Dietary exposures, lead

Melhuus, A., K.L. Seip, H.M. Seip, and S. Mykelstad. 1978. A preliminary study of the use of benthic algae as biological indicators of heavy metal pollution in Sorfjorden, Norway. Environ. Pollut. 15 101-107. Melnyk, L.J., M.R. Berry, L.S. Sheldon, N.C. Freeman, and E. Pellizzari. 1999. Dietary exposure of children to lead. Book of Abstracts, Part 1, ENVR 33. 218th American Chemical Society National Meeting, New Orleans, August 22-26, 1999. 

Mykkanen, H.M., M.C. Lancaster, J.W.T. Dickerson. 1982. Concentrations of lead in the soft tissues of male rats during a long-term dietary exposure. Environ. Res. 28 147-153. 

Stendell, R.C. 1980. Dietary exposure of kestrels to lead. Jour. Wildl. Manage. 44 527-530. 

The exposure to lead in food by the general population in the UK is well within international tolerable limits. Results from the TDS indicate that during the period 1976 to 1997 the dietary exposures over the whole population fell from 0.11 to 0.026 mg per person/day (Table 7.1).6 This excludes any contribution from drinking water, which is likely to be higher in areas with soft water. The PTWI recommended by JECFA is 0.025 mg/kg bodyweight, equivalent to 0.21 mg/day for a 60 kg adult. The dietary exposures for mean and 97.5th percentile consumers in 1997 were 0.024 mg/day and 0.043 mg/day respectively, well below the PTWI. These dietary exposures to lead in the UK are similar to those in Canada (0.024 mg/day),7 The Netherlands (0.01 to 0.032 mg/day),8 and the USA (0.015 mg/day).9... 

Although dietary lead intakes in the UK are currently well within recommended intakes, it is the UK Government s policy to ensure that exposure to lead is reduced wherever practicable and, more specifically, to reduce blood lead levels in children to below 10 pg/dl. Food is one of the major sources of lead exposure in the UK the others are air (mainly lead dust originating from petrol) and drinking water. Exposure from all of these sources has been reduced, as demonstrated by the reduction in blood levels over the past 15 years.10 The decrease in dietary exposure reflects the success of the measures taken to reduce lead exposure and contamination of food, such as the use of lead-free petrol, welded food cans, and the banning of tin-coated lead capsules for wine bottles. 

Table 7.1 Population dietary exposures to lead from UK Total Diet Studies (mg/day)...

Cadmium is present at low concentrations in most foods, with those that are consumed in larger quantities making the largest contribution to the population dietary exposure. Although the concentrations of cadmium in food in the UK are generally low, some foods of minor dietary importance such as shellfish or kidney often contain levels in excess of 0.5 mg/kg. Plant-based foods rarely contain more than 0.2 mg/kg on a fresh weight basis, although some root crops such as carrots and parsnip, and some leafy crops, such as spinach and lettuce, tend to contain more cadmium than other plant foods. This is also true of cereals, which indicates that plants tend to take up cadmium from the soil, unlike lead. 

YSART G E, MILLER P F, CREWS H, ROBB P, BAXTER M, DE L ARGY C, lofthouse s, sargent c and Harrison N, 1997 UK total diet study -dietary exposures to aluminium, arsenic, cadmium, chromium, copper, lead, mercury, nickel, selenium, tin and zinc, Food Additives and Contaminants, 2000 17 775-86. 

The data concerning dietary exposure to iron, zinc, copper, molybdenum, iodine, arsenic, cadmium, and lead are insufficient and provide no basis for conclusions about the association of these elements with carcinogenesis. 

Ingestion of contaminants is the primary exposure pathway for drinking-water. Dermal absorption and inhalation of contaminants during bathing are other common pathways. When contaminated surface waters serve as recreational areas for children, accidental ingestion (water or sediment) and dermal contact become additional pathways for exposure. Finally, aquatic organisms can bioaccumulate contaminants in surface waters, which can lead to dietary exposure through the food-chain. 

The above calculations estimate that for a typical adult in a developed country, daily uptake of lead from air, diet, and drinking water is, respectively 1.4 pg, 6 pg, and 1.1 pg. Exposure to lead from all of these sources has fallen rapidly over the past 20-30 years. Figure 12 contrasts the temporal trends in use of lead in petrol (gasoline) and blood leads in the general population of the UK over the period when much of this decline took place. It is interesting to note that from 1971 to 1985 use of lead in petrol was relatively steady, but blood leads declined by a factor of more than two over this period mainly as a response to reductions in dietary exposure, particularly associated with the cessation of use of... 

Chung, S.W.C., Kwong, K.P., Yau, J.C.W., Wong, W.W.K. Dietary exposure to antimony, lead and mercury of secondary school students in Hong Kong. Food Addit. Contam. 25, 831-840 (2008)... 

Karlowski, K., and Wojiciechowska-Mazurek, M., Dietaiy Monitcdng Studies on Lead and Cadmium Exposures in Poland, in Proceedings of the Symposium on the Bioavailability and Dietary Exposure to Lead, Chemical Speciation and Bioavailability, 1991, 3, 21-29. 

Table 15. Lead dietary exposure in children in the Slovak Republie...

Table 19. Lead dietary exposure in infants in the Slovak Republic...

To define the contamination levels, one approach is to correct the results from the recoveries of the analytical methodology (commonly obtained by using one, two or three spiked levels), which may lead to error, as recoveries depend on the different contamination levels. To use this approach, it is necessary to estimate recoveries in more levels within the range of the analytical methodology. The Committee also concluded that it was better to restrict data used in the dietary exposure assessment to those with validated recoveries greater than 70% than to correct for lower recoveries. 

Fig. 1 Relationship between trophic transfer factors for different taxonomic groups and dietary exposure concentration from laboratory studies (a) cadmium, (b) copper, (c) lead, (d) nickel, and (e) zinc. The horizontal dashed line indicates a TTF of 1. Solid lines represent regressions of TTF vs. dietary metal for individual taxa. The dotted boxes in (b) and (e) identify the range nutritional requirements for fish and some invertebrates (from Brown 2005)...

The relationship between air lead concentration and BLL is complex. Exposure to lead can occur through multiple pathways. BLL is the exposure metric most commonly described in association with health effects in humans, and lead exposure is typically assessed by using a pharmacokinetic model to relate air (or dietary) exposure concentratiorrs to BLLs. The committee s goal was not to review in depth the various dosimetry models available for lead but to explore how dosimetry models were used in the development of the OSHA generd industry lead standard and to evalirate the models and their assumptions (see Table 3-1). 

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