A DEVICE FOR STUDYING THE EFFECTS OF RADI ATION ON THE PERSISTENCE OFPATHOGENIC MICROORGANISMS

A system was devised for separate analysis of the photic effect and th e thermal effect of solar radiation on the persistence of pathogenic m icroorganisms under both artificial and natural light. The objective o f the authors was also to investigate these effects in varying waveban d and irradiance. The irradiation chambers consisted of controlled-env ironment incubators with 2 high-pressure metallic halogen lamps (400 W ) irradiating a large temperature-controlled platform (3 600 cm(2)). T he light quality was modified by using 2 long pass glass filters. In u sing a 295 nm cutting filter, the UVB irradiance ranged from 1.6 to 0. 4 W.m(-2) according to the distance from the source to the target plan e. At 1.50 m distance the gradient of distribution of UVB irradiance o n the target surface was less than 12%. The thermal gradient did not e xceed 5%. The difference between the target temperature and the measur ed temperature at the sample surface support was less than 1 degrees C . The relative humidify remained stable around 60% during the inoculum exposure. The device has been adapted for studies in 'semi-field' con ditions (constant temperature for the support of inoculum and solar ra diation).