@Copyright 1987 by The Humana Press Inc. All rights of any nature, whatsoever, reserved. 0163-4984/87/1200=0223502.00
Stable Isotope Mass Spectrometry in Childhood Lead Poisoning MICHAEL B. F~ABfNOWITZt lVlental Retardation Unit, Department of Neurology, Children's Hospital, H a r v a r d ,Medical School, Cambridge,/t'lA ABSTRACT In order to better understand the relative importance of various sources of lead in childhood lead poisoning, high-precision, isotoperatio, solid-source-mass spectrometry of microgram-sized lead samples was applied to three hospitalized cases in Boston, ranging in age from 1.5 to 14 yr, that had blood-lead levels of 0.7-1.2 p~g/g. The lead isotopes in the ambient Boston environment (air, soil, and dust) were also measured. In each case, the isotopic composition (IC) of the child's blood lead was identical with the IC of lead paint taken from the child's residence at a site accessible to the child. Fecal lead samples were also identical to that particular paint. Soil lead IC did not always match the IC of local paints. Paint samples vary widely in their IC's (206/204 = 17.5-19.4, about 200 times analytical reliability). Dust in homes that never had lead paint contained lead that resembled lead in urban soils. Dust lead IC did not necessarily have the same IC as current automobile lead emissions, but appeared to reflect the long-term accumulation of several sources of urban lead fallout. Limitations and implications of this data are discussed. Index Entries: Lead; lead poisoning, in children; isotopes; mass spectrometry; soil; paint, dust; urban environment.
INTRODUCTION W h e n a child is d i s c o v e r e d to be lead p o i s o n e d , it b e c o m e s n e c e s s a r y to identify the source(s) a n d route(s) of exposure. Often, the source m a y be obvious; a w i n d o w s i l l p a i n t e d w i t h lead a d o r n e d w i t h a t o d d l e r ' s tooth m a r k s or a hole in the wall b e h i n d a sofa that has g o t t e n larger. T h e tPresent address: Gardner 601, Children's Hospital, 300 Longwood Ave., Boston, MA 02115 Biological Trace Element Research
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Rabinowitz
dwelling is then deleaded before the child returns or at least the offending surface is fixed so that the child will not be repoisoned. We have applied stable-isotope tracer methods to document the specific sources and pathways of lead exposure in three cases of childhood lead poisoning in Boston. This technique has a long history and exploits the natural variability of the relative abundance of lead's four stable (nonradioactive) isotopes (204, 206, 207, and 208) among different ore bodies. Lead's isotopic makeup does not change as it moves through the environment or ages in place. It only changes when it mixes with lead of a different origin and composition. This approach has been used in cases of horses poisoned from exposure to smelter exhaust and alkyl lead (1) and following the dispersion and human uptake of automobile exhaust in clinical (2) and community populations (3,4). Recently, several cases of childhood lead poisoning in California were examined with this method to show that the lead in the childrens' blood resembled the lead in their dwellings' paints and in nearby soils (5).
METHODS Three children admitted for hospital treatment of lead poisoning were examined. A 7-mL blood sample was collected for isotopic analysis before chelation. Feces were collected after oral administration of magnesium citrate.
Case 1 Upon hospital admission, this 4-yr-old, asymptomatic boy had a blood lead level of 120 p~g/dL and free erythrocyte protoporphyrin (FEP) of 399 p~g/dL, both greatly elevated. X-ray examination showed radioopaque flecks in the rectosigmoid region and densities of the proximal femurs and illiac wings, indicating both recent and long-term lead ingestion. He lived on the third floor of an apartment that had high lead concentrations (>10% lead) in the trim and interior paints. Soil from the house yard contained 2480 ~/g lead.
Case 2 This asymptomatic 1.5-yr-old boy had a blood lead level of 83 ~g/dL and abnormally increased calcifications of the illiac crest, indicating longterm lead exposure. At his home the kitchen sill, bedroom wall, and trim paint were all high in lead. Soil from the yard contained 503 ~g/g lead.
