InternatlOn: Archsves of

Int Arch Occulp Environ Health 42, 69-81 ( 1978)

( l(kit Hnal aml Eni Yirwmu 1 W tal Health , Sprnger-Verlag 1978

Lead Concentration in Single Hairs as a Monitor of Occupational Lead Exposure P Grandjean' Institute of Hygiene, University of Copenhagen, Blegdamsvej 21, DK-2100 Copenhagen 0, Denmark

Summary A rapid method for the analysis of 1-cm segments of single hairs has been developed The hairs are washed with Freon TF in an ultrasonic bath and analyzed by electrothermal atomic absorption spectrometry Due to diffusion of exogenous lead into the hairs the lead concentration increases along the hair shaft Thus only the first -cm segment close to the hair root is used In a reference population of 44 males no association was found between the hair lead concentration and age of the individual Dark hairs tended to contain more lead than white hairs, but such difference was not apparent in occupationally exposed males During four weeks blood and urine samples were collected from 87 males with occupational lead exposure, and hairs which had grown I cm during this period were then sampled and analyzed The lead concentration in the first 1-cm segment of the hairs correlated significantly with the average lead concentration in blood and in urine, and 8-aminolevulinate in urine Hair lead increases exponentially with increasing blood lead A permissible limit of 60 pg lead/100 ml blood corresponds to about 70/g lead/g hair or 3 ng lead/cm hair The analysis of single hairs for lead is recommended as a screening method. Key words: Lead in hair Screening methods.

Occupational lead exposure

Permissible limits -

Small amounts of lead are excreted in the hair, and the lead concentration in scalp hair (Pb H) has been used in several investigations as a monitor of long-term environmental or occupational lead exposure l2, 3, 6, 7, 10, 11, 12, 16, 18, 21, 23, 25 l The average growth rate of human scalp hair is close to I cm per month l 15l Thus, the hair may serve as a calendar of past lead exposure l 17l In acute lead exposure, an increased PbH will occur with a latency period of a few weeks l20 l A major problem in dealing with PbH is the possible contamination with exogenous lead, and different washing techniques have been proposed Non-ionic detergents and organic solvents are sufficiently effective in removing the surface contamination l 2, 10, 12, 14, 18 l, and the Present address: Dr Philippe Grandjean, Environmental Sciences Laboratory, Mount Sinai Hospital, Fifth Ave & 100th St , New York, NY 10029, U S A.

