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A survey of arsenic levels in human hair and nails—exposure of wood treatment factory employees in Nigeria
Environmental Pollution (Series B) 9 (1985) 95 105
A Survey of Arsenic Levels in Human Hair and Nails--Exposure of Wood Treatment Factory Employees in Nigeria
Ch. L. N d i o k w e r e Chemistry Department, University of Benin, Benin City, Nigeria
ABSTRACT Arsenic levels have been determined in the hair and nails of male employees of a wood preservative treatment factory in Nigeria. Mean As concentrations of 11.6, 7.5, 4.1 and 1.6pgg-1 were measured in hair samples from four groups of employees, depending on the nature of their work and the duration of their employment in the factory. Mean As levels of 7.4, 4.8, 2.7 and 1.0 I~g g-1 were also measured in nails for the same groups. The employees involved in the preparation of the treating fluids, the chemical impregnation process and handling of the treated timber showed consistently higher As levels in both tissues than those who were less exposed to the chemicals. No correlation between the measured As levels and age of the donors was established, nor was a reasonably good hair As-nail As correlation obtained for an)' of the four exposure groups. This study, however, minimized possible effects of age, sex, hair colour and chemical treatment. Mean As levels of 1.2 and 0.64ltgg -~ as 'control' values were also determined in hair and nails, respectively of 'non-exposed' persons in the same age group as the factory workers. The elevated As levels measured in both tissues reflected a relatively high degree of exposure to the chemicals. 95 Environ. Pollut. Ser. B. 0143-148X/85/$03' 30 © Elsevier Applied Science Publishers Ltd, England, 1985. Printed in Great Britain
96
Ch. L. Ndiokwere
INTRODUCTION
Human tissues such as hair and nails, as well as body fluids, are increasingly considered as useful monitors for environmental exposure to some toxic heavy metals. Some authors (Kopito et al., 1967; Renshaw et al., 1972; Petering et al., 1973; Valkovic et al., 1975; Chattopadhyay et al., 1977; Fergusson et al., 1981) have explored the quantitative analysis of lead in scalp hair as an aid in the clinical diagnosis of chronic or acute lead poisoning. Some trace metals have also been measured in hair and nails (Schroeder & Balassa, 1966; Harrison et al., 1969: Schroeder & Nason, 1969: Hammer et al., 1971; Gordus, 1973). Boylen & Hardy (1967) studied the distribution of As in hair, liver and urine of nonexposed persons. The analysis of human hair and nails for trace elements has also been extended to forensic investigations (Perkons & Jervis, 1962; Forslev, 1966; Shapiro, 1967). Since hair and nails accumulate trace elements for longer periods and are metabolically inert, the tissues may serve as important indicators for occupational exposure to heavy metal pollutants which can be toxic to humans. Also, the use of hair and nails for such analyses, rather than urine or blood, as has been the convention in poisoning incidents and similar studies, has the advantage of facilitating specimen collection and storage. In contrast with blood and urine, which normally must be collected by specialists under very careful conditions to avoid contamination, samples of hair and nails can easily be collected by unskilled personnel. The treatment of wood for long-term protection from attack by fungi and insects such as termites is usually effected by impregnation with a mixture of solutions of salts of arsenic, chromium and copper. The workers handling the mixed solutions in vacuum-pressure cylinders and treated timber may be directly exposed to the fumes of these chemicals. In this investigation, the study population consisted mainly of the male employees of the wood treatment factory in Benin City. There has been much concern about the possible hazards of these chemicals to the employees of the factory and to its environs. Arsenic compounds, in particular, are known to be toxic to plants and humans (Vallee et al., 1960: Kyle & Pease, 1966) and so it was important to ascertain if any significant contamination of the environment by the chemicals had occurred. This quantitative analysis of the tissues for As may therefore
Arsenic in human hair
97
afford an opportunity for monitoring As levels, which may reflect its abnormal concentrations in the body after exposure to the metal.
MATERIALS AND M E T H O D
Sampling Samples of hair were taken with stainless steel clippers from 46 male employees (aged 23 to 54 years) of the Bendel wood treatment factory, Benin City. The information supplied by the donors showed that most of the scalp hair samples had not been dyed or bleached. Only in a few cases had the donors from time to time dyed their grey hair. In some cases, the samples consisted of mixtures of black and grey hair. Each sample mixture was, however, treated as a unit for the purpose of this analysis. The hair samples were stored in polyethylene bags and identified with the age of donor, duration of employment and nature of work in the factory. Samples of finger nails were mostly obtained from the same donors who supplied the hair. The nail clippings were cut with stainless steel nail cutters and preserved in polyethylene capsules. Specimens of hair and nails to serve as ~controls' were similarly obtained from 15 supposedly non-exposed male residents of Benin City in the same age group as the factory employees. This was to establish normal As levels in the tissues. Difficulties were encountered in obtaining these samples because people in this part of the world are usually hesitant at giving such human tissues for non-clinical reasons.