Case 3 This 14-yr-old, multiply handicapped, retarded, and blind boy, living in an institution, had a blood lead level of 66 ~g/dL and an FEP of 305 Biological Trace Element Research
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bLg/dL. Exterior, bedroom, and classroom paints were all high in lead, and soil in a play area contained 1906 p~g/g lead. All environmental samples were collected on site by the author. Lead concentrations were measured by atomic absorption spectrometry and anodic stripping voltammetry (6). Lead was extracted for isotopic analysis from the various types of samples (paint, soil, feces, dust, and blood) by the standard two-step dithizone technique, which uses citrate and cyanide masking agents (7). It was necessary to use distilled acids, purified reagents, filtered air, and acid-washed Teflon apparatus to minimize background laboratory contamination. To avoid cross-contamination, separate vessels were used for processing the lower lead concentration blood samples. Sufficient sample was extracted to yield about 5 ~g of purified lead, which is adequate for several separate isotopic determinations. Isotope ratio measurements were made with the NIMA-B Nier type, high-resolution mass spectrometer in the Department of Earth and Planetary Sciences, Massachusetts Institute of Technology. Less than 1 bLg of the lead sample was mounted on a silica gel bed with phosphoric acid upon a degassed rhenium filament. After a stable ion beam was established, the magnetic field was stepped, each of the four isotopes counted in turn, and sets of ratios and their intrasample variability calculated by a dedicated PDP-11 (Digital Equipment Corp, Maynard, MA). Although all four isotopes were measured and recorded, only two ratios describing each sample are shown here (Tables 1 and 2). The three ratios (206/204, 206/207, and 206/208) strongly covary and would be redundant. Enough sets of these peak height ratios are then collected from a sample to achieve the desired statistical precision. In this study, about 36 sets of ratios are usually measured, with a mean standard deviation of less than 0.05% (2 sigma).
RESULTS A series of environmental samples were analyzed in order to characterize ambient or background lead present throughout Boston. Current automobile exhaust lead was sampled from two sites in the top layer of undisturbed snow, which had fallen 2 wk before, 10 m from, 19 km apart on an interstate highway, in January 1981. The snow contained about 6 ~g/g lead. As shown in Table 1, these samples very closely resembled each other and the aerosols in the hospital parking garage. Another component of the ambient exposure resides in soil. Urban soils, containing 500-2000 >g/g lead, from sites not within 75 m of any building were chosen. These were from parks and public land that have remained undisturbed for many decades and contain lead accumulated from airborne lead fallout (almost entirely automobile exhaust). This lead appeared distinctly less radiogenic than currently used lead. Lead in houseBiological Trace Element Research
VoL 12, 1987
Rabinowitz
226
TABLE 1 Stable Lead Isotope Ratios in Samples of the Ambient Environment of Boston Sample description
Atomic abundance ratios
Recent auto exhaust Snow--roadside 1 Snow--roadside 2 Aerosols--garage Average (SE)
206/204 19.28 19.40 19.20 19.3 (0.1)
206/207 1.210 1.207 1.204 1.207 (0.002)
Older accumulated fallout Soil--dorchester park Soil--fenway Soil--commons burial yard Soil--route 3 Average
18.38 18.40 18.73 18.50 18.5 (0.1)
1.179 1.199 1.199 1.187 1.191 (0.005)
Homes with No lead paint Dust--home A Dust--home B Dust--home C Dust--home D Average
18.52 18.41 18.63 18.54 18.5 (0.05)
1.187 1.181 1.193 1.185 1.187 (0.003)
16.93 18.14 17.57 17.45 17.70 17.84 18.88 18.98 18.97
1.094 1.165 1.129 1.129 1.140 1.145 1.190 1.203 1.190
Homes with lead paint Paint, windowsill--home X Dust, windowsill--home X Paint 1--home Y Paint 2--home Y Paint 3--home Y Soil--adjacent home Y Paint--home Z Soil-home Z Dust--home Z
hold dust has been s h o w n to correlate with infant blood lead levels in Boston and elsewhere (6). Samples of dust from furniture tops in homes that never had lead paint revealed lead (200-1000 ~g/g) that closely resembled isotopically the background soils, not current automobile emissions. Lead paint has a highly variable isotopic composition, d e p e n d i n g on its source, but is usually very different from either n e w or old gasoline additive. In H o m e X (see Table 1), lead in the dust apparently represents a mixture of 20-30% from paint and 70-80% from urban soil. At H o m e Y, the soil lead appeared to be a mixture of about 70% from local paint and 30% from background urban soil. At H o m e Z, the soil and the dust resemble the local house paint. However, that paint is isotopically between
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current automobile emissions and background soil, making further resolution at this site impossible. After examining these samples, which characterize the ambient Boston situation, three cases of lead poisoning were analyzed. In both Cases 1 and 2, the lead in the feces was nearly identical with the blood, and both were quiet distinct from the general urban background lead (Table 2). In Case 1, they resembled one of the three paint samples that was from the child's bedroom wall. The soil at that house (Y) also had the same isotopic composition (IC). The blood and feces leads in Case 2 were also very similar to each other and not like the background air or soil. They did match very closely the lead in the windowsill paint, but not the kitchen wall or garden earth. The blood lead level of Case 3 was very close to that of the paint in his bedroom, which was a likely source of his chronic exposure. His feces, which reflected ingestions over the past day, appeared very much like the fallout from current automobile emissions, perhaps mouthed from surfaces by this automatistic boy.
