Modelling prevalence development in a population group exposed to vibration, and noise: Application to hand-transmitted vibration

An invertible, generalisable population model for the time course of the prevalence of a health effect resulting from habitual exposure to a physical agent, such as vibration, and noise, is proposed. The model includes a time-dependent factor representing the daily exposure, expfac ( t ), applied to a polynomial fit of prevalence-time data recorded in a population group and one additional numerical parameter, a ' 1 , to adjust the model for exposure-specific conditions. A model is constructed for the prevalence of vibration-induced white finger (VWF) to confirm and validate its performance. A 4th-order polynomial fits representative data recorded in a population group from the commencement of exposure. Using the same polynomial coefficients and solely adjusting expfac ( t ) enables the model to fit period prevalence data for VWF from all available population groups as a function of time. Adjusting a ' 1 enables the model to predict the point prevalence. If expfac ( t ) is specified in terms of the daily 8-h, energy-equivalent, frequency-weighted triaxial acceleration, the prevalences observed in different populations groups can be interrelated and interpolated to a common value (e.g., 10%) by inverting the model. This will enable tolerable daily exposures suitable for occupational environments to be defined for hand-transmitted vibration.