Pretreatment of the samples Each hair sample was soaked in deionized water with stirring to remove any externally attached dust particles and other contaminants, which might also contain trace metals. After each wash, the water was decanted and the sample was further boiled for a few minutes, rinsed with deionized water and dried between clean filter papers. The sample was finally washed with CCI 4 by allowing a sufficient amount to cover the hair. This was necessary to remove any oils or greasy substances. The hair was thereafter rinsed with CC14 and air-dried. The nail samples were also briefly boiled and washed with deionized water and dried at 110 °C. The washing procedure was necessary also to ensure that salts of Na, K,
98
Ch. L. Ndiokwere
Mg and Ca, which are normally accumulated by these tissues during growth, were quantitatively removed. This would, in particular, minimize the effect of the 24Na Compton continuum on the counting of 76As activities after irradiation and interference by the 554keV photopeak of S2Br. A comparison between the As levels obtained for representative unwashed and washed hair and nail specimens showed that little or no As was lost during washing. Any differences were probably due to analytical precision, rather than to the pretreatment itself. This was in agreement with the observation of Bate & Dyer (1965) that the concentrations of some heavy metals in hair were not essentially affected by a similar washing procedure because of their great tendency to complex with the sulphydryl groups in the follicular proteins.
Analysis An accurately weighed hair sample was ashed in a muffle furnace at 450 °C for several hours until a white powder remained. The residue was dissolved in 2ml H N O 3 and carefully transferred into an irradiation capsule and heat-sealed. The dry weight of the samples ranged from 1.3 g to 3 g. The nail clippings were further cut into very small pieces, accurately weighed into irradiation capsules and similarly heat-sealed. The dry weight of the nail samples was between 0.1 g and 0.15 g. The samples and the comparator standards, prepared by dissolving accurately weighed As20 3 in HNO3, were irradiated simultaneously in the rotary specimen rack of the TRIGA Mark I nuclear reactor of the University of California, Irvine, for 3h at a thermal neutron flux of 1.0 × 10~2ncm-2s-1. After appropriate decay times the irradiated samples and standards were counted in the usual way using a 90cm 3 coaxial Ge(Li) detector connected to a 4096-channel pulse-height analyser. The As levels were calculated after corrections for decay and photopeak baselines were made. Replicate analyses of samples were always within + 4.6 10')J,~of the reported mean values. Both gamma-ray peaks 559keV and 657keV of 76As (t~/2--264h) were used for the measurement of As concentrations. RESULTS AND DISCUSSION The As levels measured in the hair and nails of the 46 male employees of the factory are presented in Table 1, which also shows the ages of the
Arsenic in human hair
99
donors and the duration of employment in the factory. The As levels in the same tissues from 15 'non-exposed' persons resident in Benin City are also presented in Table 2. The reported As levels represent mean values of two replicated analyses of each sample. The frequency distribution of As levels in the hair and nails of the four exposure groups is shown in Table 3. The mean concentrations have been calculated as 11.6, 7.5, 4.1 and 1.6/~gg -1 for exposure groups A, B, C and D, respectively. The frequencies have been modified because the hair and nail As concentration interval sizes were not constant. Histograms for the four exposure groups are given in Fig. 1. The two exposure groups, A and B, exhibited hair and nail As levels well above the concentration range measured for the 'control' group. At one time or another during the previous five years or more most of these highly exposed employees had been directly involved in the preparation of the solutions and in the impregnation processes. Moderately high levels of As occurred in 13 workers, who had also been associated with the chemicals and the treated timber, while 20 other workers appeared less exposed and maintained low levels of As in hair and nails. It is interesting to note that, in establishing the control, or normal, arsenic levels in human hair and nails, the results have shown that As levels within the age group of the non-exposed persons varied considerably (hair As: 0"34 2.1/~gg- 1 and nail As: 0"18- 1 . 