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Appendix E Evaluation of the Hazard of 0.5 Percent Lead Paint No single study of children with pica for paint has combined the numerous measurements necessary to estimate a "safe level" of lead in paint. Therefore, a decision regarding the safety of 0.5 percent lead paint must be made by relating measurements found in various studies. Ultimately, the estimated intake of paint chips in a child with pica must be related to the appearance of adverse effects in that child. The potential hazard of ingesting lead-containing paints is related to the average amount absorbed on a daily or weekly basis over a period of months. The percentage of ingested lead that is actually absorbed from the gastrointestinal tract into the body varies according to the chemical and physical form of the ingested lead (i.e., paints, dust, etc.), age and other factors. Differences in the rates of absorption of lead from each source can be largely compensated, if the available data are recalculated as yg Pb absorbed/kg body weight/day. In this way, a reasonable estimate of the amount of paint containing 0.5 percent lead necessary to raise Pb-B to a hazardous level can be made. We will use two methods for estimating the hazard of paint containing 0.5 percent lead: Method A - The first method of estimating the safety of 0.5 percent lead paint will be made by relating estimated paint intake to fecal lead outputs found in children with blood lead levels (Pb-B) >60 yg Pb/dl. Pica for paint has been observed to be episodic, occurring up to two to three times per week. The analysis of lead in consecutive fecal samples seems to confirm this observation. ' Through the use of abdominal x-rays, Sachs has demonstrated that some children with pica for paint are capable of consuming more than 1 gram of paint in the 24-36 hour period preceding the time of x-ray.^° One child was esti- mated to have consumed 20 grams of paint during this time. °^ An estimated range of lead intake can be calculated, using a figure of 0.5 percent lead in paint (5000 Pg Pb/g paint), a figure of 1 gram paint per ingestion and a figure varying from one to three for frequency of ingestions per week. The estimated weekly intake is then divided by seven to obtain an average daily intake. Using these figures, the average daily intakes would be 714 yg Pb, l,429 yg Pb and 2,143 ug Pb, respectively, for one, two and three ingestions per week. It is estimated that 50 percent of lead from foods is absorbed by a young child. However, studies in rats have shown that lead chromate in paint films is not as well absorbed as the simple inorganic salts of lead. Gage and Litchfield estimate that lead chromate pigment in paint is absorbed one-fourth to one-third as well as the simple inorganic salts, when incorporated into standard laboratory rat feed, and that lead napthenate is absorbed about one-half as well. Similarly, lead octoate in dried ground paint, when fed to monkeys, yields Pb-R's one-third to 45
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one-half as high as when lead octoate is fed directly. These data indi- cate that lead compounds, incorporated into a paint matrix, are absorbed only one-fourth to one-half as well as the free lead salts. We will use an average of one-third for estimating a child's absorption of lead from paint. This average is used because a variety of lead compounds are used in paint. Thus, if children absorb 50 percent of dietary lead, experi- mental data indicate that they will absorb only one-third of this amount or an average of 17% of the lead from paint. Table I gives the estimated amounts of lead absorbed and excreted, based on an absorption factor of 17% and estimates of weekly intakes of 1, 2 or 3 grams of 0.5 percent paint. Average daily intakes are also calculated on a per kilogram basis for an average two-year-old child weighing 12.5 kg. Table I Calculated Lead Intake and Absorbed Dose fiom Paint Pica Amount of Paint Intake If Paint Contains Amount Pb Amount Pb Ingested/Week 0. S per cent Pb (5, 000 Absorbed (17 percent) Excreted In F«ces (grams paint) |ig Pb/g paint) (tig Pb/ (83 percent) (,ig Pb/day) (,ig Pb/kg/day)* (tig Pb/day) kg/day)* (|ig Pb) Z 714 57.1 121 9.7 593 i 1.429 114.3 243 19.4 1,186 3 2.143 171.4 364 29.1 1.779 •For average two year old child weighing 12. 5/kg. Chisolm and Harrison found a median fecal lead output of 1,110 yg Pb/day in asymptomatic children with blood lead levels >60 yg Pb/dl and positive roentgenographic evidence of lead storage in bones. Some also had elevations in urinary coproporphyrin levels. * Barltrop found fecal lead outputs ranging from 570 - l,900 yg Pb/stool sample in three two-year-old symptomatic children with blood lead levels ranging from 68-92 yg Pb/dl, positive roentgenographic evidence of lead storage and hemoglobin levels <10 g/dl.7 From the estimates given in Table I and the studies of chisolm and Harrison and Barltrop and Killala, it appears that the ingestion of between 1 and 2 grams of paint (containing 0.5 percent Pb) per week could produce fecal lead outputs equal to those found in children with >60 yg Pb-B. Clinical studies in children have indi- cated that blood lead levels >60 yg Pb/dl are associated with increased risk of later CNS effects.3'23'24'57'73 In contrast, Alexander's balance studies in eleven healthy children receiving a normal diet showed a mean lead intake of 10.61 yg Pb/kg body weight/day and a mean fecal lead output of 5.13 yg/kg/day.4 Using the 46
