The influence of color, age, and sex on the content of zinc, copper, nickel, manganese, and lead in human hair

A State-of-the-Science Review on Metal Biomarkers

PURPOSE OF REVIEW

Biomarkers are commonly used in epidemiological studies to assess metals and metalloid exposure and estimate internal dose, as they integrate multiple sources and routes of exposure. Researchers are increasingly using multi-metal panels and innovative statistical methods to understand how exposure to real-world metal mixtures affects human health. Metals have both common and unique sources and routes of exposure, as well as biotransformation and elimination pathways. The development of multi-element analytical technology allows researchers to examine a broad spectrum of metals in their studies; however, their interpretation is complex as they can reflect different windows of exposure and several biomarkers have critical limitations. This review elaborates on more than 500 scientific publications to discuss major sources of exposure, biotransformation and elimination, and biomarkers of exposure and internal dose for 12 metals/metalloids, including 8 non-essential elements (arsenic, barium, cadmium, lead, mercury, nickel, tin, uranium) and 4 essential elements (manganese, molybdenum, selenium, and zinc) commonly used in multi-element analyses.

RECENT FINDINGS

We conclude that not all metal biomarkers are adequate measures of exposure and that understanding the metabolic biotransformation and elimination of metals is key to metal biomarker interpretation. For example, whole blood is a good biomarker of exposure to arsenic, cadmium, lead, mercury, and tin, but it is not a good indicator for barium, nickel, and uranium. For some essential metals, the interpretation of whole blood biomarkers is unclear. Urine is the most commonly used biomarker of exposure across metals but it should not be used to assess lead exposure. Essential metals such as zinc and manganese are tightly regulated by homeostatic processes; thus, elevated levels in urine may reflect body loss and metabolic processes rather than excess exposure. Total urinary arsenic may reflect exposure to both organic and inorganic arsenic, thus, arsenic speciation and adjustment for arsebonetaine are needed in populations with dietary seafood consumption. Hair and nails primarily reflect exposure to organic mercury, except in populations exposed to high levels of inorganic mercury such as in occupational and environmental settings. When selecting biomarkers, it is also critical to consider the exposure window of interest. Most populations are chronically exposed to metals in the low-to-moderate range, yet many biomarkers reflect recent exposures. Toenails are emerging biomarkers in this regard. They are reliable biomarkers of long-term exposure for arsenic, mercury, manganese, and selenium. However, more research is needed to understand the role of nails as a biomarker of exposure to other metals. Similarly, teeth are increasingly used to assess lifelong exposures to several essential and non-essential metals such as lead, including during the prenatal window. As metals epidemiology moves towards embracing a multi-metal/mixtures approach and expanding metal panels to include less commonly studied metals, it is important for researchers to have a strong knowledge base about the metal biomarkers included in their research. This review aims to aid metals researchers in their analysis planning, facilitate sound analytical decision-making, as well as appropriate understanding and interpretation of results.

Comparative susceptibility of children and adults to neurological effects of inhaled manganese: A review of the published literature

BACKGROUND

Manganese (Mn) is neurotoxic in adults and children. Current assessments are based on the more extensive adult epidemiological data, but the potential for greater childhood susceptibility remains a concern. To better understand potential lifestage-based variations, we compared susceptibilities to neurotoxicity in children and adults using Mn biomarker data.

METHODS

We developed a literature search strategy based on a Population, Exposures, Comparators, and Outcomes statement focusing on inhalation exposures and neurological outcomes in humans. Screening was performed using DistillerSR. Hair biomarker studies were selected for evaluation because studies with air measurements were unavailable or considered inadequate for children. Studies were paired based on concordant Mn source, biomarker, and outcome. Comparisons were made based on reported dose-response slopes (children vs. adults). Study evaluation was conducted to understand the confidence in our comparisons.

RESULTS

We identified five studies evaluating seven pairings of hair Mn and neurological outcomes (cognition and motor effects) in children and adults matched on sources of environmental Mn inhalation exposure. Two Brazilian studies of children and one of adults reported intelligent quotient (IQ) effects; effects in both comparisons were stronger in children (1.21 to 2.03-fold difference). In paired analyses of children and adults from the United States, children exhibited both stronger and weaker effects compared to adults (0.37 to 1.75-fold differences) on postural sway metrics.

CONCLUSION

There is limited information on the comparative susceptibility of children and adults to inhaled Mn. We report that children may be 0.37 to 2.03 times as susceptible as adults to neurotoxic effects of Mn, thereby providing a quantitative estimate for some aspects of lifestage variation. Due to the limited number of paired studies available in the literature, this quantitative estimate should be interpreted with caution. Our analyses do not account for other sources of inter-individual variation. Additional studies of Mn-exposed children with direct air concentration measurements would improve the evidence base.

Direct digestion of human scalp hair on the substrate used for total reflection X-ray fluorescence analysis

It is important to determine the elemental content of scalp hair to evaluate human health and environmental contamination. Here, a new sample preparation method for total reflection X-ray fluorescence analysis was developed by directly digesting the human hair on the sample holder. A human hair sample was subjected to thermal nitric acid treatment for sample digestion and homogenization. The Zn concentration was estimated to be ~ 1.89 × 10² μg/g. We can evaluate other elements of human hair by using this method.