4 # g g - 1). This indicated that the As levels were not necessarily dependent on the ages of the donors. Similarly. the As levels measured in hair and nails from the 46 factory employees could not be correlated with the age of the donors. The factory workers exposed to the chemicals could be distinguished by the following departures from the 'normal': (a) considerably high As levels in both tissues from the workers involved in the wood treatment processes, compatible with probable inhalation of the fumes from the chemicals and (b) similar and significantly elevated As levels in workers who had been associated with the treated timber, also indicating contact with the chemicals for some time. An attempt has been made in this study to correlate the hair As content with As level in the nails of the same persons. A graph of hair and nail As levels for three exposure groups, A and B, C, and D, is presented in Fig. 2. The hair and nail As levels for exposure groups A and B showed a weak correlation corresponding to a calculated correlation coefficient of - 0 . 2 4 . The correlation of As levels in both tissues for the 'intermediate' and 'low' exposure groups, C and D, respectively, is relatively good, corresponding
Ch. L. Ndiokwere
100
TABLE 1 Arsenic Levels Measured in Hair and Nails of Employees of a Wood Treatment Factory
Donor
Approx. age Approx. duration (years) o f employment (.years)
1
24
3
2 3 4 5 6 7 8 9 10
37 41 35 24 23 37 41 36 31
5 4 5 5 2 3 4 6 3
11
36
6
12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38
24 33 38 33 29 31 36 28 38 26 47 44 41 37 35 33 27 34 36 32 29 30 43 36 31 31 29
2 7 6 3 4 6 4 5 5 3 4 6 6 5 5 3 4 3 4 4 5 4 6 4 4 3 5
Arsenic level in hair (l~gg 1 dr)' weight)
Arsenic level in nails (l~gg i dry weight)
9.7 11 9.8 13 8.9 6.5 7-8 64 11 12 14 7.8 12 4.5 5'4 4-1 4.6 3.6 4-7 3.5 4-4 3.0 4.8 3.6 4.1 3.4 2.3 2.3 1.9 0-92 2.0 1-7 1.3 1.8 1-7 0.87 2.0 1.2
6.4 8.7 4"6 5.5 4.5 8.1 7.5 6-3 4"1 4-8 5-2 3.1 3.3 3.0 2'7 2"8 * 2-8 2.6 3~ 2.9 30 3-3 * * 3.4 3.2 2-7 1.1 0"37 064 1.3 1.3 0"46 0.87 I0 1.6 1.8
Arsenic in human hair TABLE 1
Donor
39 40 41 42 43 44 45 46
Approx. age Approx. duration (years) of employment ()'ears) 27 34 34 26 29 29 33 31
101
contd.
Arsenic level in hair (l~gg-1 dr)' weight)
Arsenic level in nails (#gg-1 do' weight)
1.8 1.5 1.9 1.3 2. I 1.1 1.8 1.4
0-94 1.2 1.5 0.88 * 1.1 1.3 1.6
4 6 5 3 4 5 5 4
* Nails could not be o b t a i n e d from the employees.
to the calculated correlation coefficients of -0-45 and 0.51, respectively. The weak correlation observed for exposure groups A and B indicated that persons exhibiting high hair As levels do not necessarily show elevated As levels in nails. Hair and nail As levels measured for donors 3, 4 TABLE 2 Arsenic Levels Measured in Hair a n d Nails of ~Non-exposed" Male Residents in Benin City
Donor
Approx. age (years)
Arsenic in hair (pgg i dry weight)
Arsenic in nails (pgg- 1 dry weight)
I 2 3 4 5 6 7 8 9 10 11 12 13 14 15
22 26 35 44 28 23 34 36 34 21 26 45 47 38 41
0.34 1.8 0.82 0.43 1.9 2.0 0.73 1.4 1.3 1.2 0-92 2.1 0.64 I-5 0-37
0.18 0.27 1.4 1.1 0.46 0.54 1.4 0-63 0.41 1.0 0-82 0.33 0.24 0-20 0.57
102
Ch. L. Ndiokwere
20
i5
a: hair
i0 0
o~ ~o
I
I
20
15
10 b: nails
--1
1 8
i'O
Arsenic ~oncentration
Fig. 1.
i'2
1'4
16
(~gg-l)
Frequency distribution of As levels in (a) hair and (b) nails for four exposure groups from a wood treatment factory.
and 9-13 are good examples. However, the tendency for persons exhibiting relatively high As levels in hair, especially in the case of exposure group C (Fig. 2), to show lower As levels in nails is noteworthy. The possibility of hazard due to direct exposure to high doses of the chemicals was further confirmed by the observation during sampling that most of the workers involved in the solution preparation and treatment processes were not wearing gloves or gas masks. This might account for the high As levels recorded in hair and nails from these workers. Although As is known to be highly toxic to humans, the levels measured in hair and
TABLE 3 Summaries of Arsenic Levels in Hair and Nails: Distribution According to Degree of Exposure
Human Exposure rating tissue
Hair
Nails
A B C D E A B C D E
Number of persons
Highest High Intermediate Low Non-exposed Highest High Intermediate Low Non-exposed
Arsenic level Mean Standard deviation range (#gg-l) (izgg-,) (pgg-1)
8 5 13 20 15 5 6 18 13 15
9.7-14.0 6.4-9.0 3.0-5-4 0.85-2.3 0.34-2.1 6.3 8-7 4.1-5.5 1.5 3.8 0-37 1-3 0.18 1.4
11.6 7.5 4.1 1.6 1.2 7.4 4.8 2.7 1.0 0.64
i-4 1.0 0.7 0.4 0-6 1-0 0.5 0.7 0.3 0.4
16¸
14.
