Significance of cross-sectional surveys in occupational epidemiology.

This communication discusses the possibility of cross-sectional occupational surveys concealing real occupational risks. For example, occupational factors constitute only one of the etiologic determinants of multifactorial diseases. In addition the diversity of industrial processes leads to a dispersion of risks, and it is difficult to avoid sampling biases both for cases and for referents. The conclusion is drawn that only after several surveys, conducted by different groups and under different circumstances, have shown no risk for a certain occupational factor can such results be considered valid.