Behavior outdoors and its effects on personal ultraviolet exposure rate measured using an ambulatory datalogging dosimeter.

We describe the construction of a small device incorporating a UVB (290-320 nm) sensor that can be worn on the lapel site or waistband and which is electrically coupled to a portable data logger carried in a trouser pocket or worn on a belt. The detector has an approximate cosine-weighted angular response and is linear over a wide dynamic range. It has a spectral sensitivity that follows closely the erythema action spectrum in the UVB region, is less than one order of magnitude greater than this action spectrum in the UVAII region (320-340 nm) and between one to two orders of magnitude greater in the UVAI region (340-400 nm). The instrument has been used to monitor variations in erythemally effective exposure rate that occurred during three outdoor activities with differing weather conditions. Erythemal irradiance incident on the trunk was recorded every 2 s for periods ranging from 1 to 2.2 h. The results demonstrated that behavior outdoors can be a more dominant factor in determining personal exposure than ambient ultraviolet and highlighted the very important role that shade from trees plays in reducing exposure.