A new method for measurement of erythemal irradiance.

A composite system of four dosimeter materials, nalidixic acid (NDA), polysulphone, 8-methoxypsoralen (8-MOP) and phenothiazine, is presented for the passive measurement of the UV spectrum. The properties of the materials were investigated and found to be suitable to allow the materials to be applied in a system to evaluate the UV spectrum. The evaluation of the spectrum reduces by 70% the errors arising when only polysulphone dosimeters are employed to measure the exposure due to a source spectrum that differs from the spectrum they have been calibrated against. Knowledge of the spectrum provides an advantage over the Robertson-Berger meter and polysulphone dosimeters, as the biologically effective exposure for any biological process may be calculated with better than 20% accuracy. The composite system was miniaturised to a size of 3 cm x 3 cm to eliminate errors due to spatial variation of the spectrum and to allow the application at any site on objects with complicated topography in a similar way as polysulphone dosimeters. Unlike the polysulphone dosimeters, the composite system does not require calibration against a specific source of UV in order to maintain a high degree of accuracy in the collected data.