(4) Iron. Iron is a highly objectionable constituent in water for either
domestic or industrial use. It imparts a brownish color to laundered goods and
appreciably affects the taste of beverages. It also forms crusts in plumbing and piping.
The limit established to prevent laundry staining and objectionable taste is only a small
fraction of the daily nutritional requirement and, therefore, is unlikely to have any
toxicological significance.
(5) Manganese. Manganese, Iike iron, is an essential nutrient. However, it
imparts a brownish color to laundered goods, even in small quantities, and impairs the
taste of beverages, including coffee and tea. The primary reason for Iimiting the
concentration of manganese in water is to provide water quality and reduce aesthetic
and economic problems.
(6) Zinc. Zinc is an essential and beneficial element in human metabolism.
A zinc deficiency in animals results in growth retardation that is overcome by supplying
the necessary amount of zinc in the diet. Zinc salts act as gastrointestinal irritants;
however, water supplies containing up to 50 mg/l have been used for a protracted
period without noticeable harm. Soluble zinc salts impart a miIky appearance to water
at concentrations of 30 mg/l and a metallic taste at 40 mg/l. In as much as zinc in water
does not cause serious effects on health, but produces undesirable aesthetic effects, it
is recommended that concentrations of zinc be kept below 5 mg/l.
c. Other Chemical Substances. The US Public Health Service recommended
the following chemical substances in 1962 as a possible water quality parameter (see
Table 4-4).
(1) Carbon chloroform extract. Carbon chloroform extract (CCE) is not, in
itself, an identifiable chemical substance. It is an extract obtained by filtering a
measured sample of water through a carbon filter, then extracting the organic impurities
from the filter with chloroform solvent. This procedure does not detect all organic
substances in the water since some compounds are not absorbed by carbon or
extractable by chloroform. However, the method is effective for detecting and
measuring quantities of simple hydrocarbons, chlorinated pesticides, and many
industrial pollutants. The CCE procedure does not ensure against the presence of
organic pollutants, but CCE levels above 0.2 ppm indicate that the consumer is
receiving an exceptional and unwarranted dosage of ill-defined chemicals. Public water
supplies in which CCE concentrations have exceeded the maximum recommended
concentrations have invariably received customer complaints because of tastes and/or
odors.
(2) Cyanide. A single dose of 50-60 mg of cyanide is considered fatal for
humans. A dosage of 19 mg is a threshold dose, which is approximately 100 times the
limit established for rejection of the water supply. Since proper treatment will reduce
cyanide levels to 0.01 mQ/1 or less, it is recommended that concentrations in water be
kept below this level.
MD0160
4-7
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