DISCUSSION In each case, the poisoned child's burden of lead was identical to a sample of lead paint taken from his dwelling area. Each of these three cases represent chronic, high-level poisoning severe enough to warrant medical intervention. All had lead paint present in their homes in broken and cracked surface conditions. These findings are not intended to be representative of all urban lead-poisoned children, some of whom may be ingesting nonpaint sources of lead, such as contaminated dust and soil, but were selected to demonstrate this analytical technique among children with very high blood lead levels, above 65 p,g/dL, in which timed fecal collection and X-ray diagnosis are possible. The difference in the isotopic compositions of older and current automobile exhausts that we see in Boston, about 2%, is similar to but smaller in magnitude than a change observed in aerosol lead in California (8). This shift has been attributed to increased relative usage of Missouri Valley lead ores in making gasoline additives, which began in the early 1970s. At times, the analytical methods used in this study present some ambiguities. In Case 1, for example, in which the soil, one paint, and the child all had the same isotopic compositions, it is not possible to distinguish isotopically whether the child was ingesting lead from the paint or from the soil. The data are consistent with the paint being the proximate or remote source of the toxic lead, however. These findings may not be directly representative of the sources of lead among children with lower but still excessive blood levels (i.e., in the range of 15-30 ~g/dL). The lead in the dust in their homes appears to be coming from a large reservoir in the urban soil, which has accumuBiological Trace Element Research
VoL 12, 1987
228
Rabinowitz TABLE 2 Lead from Cases of Childhood Poisoning
Sample
Lead content
206/204
206/207
Case 1 (Home Y) Paint--exterior trim Paint--interior trim Paint--wall Soil Blood Feces
35% 10% 2% 2480 p~g/g 120 p~g/dl 77 ~g/g
17.57 17.45 17.70 17.84 17.53 17.81
1.129 1.129 1.140 1.145 1.140 1.141
Case 2 Paint--walt Paint--windowsill Paint--wall kitchen Garden soil Blood Feces
10% 10% 5% 503 ~g/g 83 ~g/dl 4 ~g/g
18.72 18.79 18.04 19.02 18.81 18.85
1.197 1.205 1.151 1.189 1.204 1.204
18.17 17.77 18.32 18.33 19.18
1.159 1.133 1.163 1.163 1.224
Case 3 Paint--exterior Paint--classroom Paint bedroom Blood Feces
2% 2% 1% 66 p~g/dl 0.6 ~g/g
lated over m a n y decades of using lead additives in gasoline. Over the past 10 yr, because of the regulation of lead in gasoline and the pretreatm e n t of potable water, blood lead levels in Boston have declined. Childh o o d exposure from old residential lead paint and soil appears to be the most intractable sources.
SUMMARY (1) Current automobile emissions of lead contribute negligibly to the lead in urban soil and dust. (2) In the absence of lead paint, the leads in urban soils and h o u s e h o l d dust have nearly identical isotopic compositions and are the product of decades of accumulated fallout. (3) Lead paint, w h e n present, can be responsible for 20-70% of the lead in household dust and m u c h of the lead in yard soil. (4) In cases of severe lead poisoning, the lead in the child's blood and feces resembles very closely the lead in the paint from an accessible surface.
