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Environmental Health
The Chief Public Health Inspector, Mr. A. Makin, reports:—
During 1966, because of the improvement of the staff position, it was possible to make considerable
progress, particularly in connection with offices, shops and food premises, and good progress was made
on the slum clearance programme.
GENERAL
Accidents
Any accident incapacitating a person from work for three days or more is notifiable and all accidents
notified to the department have been investigated.
Statistics of the reported accidents, the action taken and the cause of the accident are set out
on page 70.
Aircraft Drinking Water
The pattern of results of bacteriological examinations of drinking water on aircraft remains the
same as in previous years. All samples from fixed tanks proved satisfactory. The supply by means of
portable flasks on the older type of aircraft is unreliable, although compared with previous years there
is an improvement in the percentage of satisfactory samples. Notwithstanding that both steam and
chemical sterilization of flasks before each filling is practised by one operating company, many results
were unsatisfactory. It can only be assumed that such bad results are caused by unsatisfactory handling
of the containers during and after filling.

Chironomus Midges
Problems arising from the discharge of sewage effluent from the Maple Lodge Works of the West
Hertfordshire Main Drainage Authority into the Grand Union Canal at Harefield have been of concern
for several years past. In particular, the appearance of large numbers of chironomus midges in the
spring and summer, and the nuisance to which their presence gives rise, has resulted in many complaints
from local residents.
The midge incidence depends on climatic conditions, and in 1965 there was only a minor problem
and few complaints. In 1966, however, there was a massive infestation and, consequently, a large
number of complaints were received. The unusual aspect of the problem in 1966 was that the nuisance
began early, and complaints were received from mid-March onwards. The infestation extended
several miles southwards—to the centre of Uxbridge.
Following urgent consultations with officers of the Thames Conservancy and the Water Pollution
Research Laboratory, it was agreed that disinfestation measures along the canal were necessary. Thames
Conservancy remained firmly opposed to the use of chlorinated hydrocarbons in the water, and it was
therefore decided that the treatment should take the form of applying to the surface of the canal and
the banks a Pyrethrum "fog". This treatment was carried out by the Metropolitan Water Board on
continued on page 71