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rough indication of duration of exposure to the London atmosphere and atmospheric
pollution because recent works* tend to incriminate a dirty atmosphere as much, or
more, than tobacco smoking as a cause of cancer of the lung.
The indices of atmospheric pollution which are taken from the twenty-seventh
report of the Department of Scientific and Industrial Research are somewhat unsatisfactory.
As I have indicated before (see Appendix B to my annual report for 1956) the
readings are from a mixture of instruments sited at different levels and, often, for
particular local problems ; to ensure as much homogeneity as possible readings from
the more numerous deposit gauge stations have been used—these relate to the ten
years ended March, 1954, but only 9 of the 51 stations operated over the whole ten
years and 24 of them were in operation for one year only. For these reasons the use of
any one station, or group of stations, to give a representative figure for an area as large
as a metropolitan borough is of doubtful value, but for what it is worth the stations in
a borough have been averaged.
Some indication of the extent of variation from recording stations is given by the
following figures taken from one borough, for the winter of 1953-54, viz:—
Solid deposit SO4
296 105
556 144
296 122
1,222 182
Average 593 138
However, the figures given in table (ix) are the best available and their use should be
viewed against the background of the foregoing reservations.
The interaction of these various indices is perhaps best summarised by the calculation
of the product-moment correlation coefficient (r) and these are given below for the
standardised mortality ratios and the other indices listed (figures for the City of London
have been excluded from the calculations).
Correlation coefficients for standardised mortality ratios for cancer of the lung (males only), London boroughs
(excluding the City of London) and :
r
Percentage in social classes IV and V +0.570
Percentage born in London .. +0.476
Solid deposit +0.106
Sulphate ions (SO4. +0.341
The two first are statistically significant (P<.001 and P<.02 respectively); such a
highly significant relationship with percentage in social classes IV and V is to be
expected because of the known social class gradient of mortality from cancer of the lung.
The lower, but nevertheless significant, value for the correlation with percentage born
in London conforms with the known increase in mortality from cancer of the lung
with increase in the degree of urbanisation, though the index used here is only a crude
measure of exposure to the atmosphere of various parts of London and takes no account
of movement within the County for work, pleasure or residence, and thus may not be
altogether representative of the average environment experienced by the differing
populations. The poor correlation with the two indices of atmospheric pollution is not
altogether surprising in view of the differing quantity and quality of the measurements.
To summarise, over the past ten years there has been an increase in mortality from
cancer of about 14 per cent., attributable, in the main, to men aged 45 and over. In
terms of sites for both sexes the greatest absolute increase has been in cancer of the lung.
* Stocks, P. (1959) British Medical Journal 1, 74.
Pybus, F. C. (1959) The Medical Press, CCXLI, 122, 149.
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