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28
AIR POLLUTION
In Stoke Newington, measurements of air pollution are regularly
taken by means of a Deposit Gauge and a Lead peroxide apparatus installed
at the Town Hall, giving monthly records or the deposited matter and the
sulphur contained in the air- These instruments hare been in use for
several years The results are given in Tables 1 and 2.
In addition a daily smoke Filter has now been installed, and has
been in operation for the year under review. In this instrument, air
is drawn continuously through a filter paper, and the smoke particles
retained in the surface of the paper leave a stain of varying intensity.
The apparatus includes a meter measuring the amount of air passing
through the filter. The density of the stain is read on a standard shade
card, calibrated by the National Physical Laboratory, and from this and
the meter readings, the quantity of smoke in the air is calculated.
Table 3 gives the pollution recorded by the Daily 3noke Filter in
milligrammes for 100 cubic metres. The smoke recorded during the winter
months is approximately 10 times more than for the summer months, and
this large seasonal variation is more clearly shown in Figure 1.
There is comparatively little industrial smoke produced in Stoke
Newington, the principal source of pollution being from domestic fires,
and this is reflected in the results obtained. Results of similar readings
in one of the industrial towns in Lancashire, where there is much
industrial smoke, do not show such a marked seasonal variation, the winter
readings being only about 4 times greater than during the summer. Figure 2
gives graphs comparing the monthly results for this town and for Stoke
Newi ngton.
Pollution is at its maximum during fog periods. In one such spell
or weather in January the smoke readings reached 118 milligrammes per 100
cubic metres; by contrast, the lowest reading recorded during the simmer
months was 2 milligrammes per cubic metre.