Cancer mortality and occupational exposure to aromatic amines and inhalable aerosols in rubber tire manufacturing in Poland
Introduction
The rubber manufacturing industry has been classified as entailing exposures that are carcinogenic to humans as early as 1987 by the International Agency for Research on Cancer (IARC) [1], [2]. In a review of the available literature published after the IARC evaluation [3], Kogevinas et al. concluded that the diversity of chemicals used or generated during rubber manufacture and the paucity of measured exposure data preclude elucidating causal associations with specific substances. Exposure assessment studies have shown that workers employed in this industry are exposed to numerous airborne chemicals, including aromatic amines, polycyclic aromatic hydrocarbons, n-nitrosamines, solvents, rubber process dusts, and rubber fumes, all of which have been shown to be carcinogenic and/or mutagenic [4], [5], [6], [7], [8], [9], [10], [11], [12], [13].
Most of the data on carcinogenic risk in the rubber industry come from the studies that have been carried out in factories in the United States and Western Europe [14], [15], [16], [17], [18], [19], [20], [21], [22], [23], [24], [25], [26], [27], with only few studies being conducted in other parts of the world [28], [29], [30]. In Poland a retrospective cohort study of rubber workers employed after 1950 was set up in the early 1990s with the results published for the first time in 2001 [30] after a follow-up until 1995. There was some suggestion from these data of excess risks for several cancer sites including that of the lip, tongue, pharynx, stomach, gallbladder, pancreas, peritoneum, articular cartilage, connective tissue, skin, testis, prostate, bladder, kidney, brain, as well as Hodgkin's disease, multiple myeloma and leukaemia. However, these excess risks did not achieve statistical significance, perhaps because of the small numbers of cancers affecting the relatively young age group of the cohort, which placed limitations on the statistical power of the study.
Simultaneously with the cohort study an exposure measurement survey was conducted [31]. These data have subsequently been included in the EU-EXASRUB database [32], which aimed at collecting exposure data from the rubber industry throughout Europe in order to create a common exposure matrix for studies of health effects of exposures among workers in the European rubber manufacturing industry, either through pooled analysis, meta-analysis or comparable national analyses. The EXASRUB data relevant to the Polish cohort were extracted from the database and used to derive a population-specific job-exposure matrix (JEM) for exposure to inhalable aerosols, aromatic amines, and rubber fumes [33].
The present study aims at assessing cancer risks in the updated Polish cohort for which the follow-up has now been extended by an additional 7 years (up till 2002) as compared to the initial observation. In addition to the increased duration of the study period quantified exposure estimates are utilised instead of relying on job title as proxies of exposure and external comparisons with the general population. These analyses of the risks, relying on quantified exposure metrics based on exposure measurements are in agreement with recommendations by Kogevinas et al. [3].
Section snippets
Materials and methods
This study was conducted in a Polish rubber tire plant that was established in 1939, and became fully operational in 1950. The factory has produced tires for cars, trucks, lorries, trolleys, tractors, agricultural vehicles, motor-cycles, bicycles, as well as inner tubes and protectors. A more specific description of the factory and its history can be found in published literature [30], [33].
The study population (Table 1) included 17,636 subjects (11,582 men and 6,054 women) who had been
Results
Utilizing a 5-year lagging period provided the best description of exposure-response associations and these results have been presented in Table 3, Table 4, Table 5.
The 5-year lagged results for the full cohort (Table 3) with 488,063 person-years did not suggest any statistically significant increased risks for total cancers, nor more specifically for cancers of the respiratory and intrathoracic organs, digestive organs and peritoneum and lymphatic and haematopoietic tissue cancers associated
Discussion
This study addressed cancer risks in a retrospective cohort of over 17,000 subjects with almost half a million person years of follow-up employed between 1950 and 2002 in a tire-manufacturing plant in Poland. It specifically examined risks associated with 5-year lagged cumulative occupational exposure to aromatic amines and inhalable aerosols generated in the production of rubber products.
The main findings show statistically significant increased risks for urinary bladder cancer in the whole
Conflict of interest
None declared.
Acknowledgements
This work was sponsored by the European Union 6th Framework Programme's Environmental Cancer Risk, Nutrition and Individual Susceptibility (ECNIS) project (FOOD-CT-2005-513943). Exposure data came from the EXASRUB database that was elaborated in a Concerted Action sponsored by the European Union (QLK4-CT-2001-00160, QLRT-2001-02786) and the JEM was constructed within the European Union Transfer of Knowledge in Molecular and Epidemiology of Occupational and Environmental Cancer (EPITOK)
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