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Ozone depletion and CFCs

This page introduces one aspect of the impacts imposed by humans our planet – which is fairly well known but often misunderstood.

See also Climate and environmental risks.


Ozone is a natural constituent of the atmosphere which protects the earth and humans from the sun’s harmful UV radiation. It has been depleted by CFCs (chlorofluorocarbons) leaking from older fridges, air conditioning and aerosols.


CFCs are regulated by the Montreal Protocol of 1987 – the ozone hole was getting less, but recently it has got worse again over the Arctic. Even where it seemed to be recovering, there has been a rise in ozone levels, probably due to violations of the Montreal rules by industries in one or more countries.

International observance of Montreal needs to remain tight, and we should make sure any very old fridges or spray cans are safely disposed of.

The greenhouse effect

CFCs don’t just cause ozone depletion; they are also among several greenhouse gases (besides CO2) that cause global warming.

The hole in the ozone layer is often confused with the greenhouse effect – they are distinct issues though in different ways they both affect the climate.

Some of the substitutes for CFCs are themselves exceptionally powerful greenhouse gases. A case of out of the frying pan into the fire! Work is going on to regulate these too.

Global warming caused by greenhouse gases remains the dominant concern.

Low level pollution

Paradoxically, while ozone is useful and necessary in the upper atmosphere to protect against UV radiation (which is carcinogenic), it is harmful in other ways – especially when there is too much of it, or at the wrong level in the atmosphere.

Contrary to myth, that seaside smell is not ozone. Breathing ozone is not good for you. Even breathing sea air may not be specially good for you. Not that breathing city air is much to be recommended. Fresh unpolluted air is best. The way God made it.

Basically, ozone belongs in the upper atmosphere – in the stratosphere and upper troposphere. At lower levels, ozone too is a greenhouse gas, adding (in excess) to global warming, together with CO2 and several others.

At street level, ozone is directly toxic to human health. Unfortunately as an unintended side effect of measures to control pollution from vehicle exhausts, the chemistry of ozone formation has been disrupted, keeping it at an unnatural concentration. Scientists are starting to getting to grips with this – but it would be better not to produce those tailpipe emissions to begin with.

The answer is to drive less.

To read more

See Resources on the environment.

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