Determination of scalp hair selenium concentrations in Algerian psoriatic individuals using k 0 -standardization based on neutron activation analysis method

Psoriasis is a dermatological disease that affects 2–3% of the Algerian population. Selenium has a positive impact on psoriasis. Selenium plays an important role in protecting free radical damage as a component of the glutathione peroxidase enzyme. The objective of this investigation was to assess the status of selenium in the hair of Algerian patients suffering from psoriasis. Fifty-eight scalp hair samples were collected from Algerian patients with psoriasis, classified by gender and four age groups: 36 females and 22 males, aged between 9 and 79 years. Thirty healthy subjects aged 9–74 years were also surveyed for control purposes. Selenium content was measured for all scalp hair samples using the k 0-standardization of neutron activation analysis. The average selenium concentration for controls and patients were 0.39 ± 0.18 and 0.28 ± 0.13 μg/g respectively. Selenium concentration for female and male controls and patients, were 0.35 ± 0.17, 0.47 ± 0.19, 0.28 ± 0.14, and 0.28 ± 0.11 μg/g, respectively. There is a significant difference (p < 0.05) between selenium level in patients and in controls. Selenium concentrations in psoriatics’ scalp hair can be affected by both gender and age. Measured selenium contents have been approved by the quality assurance and quality control procedure (QA/QC).

Age- and sex-dependence of five major elements in the development of human scalp hair

Background

Human scalp hair is composed of bio-synthesized protein that stores and excretes excess elements from the body. Thus, the concentration of major and trace elements in the hair may provide insight into both the physiology and health status of humans. Monitoring of health status by hair analysis is limited by the uncertainty surrounding natural changes in composition based on age and sex parameters.

Methods

A total of 322 hair samples from subjects aged 0–89 years were collected and analyzed to determine their sulfur, calcium, magnesium, zinc, and copper concentrations by inductively coupled plasma mass spectrometry. The age- and sex-dependence of the concentrations of these elements within scalp hair was evaluated. Age-dependence was analyzed by least squares fitting of the data from young people (up to 25 years old). Sex-dependence was evaluated by comparing the average element concentrations of males and females in each age groups.

Results

The concentration of mineral elements increased with age up to 25 years old. Calcium and magnesium contents were strongly affected by age, whereas the effects were weaker for zinc and copper. In participants over 20 years old, sex and the concentrations of calcium and magnesium were significantly associated. The concentrations of these elements were higher in most of the subgroups of adult women. The concentrations of sulfur, zinc, and copper were not significantly associated with age or sex.

Conclusions

The concentrations of major inorganic elements in scalp hair showed an increasing trend up to 25 years of age, and a strong sex dependence of calcium and magnesium concentrations in the subjects older than 20 years. More research is needed to understand the physiology of calcium and magnesium excretion though scalp hair.

Dietary Manganese Exposure in the Adult Population in Germany-What Does it Mean in Relation to Health Risks?

Manganese is both an essential nutrient and a potential neurotoxicant. Therefore, the question arises whether the dietary manganese intake in the German population is on the low or high side. Results from a pilot total diet study in Germany presented here reveal that the average dietary manganese intake in the general population in Germany aged 14-80 years is about 2.8 mg day^-1 for a person of 70 kg body weight. This exposure level is within the intake range of 2-5 mg per person and day as recommended by the societies for nutrition in Germany, Austria, and Switzerland. No information on the dietary exposure of children in Germany can be provided so far. Although reliable information on health effects related to oral manganese exposure is limited, there is no indication from the literature that these dietary intake levels are associated with adverse health effects either by manganese deficiency or excess. However, there is limited evidence that manganese taken up as a highly bioavailable bolus, for example, uptake via drinking water or food supplements, could pose a potential risk to human health-particularly in certain subpopulations-when certain intake amounts, which are currently not well defined, are exceeded.

Hair geochemical composition of children from Vilnius kindergartens as an indicator of environmental conditions

The research is based on analysis data of Cr, Cu, Mn, Ni, V, Zn (metals) and S in the hair of 47 girls and 63 boys from eight Vilnius kindergartens and the distribution pattern of high metal concentrations and bioavailability in snow-cover dust, also dust samples from vents of characteristic pollution sources. The kindergartens were selected according to topsoil total contamination index and dust-related indices. Significantly higher Cu, Mn, Ni and Zn concentrations in the hair of girls (means are 1.1, 1.9, 1.3, 1.2 times higher) and the differences between hair of genders according to inter-element correlation and clustering were found. Analysis of Spearman correlation coefficients between metal concentrations in hair of each gender and dust metal concentrations or metal loading rates at their residence sites revealed that for Mn, Cu and Zn, they are insignificant, while for Cr, Ni, Pb and V, they are mainly significant positive (except V in female hair). The correlation of the contents of Cr, Ni and V in dust with respective concentrations in hair was more significant for boys (p < 0.001) than for girls. Only a few cases with a significant Cr, Ni, Cu, Pb and Zn increase were revealed in hair of children attending polluted kindergartens in comparison with control. It was concluded that relationship between metal concentrations in hair and dust-related indices is more expressed for children's residence sites than for their kindergarten sites. The gender-based grouping and site-by-site study design are recommended in the studies of reflection of environmental exposure in hair.

