialization and occupational health regulation. This is followed by a review of Italian epidemiologic studies of occupational cancer risks considered in terms of relative measures of risk and attributable risk of carcinogenic agents or exposure circumstances. We attempt to establish the number of workers exposed to carcinogens in Italy and the intensity of their exposures. Finally, the Italian system of compensation for occupational cancer is discussed. Several cohort and case-control studies have addressed the issue of occupational risks, mostly among male workers. The results of these studies suggest that the growing incidence of and mortality by mesothelioma is explained by the widespread and intense exposure to asbestos in some Italian industrial settings. A high attributable risk of lung tumors among male populations in industrial areas of northern Italy is explained by occupational exposures. However, insufficient data are available for clear definition of the extent and intensity of occupational exposure to carcinogenic substances. In Italy, we must prioritize and maximize resources in occupational cancer epidemiology and revitalize the role of national institutions. Recent legislation has established new regulations on the handling of carcinogenic substances in industrial settings, a new list of occupational diseases, and a national registry of mesothelioma linked to asbestos exposure. These legislative changes are expected to have positive effects.

Workplace risk factors for cancer in the German rubber industry: Part 2. Mortality from non-respiratory cancers

OBJECTIVES

To determine the mortality from non-respiratory cancers by work area among active and retired male workers of the German rubber industry.

METHODS

A cohort of 11,633 male German workers was followed up for mortality from 1 January 1981 to 31 December 1991. Cohort members were active (n = 7536) or retired (n = 4127) on 1 January 1981 and had been employed for at least one year in one of five study plants producing tyres or technical rubber goods. Work histories were reconstructed from routinely documented "cost centre codes" and classified into six categories: I preparation of materials; II production of technical rubber goods; III production of tyres; IV storage and dispatch; V general service; VI others. Standardised mortality ratios (SMRs) and 95% confidence intervals (95% CIs), controlling for age and calendar year and stratified by work area (employment in respective work area for at least one year) and time related variables (year of hire, lagged years of employment in work area) were calculated from national mortality rates as the reference.

RESULTS

Significant increases in mortality were found for pharyngeal cancer in work area IV (three deaths, SMR 486, 95% CI 101 to 1419), oesophageal cancer in work area III (11 deaths, SMR 227, 95% CI 114 to 407), and leukaemia in work areas I (11 deaths, SMR 216; 95% CI 108 to 387) and II (14 deaths, SMR 187; 95% CI 102 to 213). Furthermore, increased SMRs were found for stomach cancer in work area I (22 deaths, SMR 134; 95% CI 84 to 203), colon cancer in work area II (27 deaths, SMR 131, 95% CI 86 to 191), prostatic cancer in work area V (27 deaths, SMR 152, 95% CI 99 to 221), and bladder cancer in work areas IV (six deaths, SMR 253; 95% CI 93 to 551) and V (12 deaths, SMR 159, 95% CI 82 to 279). Mortality from cancer of the liver or gall bladder, pancreas and kidney, and from lymphomas was not substantially increased in any of the work areas.

CONCLUSIONS

Mortality from cancer of several sites was associated with specific work areas. Some of these associations have been reported previously. Future analyses of our study will have to determine the role of specific exposures in the aetiology of these cancers.

Workplace risk factors for cancer in the German rubber industry: Part 1. Mortality from respiratory cancers

OBJECTIVES

To determine the cancer specific mortality by work area among active and retired male workers in the German rubber industry.

METHODS

A cohort of 11,663 male German workers was followed up for mortality from 1 January 1981 to 31 December 1991. Cohort members were classified as active (n = 7536) or retired (n = 4127) as of 1 January 1981 and had been employed for at least one year in one of five study plants producing tyres or technical rubber goods. Work histories were reconstructed with routinely documented "cost centre codes" which were classified into six categories: I preparation of materials; II production of technical rubber goods; III production of tyres; IV storage and dispatch; V maintenance; and VI others. Standardised mortality ratios (SMRs) adjusted for age and calendar year and 95% confidence intervals (95% CIs), stratified by work area (employment in respective work area for at least one year) and time related variables (year of hire, lagged years of employment in work area), were calculated from national reference rates.

