Actinic rays and aerosol sprays.

Ophthalmologists working in equatorial regions have long been familiar with the syndrome of solar conjunctivo-keratopathy. This condition, which affects only the interpalpebral area of the conjunctiva and cornea, is characterized by chronic discomfort and irritation, hypersensitivity to wind, dust, smoke, and sunlight, chronic conjunctival injection, fleshy protuberant pingueculae, usually containing collections of hyaline material and, in the most advanced cases, progressive pterygia. Individual response to apparently identical environmental influences is extremely variable and it seems likely that the aetiology may involve factors beyond the purely radiational but it is clear that exposure to ultraviolet light (UVL) in the wavelength range of 290 to 300 nm is an indispensable precursor. A new factor has now arisen which threatens significantly to increase this hazard and possibly to extend the geographical area in which this minor but apparently incurable syndrome may be encountered. It is the purpose of this note to bring the new circumstances to the attention of ophthalmologists. Ozone is being formed continuously in the stratosphere by the action of sunlight on 02 molecules. These are split into single atoms which immediately combine with other molecules of 02 to form ozone 03. The concentration of ozone is controlled by the balance between the rate of formation by this process and the rate of its destruction by reaction with other elements. The ozone belt is confined to the stratosphere between io and 40 km and is virtually the only absorber of solar ultraviolet radiation of wavelength between 240 and 300 nm. Attenuation of UVL intensity varies with the angle of incidence of the light on the ozone belt (which is why effects are currently confined largely to the tropical zone) but if the ozone concentration were to be reduced, UVL-induced ocular lesions may be expected to be encountered over a wider area. The new factor is the growing threat to the ozone layer from the ever-increasing quantities of chlorofluoromethane gases released into the atmosphere, mainly from aerosol sprays. The gases, CFC13 and CF2C12, which are currently being produced world wide, at the rate of about i million ton/yr, give rise to free atomic chlorine radicals which act