Hair Zinc: an Index for Zinc Status in Under-Five Children from Low-Income Communities in Kanam Area of North-Central Nigeria

Nutritional deficiencies of trace elements are among the top ten causes of death in Sub Saharan Africa. In Kanam Local Government Area of Nigeria, the problem is compounded by high levels of poverty and illiteracy. Abnormally low hair zinc levels are important, sensitive diagnostic biochemical indices of Zinc deficiency. The purpose of this study is to assess the zinc status of children less than 5 years in Kanam local government area, north-central Nigeria, by measuring the zinc level in hair samples collected from 44 under-5 children across the area. A household survey was made to assess the pattern and frequency of consumption of zinc-rich foods which was done by means of questionnaire. Hair samples were analysed for zinc content by the inductively coupled plasma-mass spectrophotometry (ICP-MS). The data were analysed statistically using the Student's t test, z test, and Pearson correlation, while questionnaire-captured data were analysed by simple arithmetic. The results of the analyses showed that the average hair zinc level was 74.35 ± 48.05 μg/g. This was below the normal range of 130-140 μg/g, for children less than 5 years. Based on the results, 86.36% have hair zinc level below the lower limit of the normal range of 130 μg/g. Between the gender, boys have higher hair zinc content than girls. Data from the questionnaire showed that 53.45% of the population studied have poor/inadequate intake of zinc-rich foods of animal origin, a dietary behaviour reported to predispose to micronutrient deficiency, including zinc.

Assessment of gender and age effects on serum and hair trace element levels in children with autism spectrum disorder

The primary objective of the present study was to investigate the levels of essential trace elements in hair and serum in children with autism spectrum disorder (ASD) and investigate the age and gender effects. Children with ASD were characterized by significantly higher levels of copper (Cu) (+8%), iron (Fe) (+5%), and selenium (Se) (+13%) levels in hair and only 8% higher serum Cu levels. After stratification for gender, ASD boys were characterized by significantly increased hair Cu (+ 25%), Fe (+ 25%), and Se (+ 9%) levels, whereas in girls only Se content was elevated (+ 15%). Boys and girls suffering from ASD were characterized by significantly higher serum manganese (Mn) (+20%) and Cu (+18%) as compared to the control values, respectively. In the group of younger children (2-5 years), no significant group difference in hair trace element levels was detected, whereas serum Cu levels were significantly higher (+7%). In turn, the serum concentration of Se in ASD children was 11% lower than that in neurotypical children. In the group of older children with ASD (6-10 years), hair Fe and Se levels were 21% and 16% higher, whereas in serum only Cu levels were increased (+12%) as compared to the controls. Correlation analysis also revealed a different relationship between serum and hair trace element levels with respect to gender and age. Therefore, it is highly recommended to assess several bioindicative matrices for critical evaluation of trace element status in patients with ASD in order to develop adequate personalized nutritional correction.

Gender as a key factor in trace metal and metalloid content of human scalp hair. A multi-site study

This multi-site study discusses the content of metals and metalloids (MM) in scalp hair of children, living in different environmental contexts, with the purpose of verifying if hair level of some MM is distinctively gender-specific. A total of 943 hair samples (537 females and 406 males) from adolescents were analyzed for their content of Al, As, Ba, Cd, Co, Cr, Cu, Li, Mn, Mo, Ni, Pb, Rb, Sb, Se, Sr, U, V and Zn. Elemental quantification was performed by ICP-MS. The obtained data identified different metal distributions in adolescent girls which exhibited significantly higher hair concentrations of some trace metals, especially Sr, Zn and Ni, than boys. On the base of the median value, hair of female donors contained 3.8 times more Sr (6.6μg/g) than males (1.7μg/g). Highest concentrations of Zn in females were observed in samples from the mining area of Sardinia (587μg/g). Nickel showed significant differences resulting 2.5-fold higher in female hair. Regardless of the residence site, these elements resulted always significantly different (at p<0.01) between female and male indicating that gender is a confounding factor that has to be more extensively considered for a correct interpretation of metal profiles in human hair.

Age-related differences in hair trace elements: a cross-sectional study in Orenburg, Russia

BACKGROUND

Age-related differences in the trace element content of hair have been reported. However, some discrepancies in the data exist.

AIM

The primary objective of this study was to estimate the change in hair trace elements content in relation to age.

SUBJECTS AND METHODS

Six hundred and eighteen women and 438 men aged from 10-59 years took part in the current cross-sectional study.

RESULTS AND CONCLUSIONS

Hair Cr, Mn, Ni, Si, Al, As, Be, Cd and Pb tended to decrease with age in the female sample, whereas hair Cu, Fe, I, Se, Li and Sn were characterised by an age-associated increase. Hair levels of Cr, Cu, I, Mn, Ni, Si and Al in men decreased with age, whereas hair Co, Fe, Se, Cd, Li and Pb content tended to increase. Hair mercury increased in association with age in men and in women, whereas hair vanadium was characterised by a significant decrease in both sexes. The difference in hair trace element content between men and women decreased with age. These data suggest that age-related differences in trace element status may have a direct implication in the ageing process.