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figures from Table I, a 12.5 kg child consuming 1 gram of 0.5 percent PB paint per week would have a daily lead intake of 57.1 yg Pb/kg body weight, a five-fold increase above that found in a normal diet. Two grams of paint would produce an eleven-fold increase and 3 grams, a sixteen- fold increase. Since the best available clinical evidence indicates that children with pica can and do ingest 1-3 grams of paint per week and, since the ingestion of between 1 and 2 grams of 0.5 percent lead paint per week would be sufficient to produce daily fecal lead outputs equivalent to those found in children with >60 yg Pb-B, a level of 0.5 percent lead in paint cannot be considered a "safe level." Method B - An alternate method for determining the safety of 0.5 percent lead paint is based on the absorption studies carried out by Kehoe on adult volunteers.^ Kehoe found that blood lead levels increased 17 yg/dl over a period of nine months for each additional mg of lead administered per day. Lead acetate or lead chloride were administered with the diet at dosages of 0.3, 1.0, 2.0 and 3.0 mg Pb/day. Increases in blood lead levels were proportional to dosage. For the sake of sim- plicity, we will discuss the subject receiving 1.0 mg Pb/day. An observed intestinal absorption rate of 10 percent resulted in an absorption of 100 yg Pb/day. Calculated on a body weight basis for a standard 70 kg man, this represented 1.43 yg Pb absorbed/kg/day. Thus, the absorption of 1.43 yg Pb/kg/day would be sufficient to produce a rise in blood lead of 17 yg/dl and an absorption of 2.86 yg Pb/kg/day could produce a rise of 34 yg/dl. Similar increments in blood lead concentration have recently been reported by Stuik^' who has administered lead acetate at 20 yg Pb/kg/day to 5 adult male and 5 adult female volunteers over a period of 12 weeks. If one assumes an absorption of 10% of the dose, the rate recently found by Rabinowitz et jil,80 then these healthy volunteers would have absorbed 2.0 yg Pb/kg/day. In Stuik's subjects blood lead concentrations increased by 17.7 yg Pb/dl in the females and 20.3 yg Pb/dl in the males after 2-1/2 weeks. These short-term studies essentially confirm and extend the earlier long-term study of Kehoe in adult volunteers. The average blood lead level in normal unexposed children is approximately 20 yg Pb/dl.^^ Early metabolic changes in the hematologic system begin to occur in children when blood lead levels reach the range of 30-40 yg Pb/dl. From the standpoint of preventive medicine, it would seem appropriate to insure that mean blood lead levels for groups do not exceed 20 yg Pb/dl. An additional daily absorption of 1.43 yg Pb/kg/day could increase blood lead levels from 20 yg Pb/dl to 37 yg Pb/dl, while an additional absorption of 2.86 yg Pb,/kg/day could increase levels to 54 yg Pb/dl. Based on an absorption factor of 17 percent for lead in paint, Table II shows the amount of lead intake necessary to produce absorption of either 1.43 yg/kg/day or 2.86 yg/kg/day. Total daily intakes are also calculated for an average one-year-old 10 kg child and a two-year- old 12.5 kg child. 47
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Table II Calculated Dally External Dose «nd Associated Internal DOM Increase In Hood Lead (Pb-B) (jjg/dl) 17 J* Lead Absorbed N«cetiary Intake Total Ir.take Total Intake to Produce Corresponding Necessary for Necessary for Absorption* 10 kg child 12. 5 kg child (ng Pb/d»y) (tig Pb/day) Each Day (|ig Pb/kg/day) dig Pb/kg/day) 1.43 Z.86 8.41 16.82 84. 1 1SS.2 105.1 •Based on absorption factor of 17 percent fo: lead In mint. Absorption of lead from foods is approximately 50 percent. The safety of 0.5 percent lead paint can be determined from Table II. The ingestion of 16.82 mg paint/day or 33.64 mg paint per day containing 0.5% lead would result in raising blood lead levels by 17 ug/dl or 34 yg/dl, respectively, in a 10 kg child. Similarly, a 12.5 kg child would need to ingest either 21.02 mg paint/day or 42.06 mg paint per day. King and Schaplowsky have summarized the work of Sachs wherein she demonstrated that some children can consume more than 1 g (l,000 mg) paint per week or 143 mg paint per day. For a child with pica for paint, a level of 0.5 percent lead in paint clearly represents a hazard. Because multiple factors serve to modify lead intake, absorption rates and individual susceptibility, the foregoing mathematical calcula- tions used for determining the hazard of 0.5 percent lead paint, cannot be considered suitable for application to every child. Age, frequency of pica, dietary constituents, and nutritional status all contribute toward increasing or decreasing the amount of lead absorbed by any one individual (see Appendix D). The first method used for determining the hazard of 0.5 percent lead paint is based on relating lead intake to the appearance of early clinical illness and significant risk of later CNS effects. The second method relates lead intake to blood lead levels known to be associated with the appearance of early metabolic effects in children. In either case, a level of 0.5 percent lead in paint cannot be considered a "safe level." 48