Q
12~ Q
0
IC~ Q
0
0
~8 e
0
7 @ ~U
2
-.o.-
As level
Fig. 2.
in Nails
(~gg-l)
Hair arsenic nail arsenic correlation. Q, exposure groups A and B. x, exposure group C. Q, exposure group D.
104
Ch. L. Ndiokwere
nails could not be associated with any toxic effects on the affected workers. Possible subclinical biochemical abnormalities and other health effects as a result of increased As burden in the body should be further investigated. There is, as yet, no evidence that hair and nail As levels reflect the total As burden in the body.
CONCLUSIONS The relatively high As levels measured in hair and nails were mainly due to exposure to the chemicals used for the treatment of wood. Since these tissues are readily available and easy to obtain, the analysis may provide a convenient means of monitoring abnormal levels of As in the body. While a good correlation existed between the As levels and duration of employment for the workers with almost similar exposure ratings, there was none between the As levels and the age of the donors. Preventive measures against direct exposure to the chemicals, such as wearing of gloves and gas masks at work, should be maintained.
ACKNOWLEDGEMENTS The author wishes to express his profound gratitude to the donors of the hair and nail samples for their co-operation, the management of Bendel wood treatment factory for granting permission to carry out this survey and Mr A. Osazuwa, the wood chemist, for his assistance throughout this investigation. The use of the UCI TRIGA Mark I nuclear reactor and other facilities is also acknowledged.
REFERENCES Bate, L. C. & Dyer, F. F. (I 965). Trace elements in human hair. Nucleonics, 23, 72 6. Boylen, G. W. & Hardy, H. L. (1967). Distribution of arsenic in non-exposed persons (hair. liver and urine). J. Am. Ind. Hvg. Ass., 28, 148-50. Chattopadhyay, A., Roberts, T. M. & Jervis, R. E. (1977). Scalp hair as a monitor of community exposure to lead. Arch. environ. Hlth, 32, 226-36. Fergusson, J. E., Hibbard, K. A. & Ting, R. L. H. (1981). Lead in human hair: General survey--Battery factory employees and their families. Environ. Pollut. (Ser. B), 2, 235 48.
Arsenic in human hair
105
Forslev, A. W. (1966). Nondestructive neutron activation analysis of hair. J. Forensic Sei., 11, 217-32. Gordus, A. (1973). Factors affecting the trace metal content of human hair. J. Radioanal. Chem., 15, 229-43. Hammer, D. I., Finklea, J. F., Hendricks, R. H., Shy, C. M. & Horton, R. J. M. (1971). Hair trace metal levels and environmental exposure. Am. J. Epidemiol., 93, 84-92. Harrison, W. W., Yurachek, J. P. & Benson, C. A. (1969). The determination of trace elements in human hair by atomic absorption spectroscopy. Clin. Chem. Acta., 23, 83 91. Kopito, L., Byers, R. K. & Shwachman, H. (1967). Lead in hair of children with chronic lead poisoning. New Engl. J. Med., 276, 949 53. Kyle, R. A. & Pease, G. L. (1966). Hematologic aspects of arsenic intoxication. New Engl. J. Med., 273, 18 23. Perkons, A. K. & Jervis, R. E. (1962). Application of radioactivation analysis in forensic investigations. J. Forensic Sei., 7, 449-64. Petering, H. C., Yeager, D. W. & Witherup, S. O. (1973). Trace metal content of hair. I1. Cadmium and lead in human hair in relation to age and sex. Arch. environ. Hlth, 27, 327 30. Renshaw, G. D., Pounds, C. A. & Pearson, E. F. (1972). Variation in lead concentration along single hairs as measured by non-flame atomic absorption spectrophotometry. Nature, Lond., 238, 162 3. Schroeder, H. A. & Balassa, J. J. (1966). Abnormal trace metals in man: Arsenic. J. chron. Dis., 19, 85-106. Schroeder, H. A. & Nason, A. P. (1969). Trace metals in human hair. J. invest. Dermatol., 53, 71 8. Shapiro, H. A. (1967). Arsenic content of human hair and nails and its interpretations. J. Forensic Med., 14, 65 71. Valkovic, V., Rendic, D. & Phillips, G. C. (1975). Elemental ratios along human hair as indicators of exposure to environmental pollutants. Environ. Sci. & Teehnol., 9, 1150 2. Vallee, B. L., Ulmer, D. D. & Wacker, W. E. C. (1960). Arsenic toxicology and biochemistry. Arch. Ind. Hlth, 21, 132 51.