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ultrasonic wash adopted by Hecker 112 l makes the procedure rapid New developments in electrothermal atomic absorption allow the analysis of single hair segments l 1, 22 l The present study deals with the excretion of lead in single hairs in occupationally exposed workers in relation to other indicators of lead exposure, viz lead n blood (Pb B), lead in urine (Pb U), and $-aminolevulinate in urine (ALAU). Material and Methods Reference Population Hairs with their roots were collected at the Institute of Forensic Medicine in Copenhagen from autopsies of 44 males aged 2 to 79 years From the death certificates it was concluded that all individuals died suddenly and that none were employed in a job with high lead exposure For precision and recovery studies several hundred hairs were obtained from a male aged 18 years. Exposed Populations A total population of 87 workers was studied Thirty-five were employed at a nonferrous foundry, 15 at an electric storage battery manufacturing enterprise, and 37 at a secondary lead smelter All were adult males with at least one year of occupational exposure to lead Blood samples were drawn on four successive Wednesdays or Thursdays, and spot urine samples were collected by the workers on the same days after sleep (normally in the morning) Three to five single hairs with their roots were drawn from the crown 7-10 days after the last blood and urine samples had been collected Of the 87 workers, 69 supplied four urine samples, 15 supplied three, and 3 workers only two Four blood samples were obtained from 22 workers, three from 47, and two from 18. Pretreeatmentof Hair From each hair a segment of precisely I cm close to the hair root was cut by means of an apparatus constructed for this purpose (details are available on request) Four different washing methods were tested: 1 Wash for 30 sec in a Millipore ultrasonic cleaner (working capacity 300 ml) with Freon TF solvent (du Pont de Nemours); or 2 the same procedure with acetone (technical grade) 1121 ; 3 Wash with diethyl ether (technical grade) for 2 h in a Soxhlet's apparatus 11, 221 ; or 4. Shake the hairs in a flask with a sodium lauryl sulphate solution (g in 100 ml doubly distilled water) for min; after filtering wash with doubly distilled water to remove detergent and then with acetone (technical grade) to remove water The latter method is comparable to the one used by other authors 13, 10, 14, 18, 21, 231 After drying, each hair was placed on a Beckman Microbalance LM 500 and weighed to O41g Four pieces of hair each washed by one of the four methods were coated with a 100-150,um layer of gold and studied in a Cambridge scanning electron microscope. Hair Analysis The analyses were carried out by means of a Perkin-Elmer atomic absorption spectrophotometer model 300 S with an HGA-72 graphite tube, a deuterium background corrector, and a strip-chart recorder Single hair pieces were inserted into the tube with a tantalum spoon in order to secure a reproducible geometry Loss of lead from the sample during the charring process was prevented by the addition of 101i diluted sulphuric acid (5 ml suprapure H 2 SO 4 , Merck, in 95 ml doubly distilled water) Standards and sulphuric acid were injected into the tube by means of an Eppendorf pipette with Sarstedt pipette tips The atomic absorption was detected at 283 3nm (slit width 0 7nm). The sample was dried at 1000 C for 15 sec, charred at 550 0 C for 15 sec, gradually heated to about 700 °C through 30 sec, and finally atomized at about 20000 C for 10 sec With this temperature program no significant interference from smoke occurred The accumulation of ash in the tube was prevented by regularly heating to maximum temperature (2,650 0 C) for a few seconds Flow of argon was 1 5-2 0 I/min with gas stop during the atomization phase Standards were prepared from lead acetate (analytical grade, Merck), and the results were measured by interpolation after

71

Lead Concentration in Single Hairs

Table 1 Blood lead levels (g/100 ml) in 14 individuals as determined in capillary and in venous blood by atomic absorption spectrometrya Individual number 1 2 3 4 5 6 7 8 9 10 11 12 13 14

Capillary blood lead 43 48 48 60 65 69 69 78 79 82 84 84 92 108

Venous blood lead 44 38 51 69 59 72 77 80 85 80 80 85 85 82

apaired -test: t = 0 91, p > 0 3 Average coefficient of variation 9 %

subtraction of the absorbance of the sulphuric acid Additions of O 5-5 Ong Pb to a hair piece were recovered by 82-101 %. Analysis of Blood and Urine Capillary blood was drawn from the ear lobe after thorough washing of the skin with soap and water followed by propyl alcohol The skin was punctured with a disposable lancet, and the first drop of blood was disgarded A 100/Jl heparinized capillary tube was used for the collection of blood which was immediately poured into a polypropylene tube with 1 ml doubly distilled water. The samples were frozen until analysis by electrothermal atomic absorption similar to the method described by Fernandez (81 In 14 individuals venous blood samples were collected in Vacutainer tubes at the same time and analyzed at the National Institute of Occupational Hygiene by Hessers l131 method (Table 1) An intercomparison program showed that both methods gave reliable results (Table 2) The average coefficient of variation of duplicate PbB determinations was 5% for Pb B above 4041/100 ml, and 9% for lower Pb B levels. For the analysis of lead in urine the method described by Fjerdingstad 191 was used To Iml of urine was added O Sml 30% H, 0, (pro analysi Merck) and after 1-2 h O5 ml HCI 0, (60% pro analysi, Merck) The sample was left overnight and analyzed by electrothermal atomic absorption. This method has proved reproducible and reliable l 91 The coefficient of variation in this study was 17 %for PbU levels above 80/4/1 and 28 % for lower Pb U levels. Urine samples for ALA analysis were preserved with tartaric acid and stored at -18 °C in the dark until analysis was performed by means of prefilled ion-chromatography columns as recommended by Davis and Andelman 141 The instruction manual from Bio-Rad Laboratories was followed precisely, and the calibration standard line was prepared with the standard solution accompanying the batch of columns Absorbance of the pink color was measured at 552 nm with a Beckman model C calorimeter equipped with a Leitz interference filter The average recovery of ALA was 90%,and all results were corrected for this bias The coefficient of variation of duplicate analyses was 8% for ALAU above 8mg/I and 14 %for lower levels.

