Diets, lead daily human intakes

Sampling and analysis of lead in diets of human populations require taking account of some characteristics of lead in human diets. First, any given dietary item will have relatively low amounts of lead but the amounts consumed daily can lead to relatively high total lead intakes. Second, while human populations aU receive some fraction of their lead exposures Ifom their diets, the size of the fractional intakes and uptakes of lead from diet will vary with such factors as the subset of the population, the amount of the centralized... 

Calcium is readily abundant in the mammalian diet. A 70 kg human contains approximately 1200 g of calcium and has a daily intake of 1100 mg/day. There are no pubHshed exposure limits (38). Low levels of calcium in the blood, hypocalcemia, can lead to tetany high levels, hypercalcemia, can lead to coma and death. Calcium toxicity, above 160 mg/L in the blood, is not related to an excessive intake of calcium. 

We might ask, however, what the optimum daily amounts of these important substances are, what amounts should be ingested to lead to the best health. The Food and Nutrition Board has not attempted to answer this question, and in fact there is little evidence available for human beings. The recommended diet for laboratory monkeys contains about 100 times the amount of ascorbic acid that is recommended for man, and there is experimental evidence showing that the general health and resistance to disease of the monkeys are better on this diet than on one containing less ascorbic acid. There is also some evidence for man, as mentioned above. It is likely that the optimum intake of vitamin C for most people is much greater than the RDA. 

Intake of lead or other substances in humans is typically indexed as daily intake. However, intakes scaled for different time frames have been employed in different settings over the years, e.g., weekly intakes (FAO/ WHO, 1993) of Pb and other contaminants per body weight. This specifically applies to ingestion, inhalation, and, in some cases, dermal application. Daily lead intake into body compartments is the product of lead concentration in some medium and the mass (diet Pb) or volume (air Pb, water Pb) of lead-containing medium taken in daily. High levels of lead in an environmental medium can be quite toxic when ingested in relatively modest quantities daily. 

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