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It is significant also that with the reduction of the rat population, the mouse population appears
to have increased, a situation which has not escaped the notice of your Medical Officer and Dock
Staff.
It would appear, unfortunately, that the measures used for the destruction of rats are not so
successful for mice and new techniques are therefore being tried out.
One factor which is receiving attention is the method of stowing cargoes in dock warehouses.
Experience has shown that when a mouse attractive cargo (one which gives the mouse all the
food and moisture it wants) is stacked in bulk, the mice penetrate to the centre of the pile where
they live and breed undisturbed until the pile is eventually broken down.
Every effort is now being made to persuade the Port of London Authority and Stevedoring
Companies to stow the bulk cargo in such a manner as to afford the Rodent Inspectors access
to the centre of the stacks.
It is realised that any vacant pockets thus provided in the stowage will mean a slight reduction
in the cargo capacity of the warehouse, but this would be materially compensated for by the
reduced losses from depredations by mice.
*Appended are two graphs showing the number of rats and mice destroyed month by month over
the past five years (1951-1955 inclusive), Graph A in relation to vessels and Graph B in relation
to shore premises gives a clear indication of the contention made above that, with the reduction
of the rat population in warehouses, the mouse population has apparently increased and this
increase is most noticeable in the London Docks where, in recent years, large quantities of such
commodities as millet seed (imported for feeding budgerigas) have been stored.
Use of Sodium Fluoracetate ("1080") in the Port of London
A question was raised by an Honourable Member of the Public Health Committee about the use
of the rodenticide Sodium Fluoracetate ("1080") in the City Sewers and the precautions taken.
Arising out of this question your Medical Officer thought it opportune to bring to the attention
of your Worshipful Committee some details about the employment of "1080" in ships and dock
premises within the Port of I ondon and in his dual capacity of Medical Officer of Health of the
Port and City of London to report similarly to the Public Health Committee about the use of
"1080" in the City.
"1080" was first employed as a poison in the United States during the war. It is, with the
exception of hydrogen cyanide, the most effective and rapid poison available, but it is at the
same time also one of the most dangerous and, accordingly, adequate precautions must be taken.
It is a light, white, crystalline powder, odourless and tasteless and very soluble in water.
One or two cubic centrimetres of a quarter per cent solution in water will put a rat out of action
in a few minutes and it is quite common to find the bodies of rats lying within a few feet of the
solution which they have been drinking.
The use of a solution rather than a solid bait is of great advantage since rats are great water
drinkers and will not establish themselves where there is not an abundance of water. In theory,
therefore, it is only necessary to lay down small quantities of the watery solution of "1080" in
suitable containers at strategic points ; there is no need for prebaiting and results can be
expected in a matter of hours.
It is obvious that such a poison should not be made available to the general public for domestic
use or in places like restaurants; but if it is used by trained personnel it is of the greatest
value in destroying rats in warehouses, ships or other enclosed premises which can be safely
locked or closed down for a period and to which the public do not have access. Again the use
of "1080" in the holds of ships has the great advantage that it replaces the cost of expensive
fumigations and does not necessitate putting the crew ashore during the operation — always a
difficult and costly problem for the shipowner.
The toxic quality of "1080" makes it imperative that "1080" operations should be carried out
only by servicing companies who can be relied upon to ensure that the correct concentration of
solution is used and that their staff conform to certain requirements laid down by the Port Medical
Officer. Six firms were approved in 1953 for the purpose of using "1080" on ships and each firm
was required to give an undertaking to follow, in principle, the methods and precautions prescribed
below
Conditions governing the use of Sodium Fluoroacetate ("1080") by Servicing
Companies for the Deratting of ships in the Port of London
1. The "1080" powder employed shall contain not less than 90% pure sodium fluoroacetate,
with an inert soluable substance.
2. "1080" is to be used in solution in clean fresh water, the concentration of "1080" to be
not less than 0.25%, nor more than 0.3%.
*See Appendices pages 45 and 46.
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