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P Grandjean

Table 2 Blood lead levels (Jg/ 100 ml) in three blood samples determined by the two methods used in this study and four other methods. Data from the intercomparison study performed by the National Agency of Environmental Protection, Copenhagen, 1977 All samples were analyzed in triplicate Sample number 1 2 3

Capillary blood method

Venous blood method

18 36 52

Average of four other methods

19 36 54

16 32 48

Table 3 Lead concentration (ng/cm) in single hairs washed by four different methods (see Pretreatment of Hair) Lead concentration in hair Washing method

Number of hairs

Median

95% confidence limits to median

1 2

57 52

0 08 0 11

0 07 0 09

0 08 0 14

3

47

0 18

0 16

0 22

4

51

0 10

0 09

0 12

/ Ji

P

111111111 iff 1:

_r

-1 IAASMMEI'k

M \

"

11111

Fig 1 Scanning electron micrographs of hairs prepared in different ways: no washing at all (upper left), washed for two hours with diethyl ether (upper right), washed with sodium lauryl sulphate and acetone (lower left), and washed with Freon TF in an ultrasonic bath (lower right) Only the latter method removes both the large and the small particles The diameter of the hairs is about 60,um

73

Lead Concentration in Single Hairs Table 4 Lead concentration ng/cm) and weight (Uglcm) of -cm segments of hair after submergence in a sweat solution containing 13 mg Pb/1 Submergence time I 5 30 24 100

min min min h h

Number of hairs 11 8 7 9 8

Lead concentration Range Median 0 08 0 18 0 26 0 49 0 98

0 05 0 05 0 11 O25 0 43

0 18 0 36 0 35 0 64 1 62

Median weight 51 7 52 2 55 9 53 8 49 1

1

E o 01 C

.

0

.o c 4a u U

C 0

o 'O a Cl 0

Distance from root (cm) Fig 2 Lead content of 1-cm segments of single hairs from four males with occupational lead exposure

Results The four washing methods were not equally effective in removing surface contamination from the hairs The lowest lead concentrations were obtained after ultrasonic washing, and Freon TF was somewhat better than acetone (Table 3) None of the wash solutions contained significant amounts of lead Scanning electron micrographs suggest that the ultrasonic wash removes more particles from the surface of the hair than the other methods used (Fig 1) Thus the ultrasonic wash with Freon has been used as the routine method. In order to evaluate the possible diffusion of lead into the hair matrix, a sample of hairs was submerged in a sweat-like solution l 15l containing 13 pg Pb/ml At different times single hairs were taken out, washed and analyzed (Table 4) After four days the lead concentration of the hairs exceeded that of the water.

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P Grandjean

~~ ~ ~

1.0

U

I-. o

o 0. c o

a, 0 -J

o II

I

l

2

l

l

4

6

8

10

Distance from root (cm) Fig 3 Lead content of l-cm segments of single hairs from four individuals with low-level lead exposure The scale on the y-axis is 10 times lower than in Fig 2

o blond * dark x grey

x

20 10 -cn

x *

o

x

x

o eX

5

_

·

X X

X

o

X

X

.0

C-

x a

2

20

1

.2

10

20

30

40

X I

I

I

I

I

0

X

X

50

60

70

80

Age (years ) Fig 4 Lead concentration in hairs in relation to age and hair color The scale on the y-axis is logarithmic

