London's Pulse: Medical Officer of Health reports 1848-1972

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City of London 1952

[Report of the Medical Officer of Health for Port of London]

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Suitable lacquers are now on the market. They are at present somewhat expensive, hut against
their cost must he set the fact that once applied over a clean painted surface there is no need to
repaint and indeed to paint over the lacquer would obviously destroy all its properties and in view of
the duration of the insecticidal properties of the lacquer fresh application of the lacquer need only
be applied during a refit. A gallon of lacquer should cover approximately 750 square feet of surface.
It must be repeated that to be effective the lacquer must be skillfully applied by a man trained in the
habits and locations of cockroach infestations with particular emphasis on their breeding places and
harbourages.
The lacquer is quite transparent, indeed almost invisible. It is very tough, will not crack or peel
provided, of course, it is applied to a clean grease free surface.
The results of lacquer treatment have been extraordinary. The following table gives examples
derived from a number of ships treated:—

TABLE SHOWING THE RESULTS OF SOME OF THE EXPERIMENTS IN SHIPS' ACCOMMODATION WITH INSECTICIDAL RESINS CONTAINING ALDRIN AND DIELDRIN FOR CONTROL OF THE GERMAN COCKROACH. Blatella germanica.

Class of ship.Date Treatment applied.Locations treated.Degree of Infestation before treatment.Control achieved from latest reports.
Cargo vessel 8,200 dw. (Australia and East Indies).31.8.51GalleyHeavyInfestation cleared completely. Still 100 per cent. clear 1½ years after treatment.
31.8.51PantryLight
31.8.51StoreNil
Cargo vessel 1,560 dw. (London- Continent).17.1.52Pantry (Officers)Medium (Persistent)Infestation cleared completely. Still 100 per cent. clear 1¼ years later.
18.9.52GalleyHeavyStill 100 per cent. clear after 6 months.
18.9.52Mess RoomMediumStill 100 per cent. clear after 6 months.
Cargo vessel 2,250 dw. (London-Mediterranean).26.3.53All Accommodation.Light to Medium.Infestation cleared completely. Still 100 per cent. clear one month after treatment.
Trooper 5,554 gt. (Harwich- Continent).15.10,52All Messes, Galleys and Corridors.History of very persistent infestation from 1944.Infestation cleared' completely. Still free 6 months later.
Pilgrim Ship 5,307 (India and Jeddah).15.5.52Saloon Pantry. Saloon Galley. Crews quarters. Hospital. Pilgrim's Galley.History of persistent infestation prior to refit.Accommodation treated free of cockroaches after complete Pilgrim season. No evidence of fresh infestation December, 1952. Appearance of bloom as when new. Surfaces regularly washed down with soap and water.

In one ship the Master reported that not a single cockroach had been seen throughout the entire
ship since about the end of the first week out from home. He estimates that the treatment takes two
or three weeks to become complete, first the big or adult cockroaches disappear, the baby ones keep
showing up for the first week or so; then a complete disappearance. The same Master concludes by
saying that the test had been a very fair one, the steam heaters were on leaving home in the cold
weather and later they had plenty of tropical heat but no cockroaches seen. He points out that
before this treatment is given to a ship the Chief Steward and the Chief Officer must be given ample
warning so that the accommodation can be washed clean. If the lacquer is sprayed or brushed on to
dirty paintwork it leaves an ugly mark which cannot afterwards be washed off. The lacquer should
be applied on a clean painted surface.
In conclusion, I believe that we have not yet reached perfection despite the already excellent
results that have been obtained. Experimental work is proceeding with a view to raising the flash
point of the lacquer without at the same time affecting its blooming properties both in amount and
duration. Obviously, a non-toxic solvent would be an advantage and no doubt will be forthcoming
in the near future.
I am indebted to Mr. J. L. Hitchon, B.A., formerly the Entomologist of the Fungicide and
Insecticide Research Co-ordination Service of the Agricultural Research Council who has been closely
concerned in the elaboration and application of these insecticidal lacquers, for much useful technical
information and for his collaboration in trying out the lacquers in ships treated in the Port of London.
These insecticidal lacquers are the subject of a patent by the Ministry of Supply and are being
manufactured by several well-known paint manufacturers, under licence. The National Research
Development Corporation is in constant touch with the products produced in order to ensure maintenance
of their insecticidal properties.
SECTION XIV—Public Health (Shellfish) Regulations, 1934 and 1948.
There are a number of shellfish beds or layings within the jurisdiction of the Authority particularly
in the lower reaches of the River Thames and part of the River Roach and tributary creeks in Essex,
and in view of the close proximity of these layings to the sewage outfalls, the Mayor and Commonalty
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