View report page

38
demand (BOD) is raised from 3.1 to 23.9 parts per million. A Royal
Commission took the view that a river water taking up more than
4 parts per million oxygen will almost certainly show signs of pollution,
except possibly in very cold weather. The river therefore before entering
the gasworks is in a fairly clean condition, but is more than " bad "
according to the Royal Commission standard when it leaves the gasworks.
In point of fact the Royal Commission's recommendation for a standard
for sewage effluent was that it should not contain more than 30 parts
per million suspended matter nor have a BOD of more than 20 parts per
million. It will be seen therefore that after passage through the gasworks
the river Pool fails even to reach the standard of sewage effluent.
Soon after leaving the gasworks the Pool undergoes two or three
almost right-angle bends and at these bends naturally a deposit of mud
accumulates. This deposit when stirred produces an oily film on the
river, and the water has a phenolic smell. Recent analysis of a sample
of the mud scooped up from near the surface showed that it contained
0.8 percent tar, 36.8 percent mineral matter, 40 percent other organic
matter and 22.6 percent water (this being the equivalent if the mud
were dried to 1 percent tar, 47 percent mineral matter and 52 percent
other organic matter). A large proportion of the organic matter is coal.
The river water some 30 feet downstream from where the mud was
lightly stirred, was found to contain 0.8 parts per million of phenols.
(3) Effects on riverside allotments and gardens
The analyses set out in (2) above confirm complaints we have had
from time to time, particularly from Pool Allotments holders, but
also from other riparian occupiers much further downstream, that
the water is harmful to plant life. There is a widespread local belief
that in times of flood the gasworks "wash out their tanks into the
river." The gasworks deny this and the explanation is probably
that in times of flood the increased rapidity of the stream stirs up this
tarry and phenolic mud, some of which settles out on the banks and
the gardens lower down the stream. It is possible however that after
heavy rain the surface water from the gasworks contains various matters
derived from coal.
(4) Effects on illhealth and deaths associated with fog
In my annual report for 1952 I have dealt at length with the fog
that December and although the evidence for incrimination of the
gasworks was not complete the fact that the Sydenham East ward had
the highest mortality (and Forest Hill ward, which adjoins it, the next
highest) was in itself suspicious of gasworks' influence.
(5) Effects on the incidence of lung cancer
Lung cancer is nowadays accepted as being associated with both
smoking of tobacco and with atmospheric smoke in industrial areas.
It is unwise to go too deeply into these matters, which are still not
fully explained, but it seems likely that it is not entirely a coincidence
that the East Sydenham ward had the highest number of deaths from
lung cancer in the period 1946 to 1952.