A Stady of Eye Complaints Produced by Ultraviolet Radiation from Fluorescent Lighting

Abstract

Concerning the studies of eye complaints produced by ultraviolet radiation from fluorescent lighting, there have been both positive and negative conclusions.Quite recently in Japan, Dr. Otsuka claimed that 2 patients suffered from diffuse superficial keratitis produced by ultraviolet radiation from fluorescent lights. On the other hand, Dr. Hamano reported that the quality and the quantity of ultraviolet radiation between 3100-4000 Angstrom from fluorescent lights were not harmful to the human eye.In order to investigate these opinions more carefully, we tried some experiments in co-operation with the Fifth Busines Section of the Matsushita Electric Industrial Co.Experiment 1: Spectro-photometry and measurement of the penetration ratio through a fluorescent glass. tube-wall coated with fluorsscent substances from ultraviolet radiation.Ultraviolet radiations shorter than 3126 Angstrom do not pass through the wall of the glass tube, but slightly longer radiations do. Of the radiations between 3126-3132 Angstrom, about 10% pass through the glass wall.Experiment 2: Measurement of the quantity of ultraviolet radiation.Using the Keller form of the Bering-Meyer method, we measured quantitatively the ultraviolet radiation of: the fluorescent light, the high-pressure mercury-vapor quartz lamp, sunlight, and the daylight radiation falling on the surface of the desk in a room.We found the desk-surface radiation to be nearly the same as that given off by a fluorescent light of about 10-20cm. distance (especially when approximating 20cm.) (cf. the table)Experiment 3: As to whether electrical ophthalmy will or will not occur on the eyes of rabbits and/or human adults by ultraviolet radiation.4 female adult rabbits (1 albino and 3 of dark color) were used by applying the fluorescent light to the cornea at a distance of 3cm. over a period of 3 hours.3 men, aged 23, 24, and 39 resp, and 3 women, aged 19, 22 and 27 resp., were used. All were free from pathological symptoms. Only the right eye in each case was used, leaving the left eye free asa control_ To the eye, with the tube touching the eyelash, a 20W Daylight fluo escent light was applied in five cases (yielding a light intensity of 5000 lux), and a lOW Daylight fluorescent light in one (yielding a light intensity of 8000 lux ; this increase rather than decrease in this case was dueto high brightness). This experiment lasted 1 hour.Result: Immediately after the cease of application, 1 man (aged 38) and 2 women (aged 22 and 27) felt a drying sensation which continued from 30' to 1 hour. All cases (rabbits and human adults) were given both a slit-lamp examination and a fluorescein test 3 hours after the experiment ; these examinations were repeated 20 hours after the experiment.The findings in all cases were negative.Conclusion1. The ultraviolet radiation given off by fluorescent lighting is longer than 3126 Angstrom and so is not injurious to the human cornea.2. According to Birch-Hirschfeld & Hoffmann, Triimpy, Vogt, Kinsey, et al, wave lengths shorter than 3100 Angstrom are harmful.3. It is generally recognized that wave lengths shorter than 3100 Angstrom do not penetrate the glass-tube-wall except in negligible amounts.4. Daylight 20W fluorescent lights at 20cm. distance is e-Tuivalent in ultraviolet radiation to the amount of summer daylight ultraviolet radiation coming in through a closed glass window facing north on the desk.5. The human eye is not likely to be exposed to an intensity of 5000-8000 lux (to the eye, with the tube touching the eyelash) over the 5-10 hour period that fluorescent lighting may be used6. Fluorescent desk lamps are usually 10-30cm. away from the cornea and fluorescent ceilling lamps are over 1-2m. distant. Therefore, the intensity, decreasing by the square of the distance, would be negligible.