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60
have constantly stressed the enormous and costly damage to life
and property occasioned by air pollution.
Reduction in atmospheric smoke and grit has been achieved
on a substantial scale by improved methods of combustion in
industry and the use of smokeless fuels domestically. Indeed, at
long last, there seems to be general acceptance in the minds of
the public that smoke control should be exercised over the emission of smoke and grit. Perhaps this is because improvement
resulting from control over these is tangible and the public can
actually see and is aware of its beneficial effects.
Sulphur dioxide, however, is not so easily reduced for. unlike
smoke, it cannot be eliminated by burning fuel more efficiently
and, of all the air pollutants, this substance is perhaps the most
important medically by reason of its irritating and damaging
effects upon human tissues and vegetation.
Recent estimations by the Warren Spring Laboratory of the
D.S.I.R. put the reduction of smoke from Britain's chimneys at
35% less than ten years ago, but the emission of sulphur dioxide
as 23% higher. In the London area, in particular, the changes
have been more significant; while smoke emission has dropped
by 60% that of sulphur dioxide has risen by 32% and it would
appear that the bulk of this latter increase is from industry and
power stations burning coal and fuel oil. Since most of these
pollutants are discharged from high chimneys, the increase in
the oxides of sulphur has not shown itself at ground level. The
latest figures published by the Laboratory show that although
in controlled areas smoke was down by 30% at ground level, the
fall in sulphur dioxide was only of the order of 4%. Consequently,
we now have the paradoxical position of inhabitants of modern
high flats being exposed to a higher concentration of sulphur
dioxide than those living near the ground. This situation will
inevitably give rise to problems in the housing field, especially
where urban councils are committed to high-density re-housing
in the vicinity of industrial areas, or close to existing power
stations.
Recognition of the dangers arising from pollution by sulphur
dioxide was evidenced as long ago as 1927, when, at the time of
the erection of the Battersea Power Station, the Electricity Commissioners insisted that the evolution of this gas should, as far
as practicable, be prevented. This led to flue-gas scrubbing, i.e.
the flue gas was washed with river water to which had been added
an alkali to counteract acidity. Naturally, such a process is
limited to the actual physical amount of by-products which the
river can safely absorb. Other processes have been tried, some
of which, although technically sucessful, have proved uneconomical,