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Background: Although the role of asbestos in the genesis of mesothelioma and primary bronchopulmonary cancers has been established, results from studies focusing on the relationship between occupational exposure to asbestos and digestive cancer remain contradictory., Aim: To determine whether occupational asbestos exposure increases the incidence of digestive cancers., Methods: Our study was a retrospective morbidity study based on 2024 subjects occupationally exposed to asbestos. The incidence of digestive cancer was calculated from 1st January 1978 to 31st December 2004 and compared with levels among the local general population using Standardized Incidence Ratios. Asbestos exposure was assessed using the company's job exposure matrix., Results: Eighty-five cases of digestive cancer were observed within our cohort, for an expected number of 66.90 (SIR = 1.27 [1.01; 1.57]). A significantly elevated incidence, particularly notable among women, was observed for peritoneal mesothelioma, independently of exposure levels. A significantly elevated incidence was also noted among men for cancer of small intestine and oesophagus, for cumulative exposure indexes for asbestos above 80 fibres/mL x years. A significantly elevated incidence of cancer of the small intestine was also observed among men having been exposed to asbestos for periods in excess of 25 years and for mean exposure levels in excess of 4 fibres/mL., Conclusions: This study suggests the existence of a relationship between exposure to asbestos and cancer of the small intestine and of the oesophagus in men.

While the role of exposure to asbestos in the development of several cancers such as mesotheliomas and bronchopulmonary cancers is now well established, the possible relationship between digestive cancers, other than peritoneal mesotheliomas, and occupational exposure to asbestos is still controversial. The great majority of the studies are based on mortality data. The aim of the study was to analyse the relationship between digestive cancer incidence and occupational exposure to asbestos in a population of subjects for whom precise occupational exposure data and precise incidence data were available. The population consisted of salaried and retired workers from a company using asbestos to manufacture fireproof textiles and friction materials. There were 1454 men (79.9%) and 366 women (20.1%). A cumulative exposure index and a mean exposure concentration in fibres/ml for each subject were calculated with the aid of an in-house job-exposure matrix. The number of cases of digestive cancer observed was compared with the expected and Standardized Incidence Ratio (SIR) was estimated. Precise occupational exposure data allowed us to study the dose-response relationship between asbestos exposure and risk of digestive cancer using Cox model. Fifty-six digestive cancers occurred in the study population over the 18-year follow-up period for 48.4 expected (SIR = 1.16 [0.87-1.50]). Comparing with incidence in the county, SIR was not significant for any of the digestive localization, but for peritoneum. However, even after taking into account the potential confounders via the Cox model, there was a significant dose-response relationship between the occurrence of digestive cancers and the mean exposure concentration, even after exclusion of peritoneum cancers. Our study provides initial evidence suggesting a relationship between occupational exposure to asbestos and the risk of digestive cancer: first, it is a study of incidence although the risk evidenced is not significant; secondly, a dose-effect relationship is demonstrated in the whole population. However, these preliminary results require confirmation by more powerful studies focusing on larger series.

A cohort study is presented on the mortality of blue-collar workers in an asbestos-cement production plant that has been operating since 1907. Use of both crocidolite and chrysotile is reported. The cohort includes 2608 men and 759 women who were employed in the plant on Jan. 1, 1950 and those who started to work between 1950 and 1980. Follow-up was terminated on April 15, 1986 with 97.9% traced. Expected deaths were estimated from the age- and sex-specific regional mortality rates for the years 1969 to 1981. The data have been analyzed for the period 1964 to 1986 based on person-years at risk: 43,000 for men and 14,494 for women. A statistically significant increase was found in both sexes for mortality from all causes. From 1964 to 1986, 728 men died from all causes (608 expected), 275 with cancer at any site (158 expected) 110 with lung cancer (41 expected), 28 with pleural tumors (1 expected) and 85 with asbestosis (less than 1 expected). Corresponding figures for women were--all causes: 136 deaths versus 102 expected; all cancers: 79 verses 32 expected; lung cancer: 7 versus 2 expected; pleural tumor: 15 versus 0 expected and asbestosis: 4 versus 0 expected. Deaths from digestive tract cancer were in excess only among women (18 observed versus 10 expected, p less than 0.01). No excess was found for deaths from laryngeal cancer. Standardized mortality rates (SMR) for lung cancer among males showed a clear increase in direct relationship with length of follow-up. SMR according to length of employment were 234 for length 10 to 19 years, 363 for 20 to 29 years, and 256 for 30 years or longer (p less than 0.05 and lower).

