with moisture contents u p to about 35% was evaluated and found acceptable as feedstocks. The other feature of the process is that it requires no process water, which eliminates the problem of heating or purifying large amounts of the process water.
( 2 ) Friedman, S.,Ginsberg, H. H., Wender, I., Yavorsky, P. M., Third Mineral Wastes Utilization S ~ m p .IIT, , March 1972. ( 3 ) Fu, Y. C., Metlin, S. J., I l k , E. G., Wender, I., Preprints, Div. Fuel Chem., Amer. Chem. S O C . , Vol. 17, No. 1. p p 37-43, 1972.
Literature Cited
Receiced for reciew December 3, 1973. Accepted March 18, 1974 Pre.sented before the 16'6th .Vationa/ Meeting of the A m e r i can Chemical Society, Chicago. Ill., August 26'-31, 1973. Mention of commercial product\ is for identification only and doe\ not con..titute endoreument by the C'.Y. Bureau of Miner.
(1) Appell. H. R., Fu. Y. C.. Friedman, S., Yavorsky, P. M., Wender, I.. BuMines RI 7560, 5 pp, 1971: Agr. Eng.. p p 17-19, March 1972.
Cadmium, Lead, and Zinc Concentrations in Whole Blood Samples of Children John D. Bogden," Narayani P. Singh, and Morris M. Joselow Division o f Environmental Toxicology, Department of Preventive Medicine and Community Health, College of Medicine and Dentistry of New Jersey-New Jersey Medical School, 100 Bergen S t . , Newark, N.J. 07103
Mean whole blood concentrations for cadmium, lead, and zinc have been established for children residing in Newark. N.J., and frequency distributions for various concentration ranges for each metal have been determined. Significant positive correlations have been found between whole blood concentrations of zinc and cadmium and between concentrations of lead and cadmium. Paint is suggested as the source for the simultaneous ingestion of lead and cadmium. and air is suggested as a source for the simultaneous absorption of all three metals studied.
The concentrations of trace metals in human blood are only one aspect of the total body content and distribution of each metal in the various body tissues. Nevertheless, the determination of these concentrations can provide important information about the health status of a patient, since trace metals have been associated with a variety of disease states ( 1 ) . The objective of this study was to establish normal blood concentrations of zinc and cadmium in a population of children a t high risk with regard to exposure to potential sources of lead absorption. These were children living in a city environment who were being tested for evidence of lead poisoning.
Experimental Whole blood samples were collected from children in Newark, N.d.. in connection with the childhood screening program in the city. The age range for the subjects was 1-8 years. The lead content of the blood was first determined by a modification of the Hessel procedure (2, 3 ) . Approximately 5 ml of blood was collected from each subject by venepuncture into heparinized lead-free vacutainers (BectonDickinson). The blood sample was then treated with 2 ml of a 2% solution of ammonium pyrrolidine dithiocarbamate (APDC)-,570 Triton-X-100 and a volume of methyl isobutyl ketone (MIBK) equal to the original volume of blood. This was followed by vigorous shaking for 10 min and centrifugation a t 2100 rpm for 20 min to separate the aqueous and organic phases. The MIBK (upper) layer containing the extracted metals was then aspirated into the flame of a Perkin-Elmer Model 403 atomic absorption spectrophotometer equipped with a Boling three-slot burner head, 740
Environmental Science & Technology
T o determine the zinc concentration it was necessary to dilute the extract 5 : l with MIBK to obtain absorbances that were linear with concentration. Standards were prepared by extracting known aqueous concentrations of the metal with the APDC-Triton-X-100 mixture and MIBK. Under the conditions of hemolysis and extraction by the procedure described, lead and cadmium have been shown to be quantitatively extracted (2, 4 ) . However, this is not true for zinc. To determine the extraction efficiency for zinc by this technique, comparisons of zinc analyses on the same samples were made by 2 different atomic absorption procedures: chelate/solvent extraction and wet ashing, followed by dilution with water. Extraction efficiency was determined by analyzing 20 blood samples by both our extraction technique and also by a validated wet ashing atomic absorption procedure ( 5 ) . Under the experimental conditions used, a relatively constant fraction, 0.32 f 10% (mean f relative standard deviation) of the zinc present was extracted by the APDC-MIBK procedure. Therefore, the zinc concentrations determined were corrected by taking both the required dilution and the extraction efficiency into account.