Manganese and selenium concentrations in umbilical cord serum and attention deficit hyperactivity disorder in childhood

Existing evidence on the effects of manganese and selenium during fetal life on neurodevelopmental disorders is inadequate. This study aims to investigate the hypothesized relationship between fetal exposure to manganese and selenium and attention deficit hyperactivity disorder (ADHD) diagnosis in childhood. Children born between 1978 and 2000 with ADHD (n=166) were identified at the Department of Child and Adolescent Psychiatry in Malmö, Sweden. Controls from the same region (n=166) were selected from the Medical Birth Register and were matched for year of birth and maternal country of birth. Manganese and selenium were measured in umbilical cord serum. The median cord serum concentrations of manganese were 4.3μg/L in the cases and 4.1μg/L in the controls. The corresponding concentrations of selenium were 47 and 48μg/L. When the exposures were analyzed as continuous variables no associations between cord manganese or selenium concentration and ADHD were observed. However, children with selenium concentrations above the 90th percentile had 2.5 times higher odds (95% confidence interval 1.3-5.1) of having ADHD compared to those with concentrations between the 10th and 90th percentiles. There was no significant interaction between manganese and selenium exposure (p=0.08). This study showed no association between manganese concentrations in umbilical cord serum and ADHD. The association between ADHD diagnoses in children with relatively high cord selenium was unexpected and should be interpreted with caution.

Association of hair manganese level with symptoms in attention-deficit/hyperactivity disorder

OBJECTIVE

The study examined the association between hair manganese level and symptoms of attention-deficit/hyperactivity disorder (ADHD) in Korean children.

METHODS

Forty clinic-referred children with ADHD and 43 normal control children participated in this study. The participants were 6-15 years old and were mainly from the urban area of Seoul, Korea. ADHD was diagnosed using the Diagnostic and Statistical Manual of Mental Disorders, 4th edition and Kiddie-Schedule for Affective Disorders and Schizophrenia-Present and Lifetime Version-Korean Version. The severity and symptoms of ADHD was evaluated according to the ADHD Diagnostic System, and parent's Korean ADHD Rating Scale (K-ARS). All participants completed intelligence test and hair mineral analysis. We divided the data of hair Mn into two groups to determine whether a deficit or excess of Mn are associated with ADHD. Multiple logistic regression analyses were performed to identify hair manganese levels associated with ADHD, controlling for age, sex, and full scale intelligence quotient (IQ).

RESULTS

The proportion of abnormal range Mn group was significantly high in ADHD compared to controls. However, after statistical control for covariates including age and sex, abnormal range Mn group was significantly associated with ADHD (OR=6.40, 95% CI=1.39-29.41, p=0.017).

CONCLUSION

The result of this study suggests that excess exposure or deficiency of Mn were associated with ADHD among children in Korea. Further investigation is needed to evaluate the effects of hair manganese levels on symptoms in ADHD.

Significance and Usefulness of Biomarkers of Exposure to Manganese

Manganese (Mn) accomplishes functions essential to maintaining human health, but at the same time this trace element can be toxic at low levels of exposure and accurate estimation of internal exposure is needed. A biomarker of exposure to Mn is meaningful only if there is sufficient knowledge of the toxicokinetics determining its presence in a biological medium (e.g. whole blood, plasma, urine, hair, nail). Moreover, biological monitoring of exposure to Mn is useful only when the biomarker is sufficiently specific and sensitive to distinguish exposed from non-exposed subjects, when it is dose-related to the external exposure (current, recent, or time-integrated), and when it displays reasonable dose–effect/response relationships with the occurrence of adverse effects on the central nervous system, the critical target for Mn exposure. Human investigations in which biomarkers of Mn exposure meet all these criteria are hard to locate. Overall, the available studies report poor or no associations on an individual basis between external (Mn in air or drinking water) and internal (Mn in blood, urine, hair, or nail) Mn exposure indices. This may be to some extent explained by features inherent of the Mn metabolism (homeostatic control), the Mn biomarker's half-life with respect to the exposure window, and the variable nature of external exposure scenarios. Studies particularly dealing with Mn inhalation exposure, different or poorly described methodological approaches, or air sampling strategies may render direct comparison and interpretation of results a tedious task. Nevertheless, several studies report significant dose–effect associations between biomarkers of Mn exposure and subclinical deficits of psychomotor or neuropsychological test performances. Because directly associated with the site of toxic action and providing the magnetic resonance imaging is done no later than three months after Mn exposure ceased, the Mn T1 relaxation time is potentially the better biomarker of Mn exposure in a clinical context (e.g. after long-term parenteral nutrition, chronic liver failure, methcathinone drug abuse). Magnetic resonance imaging is, however, unpractical as a tool for biological monitoring of exposure to Mn in the occupational setting (inhalation) and in the general population (air, drinking water). In conclusion, it would be inappropriate to recommend, on the basis of the currently available evidence, a reliable well-validated biomarker of exposure to Mn, or to establish a health-based threshold value for subclinical neurotoxic effects.

