THE ERYTHEMAL ULTRAVIOLET EXPOSURE FOR HUMANS IN GREENHOUSES

A spectrum evaluator has been employed to evaluate the erythemal expos ure in late spring and late summer at three sites and five orientation s at each site inside a glass greenhouse with black shadecloth over th e glass roof. The maximum in the erythemal irradiance in the greenhous e is not necessarily at noon. Over a day, the maximum erythemal exposu re occurred on the eastern side of the greenhouse in the morning and o n the western side in the afternoon. The erythemal irradiance on the e astern side in the morning was higher by 26% and 50% for horizontal an d vertical surfaces respectively compared with the same site at noon. On the western side the irradiance was higher by 45% and 78% for the h orizontal and vertical surfaces respectively compared with the same si te at noon. The erythemal irradiance inside the greenhouse does not va ry as much during the day as it does outside; far example, for horizon tal surfaces, the ratio of the erythemal irradiance outside to the ave rage inside the greenhouse varies from 66 to 112 to 74 for the morning , noon and afternoon periods respectively. Over a 6 h period, the eryt hemal exposure to the shoulder for a standing posture in the greenhous e was 5 mJ cm(-2).