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Fig 1: Hazardous driving conditions
due to smog
The smoke-laden fog that shrouded the capital from Friday 5
December to Tuesday 9 December 1952 brought premature death
to thousands and inconvenience to millions. An estimated 4,000
people died because of it, and cattle at Smithfield, were, the
press reported, asphyxiated. Road, rail and air transport were
brought almost to a standstill and a performance at the Sadler's
Wells Theatre had to be suspended when fog in the auditorium
made conditions intolerable for the audience and performers.
The death toll of about 4,000 was not disputed by the medical
and other authorities, but exactly how many people perished
as a direct result of the fog will never be known. Many who
died already suffered from chronic respiratory or cardiovascular
complaints. Without the fog, they might not have died when
they did. The total number of deaths in Greater London in
the week ending 6 December 1952 was
2,062, which was close to normal for the time of year. The
following week, the number was 4,703. The death rate peaked
at 900 per day on the 8th and 9th and remained above
average until just before Christmas. Mortality from bronchitis
and pneumonia increased more than sevenfold as a result of
the fog.
Fig 2: The London smog disaster of
1952.
Death rate with concentrations of smoke
The fog of December 1952 was by no means the first
to bring death and inconvenience to the capital. On 27 December
1813 fog was so dense that the Prince Regent, having set out
for Hatfield House, was forced to turn back at Kentish Town.
The fog persisted for almost a week and on one day was so thick
that the mail coach from London to Birmingham took seven hours
to reach Uxbridge. Contemporary accounts tell of the fog being
so thick that the other side of the street could not be seen.
They also tell of the fog bearing a distinct smell of coal tar.
After a similar fog during the week of 7–13 December 1873, the
death rate in the Administrative County of London increased
to 40 per cent above normal. Marked increases in death rate
occurred, too, after the notable fogs of January 1880, February
1882, December 1891, December 1892 and November 1948. The worst
affected area of London was usually the East End, where the
density of factories and domestic dwellings was greater than
almost anywhere else in the capital. The area was also low-lying,
which inhibited fog dispersal.
At the beginning of January 1900, when he reported
for duty as the newly appointed Director of The Meteorological
Office, Dr (later Sir) Napier Shaw received from the Bishop
of London a 'letter of condolence', expressing sorrow that he
(Shaw) should have to work in 'this place of darkness' - a reference
to the smoke-laden fogs of London and the fogginess of that
winter in particular. One of the projects initiated by Shaw
soon after he became Director, was an inquiry into the occurrence
and distribution of fog in the capital. The investigation confirmed
that smoke from the chimneys of London served to aggravate fog
problems.
As long ago as the 13th century, air pollution
was recognised as a public-health problem in the cities and
large towns of the British Isles, and the burning of coal
was identified as the principal source. Four centuries later,
in his Fumifugium, published in 1661, John Evelyn
wrote of the 'Hellish and dismall cloud of sea-coale' that
lay over London and recommended that all noisome trades be
banished from the city. The authorities did not, however,
take his advice. The burning of coal continued and the pall
of soot over London grew worse.
The industrial revolution brought factory chimneys
that belched gases and huge numbers of particles into the
atmosphere. Some of these particles caused lung and eye irritations.
Others were poisonous. All were potentially condensation
nuclei, the tiny hygroscopic particles on which condensation
forms. From the gases, corrosive acids were formed, notably
sulphuric acid, which is produced when sulphur dioxide combines
with oxygen and water.
As if it were not enough that they brought
on agues, rheumatism and fevers and carried particles of
soot from coal fires, the fogs of the British Isles now became
even more unpleasant, for the noxious emissions from factory
chimneys gave them an acrid taste, an unpleasant odour and
a dirty yellow or brown colour. These fogs, so different
from the clean white fogs of country areas, came to be known
as 'pea soupers', not only in London but also in other industrial
areas of the British Isles. The particles in the atmosphere
made buildings dirty and the acids attacked ironwork, stonework
and fabrics.
In early December 1952, the weather was cold, as
it had been for some weeks. The weather of November 1952 had
been considerably colder than average, with heavy falls of snow
in southern England towards the end of the month. To keep warm,
the people of London were burning large quantities of coal in
their grates. Smoke was pouring from the chimneys of their houses
and becoming trapped beneath the inversion of an anticyclone
that had developed over southern parts of the British Isles
during the first week of December. Trapped, too, beneath this
inversion were particles and gases emitted from factory chimneys
in the London area, along with pollution which the winds from
the east had brought from industrial areas on the continent.