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ACKNOWLEDGMENT The cooperation of the children and their families and guardians is gratefully acknowledged. Dr. John Graef, Director of the Children's Hospital Lead Clinic, assisted in locating these cases. Professor Stanley Hart generously allowed me to use his NIMA-B mass spectrometer and other facilities. Funds were provided by a grant from the National Institute of Child Health and H u m a n Development (HD-08945). Analyses performed at the Mass Spectrometry Laboratory, Professor Stanley Hart, Massachusetts Institute of Technology, Department of Earth and Planetary Sciences.
REFERENCES 1. M. B. Rabinowitz and G. W. Wetherill, Environ. Sci. Tech. 6, 705 (1972). 2. M. B. Rabinowitz, G. W. Wetherill, and J. D. Kopple, [. Lab. Clin. Med. 90, 238 (1977). 3. S. Facchetti and F. Geiss, Isotopic Lead Experiment: Status Report. Community of European Communities, Luxembourg, Pub. # EUR 8352 EN, 1982. 4. W. Manton, Arch. Environ. Health. 32, 149 (1977). 5. Y. Yaffe, C. Flessel, J. Wesolowski, A. Del Rosario, G. Guirguis, V. Matias, T. DeGarmo, G. Coleman, J. Gramlich, and W. Kelly, Arch. Environ. Health. 38, 237 (1983). 6. M. B. Rabinowitz, A. Leviton, H. L. Needleman, D. C. Bellinger, and C. Waternaux, Environ. Res. 38, 96 (1985). 7. G. Tilton, C. Patterson, H. Brown, M. Inghram, R. Hayden, D. Hess, and E. Larsen Bull. Geol. Soc. Am. 66, 1131 (1955). 8. C. C. Patterson, Geochem. Cosmochem. Acta 47, 1166 (1983).
Biblogical Trace Element Research
VoL 12, 1987
Stable Isotope Mass Spectrometry in Childhood Lead Poisoning MICHAEL B. F~ABfNOWITZt lVlental Retardation Unit, Department of Neurology, Children's Hospital, H a r v a r d ,Medical School, Cambridge,/t'lA ABSTRACT In order to better understand the relative importance of various sources of lead in childhood lead poisoning, high-precision, isotoperatio, solid-source-mass spectrometry of microgram-sized lead samples was applied to three hospitalized cases in Boston, ranging in age from 1.5 to 14 yr, that had blood-lead levels of 0.7-1.2 p~g/g. The lead isotopes in the ambient Boston environment (air, soil, and dust) were also measured. In each case, the isotopic composition (IC) of the child's blood lead was identical with the IC of lead paint taken from the child's residence at a site accessible to the child. Fecal lead samples were also identical to that particular paint. Soil lead IC did not always match the IC of local paints. Paint samples vary widely in their IC's (206/204 = 17.5-19.4, about 200 times analytical reliability). Dust in homes that never had lead paint contained lead that resembled lead in urban soils. Dust lead IC did not necessarily have the same IC as current automobile lead emissions, but appeared to reflect the long-term accumulation of several sources of urban lead fallout. Limitations and implications of this data are discussed. Index Entries: Lead; lead poisoning, in children; isotopes; mass spectrometry; soil; paint, dust; urban environment.