75

Lead Concentration in Sinele Hairs Table 5 Median lead concentration in hair in relation

to hair color in 44 individuals from the reference group and 35 industrial workers with low lead exposure Number of Hair

Lead concentration

individuals

ng/cm

Dark Blond Gray

44 14 21

0 40 0 26 0 18

ig/g

7O 50 37

a The differences are not statistically significant as determined by a Kruskal-Wallis test

Table 6 Median lead concentration in hair in relation to hair color and median blood lead level in 52 industrial workers with high lead exposure Number of individuals Dark Blond Gray

31 10 11

Lead in hair ng/cm / 11 gg 48 38 37

100 100 98

Lead in blood Pg/100 ml 58 66 63

a The differences are not statistically significant as determined by a Kruskal-Wallis test

Table 7 Median lead concentration and weight of dark and white hairs from a gray-haired adult male with low-level lead exposure Hair color

Number of hairs

Dark White

7 7

Weight /g/cmb

Lead concentration 1/ga nglcmb

59 7 47 1

0 67 0 41

11 0 85

ao.05 < p < 0 10, and bp < 0 01 as determined by comparison of the two colors by a two-tailed MannWhitney U-test

Table 8 Median lead concentration and weight of dark and white hairs from a gray-haired adult male with occupational lead exposure Hair color Dark White

Number of hairs 10 6

Weight /g/cma

Lead concentration /4/g ng/cm

35 8 47 9

51 59

160 120

a 0.05 < p < O 10 as determined by comparison of the two colors by a two-tailed Mann-Whitney U-test

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Table 9 Associations between four exposure tests: lead in hair (PbH), lead in blood (PbB), lead in urine (Pb U), and 6-aminolevulinate in urine (ALAU), as determined by Spearman rank correlation coefficients of the average test results in 87 industrial workers exposed to lead Pb Ha

Pb Hb

PbU

ALAU

PbB

0 78

0 77

0 79

0 80

PbU

0 67

0 65

ALAU 0 63 ang/cm, bpg/g

0 60

0 81

0 81

-

a

IL

Pb B (pg/100 ml) Fig 5 Relationship between the average lead concentrations in blood samples and single hairs in 87 workers exposed to lead The regression lines are shown The scale on the y-axis is logarithmic and indicate the concentration in lg/g

With increasing distance from the scalp, hair segments have been exposed to exogenous lead from sweat and dust for increasing periods of time Thus, a considerable increase in Pb H along the hair shaft was found in four males with occupational lead exposure (Fig 2) but such increase was not apparent in hairs from individuals with low-level lead exposure (Fig 3) Especially in occupationally exposed subjects it is therefore of importance to analyze only the segment of the hair closest to the scalp.

77

Lead Concentration in Single Hairs

E

U C

a

Pb8B (j g/100 ml) Fig 6 Same as Fig 5, but the concentration of lead in hair is shown in ng/cm Table 10 Validity of determinations of lead in hair (Pb H), lead in urine (Pb U), and 6-aminolevulinate in urine (ALAU), compared to the permissible limit for lead concentration in blood, viz , 60 /4/100 mia, in 87 lead-exposed workers Validity (sensitivity + specificity)

Sensitivity (%true positives)

Specificity (%true negatives)

1004g/g

71

76

147

70 50 4ng/cm 3 2

69 71 68 70 66

82 86 76 86 89

151 157 144 156 155

PbU: 100 ag/la ALAU: 10 mg/la

77 86

82 78

159 164

Cut-off level PbH:

apermissible levels from Zielhuis 281

From Fig 4 it appears that there is no correlation between Pb H and the age of the individual in the reference group Gray-haired males had slightly lower PbH than individuals with blond or dark hair (Fig 4) Table 5 shows the PbH in relation to hair color in the total reference group plus the 35 industrial workers with low lead exposure at the nonferrous foundry, and in Table 6 the same relationship is shown for the 52 workers with high lead exposure No significant difference between the groups