Biomonitorization of chromium, copper, iron, manganese and nickel in scalp hair from orthodontic patients by atomic absorption spectrometry

The study was aimed to assess Cu, Cr, Fe, Mn and Ni levels in human scalp hair from a broad population group treated with orthodontic appliances (n=70) to determine, whether the concentration of a given metal was significantly influenced by the orthodontic treatment in comparison to control group (n=56). Levels of metal compounds were determined by atomic absorption spectrometry. The mean, ranges, median and 5th and 95th percentiles of metals analyzed in hair that were hypothesized to be systemically absorbed from stainless steel, are provided. The influence of individual factors on metal concentrations was considered (gender, age), and inter-element interactions were studied by evaluation of correlation coefficients between elements, as well as by multiple regression analysis. Differences in the content of metals in hair were only significantly increased for Mn when compared to the control group, but their levels were of the same magnitude to other control populations, and consequently, no risks linked to the treatment have been found. The orthodontic treatment increased significantly Mn levels in young patients (<20 years old) when compared with control group. Scalp hair analysis is a good method to investigate the release of the elements from fixed orthodontic appliances.

Trace elements in scalp hair of children chronically exposed to volcanic activity (Mt. Etna, Italy)

The aim of this survey was to use scalp hair as a biomonitor to evaluate the environmental exposure to metals and metalloids of schoolchildren living around the Mt. Etna area, and to verify whether the degree of human exposure to trace elements is subject to changes in local environmental factors. Twenty trace elements were determined in 376 samples of scalp hair from schoolboys (11-13 years old) of both genders, living in ten towns located around the volcanic area of Mt. Etna (Sicily). The results were compared with those (215 samples) from children living in areas of Sicily characterized by a different geological setting (reference site). As, U and V showed much higher concentrations at the volcanic site whereas Sr was particularly more abundant at the reference site. Linear Discriminant Analysis (LDA) indicated an Etna factor, made up of V, U and Mn, and a second factor, concerning the reference site, characterized by Ni and Sr, and to a lesser extent by Mo and Cd. Significant differences in element concentrations were also observed among three different sectors of Mt. Etna area. Young people living in the Mt. Etna area are naturally exposed to enhanced intakes of some metals (V, U, Mn) and non-metals (e.g., As) than individuals of the same age residing in other areas of Sicily, characterized by different lithologies and not influenced by volcanic activity. The petrographic nature of local rocks and the dispersion of the volcanic plume explain the differences, with ingestion of water and local food as the most probable exposure pathways.

Serum iron, zinc, and copper concentration in premature graying of hair

Premature graying of hair with unclear etiology, which is known as premature canities, is a common cause of referrals to the dermatologists. We assessed the relationship between serum iron, copper, and zinc concentrations with premature canities. This study was conducted on patients under 20 years old suffering from premature canities, having a minimum of ten gray hair fibers, and referring to university hospitals of Isfahan (Iran). The results were compared with age-sex-matched controls. Demographic data and disease characteristics were recorded for two groups. We studied serum iron, copper, and zinc concentrations of 66 patients and 66 controls using atomic absorption and Ferrozine methods. The mean age of studied cases was 17.8 ± 2.0 years, and the mean age of the onset of canities was 15.5 ± 3.2 years with no significant difference between males and females (P > 0.05). Serum copper concentration was significantly lower in patients compared with controls (90.7 ± 37.4 vs. 105.3 ± 50.2 μg/dL, P = 0.048), but serum iron concentration was significantly lower in controls compared to patients (88.8 ± 39.5 vs. 108.3 ± 48.4 μg/dL, P = 0.008). Also, there was no significant difference between patients and controls in serum zinc concentration (114.8 ± 67.8 vs. 108.2 ± 49.9 μg/dL, P = 0.285). According to these results, among copper, zinc, and iron, a low serum copper concentration may play a role in premature graying of hairs in our society. Further studies are needed to find the underlying mechanism of this relationship.

Identification of human age using trace element concentrations in hair and the support vector machine method

Trace element content in hair is affected by the age of the donor. Hair samples of subjects from four counties in China where people are known to have long lifespan ("longevity counties") were collected and the trace element content determined. Samples were subdivided into three age groups based on the age of the donors from whom these were taken: children (0-15 years); elderly (80-99 years); and centenarians (≥100 years). We compared the trace element content in hair of different age groups of subjects. Support vector machine classification results showed that a non-linear polynomial kernel function could be used to classify the three age groups of people. Age did not have a significant effect on the content of Ca and Cd in human hair. The content of Li, Mg, Mn, Zn, Cr, Cu, and Ni in human hair changed significantly with age. The magnitude of the age effect on trace element content in hair was in the order Cu > Zn > Ni > Mg > Mn > Cr > Li. Cu content in hair decreased significantly with increasing age. The hair of centenarians had higher levels of Li and Mn, and lower levels of Cr, Cu, and Ni comparing with that of the children and elderly subjects. This could be a beneficial factor of their long lifespan.