Fig 3
Early on 5 December in the London area, the
sky was clear, winds were light and the air near the ground
was moist. Accordingly, conditions were ideal for the formation
of radiation fog. The sky was clear, so a net loss of long-wave
radiation occurred and the ground cooled. The moist air in
contact with the ground cooled to its dew-point temperature
and condensation occurred. Cool air drained katabatically
into the Thames Valley. Beneath the inversion of the anticyclone,
the very light wind stirred the saturated air upwards to
form a layer of fog 100–200 metres deep. Along with
the water droplets of the fog, the atmosphere beneath the
inversion contained the smoke from innumerable chimneys in
the London area and farther afield. Elevated spots such as
Hampstead Heath were above the fog and grime. From there,
the hills of Surrey and Kent could be seen.
During the day on 5 December, the fog was not
especially dense and generally possessed a dry, smoky character.
When nightfall came, however, the fog thickened. Visibility
dropped to a few metres. The following day, the sun was too
low in the sky to make much of an impression on the fog.
That night and on the Sunday and Monday nights, the fog again
thickened. In many parts of London, it was impossible at
night for pedestrians to find their way, even in familiar
districts. In the Isle of Dogs, the visibility was at times
nil. The fog there was so thick that people could not see
their own feet! Even in the drier thoroughfares of central
London, the fog was exceptionally thick. Not until 9 December
did it clear. In central London, the visibility remained
below 500 metres continuously
for 114 hours and below 50 metres continuously for 48 hours.
At Heathrow Airport, visibility remained below ten metres
for almost 48 hours from the morning of 6 December.
Huge quantities of impurities were released
into the atmosphere during the period in question. On each
day during the foggy period, the following amounts of pollutants
were emitted: 1,000 tonnes of smoke particles, 2,000 tonnes
of carbon dioxide, 140 tonnes of hydrochloric acid and 14
tonnes of fluorine compounds. In addition, and perhaps most
dangerously, 370 tonnes of sulphur dioxide were converted
into 800 tonnes of sulphuric acid. At London's County Hall,
the concentration of smoke in the air increased from 0.49
milligrams per cubic metre on 4 December to 4.46 on the 7th
and 8th.
The infamous fog of December 1952 has come
to be known as 'The Great Smog'; the term 'smog' being a
portmanteau word meaning 'fog intensified by smoke'. The
term was coined almost half a century earlier, by HA Des Voeux,
who first used it in 1905 to describe the conditions of fuliginous
(sooty) fog that occurred all too often over British urban
areas. It was popularised in 1911 when Des Voeux presented to
the Manchester Conference of the Smoke Abatement League of
Great Britain a report on the deaths that occurred in Glasgow
and Edinburgh in the Autumn of 1909 as a consequence of smoke-laden
fogs.
Legislation followed the Great Smog of 1952
in the form of the City of London (Various Powers) Act of
1954 and the Clean Air Acts of 1956 and 1968. These Acts
banned emissions of black smoke and decreed that residents
of urban areas and operators of factories must convert to
smokeless fuels. As these residents and operators were necessarily
given time to convert, however, fogs continued to be smoky
for some time after the Act of 1956 was passed. In 1962,
for example, 750 Londoners died as a result of a fog, but
nothing on the scale of the 1952 Great Smog has ever occurred
again.
Pea-soupers have become a thing of the past,
thanks partly to pollution legislation but also to slum clearance,
urban renewal and the widespread use of central heating in
the houses and offices of British towns and cities. As recently
as the early 1960s, winter sunshine totals were thirty per
cent lower in the smokier districts of London than in the
rural areas around the capital. Today, there is little difference.
We should not, however, be complacent. The air now
contains other types of pollutants, many of them from vehicle
exhausts. Among these pollutants are carbon monoxide, nitrogen
dioxide, ozone, benzines and aldehydes. They are less visible
than the pollutants of yesteryear, but are equally toxic, causing
eye irritation, asthma and bronchial complaints. To some extent,
we have simply replaced one form of air pollution with another.
We may question whether or not the major cities of the British
Isles are any less polluted now than they have been for hundreds
of years.
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