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6
ATMOSPHERIC POLLUTION.
The outstanding event was the disastrous fog from 5th to 9th December, 1952. Though more
detailed reports relating to the cause of this fog, the conditions which developed, and their effects
over a much wider area have been and will be published by others with more expert knowledge than
I possess, I think that the observations recorded in the City should be readily available for reference,
and I therefore repeat below the report which I made to the Public Health Committee in February,
1953.
The fog which formed over the country during the period from the 5th to the 9th December,
1952, resulted in abnormal concentrations of suspended impurities and sulphur dioxide. The concentration
of sulphur dioxide was exceptionally high.
This was due to the persistence for several days of weather conditions which favour the formation
of inland fogs, namely, low temperatures and lack of air movement. Normally the air at ground
level in towns is slightly warmed and rises high above the level of buildings, carrying smoke and other
impurities with it. Lateral air currents also disperse and dilute the atmospheric pollution. But in
conditions of intense cold and complete absence of wind the upward moving air is quickly cooled
and falls again. The normal convection currents, of warm air rising and cold air falling, consequently
take place within an unusually limited height above ground. Thus, since there is no lateral movement,
the polluted air rises only a short distance, is cooled and falls again to ground level and an unusually
high concentration of the products of combustion of fuel is built up.
Early in 1948 daily measurements of smoke and sulphur dioxide were commenced at Golden
Lane by the volumetric method. In this method a measured volume of air from outside the building
is drawn, by means of a small electric motor, through a white filter paper, and then through a
measured volume of dilute hydrogen peroxide. The solid particles from the air remain in the filter
paper as a stain and their weight is estimated by matching with a scale of shades which has been
calibrated against weighted stains. The sulphur dioxide is removed by the hydrogen peroxide to
form sulphuric acid and the concentration of sulphur dioxide is calculated by a formula.
When the deposit of smoke particles on a filter paper is very high the method of comparison
with the standard scale of shades fails to estimate fully the weight of the material deposited. There
is no doubt that during the period from the 5th-9th December the weight of material deposited was
much in excess of the recorded figures. This is shown by comparing the results obtained by another
method of determining the weight of the stain on the filter paper, namely, the reflectometer.
I am indebted to the Department of Scientific and Industrial Research for undertaking the
examination of the filter papers from Golden Lane by this method, and for furnishing the following
results:—

The daily mean concentrations for December, 1952, for suspended impurities and sulphur
dioxide are set out in the attached tables. As a basis for comparison details are also given of the
concentrations which occurred in the months of December in the years 1951/1948.
The figures for November, 1948, are also included as this was a bad month for fog and the figures
for June, 1952, are given for comparison between summer and winter conditions.
Concentrations of sulphur dioxide up to one part per million are believed not to be harmful to
normally healthy persons, but there is no doubt of their ill effects on those who are already suffering
from respiratory diseases or have failing hearts. The Medical Officer of Health for the County of
London reports that, compared with the average per week in the previous three weeks, deaths from
bronchitis in the week ending 13th December were ten times as many, from influenza seven times,
from pneumonia five times, from pulmonary tuberculosis four and a half times and from other
respiratory diseases nearly six times as many. Deaths from heart disease were nearly three times as
many, but there was no significant increase in deaths from other causes, except gastro-enteritis in
infants, which may have been secondary to respiratory infection. The effects on healthy animals
exhibited at the Smithfield Show received wide publicity in the Press.
Such disastrous incidents as the fog in December, 1952, are fortunately rare simply because the
special atmospheric conditions necessary to draw attention so dramatically to the results of atmospheric
pollution only occur occasionally.
Atmospheric conditions are act of God, but atmospheric pollution is act of man.
For a time there is public interest and even alarm and everybody says that something must be
done about it, but the public memory is short and some other disaster steals the head-lines. So we
relapse into toleration of a normal degree of atmospheric pollution which year after year costs the
nation millions of pounds in ill-health and in deterioration of materials of all kinds.