Impact of wear position on dosimeter performance: measurement validity under simulated indoor illumination

The light an individual is exposed to, or personal light exposure (PLE), plays an important role in human health and well-being research. PLE is typically quantified using body-worn light dosimeters (sensors), but their effectiveness as a proxy for measuring at the eye remains insufficiently understood. By combining 3D body scans and lighting simulations, we quantified the discrepancies between chest-worn and eye-level dosimeter measurements under three generalized indoor lighting scenarios. Chest-worn dosimeter performance was found to be highly context-dependent, with the smallest deviations (between -26.2% and 63.8%) observed for devices on the lower chest. Quantifying corneal light exposure, i.e., considering the field of view of the human eye, based on chest-worn dosimeter measurements proved problematic as deviations under overhead lighting exceeded a minimum 25%. To deepen our understanding of the underlying mechanisms, we disaggregated the causes of these discrepancies into three factors: the translational dosimeter displacement, the rotational dosimeter displacement, and body self-occlusion. The results indicate that minimizing the rotational displacement is key to reducing measurement discrepancies and inter-individual variability. To improve the validity of chest-worn dosimetry, an individualized approach is recommended: selecting a chest position where the dosimeter best aligns with the subject's typical view direction during expected activities.