RESULTS

SMRs for laryngeal cancer were highest in work area I (SMR 253; 95% CI 93 to 551) and were significant among workers who were employed for > 10 years in this work area (SMR 330; 95% CI 107 to 779). Increased mortality rates from lung cancer were identified in work areas I (SMR 162; 95% CI 129 to 202), II (SMR 134; 95% CI 109 to 163), and V (SMR 131; 95% CI 102 to 167). Mortality from pleural cancer was increased in all six work areas, and significant excesses were found in work areas I (SMR 448; 95% CI 122 to 1146), II (SMR 505; 95% CI 202 to 1040), and V (SMR 554; 95% CI 179 to 1290).

CONCLUSION

A causal relation between the excess of pleural cancer and exposure to asbestos among rubber workers is plausible and likely. In this study, the pattern of excess of lung cancer parallels the pattern of excess of pleural cancer. This points to asbestos as one risk factor for the excess deaths from lung cancer among rubber workers. The study provides further evidence for an increased mortality from laryngeal cancer among workers in the rubber industry, particularly in work area I.

Cancer risk in the rubber industry: a review of the recent epidemiological evidence

OBJECTIVES

To examine the recent epidemiological evidence on cancer risk among workers in the rubber industry.

METHODS

Epidemiological studies published after the last detailed review by the International Agency for Research on Cancer (IARC) in 1982 were reviewed. 12 cohort studies in nine countries that examined distinct populations of workers in the rubber industry, seven industry based nested case-control studies, 48 community based case-control studies in 16 countries, and 23 studies based on administrative data that reported risks for employment in the rubber industry were identified.

RESULTS

Excess risks of bladder cancer, lung cancer, and leukaemia were found in most studies, with risks above 1.5 in about half of the studies. A moderate excess risk for laryngeal cancer was consistent across studies. Excess risks were found in a few studies for cancers of the oesophagus, stomach, colon, liver, pancreas, skin, prostate, kidney, brain, and thyroid, and for malignant lymphoma and multiple myeloma, but overall results were not consistent for these neoplasms.

CONCLUSIONS

Magnitude of the observed risks varied considerably between studies, but overall the findings indicate the presence of a widespread moderate increased cancer risk among rubber workers. The most consistent results were for bladder, laryngeal, and lung cancer and for leukaemia. Excess risks were also found for other neoplasms but an evaluation of the consistency of the findings is difficult because of the possible selective reporting of results. Recent studies do not provide information associating specific exposures with cancer risk. The preventive measures taken in the rubber industry in recent years may decrease risks, but this has not been documented yet in epidemiological studies.

Clinical features of hematopoietic malignancies and related disorders among benzene-exposed workers in China. Benzene Study Group

Previous occupational cohort studies of benzene-exposed workers have for the most part used only death certificates to validate diagnoses of workers developing leukemia and other hematopoietic and lymphoproliferative malignancies and related disorders (HLD). In a follow-up study of 74,828 benzene-exposed workers and a comparison group of 35,805 nonexposed workers from 12 cities in China, we sought to characterized clinicopathologically and to confirm diagnoses of all cases of HLD. Using medical records, laboratory hematology results, and histopathology, U.S. and Chinese expert hematopathologists, blinded to exposure status, carried out a detailed review using standardized evaluation forms. Key among the findings were a notable diversity of malignant and nonneoplastic hematopoietic and lymphoproliferative disorders, documentation of excess myelodysplastic syndromes among benzene workers, and widespread dyspoiesis involving all hematopoietic cell lines. As sophisticated clinicopathologic characterization and corresponding classification schemes for HLD become increasingly widespread, it is recommended that future epidemiologic investigations of benzene workers incorporate similarly detailed morphologic evaluation. In extending follow-up of this cohort of young workers, we will continue to use all available clinical, laboratory hematology, and pathology data as well as cytogenetic and biochemical markers to characterized various HLD outcomes. These careful surveillance mechanisms should also provide additional insight into carcinogenic mechanisms of benzene and allow comparison of the molecular pathogenesis of HLD induced by benzene versus chemotherapy, radiation, or other exposure.

Cancer mortality among workers in the German rubber industry: 1981-91

OBJECTIVES

To determine the cancer specific mortality of active and retired workers of the German rubber industry with emphasis on cancer sites which have been associated with the rubber industry in previous studies.