A Survey of Arsenic Levels in Human Hair and Nails--Exposure of Wood Treatment Factory Employees in Nigeria
Ch. L. N d i o k w e r e Chemistry Department, University of Benin, Benin City, Nigeria
ABSTRACT Arsenic levels have been determined in the hair and nails of male employees of a wood preservative treatment factory in Nigeria. Mean As concentrations of 11.6, 7.5, 4.1 and 1.6pgg-1 were measured in hair samples from four groups of employees, depending on the nature of their work and the duration of their employment in the factory. Mean As levels of 7.4, 4.8, 2.7 and 1.0 I~g g-1 were also measured in nails for the same groups. The employees involved in the preparation of the treating fluids, the chemical impregnation process and handling of the treated timber showed consistently higher As levels in both tissues than those who were less exposed to the chemicals. No correlation between the measured As levels and age of the donors was established, nor was a reasonably good hair As-nail As correlation obtained for an)' of the four exposure groups. This study, however, minimized possible effects of age, sex, hair colour and chemical treatment. Mean As levels of 1.2 and 0.64ltgg -~ as 'control' values were also determined in hair and nails, respectively of 'non-exposed' persons in the same age group as the factory workers. The elevated As levels measured in both tissues reflected a relatively high degree of exposure to the chemicals. 95 Environ. Pollut. Ser. B. 0143-148X/85/$03' 30 © Elsevier Applied Science Publishers Ltd, England, 1985. Printed in Great Britain
96
Ch. L. Ndiokwere
INTRODUCTION
Human tissues such as hair and nails, as well as body fluids, are increasingly considered as useful monitors for environmental exposure to some toxic heavy metals. Some authors (Kopito et al., 1967; Renshaw et al., 1972; Petering et al., 1973; Valkovic et al., 1975; Chattopadhyay et al., 1977; Fergusson et al., 1981) have explored the quantitative analysis of lead in scalp hair as an aid in the clinical diagnosis of chronic or acute lead poisoning. Some trace metals have also been measured in hair and nails (Schroeder & Balassa, 1966; Harrison et al., 1969: Schroeder & Nason, 1969: Hammer et al., 1971; Gordus, 1973). Boylen & Hardy (1967) studied the distribution of As in hair, liver and urine of nonexposed persons. The analysis of human hair and nails for trace elements has also been extended to forensic investigations (Perkons & Jervis, 1962; Forslev, 1966; Shapiro, 1967). Since hair and nails accumulate trace elements for longer periods and are metabolically inert, the tissues may serve as important indicators for occupational exposure to heavy metal pollutants which can be toxic to humans. Also, the use of hair and nails for such analyses, rather than urine or blood, as has been the convention in poisoning incidents and similar studies, has the advantage of facilitating specimen collection and storage. In contrast with blood and urine, which normally must be collected by specialists under very careful conditions to avoid contamination, samples of hair and nails can easily be collected by unskilled personnel. The treatment of wood for long-term protection from attack by fungi and insects such as termites is usually effected by impregnation with a mixture of solutions of salts of arsenic, chromium and copper. The workers handling the mixed solutions in vacuum-pressure cylinders and treated timber may be directly exposed to the fumes of these chemicals. In this investigation, the study population consisted mainly of the male employees of the wood treatment factory in Benin City. There has been much concern about the possible hazards of these chemicals to the employees of the factory and to its environs. Arsenic compounds, in particular, are known to be toxic to plants and humans (Vallee et al., 1960: Kyle & Pease, 1966) and so it was important to ascertain if any significant contamination of the environment by the chemicals had occurred. This quantitative analysis of the tissues for As may therefore
Arsenic in human hair
97
afford an opportunity for monitoring As levels, which may reflect its abnormal concentrations in the body after exposure to the metal.
