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224
The above results are very satisfactory and the figures
are within the limits of the World Health Organisation
European Standards for Drinking Water Quality. This
states that the upper limit for lead in running water in the
supply should not be more than 0.1 mg/1 (Pb); but where
water undertakings continue to use lead piping the concentration
of lead (as Pb) should not exceed 0.3 gm/1
after 16 hours contact with the pipes."
Underground Water Supplies (Wells).—In August, 1947, at the
request of the Ministry of Health, a survey of underground water
supplies was made and the table accompanying my Report for 1965
gave details insofar as they were known to the department at that
time. In all, 55 wells are listed, of which only two are used for the
supply of water for drinking purposes. Of the remaining 53 wells,
19 are used for commercial purposes and 34 disused.
As far as this Borough is concerned the two wells providing
drinking water are properly supervised and have shown no sign of
deterioration.
Fluoridation of Water Supplies.—In recent years dental decay
has increased especially among the younger age groups. On an
average, a five-year-old child has at least five decayed teeth and in
fact, at the age of eleven only one child in every hundred has perfect
teeth. Modern research has discovered that a minute quantity of
fluorine assists the formation of healthy teeth and reduces the
incidence of decay.
Fluoride is present in most water supplies in small amounts as a
naturally occurring chemical. The concentration varies from a
trace to 14 parts or more per million in some areas of the world.
In combination with other elements fluorine occurs naturally in
igneous rock formations as fluorspar, fluorapatite and fluorite, all
of which are fluorides of calcium. It also occurs in the endemic
regions in soils and rocks, it is present in seawater at a concentration
of about 1 p.p.m. and it is found in many foods as a trace
element.
England's highest concentrations in water occur in Essex, West
Mersea having 5.8 p.p.m., Burnham-on-Crouch and Maldon with
3.5 p.p.m. Areas having the lowest are found in Lancashire,
Yorkshire and South Devon where it is 0.1 p.p.m. or less. Thames
water contains, on an average, 0.3 p.p.m., similar to that found in
the Deptford Well Water.