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(j) Air Pollution and Fog.
I am indebted to the Meteorological Office at London Air
port for some extremely interesting figures on the incidence of
fog. Readings are taken at intervals of three hours throughout
the year and the density of fog: as indicated by the degree of
visibility, recorded. If fog lasts for a whole day then of
course it will be recorded on eight occasions, although not
necessarily at the same density each time. During 1958 fog of
varying density up to a visibility of 1,080 yards was recorded
on 189 occasions; in 1959 the figure was 183: in 1960 76 and
in 1961 - 135. A detailed study of the figures reveals a most
interesting comparison between the number of occasions on which
dense fog was recorded in relation to the number of occasions
on which fog of any density was recorded. Taking visibility of
less than 104 yards as being a dense fog we find that in 1958
the ratio between dense fogs and lighter fogs was 1:2.2; in
1959 1:1.8; in 1960 1:3.0; in 1961 1:4.2; showing a definite
reduction in the tendency for light fogs to become dense. If
we come further down the scale and compare very dense fogs, i.e.
where visibility is less than 44 yards, the trend is even more
marked. In 1958 the ratio between very dense fogs and other
fogs was 1:5.5; in 1959 - 1:5.8; in 1960 - 1:11.7 and in 1961
1:15.0.
These figures give substance to one of the main arguments
in favour of smoke control, i.e. that a smoke free atmosphere
will prevent light mists and light fogs from developing into
dense impenetrable fogs. Once it can be established that this
is in fact happening then any question of the cost of smoke
control being a burden would be completely ruled out. Apart
from benefit to health and savings on the cost of domestic clean
sing the annual savings achieved by eliminating dense fogs would
be far in excess of the cost of the contributions which the
Council make towards the adaptation of fireplaces.
Incidentally the Ministry of Aviation and the operating
companies at London Airport must be amongst the main beneficiaries
in this respect and one wonders whether, as these savings
have been achieved by the efforts of local authorities in close
proximity to the airport, we could not expect that some of these
savings could be ploughed back to reduce the noise nuisance which
the same people inflict on residents of the district.
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