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Biological TLV's exceeded by 47 lead-exposed workers

PbH I

Pb B /

1

7

5

l3

l, L

l2

12 3

lo:

3

1

Biological TLV's: PbH 70 pg/g Pb B 60 g /100ml

1

PbU

1 j

ALA U

Fig 7 Wenn's diagram indicating the numbers of workers who had test results in excess of the permissible limits as defined in this study and by Zielhui

1281 R

PbU 100 pg /1 ALAU= 10 mg/1

was found From one gray-haired individual of the reference group and one of the exposed group several dark and white hairs were analyzed (Tables 7 and 8) It appears that hair color was not a significant confounding factor in occupational lead exposure. The PbH was found to vary from hair to hair in the same individual The average coefficient of variation was 33 % for PbH measurements both in ug/g and ng/cm. The average Pb H for each of the workers has been compared to the average values of PbB, Pb U, and ALAU (Table 9) The lead concentration in the single hairs correlates significantly with all three parameters The relationship between PbH and PbB is shown in Figs 5 and 6 The lead content in the hairs increases in an exponential way with an augmented PbB The regression lines indicate that the biological limit value of 60pg Pb/100 ml blood l28 l would correspond to about 70 jig Pb/g hair or 3 ng Pb/cm hair Different limits for PbH can be used, however, and their validity compared to the PbB limit is shown in Table 10. Forty-seven workers in the exposed group exceeded one or more of the biological limits for lead exposure l28 l or the PbH limits defined above The blood lead limit was exceeded by 70%, 19 % had only one positive test, and 26% were positive in all four tests (Fig 7). Discussion Single hairs with roots are easily and almost painlessly removed, and they are conveniently transported and stored The pretreatment and analysis of the hairs can be simple and quick as shown in the present study The PbH can be determined in a few minutes Thus this method can be used as a screening method in occupationally exposed individuals. It is of great importance to clean the hair from surface contamination, and the ultrasonic wash has proved efficient in this respect (Table 3) Exogenous lead which has diffused into the hair is impossible to remove without disturbing the original lead

Leald Concentration in Single Hairs

79

content of the hair l 5, 10, 14 l Close to the scalp only little diffusion would have taken place, and the first 1-cm segment of the hair is therefore very suitable for a determination of Pb H Such small pieces of hair can be readily analyzed by electrothermal atomic absorption, but it is difficult to assess the validity of this detection method, since no reference material is available l 1, 22 l The variation in Pb H between single hairs from the same individual is relatively large, and it is not known what proportion is due to the analytical variation Thus it is necessary to analyze a small number of hairs l3-5 l and calculate the mean value The data obtained in the present study are of the same magnitude as found in most other studies l 1-3, 6, 10, 12 18, 21,23-25 l, and it is therefore probable that the results are quite accurate. The age of the individual and the hair color may be relevant confounding factors. Thus Schroeder and Nason l23 l found that Pb H decreases in the following sequence: brown>blond>black>red Other investigations have shown that hair color is an insignificant confounding factor l 2, 3, 6, 21 l In the present study dark hairs were slightly higher in lead than blond and gray hairs in the reference group (Fig 2) A significant difference was found between dark and white hairs from a gray-haired individual of the reference group (Table 5), but this difference seemed to disappear in the occupationally exposed worker (Table 6) Thus it is presumed that hair color is of no practical importance as a confounding factor. It is more difficult to evaluate the possible influence of age on the Pb H level One study has shown that the Pb H increases from childhood to old age 16l Other investigations conclude that the PbH level is independent of age in adult males l3, 6, 18, 21 l. In the reference group of this study the Pb H levels were not significantly associated with the age of the individuals It appears therefore that age is of little importance as a confounding factor. The Pb H correlates with environmental lead exposure gradients l 2, 3,6, 10, 12, 21 l, and it has been used in the diagnosis of lead poisoning l7, 11, 17, 25 l While PbH probably represents a long-term exposure integral lI Ol, the current exposure is better reflected by other parameters such as PbB, PbU, and ALAU l27 l These measurements are subject to analytical variations l 19, 27 l, and the PbB level is very dependent upon changes in the hematocrit of the blood sample l 24, 26 l By using average values over the period when lead was excreted in the hairs, however, a fair comparison can be achieved A significant correlation between PbH and the other parameters measured has been found in this study (Table 9) PbH rises exponentially with increasing PbB (Figs 5 and 6), and this is in agreement with other studies l2, 10 l No biological explanation for this phenomenon has been proposed The very high lead concentrations in hair facilitate the analysis, and the exponential increase makes it easier to distinguish between different levels of exposure A biological limit for lead exposure of 7 0rg Pb/g hair is proposed from the results obtained Earlier, Suzuki et al l 25l recommended a limit of I Olg Pb/g hair corresponding to 80 ug Pb/100 ml blood, and this is in accordance with the findings in this study It is not surprising that PbH has been recommended as a screening method for the detection of occupational lead poisoning l7, 11, 25 l In order to make the analysis more rapid, the weighing procedure can be omitted if the hairs are very accurately cut (Fig 6) A screening limit of 2 ng/cm would be convenient (Table 10), and in this way hundreds of hairs can be analyzed per day. In low-level lead exposure only little lead is excreted in the hair (Fig 2), and this constitutes a very small part of the total daily lead loss l27 l With a total number of

