| dc.description.abstract | Workers in the aluminium industry have been exposed to coal-tar pitch volatiles, which contain considerable amounts of carcinogenic compounds, such as polycyclic aromatic hydrocarbons (PAHs). These compounds have been shown experimentally to be mutagenic and carcinogenic, and epidemiological studies of workers exposed to coal-tar pitch volatiles have provided evidence that exposure to high concentrations may give rise to substantial risks for cancers of the lung and urinary bladder and possibly elevated risks for cancers of the kidney and pancreas. The aim of this thesis was to estimate past exposures to particulate PAHs amoung workers in the Norwegian aluminium industry for use in studies of possible associations beteen cumulative exposure to coal-tar pitch volatiles, measured as PAHs, and cancers of the lung, bladder, pancreas and kidney.
The thesis includes both plant-specific studies and a combined analysis of cohorts of workers in six Norwegian aluminium smelters. The combined anlysis covered 11 103 men who had been employed for more than 3 years in one of the six aluminium smelters, contributing 272 554 person-years during follow-up from 1953 to 1996. Exposure was estimated quantitatively from industrail hygiene measurements, process parametes and description of changes in the technology over time. The numbers of cases of cancer observed were compared with those calculated from age- and calender-period specific national rates for males. Dose-response relationships were investegated by internal comparisons with Poisson regression and by stratified ananlysis of stadanrdized incidence ratios (SIR). Potential confounding by smoking was investigated in sub-analysis in three of the plants.
The total number of cancers observed in the combined study was close to that expected, giving an overall SIR of 1.03 (95 percent confidence interval (95% CI, 1.1-1.5; 130 cases), while the observed numbers of cancer of the lung, kidney and pancres were close to those expected.
The incidence of bladder cancer increased steadily with increasing cumulative exposure to PAHs, and the relative risk for persons in the upper exposure category in the analysis with a 30-year lag period was about 2.0. No association was found between cumulative exposure to PAHs and lung cancer, but we found an elevated risk for kidney cancer among the workers most heavily exposed to PAHs with a 30-year lag period. For pancreatic cancer, we found a higher incidence among the workers exposed to PAHs than among unexposed workers, but no clear dose-response relationship. Confounding by smoking was included as a variable in the internal ananlyses.
The thesis provides further evidence of a causal associotion between exposure to coaltar pitch volatiles and an increased risk for bladder cancer among aluminium reduction workers. The studies do not, however, support the earlier finding of an association between exposure to these substances in the aluminium industry and an increased risk for lung cancer. No conclusion could be reached about the potential link between exposures in the sluminum industry and cancers of the kidney or pancreas. | nb_NO |
