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9. Medical literature, especially since 1952, abounds with references to the effect of air
pollution on health. Incidences of this have been given in reports to the Port and City of London
Health Committee from time to time. The authoritative views of the Committee of Departmental
Officers and Expert Advisers, appointed by the Ministry of Health to enquire into the mortality
and morbidity during the London Fog of 1952, found that between 80% and 90% of the increase in
deaths during and immediately after the fog were due to respiratory and cardiovascular diseases,
mainly of a chronic nature, and that between 60% and 70% of the increased deaths were in people
over the age of 65. The increase in morbidity was less than might have been expected from the
excessive mortality. It was also concluded that substances in the polluted fog caused irritation
of the bronchii and of the broncholes, and so accelerated death in those already suffering from
diseases of the respiratory and cardiovascular systems, but that in the present state of knowledge,
it was impossible to state that any one pollutant was the cause of death. The report also contained
a note that no firm conclusion had been reached as to the result of the work of the Atmospheric
Pollution Research Unit in the endeavour to establish some relationship between health
and the constituents of the atmosphere. There was also contained in the report the conclusion
of Dr. Percy Stocks, the eminent Statistician, that highly significant statistical correlations were
found from bronchitis and lung cancer with undissolved deposit and smoke from the air in county
boroughs of England and Wales.
10. A recent survey in London, undertaken by the London County Council Public Health Department
and Scientific Division, includes many references from medical literature. It is shown how
the death rate from bronchitis increases with the degree of urbanisation, and that there is some
correlation between deaths from bronchitis and the amount of pollution in the atmosphere. Reference
is made to the differential death rate from bronchitis in middle aged men between industrial
cities and seaside resorts, although there is the reminder of the differences in social
classes in this context.
11. The conclusions drawn from the survey mentioned in paragraph 10 together with all the
other available information,shows that there is little doubt that living in London for a long period
increases the risk of dying from respiratory disease, particularly with bronchitis, and since these
diseases are often suffered over a number of years, morbidity too is associated with the length of
residence. No significant relationship between mortality and the two types of atmospheric pollution
so far considered, i.e., sulphur dioxide and smoke, has been demonstrated, though smoke
looks more dangerous than sulphur dioxide. This conclusion does not preclude there being a
critical level of one or both in combination that could be directly associated with increased
mortality or morbidity, but equally there may be other types of pollutants more dangerous than
either. In this respect Professor F.G. Pybus, Durham University, a cancer research worker of
some 30 years, holds the opinion that benzepyrene is the most prolific source of danger and
damage to the lungs.
12. In the short term, whilst it is difficult to disentangle the effects of duration and intensity of
atmospheric pollution and temperature from any seasonal trend, the effect of the smog of January
1956 suggests that the threshold level above which a smog incidence is likely to occur in London
is when the mean level for London attains a value of 200 milligrammes of black suspended matter
per 100 cubic metres of air, and 40 parts of sulphur dioxide per 100 million parts of air; i.e. about
four times the customary winter level. The differential effect on old people when pollution
reaches this level, has been shown, though the overall effect was much less than the catastrophe
of 1952.
13. If, as is to be anticipated, measures to diminish the amount of atmospheric pollution reduce
the amount of smoke, it may be possible to assess with greater clarity the respective parts
played by sulphur dioxide and smoke which have both so far been present concurrently in the
atmosphere in roughly the same proportions during different episodes of fog.
Mr. Engineer would say:—
14. That there is not yet any satisfactory method at reasonable cost of preventing pollution by
oxides of sulphur. Confirmation of this was obtained from Dr. Charles Forrester of the Chief
Scientists Division of Ministry of Power, who is particularly concerned with the subject of sulphur.
Research work in progress at the British Coal Utilisation Research Association, undertaken
at the request of the Minister of Power, on methods to prevent the sulphur in coal passing into
flue gases, indicated that there was a promise of technical success, but that the cost might be
high, and that there might be difficulties in putting the method into practice. Dr. Forrester states
that it is virtually impossible to remove more than a proportion — say one-tenth to one-half —
of the sulphur in coal by cleaning treatment, and quite impracticable to remove it from the heavier
fuel oils. Dr. Forrester furnished the most precise table to date on the sulphur content of British
fuels which are set out below:—
Fuel Sulphur
Petrol 0.3% to 0.16%
Kerosine 0.04% to 0.15%
Gas/Diesel oil 0.05% to 1.0%
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