Diets, lead sampling

Between 1979 and 1989 there was a virtual elimination of the use of lead-soldered food cans, with a concomitant drop in lead levels in food. Average daily intakes of lead for adults, based on an analysis of 27 market basket samples taken nationwide for a 1980-1982 Total Diet Study, were as follows (Gartrell etal. 1986b) ... 

Decongestants and diet pills result in false positives for amphetamine use in one third of the test samples given to 40 of the countries leading laboratories. There are roughly 300 over-the-counter drugs that cause false positives on the EMIT. 

For regular consumers of alcoholic beverages, wine and beer may make a significant contribution to dietary lead intake and this is reflected in the higher blood lead levels found for drinkers. Lead in beer is also absorbed more readily from the gastrointestinal tract than lead from the rest of the diet. A survey of lead in wines and beers from lead-capped bottles in 1982/1983 showed that about 90% of canned and bottled beers sampled contained < 10 /v,g/l and that nearly half the draught beers sampled contained > 10 /v,g/l 4% contained > 100 /v,g/l. All wines sampled directly from the bottle contained < 250 /ig/1.12... 

The basal activity of aminotransferase fell by 50% during consumption of the Bt-deficient diet. The stimulation occurring with addition of PLP to the enzyme incubation mixtures rose in this period from 200% (twofold stimulation) to 400% (fourfold). The basal activity of the aminotransferase, and probably of ail enzymes of the body, varies from subject to subject. It may even vary with repeated enzyme assays using the same sample of red blood cells. Thus, the basal activity is not used to assess vitamin Be, status. The percentage stimulation is relatively constant in normal subjects and is thus a more useful indicator of B status. It should be noted that the storaffe of ivti blood teiis can lead to gradual release of the cofactor from the enzyme thus, an artefactual diagnosis of Bh deficiency is possible. 

Although alcaptonuria is a relatively harmless condition, such is not the ca.se with other errors in amino acid metabolism. In maple syrup urine dis-eim, the oxidative decarboxylation of cy-kctoacids derived from valine, isoleucinc, and leucine is blocked because the branched-chain dehydrogenase is missing or defective. Hence, the levels of these cx-ketoacids and the branched-chain amino acids that give rise to them are markedly elevated in both blood and urine. The urine of patients has the odor of maple syrup-hence the name of the disease (also called branched-chain ketoaciduria). Maple syrup urine disease usually leads to mental and physical retardation ss the patient is placed on a diet low in valine, isoleucinc, and leucine early in life. The disease can be readily detected in newborns by screening urine samples with 2,4-dinitrophenylhydrazine, which reacts with a-ketoacids to form 2,4-dinitrophenylhydrazone derivatives, A definitive sis can be made by mass spectrometry. 

Lead concentrations in different plants in Poland were up to 0.3 mg/kg fresh matter in vegetables (90% of samples), <0.1 mg/kg fresh matter in fruits (90% of samples), and >0.3 mg/kg fresh matter in cereals (25% of samples). In the Katowice Province, lead contents in vegetables (carrot, red beet, parsley, celery) varied between 0.50-280 mg/kg dry matter. Exposure to lead from vegetables was 1.5 mg/week per person. The results ranged between 4.8 4.0% of PTWI, whereas in the reference area these values amounted to 6.0% of PTWI for lead. The elimination of vegetables with high contents of lead in diet may reduce the dietary intake to 2.0-18.4% of PTWI (Gzyl, 1997). 

In this chapter, we explore how genetic variations identified in samples from large population-based studies are beginning to provide hints about gene-diet and gene-environment interactions that may lead to more individualized recommendations for preventing cardiovascular disease. 

Recently we have made a couple of studies in Scotland where we have looked at the lead intake of 3 month old infants who have been exposed to above average amounts of lead from the water. In one study made in Glasgow, the lead intakes measured over one week, ten weeks after birth, ranged from 40 pg per week to about 3000 pg per week and at about the time the duplicate diets were taken, blood samples were also taken from the infants, these were measured for lead (correlation coefficients of about 0.5). One of the most striking features of all this work was that the infants who were wholly breast fed had much lower blood leads than the infants who were not breast fed but bottle fed. In other words, the mother was acting as a filter, as a protective device. 

Environmental media of interest in this section on measurement are the same as those producing potential human lead exposures ambient air, lead paints, diet, drinking water, soils and dusts, and some of the more problematic idiosyncratic sources. Sampling and laboratory measurement techniques now widely used are emphasized with comparative statements for older methods provided mainly to offer perspective. Biomarker sampling and measurement methodologies, i.e., procedures for lead in biological media directly relevant to human lead exposures, are presented in a later chapter. 

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... 

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