The results of the study of a cohort of 2403 men occupationally exposed to chrysotile asbestos dust during the manufacture of various asbestos products have been reported. The study covered the period 1945-1985. Cohort availability was 91%. Risk estimates were based on SMR and SRR calculated by the man-year method. The general Polish male population served for the reference. The analysis was performed for sub-cohorts selected according to the period of employment in the plant, taking into account the dust dose and the age at the moment of the beginning of employment under exposed conditions. A significantly increased risk of pulmonary carcinoma (SMR: 238.0-211.0) and of gastric carcinoma (SMR: 197.9-238.5) was found in men exposed to high doses of the asbestos dust (above 50 mg/m3 x years). No statistically significant increases in the mortality rates either from cancer in general or from the cancer varieties specified above were detected in men exposed to low doses of dust. One case of death from pleural mesothelioma was reported.

The report is devoted to one of the main problems of studies on death rate in industrial cohorts. In the study on cohort consisting of workers of asbestos processing plant in Lodz, the general population of Poland was selected as a reference population. Such method of analysis was used chiefly due to the fact that the data for local population of the Lodz district were unavailable. The report presents a comparative analysis of mortality based on the standardized death rate calculated for the total Polish and the Lodz district populations for the period for which appropriate data were available (1974-1985). The conclusions resulting from both analyses point to overmortality due to some selected causes regardless which reference population was taken into consideration although absolute number of these surpluses depends on selection of reference population.

In order to estimate the risk of death due to cancer in those occupationally exposed to asbestos dust, 1190 women--workers of an asbestos producing plant--employed for at least 3 months during 1945-1973, were examined. The cohort availability for 31 December 1981 was 89.6%. The risk was analyzed basing on the standardized mortality ratio (SMR) calculated by the man-years method. The reference group was that of the general population of women in Poland. In the test cohort, 136 deaths occurred (SMR = 93.3), in this 46 were caused by malignant tumours (SMR = 162.0), 25 by malignant tumours of the digestive organs and peritoneum (SMR = 226.9), 13 by malignant tumours of the liver and pancreas (SMR = 360.9). The mortality due to the above mentioned causes was significantly higher than that of the general population. In the subcohort of women employed during 1945-1955 selected for the very high concentration of asbestos dust 95 deaths occurred in this period (SMR = 111.1). Significantly higher than in the reference population was mortality of: malignant tumours totally (32 deaths, SMR = 206.1), malignant tumours of the digestive organs and peritoneum (20 deaths. SMR = 311.0), and malignant tumours of the liver and pancreas (12 deaths, SMR = 541.5).

To evaluate the magnitude of cancer risk in those occupationally exposed to asbestos dust, a historically prospective cohort has been investigated. The observation covered 2403 men employed for at least 3 months, within 1945-1973, in a factory producing various asbestos products--including chrysotile. The cohort availability on 31 Dec. 1981 was 91.3%. The risk analysis was based on the standardized mortality ratio (SMR) calculated by the man-years method. The reference group was composed of general men population in Poland. Totally, in the test cohort 401 deaths were certified, in this 73 due to malignant tumours and 31 due to the respiratory system cancer. The total standardized mortality ratio (SMR) came to 85, for malignant tumours, SMR = 104.8 for the respiratory system cancer SMR = 144.7, lung cancer-139.5%. Those values were not statistically significant. In the cohort of those employed during 1945-1955, selected due to a very high concentration of asbestos dust at this time and long observation time from the first contact with asbestos dust, the total SMR was 90.7, the one for malignant tumours-136.2 (p less than 0.05). In this cohort 21 deaths for the respiratory system cancer were observed, the total SMR = 191.1 (p less than 0.01), in this 18 for the lung cancer, SMR = 187.1 (p less than 0.05). The other cancer groups did not exhibit any statistically significant standardized mortality rate. The analysis points to a considerable lung cancer risk in those occupationally exposed to asbestos dust at the time of high non-controlled asbestos dust concentrations.

Occupational studies have shown that asbestos is a human carcinogen. Because many inhaled asbestos fibers deposited in the lung are cleared and swallowed, workers are also exposed through ingestion. Of the millions of current and former workers who have been heavily exposed to asbestos, one in ten will die from cancer of the gastrointestinal tract. A number on the order of 1 in 1,000 ingested asbestos fibers penetrate the digestive tract and ingested fibers have been recovered in such tissues as kidney, intestine, liver, and urine. One animal study showed tumor production related to ingestion of asbestos-containing material but, in general, the results of seven animal feeding studies have been inconclusive. A statistically significant relationship between male lung and stomach cancer and female peritoneal, gall bladder, and esophageal cancer and asbestos counts in drinking water was determined in one epidemiology study. Increased rates for male stomach and lung, and female pancreatic cancer related to asbestos in drinking water were reported in another study but possible occupational exposure made it difficult to draw conclusions. Data on excess gastrointestinal cancer among occupational groups has been used to estimate that drinking water containing 300,000 asbestos fibers per liter over a lifetime will result in one additional cancer among 100,000 people.