INTRODUCTION W h e n a child is d i s c o v e r e d to be lead p o i s o n e d , it b e c o m e s n e c e s s a r y to identify the source(s) a n d route(s) of exposure. Often, the source m a y be obvious; a w i n d o w s i l l p a i n t e d w i t h lead a d o r n e d w i t h a t o d d l e r ' s tooth m a r k s or a hole in the wall b e h i n d a sofa that has g o t t e n larger. T h e tPresent address: Gardner 601, Children's Hospital, 300 Longwood Ave., Boston, MA 02115 Biological Trace Element Research
223
Vo/. 12, 1987
224
Rabinowitz
dwelling is then deleaded before the child returns or at least the offending surface is fixed so that the child will not be repoisoned. We have applied stable-isotope tracer methods to document the specific sources and pathways of lead exposure in three cases of childhood lead poisoning in Boston. This technique has a long history and exploits the natural variability of the relative abundance of lead's four stable (nonradioactive) isotopes (204, 206, 207, and 208) among different ore bodies. Lead's isotopic makeup does not change as it moves through the environment or ages in place. It only changes when it mixes with lead of a different origin and composition. This approach has been used in cases of horses poisoned from exposure to smelter exhaust and alkyl lead (1) and following the dispersion and human uptake of automobile exhaust in clinical (2) and community populations (3,4). Recently, several cases of childhood lead poisoning in California were examined with this method to show that the lead in the childrens' blood resembled the lead in their dwellings' paints and in nearby soils (5).
METHODS Three children admitted for hospital treatment of lead poisoning were examined. A 7-mL blood sample was collected for isotopic analysis before chelation. Feces were collected after oral administration of magnesium citrate.
Case 1 Upon hospital admission, this 4-yr-old, asymptomatic boy had a blood lead level of 120 p~g/dL and free erythrocyte protoporphyrin (FEP) of 399 p~g/dL, both greatly elevated. X-ray examination showed radioopaque flecks in the rectosigmoid region and densities of the proximal femurs and illiac wings, indicating both recent and long-term lead ingestion. He lived on the third floor of an apartment that had high lead concentrations (>10% lead) in the trim and interior paints. Soil from the house yard contained 2480 ~/g lead.
Case 2 This asymptomatic 1.5-yr-old boy had a blood lead level of 83 ~g/dL and abnormally increased calcifications of the illiac crest, indicating longterm lead exposure. At his home the kitchen sill, bedroom wall, and trim paint were all high in lead. Soil from the yard contained 503 ~g/g lead.
Case 3 This 14-yr-old, multiply handicapped, retarded, and blind boy, living in an institution, had a blood lead level of 66 ~g/dL and an FEP of 305 Biological Trace Element Research
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Stable Isotope Mass Spectrometry
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bLg/dL. Exterior, bedroom, and classroom paints were all high in lead, and soil in a play area contained 1906 p~g/g lead. All environmental samples were collected on site by the author. Lead concentrations were measured by atomic absorption spectrometry and anodic stripping voltammetry (6). Lead was extracted for isotopic analysis from the various types of samples (paint, soil, feces, dust, and blood) by the standard two-step dithizone technique, which uses citrate and cyanide masking agents (7). It was necessary to use distilled acids, purified reagents, filtered air, and acid-washed Teflon apparatus to minimize background laboratory contamination. To avoid cross-contamination, separate vessels were used for processing the lower lead concentration blood samples. Sufficient sample was extracted to yield about 5 ~g of purified lead, which is adequate for several separate isotopic determinations. Isotope ratio measurements were made with the NIMA-B Nier type, high-resolution mass spectrometer in the Department of Earth and Planetary Sciences, Massachusetts Institute of Technology. Less than 1 bLg of the lead sample was mounted on a silica gel bed with phosphoric acid upon a degassed rhenium filament. After a stable ion beam was established, the magnetic field was stepped, each of the four isotopes counted in turn, and sets of ratios and their intrasample variability calculated by a dedicated PDP-11 (Digital Equipment Corp, Maynard, MA). Although all four isotopes were measured and recorded, only two ratios describing each sample are shown here (Tables 1 and 2). The three ratios (206/204, 206/207, and 206/208) strongly covary and would be redundant. Enough sets of these peak height ratios are then collected from a sample to achieve the desired statistical precision. In this study, about 36 sets of ratios are usually measured, with a mean standard deviation of less than 0.05% (2 sigma).
