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SMOKE PLUS FOG EQUALS SMOG
A Major Disaster.
On 5th December, 1952, a great fog descended on London and over 4,000
people lost their lives. Its effect was greatest on those over middle age,
especially the elderly, and very young infants. Fog is caused when warm moist
air is cooled quickly. Under ordinary conditions the air near the earth's
surface is comparatively warm as compared with that of the upper air; the
lower layers of air are constantly rising and they are being replaced with air
coming in from other places, causing a breeze or wind. We usually have a
certain amount of cloud in the upper air which prevents excessive radiation
of the warmth of the earth's surface; but occasionally, as on a clear starry night,
the warmth in the earth's surface can radiate rapidly and the ground can cool
quite quickly. When this happens no air rises and there is no wind; if the air
is moist fine drops of moisture condense on particles of dust, forming a mist.
If at the same time the air is laden with particles of soot or grit from chimneys,
the mist soon turns to a dense yellow fog. Sulphur dioxide, sulphur trioxide
and other products of combustion of fuel are added to the fog and give it the
objectionable taste and smell and other harmful effects.
On 4th December we had a large anti-cyclone with severe cold weather
which stayed with us until 9th December. During those days the amount of
smoke, sulphur dioxide and sulphur trioxide in the atmosphere was five times
greater than usual.
The Danger of Sulphur Dioxide.
Recent research reports tell us that when sulphur dioxide is carried to
the lungs in the presence of moisture it forms sulphurous and sulphuric acid;
in this form it becomes exceedingly poisonous and can kill an animal in four
seconds. We read last December of the distressing symptoms in the cattle
at the fat stock show at Olympia; five of the animals died. The research reports
also tell us that when people breathe air containing sulphur dioxide their pulse
and respiration rates rise, they breathe more rapidly and may have symptoms
of distress. After breathing moderate quantities of sulphur dioxide continuously
we can acquire a certain amount of immunity to the poisonous effects
of the gas, but this may only happen at the cost of a chronic inflammation of
the upper air passages and we cannot say how much permanent damage may
be taking place.
Twickenham had its share in the fog disaster. In an ordinary winter the
number of deaths each week in the Borough gradually begins to rise during
November and December and attains a maximum about February. The
number of deaths which occurred each week in the few weeks before and after
the great fog are show diagrammatically in the following figure.
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