MATERIALS AND M E T H O D
Sampling Samples of hair were taken with stainless steel clippers from 46 male employees (aged 23 to 54 years) of the Bendel wood treatment factory, Benin City. The information supplied by the donors showed that most of the scalp hair samples had not been dyed or bleached. Only in a few cases had the donors from time to time dyed their grey hair. In some cases, the samples consisted of mixtures of black and grey hair. Each sample mixture was, however, treated as a unit for the purpose of this analysis. The hair samples were stored in polyethylene bags and identified with the age of donor, duration of employment and nature of work in the factory. Samples of finger nails were mostly obtained from the same donors who supplied the hair. The nail clippings were cut with stainless steel nail cutters and preserved in polyethylene capsules. Specimens of hair and nails to serve as ~controls' were similarly obtained from 15 supposedly non-exposed male residents of Benin City in the same age group as the factory employees. This was to establish normal As levels in the tissues. Difficulties were encountered in obtaining these samples because people in this part of the world are usually hesitant at giving such human tissues for non-clinical reasons.
Pretreatment of the samples Each hair sample was soaked in deionized water with stirring to remove any externally attached dust particles and other contaminants, which might also contain trace metals. After each wash, the water was decanted and the sample was further boiled for a few minutes, rinsed with deionized water and dried between clean filter papers. The sample was finally washed with CCI 4 by allowing a sufficient amount to cover the hair. This was necessary to remove any oils or greasy substances. The hair was thereafter rinsed with CC14 and air-dried. The nail samples were also briefly boiled and washed with deionized water and dried at 110 °C. The washing procedure was necessary also to ensure that salts of Na, K,
98
Ch. L. Ndiokwere
Mg and Ca, which are normally accumulated by these tissues during growth, were quantitatively removed. This would, in particular, minimize the effect of the 24Na Compton continuum on the counting of 76As activities after irradiation and interference by the 554keV photopeak of S2Br. A comparison between the As levels obtained for representative unwashed and washed hair and nail specimens showed that little or no As was lost during washing. Any differences were probably due to analytical precision, rather than to the pretreatment itself. This was in agreement with the observation of Bate & Dyer (1965) that the concentrations of some heavy metals in hair were not essentially affected by a similar washing procedure because of their great tendency to complex with the sulphydryl groups in the follicular proteins.
Analysis An accurately weighed hair sample was ashed in a muffle furnace at 450 °C for several hours until a white powder remained. The residue was dissolved in 2ml H N O 3 and carefully transferred into an irradiation capsule and heat-sealed. The dry weight of the samples ranged from 1.3 g to 3 g. The nail clippings were further cut into very small pieces, accurately weighed into irradiation capsules and similarly heat-sealed. The dry weight of the nail samples was between 0.1 g and 0.15 g. The samples and the comparator standards, prepared by dissolving accurately weighed As20 3 in HNO3, were irradiated simultaneously in the rotary specimen rack of the TRIGA Mark I nuclear reactor of the University of California, Irvine, for 3h at a thermal neutron flux of 1.0 × 10~2ncm-2s-1. After appropriate decay times the irradiated samples and standards were counted in the usual way using a 90cm 3 coaxial Ge(Li) detector connected to a 4096-channel pulse-height analyser. The As levels were calculated after corrections for decay and photopeak baselines were made. Replicate analyses of samples were always within + 4.6 10')J,~of the reported mean values. Both gamma-ray peaks 559keV and 657keV of 76As (t~/2--264h) were used for the measurement of As concentrations. RESULTS AND DISCUSSION The As levels measured in the hair and nails of the 46 male employees of the factory are presented in Table 1, which also shows the ages of the
Arsenic in human hair
99