METHODS

A cohort of 11,663 German men was followed up for mortality from 1 January 1981 to 31 December 1991. Cohort members were active (n = 7536) or retired (n = 4127) at the beginning of the study, and had been employed for at least one year in one of five study plants producing types or general rubber goods. Vital status was ascertained for 99.7% of the cohort members, and cause of death found for 96.8% of the 2719 decedents. Age and calendar year adjusted standardised mortality ratios (SMR) and 95% confidence intervals (95% CI) were calculated overall from national reference rates and stratified by year of hire and by years since hire.

RESULTS

Mortalities from all causes (SMR 108; 95% CI 104-112) and all cancers (SMR 111; 95% CI 103-119) were significantly increased in the study cohort. Significant excesses in the mortalities from lung cancer (SMR 130; 95% CI 115-147) and pleural cancer (SMR 401; 95% CI 234-642) were identified. SMRs higher than 100 were found for cancers of the pharynx (SMR 144; 95% CI 76-246), oesophagus (SMR 120; 95% CI 74-183), stomach (SMR 110; 95% CI 86-139), rectum (SMR 123; 95% CI 86-170), larynx (SMR 129; 95% CI 69-221), prostate (SMR 108; 95% CI 84-136), and bladder (SMR 124; 95% CI 86-172), as well as for leukaemia (SMR 148; 95% CI 99-213). Mortalities from liver cancer, brain cancer, and lymphoma were lower than expected.

CONCLUSIONS

Mortalities from cancer of several sites previously associated with the rubber industry were also increased among workers of the German rubber industry. Results of the stratified analyses are consistent with a role of occupational exposure in the aetiology of some of these cancers.

Occupational exposures as risk factors for gastric cancer in Italy

Occupational associations with gastric cancer were investigated in a multicenter case-control study in Italy involving interviews with 640 histologically confirmed male cases and 959 controls, randomly selected from the resident populations of the study areas. From information on the three jobs each person held the longest, risks were evaluated according to employment in 35 occupations (ever or 21+ years) and to estimated exposure (ever or 21+ years) to six chemicals using a job-exposure matrix. All risk estimates were adjusted by personal, demographic, and dietary variables identified as gastric-cancer risk factors in previous analyses. The only significantly increased risk was observed for sailors, seamen, and allied groups (ever employed: odds ratio [OR] = 2.9; 95 percent confidence interval [CI] = 1.1-8.0; 21+ years: OR = 3.1, CI = 0.8-13). Nonsignificant increases after 21+ years of employment were observed for forestry workers, miners, and janitors and cleaners. Crude ORs were elevated significantly among farmers, but adjusting for demographic and lifestyle factors largely eliminated the association: a nonsignificant 30 percent excess risk remained for farm laborers, but there was no rise in risk among long-term farm laborers and no excess among farm owners. Application of the job-exposure matrix revealed excess risks of borderline significance associated with potential exposure to mineral dusts and nitrogen oxides. For subjects with 21+ years of potential exposure, nonsignificantly increased risks were related to mineral dusts, asbestos, fertilizers, and nitrosamines.(ABSTRACT TRUNCATED AT 250 WORDS)

Stomach cancer and work in dusty industries

The city of Stoke-on-Trent, whose major industries include coalmining, iron and steel, ceramics, and rubber, has death rates from stomach cancer some 80% above the national average. To explore the hypothesis that work in these dusty industries is responsible for the local excess of stomach cancer, we compared 95 incident cases with 190 age and sex matched community controls. Lifetime occupational histories and premorbid consumption of foods suspected of causing or protecting against stomach cancer were ascertained by a self administered questionnaire, supplemented at interview. Sixty eight cases had at some time held a manual job in one of the four dusty industries (relative risk = 1.4, 95% confidence interval 0.8-2.4). After allowance for diet, rubber manufacture was the industry most strongly associated with stomach cancer (relative risk = 2.5, 95% CI 1.0-6.4). Associations were also found with coal mining and ceramics but these were not statistically significant at a 5% level. The estimated proportion of stomach cancer attributable to the four dusty industries was 23%. It is concluded that the high incidence of stomach cancer in Stoke-on-Trent is unlikely to be explained solely by occupational exposure to dust.