P Grandjean

80

scalp hairs of 100000 l 151l, a growth rate of I cm/month l 15 l, and an average hair weight of 50/ag/cm, the daily lead excretion in the scalp hairs corresponding to the limit value can be calculated to be 121ag This calculation presupposes that the hair lead content is endogenous The lead excretion in the hair should be compared to the biological limit for PbU which is 100 lg/l l28 l, and with a daily volume of urine of 1.4 1 l 15 l, 140 Ag lead will be excreted in the urine per day Thus, though the PbH concentrations are high, the proportionate lead excretion in hair in occupationally exposed subjects is only a minute fraction of the total elimination of lead. The assessment of the validity of PbH analysis cannot be accurately determined by way of comparison with other measures of the lead exposure The parameters used in this study, PbB, PbU, and ALAU, are imprecise predictors of lead exposure and lead toxicity PbH may be used as a predictor too, but it is not yet possible to evaluate if it is better or worse than PbB Thus further studies of PbH as a diagnostic test should be encouraged The results of the present investigation indicate that PbH would be valid in screening studies for the detection of long-term lead exposure. Acknowledgements Grants for this study were given by the Danish Medical Research Council and Svend Bergste's Foundation The author is indebted to O Winding, M Pharm , for assistance in preparing scanning electron micrographs.

References 1

2 3 4 5 6 7 8 9 10

11

Alder, J F , Samuel, A J , West, T S : The single element determination of trace metals in hair by carbon-furnace atomic absorption spectrometry Anal Chim Acta 87, 313-321 (1976) Chattopadhyay, A , Roberts, T M , Jervis, R E : Scalp hair as a monitor of community exposure to lead Arch Environ Health 32, 226-236 (1977) Creason, J P , Hinners, T A , Bumgarner, J E , Pinkerton, C : Trace elements in hair, as related to exposure in metropolitan New York Clin Chem 21, 603-612 (1975) Davis, J R , Andelman, S L : Urinary delta-aminolevulinic acid (ALA) levels in lead poisoning Arch Environ Health 15,53-59 (1967) Dresch, W , Fortmann, K -M : Blei-Einschliisse in menschlichem Haar Naturwissenschaften 63, 436-437 (1976) Eads, E A , Lambdin, C E : A survey of trace metals in human hair Eviron Res 6,247-252 (1973) EI-Dakhakhny, A -A , El-Sadik, Y M : Lead in hair among exposed workers Am Ind Hyg. Assoc J 33, 31-34 (1972) Fernandez, F J : Micromethod for lead determination in whole blood by atomic absorption, with use of the graphite furnace Clin Chem 21,558-561 (1975) Fjerdingstad, E : Bestemmelse af bly i urin hos blyexponerede arbejdere pp 24-25, Dansk Kemi, marts, 1974 Hammer, D I , Finklea, J F , Hendricks, R H , Hinners, T A , Riggan, W B , Shy, C M : Trace metals in human hair as a simple epidemiologic monitor of environmental exposure In: Trace substances in environmental health, Vol V (D D Hemphill, ed ), pp 25-36 Columbia: University of Missouri 1971 Hasegawa, N , Hirai, A , Shibata, T , Sugino, H , Kashiwagi, T : Determination of lead in hair by atomic absorption spectroscopy for simple screening of lead intoxication Ann Rep Res. Inst Environ Med 18, 1-5 (1971)

