Ozone depletion

Protection against harmful ultraviolet radiation

Ozone (O3) is a bluish, pungent gas. Although it is highly toxic, ozone in the atmosphere is also vital for all life on earth, as it filters out harmful ultraviolet (UV) radiation from the sunlight. Thankfully, very little ozone occurs naturally near ground level, where it is one of the most harmful forms of air pollution. But equally fortunately, there is so much ozone at altitudes of 15-25 kilometres in the stratosphere that scientists talk about a protective ozone layer.

Holes in the ozone layer

The first worries about the state of the ozone layer arose in the 1970s, when research indicated that chemicals such as chlorofluorohydrocarbons (CFCs) and halons in the stratosphere could potentially break down the ozone in this protective layer. Subsequent research indicated that these fears were well grounded, and an international ozone committee was set up in 1977 to draft an agreement to protect the ozone layer. In 1985, the same year when the Vienna Convention was signed, the first “ozone holes” were observed in the stratosphere over Antarctica.

Intensifying UV radiation

Stratospheric ozone depletion has subsequently worsened over Antarctica, and has also become more noticeable in higher latitudes in the northern hemisphere, including Finland. The amounts of UV radiation reaching the ground have consequently increased significantly. This has led to increases in the occurrence of skin cancers, and has also been linked to eye diseases. UV radiation also reduces animals’ and humans’ resistance, and curbs the growth of plants both on land and in the sea.

Progress on protective measures

Although these problems remain serious, there has already been progress with the implementation of urgent measures to reduce the threat of ozone depletion. The use and manufacture of CFCs, halons and other ozone-depleting substances has been banned virtually throughout the industrialised world, including Finland, and the use of these substances in developing countries is also due to be phased out.

Predicting future trends in ozone depletion is complicated by uncertainties related to the greenhouse effect. If the greenhouse effect continues to increase, leading to global warming at ground level, average temperatures in the upper atmosphere are likely to drop, which would promote the depletion of stratospheric ozone, especially in the northern hemisphere.