Results and Discussion Cadmium. Table I contains the mean whole blood concentrations, ranges, and the number of analyses done for cadmium, lead, and zinc. The mean whole blood concentration for cadmium was 0.3 pg/lOO ml. Delves et al. (6) found a mean cadmium concentration of 0.5 pg/lOO ml for a group of 89 hospitalized children; Imbus et al. (7) determined a mean concentration of 0.9 pg/100 ml for a group of 153 adult males. Kubota e t al. ( 8 ) had determined a mean concentration of 1.8 pg/100 ml, but this mean did not take into consideration any values of less than 0.5 pg/100 ml, and 110 of Kubota's 243 subjects were below
Table I. Concentrations of Cadmium, Lead, and Zinc in Whole Blood Samples of Children Metal
Mean concn pg/100 A i
Obsd range, rg/100 ml
No. of analyses
Cad mi urn Lead Zinc
0.3 40 520
0.0-2.8 9-102 150-1 7 30
369 379 282
Table II. Comparisons with Whole Blood Concentrations of Trace Metals Found in Other Studies Cadmium, pg/lOO rnl
Zinc, pg/lOO m l
Lead, pg/lOO m l
___~______ Study
Population tested
Mean
Range
Mean
Range
Mean
Range
Delves et al. (6) Delves et al. (6) lmbus et al. (7) Kubota et al. ( 8 )
Hospitalized children Children with suspected pica Adult males Adult males
0.5 0.6 0.9 0.5
0.0-1.9 0.0-7.9 0.3-5.4 0.5-14.2
12 32 13
1-32 44-162 1-109
510 618 530
319-1040 210-2284 60-1987
This study
Inner city children
0.3
0.0-2.8
40
9-102
520
150-1730
(estd)
this concentration. Kubota et al. (8) did estimate, however, t h a t the mean whole blood cadmium concentration of the population they studied (male residents of 19 different U.S.cities) was about 0.5 pg/lOO ml. The mean concentration found in Ihe study is thus somewhat lower than values reported by others, b u t is nevertheless similar to the above previously reported values for various types of populations. Lead. The mean whole blood concentration found for lead was 40 pg/lOO ml. This is higher than the mean concentrations in other studies. For example, Kubota et al. (8) found a mean of 13 pg/100 ml for their population of male residents from 19 different U.S.cities. In fact, 40 pg/lOO ml is often taken as the upper limit of normal, and children with blood lead concentrations above this value are assumed to have ingested excessive lead, usually from paint chips. This high mean concentration is undoubtedly a reflection of the fact that the population sampled is composed of children residing in the older ghetto areas of Newark, N.J., where the majority of the population lives in old and deteriorated housing (9). Many of the residences have considerakile interior paint t h a t is cracked and peeling and many of the children undoubtedly have access to the peeling paint. In fact, 19 of the 379 blood samples analyzed (5%) had lead concentrations greater than 60 pg/lOO ml, the level a t which hospitalization and treatment are usually initiated. Zinc. The mean whole blood concentration determined for zinc was 520 pg/lOO ml. Delves et al. (6) found a zinc concentration of 510 pg/lOO ml in a control group of hospitalized children ($4 samples) and a concentration of 618 pg/lOO ml (192 samples) in a group of children diagnosed significant pica. Kubota et al. (8) had found a
-
Table 111. Spearman Correlation Coefficients for Pairs Zi nc-Lead, Cad mi urn-Lead, and Z inc-Ca d m iu'm Variable air
N u m b e r of pairs
Zincwith lead
Spearman correlation coeff
Level of significance,
P