RESULTS A series of environmental samples were analyzed in order to characterize ambient or background lead present throughout Boston. Current automobile exhaust lead was sampled from two sites in the top layer of undisturbed snow, which had fallen 2 wk before, 10 m from, 19 km apart on an interstate highway, in January 1981. The snow contained about 6 ~g/g lead. As shown in Table 1, these samples very closely resembled each other and the aerosols in the hospital parking garage. Another component of the ambient exposure resides in soil. Urban soils, containing 500-2000 >g/g lead, from sites not within 75 m of any building were chosen. These were from parks and public land that have remained undisturbed for many decades and contain lead accumulated from airborne lead fallout (almost entirely automobile exhaust). This lead appeared distinctly less radiogenic than currently used lead. Lead in houseBiological Trace Element Research
VoL 12, 1987
Rabinowitz
226
TABLE 1 Stable Lead Isotope Ratios in Samples of the Ambient Environment of Boston Sample description
Atomic abundance ratios
Recent auto exhaust Snow--roadside 1 Snow--roadside 2 Aerosols--garage Average (SE)
206/204 19.28 19.40 19.20 19.3 (0.1)
206/207 1.210 1.207 1.204 1.207 (0.002)
Older accumulated fallout Soil--dorchester park Soil--fenway Soil--commons burial yard Soil--route 3 Average
18.38 18.40 18.73 18.50 18.5 (0.1)
1.179 1.199 1.199 1.187 1.191 (0.005)
Homes with No lead paint Dust--home A Dust--home B Dust--home C Dust--home D Average
18.52 18.41 18.63 18.54 18.5 (0.05)
1.187 1.181 1.193 1.185 1.187 (0.003)
16.93 18.14 17.57 17.45 17.70 17.84 18.88 18.98 18.97
1.094 1.165 1.129 1.129 1.140 1.145 1.190 1.203 1.190
Homes with lead paint Paint, windowsill--home X Dust, windowsill--home X Paint 1--home Y Paint 2--home Y Paint 3--home Y Soil--adjacent home Y Paint--home Z Soil-home Z Dust--home Z
hold dust has been s h o w n to correlate with infant blood lead levels in Boston and elsewhere (6). Samples of dust from furniture tops in homes that never had lead paint revealed lead (200-1000 ~g/g) that closely resembled isotopically the background soils, not current automobile emissions. Lead paint has a highly variable isotopic composition, d e p e n d i n g on its source, but is usually very different from either n e w or old gasoline additive. In H o m e X (see Table 1), lead in the dust apparently represents a mixture of 20-30% from paint and 70-80% from urban soil. At H o m e Y, the soil lead appeared to be a mixture of about 70% from local paint and 30% from background urban soil. At H o m e Z, the soil and the dust resemble the local house paint. However, that paint is isotopically between
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227
current automobile emissions and background soil, making further resolution at this site impossible. After examining these samples, which characterize the ambient Boston situation, three cases of lead poisoning were analyzed. In both Cases 1 and 2, the lead in the feces was nearly identical with the blood, and both were quiet distinct from the general urban background lead (Table 2). In Case 1, they resembled one of the three paint samples that was from the child's bedroom wall. The soil at that house (Y) also had the same isotopic composition (IC). The blood and feces leads in Case 2 were also very similar to each other and not like the background air or soil. They did match very closely the lead in the windowsill paint, but not the kitchen wall or garden earth. The blood lead level of Case 3 was very close to that of the paint in his bedroom, which was a likely source of his chronic exposure. His feces, which reflected ingestions over the past day, appeared very much like the fallout from current automobile emissions, perhaps mouthed from surfaces by this automatistic boy.
