Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.
There are no published data relating external dose to internal dose in children with blood lead levels in the range of 40-60 yg Pb/dl. Kehoe added lead to the diet of adult volunteers. His studies have shown that the absorption of 1.43 yg Pb/kg/day due to the added lead was associated over a period of approximately nine months with an in- crease in blood lead level of 17 yg Pb/dl (see Appendix E). One can calculate that if the absorption of 4.5 yg Pb/kg/day will produce an average blood lead level of 20 yg Pb/dl in a two- to three-year-old child, then an absorption of an additional 1.43 yg Pb/kg/day or a total of 5.9 yg/kg/day could produce a blood lead level of 37 yg Pb/dl. Similarly one could calculate that the total absorption of 7.4 yg Pb/kg/day could produce a blood lead level of 54 yg Pb/dl. The external dose (amount of ingested lead) necessary to produce these blood lead levels will depend in part on the chemical and physical form of lead ingested. Because of the dearth of information relating external dose to internal dose (blood level or other tissue concentration) in children, the calculations given above are only estimates based on the best available data. WHAT IS THE ESTIMATED LEAD INTAKE IN A CHILD WITH PICA FOR PAINT? Pica, the repetitive ingestion of non-food substances, occurs in approximately 50 percent of children between one and three years of age. This habit is considered normal behavior until about three years of age. Psychosocial factors or organic brain damage may cause the persistence of pica beyond three years of age. Pica for paint generally begins at the time of ambulation or at about 10 to 12 months of age and is believed to be episodic, occurring perhaps two to three times per week (see Appendix D). Abdominal x-ray films showed radiopaque materials in the intestinal tract in 35 percent of children attending the Chicago Lead Clinic. The best available clinical evidence indicates that children with pica may ingest one to three grams of paint per week (see Appendices D, E). If the paint contained the present legal limit of 0.5 percent lead (5,000 yg/g paint), then the daily ingestion of lead from paint would be 714 yg Pb/day, l,429 yg Pb/day or 2,143 yg Pb/day, respectively, for one, two or three grams of paint ingested per week. Calculated on the basis of body weight for a two-year-old child weighing 12.5 kg, and using an absorption factor of 17 percent for lead from paint, the amount of lead absorbed would be 9-7 yg Pb/kg/day, 19.4 yg Pb/kg/day and 29.1 pg Pb/kg/day, respectively, for one, two and three grams of paint ingested per week (see Appendix E). The daily absorption of 4.5 yg Pb/kg/day has been found in children with essentially normal blood lead levels of approximatly 20 yg Pb/dl. The estimated daily absorption of lead from paint must be superimposed on the estimated absorption of lead from diet, in order to obtain a total daily absorption. Thus, the daily absorption of lead in a child with pica for paint (containing 0.5 per- cent Pb) may be three to seven times that found in a child receiving a normal diet. For a child with pica for paint, a level of 0.5 percent lead in paint clearly represents a hazard.