donors and the duration of employment in the factory. The As levels in the same tissues from 15 'non-exposed' persons resident in Benin City are also presented in Table 2. The reported As levels represent mean values of two replicated analyses of each sample. The frequency distribution of As levels in the hair and nails of the four exposure groups is shown in Table 3. The mean concentrations have been calculated as 11.6, 7.5, 4.1 and 1.6/~gg -1 for exposure groups A, B, C and D, respectively. The frequencies have been modified because the hair and nail As concentration interval sizes were not constant. Histograms for the four exposure groups are given in Fig. 1. The two exposure groups, A and B, exhibited hair and nail As levels well above the concentration range measured for the 'control' group. At one time or another during the previous five years or more most of these highly exposed employees had been directly involved in the preparation of the solutions and in the impregnation processes. Moderately high levels of As occurred in 13 workers, who had also been associated with the chemicals and the treated timber, while 20 other workers appeared less exposed and maintained low levels of As in hair and nails. It is interesting to note that, in establishing the control, or normal, arsenic levels in human hair and nails, the results have shown that As levels within the age group of the non-exposed persons varied considerably (hair As: 0"34 2.1/~gg- 1 and nail As: 0"18- 1 . 4 # g g - 1). This indicated that the As levels were not necessarily dependent on the ages of the donors. Similarly. the As levels measured in hair and nails from the 46 factory employees could not be correlated with the age of the donors. The factory workers exposed to the chemicals could be distinguished by the following departures from the 'normal': (a) considerably high As levels in both tissues from the workers involved in the wood treatment processes, compatible with probable inhalation of the fumes from the chemicals and (b) similar and significantly elevated As levels in workers who had been associated with the treated timber, also indicating contact with the chemicals for some time. An attempt has been made in this study to correlate the hair As content with As level in the nails of the same persons. A graph of hair and nail As levels for three exposure groups, A and B, C, and D, is presented in Fig. 2. The hair and nail As levels for exposure groups A and B showed a weak correlation corresponding to a calculated correlation coefficient of - 0 . 2 4 . The correlation of As levels in both tissues for the 'intermediate' and 'low' exposure groups, C and D, respectively, is relatively good, corresponding
Ch. L. Ndiokwere
100
TABLE 1 Arsenic Levels Measured in Hair and Nails of Employees of a Wood Treatment Factory
Donor
Approx. age Approx. duration (years) o f employment (.years)
1
24
3
2 3 4 5 6 7 8 9 10
37 41 35 24 23 37 41 36 31
5 4 5 5 2 3 4 6 3
11
36
6
12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38
24 33 38 33 29 31 36 28 38 26 47 44 41 37 35 33 27 34 36 32 29 30 43 36 31 31 29
2 7 6 3 4 6 4 5 5 3 4 6 6 5 5 3 4 3 4 4 5 4 6 4 4 3 5
Arsenic level in hair (l~gg 1 dr)' weight)
Arsenic level in nails (l~gg i dry weight)
9.7 11 9.8 13 8.9 6.5 7-8 64 11 12 14 7.8 12 4.5 5'4 4-1 4.6 3.6 4-7 3.5 4-4 3.0 4.8 3.6 4.1 3.4 2.3 2.3 1.9 0-92 2.0 1-7 1.3 1.8 1-7 0.87 2.0 1.2
6.4 8.7 4"6 5.5 4.5 8.1 7.5 6-3 4"1 4-8 5-2 3.1 3.3 3.0 2'7 2"8 * 2-8 2.6 3~ 2.9 30 3-3 * * 3.4 3.2 2-7 1.1 0"37 064 1.3 1.3 0"46 0.87 I0 1.6 1.8
Arsenic in human hair TABLE 1
Donor
39 40 41 42 43 44 45 46
Approx. age Approx. duration (years) of employment ()'ears) 27 34 34 26 29 29 33 31
101
contd.
Arsenic level in hair (l~gg-1 dr)' weight)
Arsenic level in nails (#gg-1 do' weight)
1.8 1.5 1.9 1.3 2. I 1.1 1.8 1.4
0-94 1.2 1.5 0.88 * 1.1 1.3 1.6
4 6 5 3 4 5 5 4
* Nails could not be o b t a i n e d from the employees.
to the calculated correlation coefficients of -0-45 and 0.51, respectively. The weak correlation observed for exposure groups A and B indicated that persons exhibiting high hair As levels do not necessarily show elevated As levels in nails. Hair and nail As levels measured for donors 3, 4 TABLE 2 Arsenic Levels Measured in Hair a n d Nails of ~Non-exposed" Male Residents in Benin City
Donor
Approx. age (years)
Arsenic in hair (pgg i dry weight)
Arsenic in nails (pgg- 1 dry weight)
I 2 3 4 5 6 7 8 9 10 11 12 13 14 15
22 26 35 44 28 23 34 36 34 21 26 45 47 38 41
0.34 1.8 0.82 0.43 1.9 2.0 0.73 1.4 1.3 1.2 0-92 2.1 0.64 I-5 0-37
0.18 0.27 1.4 1.1 0.46 0.54 1.4 0-63 0.41 1.0 0-82 0.33 0.24 0-20 0.57
102
Ch. L. Ndiokwere
20
i5
a: hair
i0 0
o~ ~o
I
I
20
15
10 b: nails
--1
1 8
i'O
Arsenic ~oncentration
Fig. 1.
i'2
1'4
16
(~gg-l)
Frequency distribution of As levels in (a) hair and (b) nails for four exposure groups from a wood treatment factory.
