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Nitrate and Nitrite in Drinking Water
the average human is assumed to weigh 70 kg. Assuming that the average human infant 0-3 months old weighs about 5 kg, the adult dosage is equivalent to an infant's dosage of about 23 mg/day.
Reproductive effects attributable to nitrite exposure have been reported in animal bioassays at dosages that might have been associated with maternal methemoglobinemia. Developmental effects of nitrite that have been reported at lower dosages in rodents appear to result from exposure after birth and not in utero (Roth et al. 1987). The effects included anemia and reduced weight gain. The lowest dosage at which the effects were reported was 275 mg/kg-day in rats (Roth et al. 1987). That dosage can be converted to a human infant dosage as follows:
(275 mg/kg-day)¾(5 kg) = 338 mg/day,
where the same assumptions were used as for nitrate.
In most mammals, including humans, the vasodilator effects of sodium nitrite overlap the dosage ranges that cause methemoglobinemia (Sollman 1957). The discussion of dose-response relationships for methemoglobinemia is thus applicable to the vasodilator effects as well. Although the stagnant hypoxia that results from prominent vasodilation might contribute to the anemic hypoxia resulting from methemoglobinemia, it is clear that methemoglobinemia is the primary cause of death. Methylene blue can reverse nitrite-induced methemoglobinemia and protect against death. Maintenance of normal blood pressure has never been shown to protect against nitrite lethality (Smith and Wilcox 1994).