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It is recognised that when a standard deposit gauge is exposed for a number of
successive months at the same site a variation in the successive results can be expected.
The standard "deviation" is at most places about 40% of the reading; this means that
about one reading in three is different from the average by more than 40%. This variation
is not, however, due entirely to changes in the rate of emissions from chimneys,
industrial plant and other sources of pollution; fluctuations in meteorological factors
such as rainfall, speed and direction of wind and turbulence of the atmosphere, have
to be taken into account also. For this reason the average readings taken over the
twelve-month period of investigation are likely to be most reliable. Reference to the
third table, column (4), shows that the average monthly deposit for Leyton's six
gauges - which includes the gauges situated within the curtilage of the Gas Works - is
17.49 tons per square mile, which is less than the officially recorded deposits over
the same period for gauges in several of the neighbouring authorities. Although
comparison with the remaining neighbouring areas is not so favourable, it will be noted
that gauge No. 5 - the one situated in the Gas Works - showed a marked decrease in the'
average of deposited material during the latter half of 1959 (22.38) as against 29.09
for the period January to June.
In making this comparison, due regard must be had to the fact that the six gauges
in Leyton are situated in close proximity to known sources of pollution (Gauge No.5
being actually in the Gas Works) whereas gauges in the neighbouring areas are for the
most part set up to check the general level of atmospheric pollution in the district
as a whole, and not, as in Leyton's case, to monitor any specific plant or installation.
In order to provide some comparison with average national figures, the following
data have been extracted from the report by vhe Department of Scientific and Industrial
Research on the Investigation of Atmospheric Pollution:-
Deposited Matter - National Average
Annual figures for the Deposited matter - tons per
whole country - square mile per month -
High 106.97 ( Average for
( Leyton's 6
Average 17.28 ( Gauges 17.49
High Values - are arithmetic means for the six sites at which the
six greatest deposits for the whole year were observed.
Average Values - refer to all sites (1,090) at which deposit gauges
were in operation.
Interpretation of the results obtained over the twelve-month period of investigation
indicates that the rate of deposition of dust and grit in the vicinity of the
works has fallen to a reasonable level having regard to the concentration of industry
in the district, but a longer period of observation is necessary before definite
conclusions can be drawn and for this reason the standard deposit gauges have remained
in position for a further twelve months.
The present situation is undoubtedly much more satisfactory than it was when
members of the Council met representatives of the Board in October, 1958. It is
significant that complaints are rarely received by the Department. This does not, of
course, necessarily mean that there is no cause for complaint, or that the problem is
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