and 9-13 are good examples. However, the tendency for persons exhibiting relatively high As levels in hair, especially in the case of exposure group C (Fig. 2), to show lower As levels in nails is noteworthy. The possibility of hazard due to direct exposure to high doses of the chemicals was further confirmed by the observation during sampling that most of the workers involved in the solution preparation and treatment processes were not wearing gloves or gas masks. This might account for the high As levels recorded in hair and nails from these workers. Although As is known to be highly toxic to humans, the levels measured in hair and
TABLE 3 Summaries of Arsenic Levels in Hair and Nails: Distribution According to Degree of Exposure
Human Exposure rating tissue
Hair
Nails
A B C D E A B C D E
Number of persons
Highest High Intermediate Low Non-exposed Highest High Intermediate Low Non-exposed
Arsenic level Mean Standard deviation range (#gg-l) (izgg-,) (pgg-1)
8 5 13 20 15 5 6 18 13 15
9.7-14.0 6.4-9.0 3.0-5-4 0.85-2.3 0.34-2.1 6.3 8-7 4.1-5.5 1.5 3.8 0-37 1-3 0.18 1.4
11.6 7.5 4.1 1.6 1.2 7.4 4.8 2.7 1.0 0.64
i-4 1.0 0.7 0.4 0-6 1-0 0.5 0.7 0.3 0.4
16¸
14.
Q
12~ Q
0
IC~ Q
0
0
~8 e
0
7 @ ~U
2
-.o.-
As level
Fig. 2.
in Nails
(~gg-l)
Hair arsenic nail arsenic correlation. Q, exposure groups A and B. x, exposure group C. Q, exposure group D.
104
Ch. L. Ndiokwere
nails could not be associated with any toxic effects on the affected workers. Possible subclinical biochemical abnormalities and other health effects as a result of increased As burden in the body should be further investigated. There is, as yet, no evidence that hair and nail As levels reflect the total As burden in the body.
CONCLUSIONS The relatively high As levels measured in hair and nails were mainly due to exposure to the chemicals used for the treatment of wood. Since these tissues are readily available and easy to obtain, the analysis may provide a convenient means of monitoring abnormal levels of As in the body. While a good correlation existed between the As levels and duration of employment for the workers with almost similar exposure ratings, there was none between the As levels and the age of the donors. Preventive measures against direct exposure to the chemicals, such as wearing of gloves and gas masks at work, should be maintained.
ACKNOWLEDGEMENTS The author wishes to express his profound gratitude to the donors of the hair and nail samples for their co-operation, the management of Bendel wood treatment factory for granting permission to carry out this survey and Mr A. Osazuwa, the wood chemist, for his assistance throughout this investigation. The use of the UCI TRIGA Mark I nuclear reactor and other facilities is also acknowledged.
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105
Forslev, A. W. (1966). Nondestructive neutron activation analysis of hair. J. Forensic Sei., 11, 217-32. Gordus, A. (1973). Factors affecting the trace metal content of human hair. J. Radioanal. Chem., 15, 229-43. Hammer, D. I., Finklea, J. F., Hendricks, R. H., Shy, C. M. & Horton, R. J. M. (1971). Hair trace metal levels and environmental exposure. Am. J. Epidemiol., 93, 84-92. Harrison, W. W., Yurachek, J. P. & Benson, C. A. (1969). The determination of trace elements in human hair by atomic absorption spectroscopy. Clin. Chem. Acta., 23, 83 91. Kopito, L., Byers, R. K. & Shwachman, H. (1967). Lead in hair of children with chronic lead poisoning. New Engl. J. Med., 276, 949 53. Kyle, R. A. & Pease, G. L. (1966). Hematologic aspects of arsenic intoxication. New Engl. J. Med., 273, 18 23. Perkons, A. K. & Jervis, R. E. (1962). Application of radioactivation analysis in forensic investigations. J. Forensic Sei., 7, 449-64. Petering, H. C., Yeager, D. W. & Witherup, S. O. (1973). Trace metal content of hair. I1. Cadmium and lead in human hair in relation to age and sex. Arch. environ. Hlth, 27, 327 30. Renshaw, G. D., Pounds, C. A. & Pearson, E. F. (1972). Variation in lead concentration along single hairs as measured by non-flame atomic absorption spectrophotometry. Nature, Lond., 238, 162 3. Schroeder, H. A. & Balassa, J. J. (1966). Abnormal trace metals in man: Arsenic. J. chron. Dis., 19, 85-106. Schroeder, H. A. & Nason, A. P. (1969). Trace metals in human hair. J. invest. Dermatol., 53, 71 8. Shapiro, H. A. (1967). Arsenic content of human hair and nails and its interpretations. J. Forensic Med., 14, 65 71. Valkovic, V., Rendic, D. & Phillips, G. C. (1975). Elemental ratios along human hair as indicators of exposure to environmental pollutants. Environ. Sci. & Teehnol., 9, 1150 2. Vallee, B. L., Ulmer, D. D. & Wacker, W. E. C. (1960). Arsenic toxicology and biochemistry. Arch. Ind. Hlth, 21, 132 51.