Measured total column ozone has fallen between about 1970 and 1994. The minimum is expected to be reached around 2000 and recovery to 1970 levels should occur after the middle of the next century. UV irradiance increases at the surface of the earth due to ozone depletion should peak at about 15 per cent in mid-latitudes. There are, however, few data that testify directly to the existence and size of this trend in UV irradiance and no satisfactory data on current and long-term trends in sun-related behaviour and actual exposure of humans to solar UV radiation. The incidence of harmful health effects of UV radiation can be expected to rise, eventually, at mid-latitudes. Measurement difficulties and confounding effects of changes in sun-related behaviour, however, will make these trends difficult to measure. The necessary environmental response to depletion of stratospheric ozone has probably been taken with the Montreal Protocol on ozone-depleting substances, provided that it works. Public health action is still necessary to reduce sun exposure and increase protection against the sun and to develop clear policies on the action that should be taken on early detection and treatment of skin cancers. From a health perspective, to monitor the adequacy of these responses it will be essential to institute or continue monitoring of stratospheric ozone levels, spectral UV irradiance at the surface of the earth, personal exposure of humans to UV irradiation, and trends in the major health consequences of UV radiation.
Bruce K. Armstrong (Mon,) studied this question.