12 Hecker L : Hair as an index of mercury and lead exposure Ph D dissertation Ann Arbor: University of Michigan 1971

Lead Concentration in Single Hairs 13 14 I5 16 17 18 19

20 21 22 23 24 25 26 27 28

81

Hessel, D W : A simple and rapid quantitative determination of lead in blood At Abs Ncwsl. 7,55 56 (1968) Hinners T A , Terrill, W J , Kent, i L , Colucci, A V : Hair-metal binding Environ Health Perspect 8, 191-199 (1974) International Commission of Radiological Protection (ICRP) Publication No 23 Report of the Task Group of Reference Man Oxford: Pergamon Press 1975 Klevay, L M : Hair as a biopsy material, 11 Assessment of environmental lead exposure. Arch Environ Health 26, 169-172 (1973) Kopito, L , Briley, A M , Shwachman, H : Chronic plumbism in children J Amer Med. Ass 209, 243-248 (1969) Petering, H G , Yeager, D W , Witherup S O : Trace metal content of hair, II Cadmium and lead of human hair in relation to age and sex Arch Environ Health 27, 327-330 (1973) Pierce, J O , Koirtyohann, S R , Clevenger, T E , Lichte, F E : The determination of lead in blood, a review and critique of the state of the art, 1975 New York: International Lead Zinc Organization 1976 Rabinowitz, M , Wetherill, G , Kopple, J : Delayed appearance of tracer lead in facial hair. Arch Environ Health 31, 220-223 (1976) Reeves, R D , Jolley, K W , Buckley, P D : Lead in human hair: relation to age, sex and environmental factors Bull Environ Contam Toxicol 14 579-587 (1975) Renshaw, G D , Pounds, C A , Pearson, E F : Determination of lead and copper in hair by non-flame atomic absorption spectrophotometry J Forensic Sci 18, 143-151 (1973) Schroeder, H A , Nason, A P : Trace metals in human hair J Invest Dermatol 53, 71-78 (1969) Streeten, D H P , Thorn, G W : Use of changes in the mean corpuscular hemoglobin concentration as an index of erythrocyte hydration J Lab Clin Med 49, 661-671 (1957) Suzuki, Y , Nishiyama, K , Matsuka, Y : Studies on lead content and physical properties of the hair of lead poisoning Tokushima J Exp Med 5, 111-119 (1958) Sorensen, G : Variations in the hemoglobin content of capillary blood and their haemometrictechnical significance Nord Med 10, 1117-1122 (1941) Word Health Organization: Environmental Health Criteria 3, Lead Geneva: WHO 1977 Zielhuis, R L : Second international workshop, permissible levels for occupational exposure to inorganic lead Int Arch Occup Environ Health 39, 59-72 (1977)

Received February 28, 1978 / Accepted June 29, 1978

Lead concentration in single hairs as a monitor of occupational lead exposure.

InternatlOn: Archsves of Int Arch Occulp Environ Health 42, 69-81 ( 1978) ( l(kit Hnal aml Eni Yirwmu 1 W tal Health , Sprnger-Verlag 1978 Lead Con...
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