Environmental Engineering Reference
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syndrome. The disease is largely confined to infants less than three months old
but may affect children up to age six years of age. Methemoglobinemia is caused
by the bacterial conversion of the nitrate ion ingested in water, formula, and other
food to nitrite. 78 Nitrite then converts hemoglobin, the blood pigment that carries
oxygen from the lungs to the tissues, to methemoglobin. The altered pigment
no longer can transport oxygen, resulting in oxygen deprivation, or suffocation.
Methemoglobinemia is not a problem in adults, as the stomach pH is normally less
than four, whereas the pH is generally higher in infants, allowing nitrate-reducing
bacteria to survive.
The boiling of water containing nitrates would cause the concentration of
nitrates to be increased. Also, certain respiratory illnesses may in themselves
cause an increase in methemoglobin levels in infants. A better epidemiologic
basis for the standard is apparently needed. The inclusion of nitrite ion and
nitrates ingested through food and air, in addition to those ingested through
water, would give a more complete basis for evaluating dietary intake. Spinach,
for example, is a high source of nitrate nitrogen.
Dental Caries
Fluoride deficiency is associated with dental caries and osteoporosis. 79 Water
containing 0.8 to 1.7 mg/1 natural or artificially added fluoride is beneficial to
children during the period they are developing permanent teeth. The incidence of
dental cavities or tooth decay is reduced by about 60 percent. The maximum flu-
oride concentration permissible in drinking water is 4.0 mg/1. Optimum fluoride
levels in drinking water for caries control, based on the annual average of the
maximum daily air temperature for the location of the community water system,
are as follows:
Temperature ( F)
Fluoride Level (mg/1)
53.7 and below
1.2
53.8 - 58.3
1.1
58.4 - 63.8
1.0
63.9 - 70.6
0.9
70.7 - 79.2
0.8
79.3 - 90.5
0.7
An alternate to community water fluoridation is a 1-minute mouth rinse by
children once a week; it is reported to reduce tooth decay by about one-third or
more. The mouth rinse also appears to be beneficial to adults in the prevention of
dental caries. Other alternatives include fluoridation of school water supplies if
there is an onsite water supply, use of fluoride toothpaste, drops and tablets, and
topical application. Milk fluoridation has been shown to be effective in the pre-
vention of dental caries, but to be clinically effective, it must be freshly prepared
and consumed immediately. 80 The Pan American Health Organization has pro-
posed adding fluoride to table salt in areas lacking fluoridated community water
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