DISCUSSION In each case, the poisoned child's burden of lead was identical to a sample of lead paint taken from his dwelling area. Each of these three cases represent chronic, high-level poisoning severe enough to warrant medical intervention. All had lead paint present in their homes in broken and cracked surface conditions. These findings are not intended to be representative of all urban lead-poisoned children, some of whom may be ingesting nonpaint sources of lead, such as contaminated dust and soil, but were selected to demonstrate this analytical technique among children with very high blood lead levels, above 65 p,g/dL, in which timed fecal collection and X-ray diagnosis are possible. The difference in the isotopic compositions of older and current automobile exhausts that we see in Boston, about 2%, is similar to but smaller in magnitude than a change observed in aerosol lead in California (8). This shift has been attributed to increased relative usage of Missouri Valley lead ores in making gasoline additives, which began in the early 1970s. At times, the analytical methods used in this study present some ambiguities. In Case 1, for example, in which the soil, one paint, and the child all had the same isotopic compositions, it is not possible to distinguish isotopically whether the child was ingesting lead from the paint or from the soil. The data are consistent with the paint being the proximate or remote source of the toxic lead, however. These findings may not be directly representative of the sources of lead among children with lower but still excessive blood levels (i.e., in the range of 15-30 ~g/dL). The lead in the dust in their homes appears to be coming from a large reservoir in the urban soil, which has accumuBiological Trace Element Research
VoL 12, 1987
228
Rabinowitz TABLE 2 Lead from Cases of Childhood Poisoning
Sample
Lead content
206/204
206/207
Case 1 (Home Y) Paint--exterior trim Paint--interior trim Paint--wall Soil Blood Feces
35% 10% 2% 2480 p~g/g 120 p~g/dl 77 ~g/g
17.57 17.45 17.70 17.84 17.53 17.81
1.129 1.129 1.140 1.145 1.140 1.141
Case 2 Paint--walt Paint--windowsill Paint--wall kitchen Garden soil Blood Feces
10% 10% 5% 503 ~g/g 83 ~g/dl 4 ~g/g
18.72 18.79 18.04 19.02 18.81 18.85
1.197 1.205 1.151 1.189 1.204 1.204
18.17 17.77 18.32 18.33 19.18
1.159 1.133 1.163 1.163 1.224
Case 3 Paint--exterior Paint--classroom Paint bedroom Blood Feces
2% 2% 1% 66 p~g/dl 0.6 ~g/g
lated over m a n y decades of using lead additives in gasoline. Over the past 10 yr, because of the regulation of lead in gasoline and the pretreatm e n t of potable water, blood lead levels in Boston have declined. Childh o o d exposure from old residential lead paint and soil appears to be the most intractable sources.
SUMMARY (1) Current automobile emissions of lead contribute negligibly to the lead in urban soil and dust. (2) In the absence of lead paint, the leads in urban soils and h o u s e h o l d dust have nearly identical isotopic compositions and are the product of decades of accumulated fallout. (3) Lead paint, w h e n present, can be responsible for 20-70% of the lead in household dust and m u c h of the lead in yard soil. (4) In cases of severe lead poisoning, the lead in the child's blood and feces resembles very closely the lead in the paint from an accessible surface.
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ACKNOWLEDGMENT The cooperation of the children and their families and guardians is gratefully acknowledged. Dr. John Graef, Director of the Children's Hospital Lead Clinic, assisted in locating these cases. Professor Stanley Hart generously allowed me to use his NIMA-B mass spectrometer and other facilities. Funds were provided by a grant from the National Institute of Child Health and H u m a n Development (HD-08945). Analyses performed at the Mass Spectrometry Laboratory, Professor Stanley Hart, Massachusetts Institute of Technology, Department of Earth and Planetary Sciences.
REFERENCES 1. M. B. Rabinowitz and G. W. Wetherill, Environ. Sci. Tech. 6, 705 (1972). 2. M. B. Rabinowitz, G. W. Wetherill, and J. D. Kopple, [. Lab. Clin. Med. 90, 238 (1977). 3. S. Facchetti and F. Geiss, Isotopic Lead Experiment: Status Report. Community of European Communities, Luxembourg, Pub. # EUR 8352 EN, 1982. 4. W. Manton, Arch. Environ. Health. 32, 149 (1977). 5. Y. Yaffe, C. Flessel, J. Wesolowski, A. Del Rosario, G. Guirguis, V. Matias, T. DeGarmo, G. Coleman, J. Gramlich, and W. Kelly, Arch. Environ. Health. 38, 237 (1983). 6. M. B. Rabinowitz, A. Leviton, H. L. Needleman, D. C. Bellinger, and C. Waternaux, Environ. Res. 38, 96 (1985). 7. G. Tilton, C. Patterson, H. Brown, M. Inghram, R. Hayden, D. Hess, and E. Larsen Bull. Geol. Soc. Am. 66, 1131 (1955). 8. C. C. Patterson, Geochem. Cosmochem. Acta 47, 1166 (1983).
Biblogical Trace Element Research
VoL 12, 1987
