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

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London County Council 1934

[Report of the Medical Officer of Health for London County Council]

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63
Various materials and apparatus for special purposes sent to the laboratory
for examination during the year included :—
(1) Gas alarm lamps of an approved design, which register a warning when there
is a dangerous amount of combustible gas present in the atmosphere, were examined
from time to time to ensure that they were correctly adjusted and sensitive to a lower
limit of gas, before being issued for use in sewers, etc.
(2) Wood, composite boards, etc., used as building material, were tested for fire
resistance in accordance with the British standard specifications and for thermal
conductivity.
(3) Fire extinguishers, of the carbon-tetrachloride and other chlor-derivative
type, were examined with a view to ascertaining to what extent the gases produced
on discharge are poisonous. The sulphuric acid-soda type were examined to
ascertain to what extent the spray given on discharge was acid and likely to be harmful
to users or materials.
(4) Fumigation of furniture, bedding, etc., with hydrocyanic acid. Tests were
carried out to ascertain to what extent the poisonous gas can be removed by exposure
to the air.
(5) Electric batteries (dry).—Tests were carried out on a series of these batteries
of different makes, to ascertain their relative durability under similar conditions of
discharge.
(6) Enamelware.—Towards the end of 1933 at the request of the chief officer of
supplies the question was considered of formulating a specification for the properties
of the glaze on enamelware for use in the Council's institutions. In view of cases
of antimony poisoning which had been recorded as having occurred in various places,
caused by the use of enamelware vessels for storing acid foods or drinks, the matter
was primarily examined from the point of view of guarding against the risk of
poisoning, but it became apparent that the test which was evolved had a very definite
bearing on the quality of the enamel and its durability when in use. After due
consideration it was decided to use hot .5 per cent, citric acid solution as being
similar to a typical acid fruit preparation. Sample vessels (pie dishes, jugs, mugs,
etc.), of reputable makers were examined to obtain precise data and on the basis
of these tests, a specification was formulated which contained, inter alia, the following
clauses:—
All enamelware shall be guaranteed by the manufacturers to be free from
antimony, lead, arsenic and any other injurious substance.
Enamelware vessels will be considered to be sufficiently resistant to acid
if when filled as full as is convenient with a boiling .5 per cent, solution of
citric acid in water and allowed to stand for 24 hours without being heated or
artificially coolea, the amount of ash yielded on ignition of the residue obtained
when a definite proportion of the solution is evaporated does not exceed 1
milligramme per square centimetre of surface exposed to the action of the
acid, and if on repetition of the treatment with a fresh similar volume of the
boiling acid solution not more than a further .5 milligramme per square centimetre
is obtained.
This year 236 samples of enamelware have been examined on this basis and of
these 58 (or 25 per cent.) have been rejected, 15 for containing antimony and 43 for
failing to comply with the acid resistance test. It is worthy of remark that the
large majority of the rejections were in the early part of the year and that latterly
the quality of the samples submitted has greatly improved. Since this subject
has been under investigation two other aspects of the importance of the acid resisting
properties of enamels have become apparent—the solution of boron and fluorine
compounds. The question as to whether small quantities of boron are deleterious
to health has given rise to considerable discussion but the general consensus of opinion
is that this is the case, and the use of boron compounds as preservatives for food
has been totally prohibited in this country. Analysis has shown that from one to
two-thirds of the acid extracts of the enamels examined has been boric acid. It
has recently been stated that fluorine, either in food or in the body is a mere contamination,
and for some years it has been recognised that excess of fluorides in the