Exposure to metals from orthodontic appliances by hair mineral analysis

The aim of the present work was to investigate the exposure of patients to metals released from orthodontic appliances in situ. The paper reports the results of biocompatibility studies of orthodontic appliances by an in vivo method using hair sampled from the group of patients (N = 28) and a control group (N = 18). The mean content of metals (Ni, Cr, Mn, Fe) in hair that were hypothesized to be systemically absorbed from stainless steel, was provided. The highest difference between the groups was found for Ni (39% higher level in hair of patients), Mn (18%), Fe (4.1%), Cr (2.5%), as calculated by a new dimensionless metal release coefficient (α). The second coefficient defined in the present work (β) corresponded to the difference in the mean content of elements between the groups. The coefficient was the highest for Fe, subsequently Ni, Mn and Cr. None of the differences was statistically significant. For each group and a given element, ranges between 10th and 90th percentile were determined. The upper value of the range differed the mostly between the groups for Ni (82.5%) showing that stainless steel of orthodontic appliance can be the source of exposure to this element. The difference was also identified for Mn (26.5%). For Cr and Fe, the lower value of the range was elevated. It was noted that 22% of patients undergoing orthodontic treatment had elevated levels of Ni in hair. A correlation matrix between the content of the elements in hair was calculated. Statistically significant correlations were found between Cr and Fe, showing similar sources of exposure. Multiple regression analysis showed the dependence of Ni content (dependent variable) on the level of Co and Mg (synergism) and V (antagonism).

Concentration and reference interval of trace elements in human hair from students living in Palermo, Sicily (Italy)

Trace element contents in specimens of hair collected from 137 children aged 11-13 years old, living in Palermo (Sicily, Italy) were determined by ICP-MS. This work reports analytical data for the following 19 elements: Al, As, Ba, Cd, Co, Cr, Cu, Li, Mn, Mo, Ni, Pb, Rb, Sb, Se, Sr, U, V and Zn. The most abundant chemical elements were zinc and copper (Zn > Cu), with concentrations exceeding 10 μg/g (Zn = 189.2 μg/g; Cu = 22.9 μg/g). Other elements with concentrations greater than 1 μg/g were, in order of abundance, Al>Sr>Ba>Pb. The remaining elements were all below 1 μg/g. The average elemental concentrations in hair were statistically compared by Kolmogorov-Smirnov's test taking children's gender into account. Al, Ba, Cr, Li, Rb, Sb, Sr, V and Zn were statistically different according to gender, with significance p < 0.001. This study thus confirms the need for hair analysis to differentiate female data from those of males. IUPAC coverage intervals and coverage uncertainties for trace elements in the analysed hair samples are also reported.

Manganese and lead in children's blood and airborne particulate matter in Durban, South Africa

Despite the toxicity and widespread use of manganese (Mn) and lead (Pb) as additives to motor fuels and for other purposes, information regarding human exposure in Africa is very limited. This study investigates the environmental exposures of Mn and Pb in Durban, South Africa, a region that has utilized both metals in gasoline. Airborne metals were sampled as PM(2.5) and PM(10) at three sites, and blood samples were obtained from a population-based sample of 408 school children attending seven schools. In PM(2.5), Mn and Pb concentrations averaged 17±27 ng m(-3) and 77±91 ng m(-3), respectively; Mn concentrations in PM(10) were higher (49±44 ng m(-3)). In blood, Mn concentrations averaged 10.1±3.4 μg L(-1) and 8% of children exceeded 15 μg L(-1), the normal range. Mn concentrations fit a lognormal distribution. Heavier and Indian children had elevated levels. Pb in blood averaged 5.3±2.1 μg dL(-1), and 3.4% of children exceeded 10 μg dL(-1), the guideline level. Pb levels were best fit by a mixed (extreme value) distribution, and boys and children living in industrialized areas of Durban had elevated levels. Although airborne Mn and Pb concentrations were correlated, blood levels were not. A trend analysis shows dramatic decreases of Pb levels in air and children's blood in South Africa, although a sizable fraction of children still exceeds guideline levels. The study's findings suggest that while vehicle exhaust may contribute to exposures of both metals, other sources currently dominate Pb exposures.

Plasma zinc and hair zinc levels, anthropometric status and food intake of children in a rural area of Brazil

OBJECTIVE: The objective of this study was to investigate the levels of plasma zinc, hair zinc, growth and food consumption in children aged 6 to 24 months in a rural area of Diamantina (MG), Brazil. METHODS: Plasma and hair zinc concentrations were analyzed using flame atomic absorption spectrometry and neutron activation analysis, respectively. Weight-for-age, weight-for-height and height-for-age, expressed as Z-scores, were measured according to the World Health Organization reference curves. Dietary zinc intake was determined by a 3-day dietary recall filled out by the mother or guardian. RESULTS: Zinc deficiency was found in 11.2% and 16.8% of the children according to plasma zinc e hair zinc levels, respectively. Mean plasma zinc and hair zinc for children <11 (49) and >11 (127) months of age were 15.4 (SD=4.2) µmol L-1 and 139.5 (SD=72.1) µg g-1 and 16.0 (SD=4.5) µmol L-1 and 134.3 (SD=110.3) µg g-1, respectively. Anthropometric measurements showed that 8.0%, 6.8% and 3.4% of the children were underweight, stunted and wasted, respectively. The mean dietary intake of zinc was 3.2 (SD=2.3) mg/day. One-third of the children did not eat enough foods that contain zinc. There were no correlations among plasma zinc level, hair zinc level, anthropometric parameters and zinc intake. CONCLUION: The results demonstrate that zinc deficiency is a problem in the studied population, not just in malnourished children. Nutritional care should be provided for this population in order to improve their consumption of high-zinc foods and monitor zinc deficiency.

