[Quantitative assessment of cancer risk following epidemiological studies]

The role of data derived from epidemiological studies in the quantitative assessment of cancer risk has been constantly growing. That results from the fact that epidemiological studies are performed directly on humans so that it is possible to avoid bias very often associated with methods of extrapolation between animals and humans. Moreover, a slow but continuous increase in the number of well designed epidemiological studies with results which can be used to estimate dose-response relationship is being observed. In this paper, the methodological foundations of cancer risk modelling on the basis of epidemiological studies are discussed, and the dose-response relationship based on epidemiological study carried out in an occupational cohort of workers employed in a pulp and paper plant was estimated. The epidemiological study was performed by the team of the Department of Epidemiology, The Nofer Institute of Occupational Medicine, Lódź. Lung cancer was adopted as the effect of occupational exposure. In oder to estimate the increase in cancer risk induced by occupational exposure, the risk for the whole occupational life was calculated by employing the methods of competitive risks, essential relative risks were modelled using Poisson means for data divided into groups, and a Cox proportional-hazards model was used for single data. The analysis indicated, that the data from epidemiological studies render it possible to carry out a more thorough investigation as compared to data obtained from animal experiments. As to the cohort under study, a certain effect of age at which workers enter into exposure on lung cancer risk was observed. A risk 'outfit' the workers bring in at the beginning of their employment is clearly visible in older age groups. A general conclusion drawn from the study may be formulated as follows: epidemiological studies play a major role in assessing the effect of working conditions on the increase in the morbidity risk, however, they are not a panacea for all the problems emerging in the cancer risk assessment in exposed persons. Therefore, information obtained from epidemiological and toxicological studies should supplement and reinforce one another, and data from both sources should be used to obtain the best possible characteristics of risk cancer in humans.