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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 almost brought 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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