Calcium, magnesium, iron, zinc and copper concentration in the hair of tobacco smokers

In the research, the content of bioelements (Ca, Mg, Fe, Zn, and Cu) in the hair of individuals who reside in similar environmental conditions was spectrometrically determined with the use of AES-ICP spectrophotometer. The relation to their tobacco-smoking habit, age, and sex was established. It was observed that the results obtained were in the range of the content identified for the Polish population. Tobacco smokers had a decreased content of all the bioelements in question, compared to non-smokers, which apparently resulted from a decreased supply (lesser appetite) and reduced absorption caused by disturbances in the digestive system functions. Also, it has been observed that in the group of elderly people, over 50 years old, there was a fall in the content of calcium, magnesium, and iron both in smokers and non-smokers, irrespective of their sex. The sex-related differences in the content of the investigated elements were not unidirectional and only in few cases did they reveal statistical significance.

High levels of hair manganese in children living in the vicinity of a ferro-manganese alloy production plant

Manganese (Mn) is an essential element, but an effective toxic at high concentrations. While there is an extensive literature on occupational exposure, few studies have examined adults and children living near important sources of airborne Mn. The objective of this study was to analyze hair Mn of children living in the vicinity of a ferro-manganese alloy production plant in the Great Salvador region, State of Bahia, Brazil and examine factors that influence this bioindicator of exposure. We examined 109 children in the age range of 1-10 years, living near the plant. Four separate housing areas were identified a priori on the bases of proximity to the emission sources and downwind location. A non-exposed group (n=43) of similar socio-economic status was also evaluated. Mn hair (MnH) concentration was measured by graphite atomic absorption spectrometry (GFAAS). Possible confounding hematological parameters were also assessed. Mean MnH concentration was 15.20 microg/g (1.10-95.50 microg/g) for the exposed children and 1.37 microg/g (0.39-5.58 microg/g) for the non-exposed. For the former, MnH concentrations were 7.95+/-1.40 microg/g (farthest from the plant), 11.81+/-1.11 microg/g (mid-region), 34.43+/-8.66 microg/g (closest to the plant) and 34.22+/-9.15 microg/g (directly downwind). Multiple regression analysis on log transformed MnH concentrations for the exposed children derived a model that explained 36.8% of the variability. In order of importance, area of children's residence, gender (girls>boys) and time of mother's residence in the area at the birth of the child, were significantly associated with MnH. Post hoc analyses indicated two groupings for exposure areas, with those living closest to and downwind of the plant displaying higher MnH concentrations compared to the others. The contribution of the time the mother lived in the community prior to the child's birth to the children's current MnH suggests that in utero exposure may play a role. A study of neurobehavioral performance with respect to Mn exposure in these children is currently underway.

Relationship between hair elements and severity of atrioventricular block in horses

The aim of this study was to investigate the relationships between the mean concentrations of trace elements and the severity of the second-degree atrioventricular (AV) block in the mane hair of horses. Electrocardiographs of horses were continually recorded for 6 h using a holter cardiac monitor to determine dropped ventricular beats (DVBs) which can be used as an indicator of the severity of the AV block. Mane hair Ca, Cu, Mg, and Zn concentrations were measured by the particle-induced X-ray emission method. The Zn/Cu ratio and Ca concentration in mane hair were significantly and positively correlated with the hourly DVBs in horse with a second-degree AV block (p<0.01, r2=0.485; p<0.05, r2=0.351, respectively). Proposed diagnostic cutoff points for hair Ca concentration and Zn/Cu ratio based on receiver operating characteristics curves analysis in detecting second-degree AV block were set at 1536 microg/g and 26.0, respectively. Those results with horse hair suggest that the evaluation of the Ca, Cu, Mg, and Zn status in mane hair by this method is strongly related to the severity of second-degree AV block and might predict the susceptibility of an individual much before the development of the symptom.

Trace element level in infant hair and diet, and in the local environment of the Moroccan city of Marrakech

A sample of 573 infants (aged 0 to 12 months) from the Moroccan city of Marrakech was studied in order to determine the level of Pb and Al contaminations. Mean values of Pb and Al in children's hair were 6.6 and 9.5 microg/l, respectively. Age, gender, and parents' occupation influenced significantly Pb content but not Al content. Larger mean values were measured for Al compared with Pb. This finding can be explained by a higher level of Al available in both the infant diet (complementary feeding) and the local environmental factors (soil and drinking water). During weaning, beverages like tea, widely used in Morocco, represent an important source of Pb and Al contamination. Al content in drinking water is above the international standard.

Manganese dosimetry: species differences and implications for neurotoxicity

Manganese (Mn) is an essential mineral that is found at low levels in food, water, and the air. Under certain high-dose exposure conditions, elevations in tissue manganese levels can occur. Excessive manganese accumulation can result in adverse neurological, reproductive, and respiratory effects in both laboratory animals and humans. In humans, manganese-induced neurotoxicity (manganism) is the overriding concern since affected individuals develop a motor dysfunction syndrome that is recognized as a form of parkinsonism. This review primarily focuses on the essentiality and toxicity of manganese and considers contemporary studies evaluating manganese dosimetry and its transport across the blood-brain barrier, and its distribution within the central nervous system (CNS). These studies have dramatically improved our understanding of the health risks posed by manganese by determining exposure conditions that lead to increased concentrations of this metal within the CNS and other target organs. Most individuals are exposed to manganese by the oral and inhalation routes of exposure; however, parenteral injection and other routes of exposure are important. Interactions between manganese and iron and other divalent elements occur and impact the toxicokinetics of manganese, especially following oral exposure. The oxidation state and solubility of manganese also influence the absorption, distribution, metabolism, and elimination of manganese. Manganese disposition is influenced by the route of exposure. Rodent inhalation studies have shown that manganese deposited within the nose can undergo direct transport to the brain along the olfactory nerve. Species differences in manganese toxicokinetics and response are recognized with nonhuman primates replicating CNS effects observed in humans while rodents do not. Potentially susceptible populations, such as fetuses, neonates, individuals with compromised hepatic function, individuals with suboptimal manganese or iron intake, and those with other medical states (e.g., pre-parkinsonian state, aging), may have altered manganese metabolism and could be at greater risk for manganese toxicity.

Hair as a biopsy material: trace element data on one man over two decades

BACKGROUND

Hair mineral analyses are being performed frequently both with and without medical advice. Reasons for analysis often are ill defined.

OBJECTIVE

To assess variability of trace element data both within a series of samples from an individual and among mean values published from other research laboratories.

DESIGN

Many samples of hair were collected carefully from a healthy man over a comparatively long period of time and were processed and analyzed under standard conditions. Extensive published data from other research laboratories also were reviewed and compared.

RESULTS

Coefficients of variation for trace elements in hair of the donor ranged from 17 to 74% for the essential elements copper, selenium and zinc and from 53 to 121% for the potential intoxicants aluminum, cadmium and lead. The ratio of high mean to low mean for values published by others on hair samples from healthy people ranged from two for selenium and zinc to 18 for aluminum.

CONCLUSIONS

Hair analysis should be based on a diagnostic hypothesis such as cadmium intoxication or copper deficiency rather than on the ease of analysis or attempts to explain vague symptoms because within-person variability is large and interlaboratory agreement on normal values is poor.

Content of lead in human hair from people with various exposure levels in Lithuania

A study has been performed to estimate if hair lead (Pb) can be used assessing environmental and occupational exposure to the metal. From 1994-1997, 622 ceramic plant employees, 520 randomly selected controls from Kaunas without occupational exposure to Pb aged 18-64 years, and 380 10-13 year old children living in Kaunas participated in this study. The concentration of Pb in the hair samples was measured by atomic absorption spectrometry. The geometric mean of Pb in the hair of workers occupationally exposed to Pb was significantly higher than that in persons not exposed to the metal (7.6 microg/g, 95% CI = 6.5-8.7 for exposed workers, 3.2 microg/g, 95% CI = 2.8-3.6 for not exposed workers and 2.6 microg/g, 95% CI = 2.4-2.9 for randomly selected controls, p < 0.05). Pb content in hair of boys and girls was 2.9 microg/g (95% CI = 2.6-3.3) and 3.1 microg/g (95% CI = 2.6-3.6), respectively. Lead in hair was not related to gender. Multiple regression analysis in adults with age as a continuous variable showed a positive relationship between Pb in hair and age. Also different exposure levels were significantly related to Pb in hair. In men, a positive association was found between Pb in hair and smoking. The data obtained suggest that human hair could be used to identify lead exposure in epidemiological surveys.

Parameters of evaluation of zinc nutritional status: comparison between zinc hair rates and serum alkaline phosphatase in pre-scholars of the Municipality of João Pessoa, Paraíba

OBJECTIVES: to evaluate the nutritional status of zinc in children from two to five years old, institutio-nalised in daycare centers in the Municipality of João Pessoa, Paraíba. METHODS: a systematic random sample comprised of 377 children. The nutritional status of zinc was evaluated according to the following parameters: mineral concentrations in the hair and enzymatic activity levels of serum alkaline phosphatase. RESULTS: inadequate zinc concentrations prevalence in the hair was of 61,9% with predominance in the form of severe deficiency, 38,5%. Prevalence of inadequate concentrations of levels of serum alkaline phosphatase activity was 40,1%. Zinc concentrations in the hair did not correlatated with serum alkaline phosphatase (r = 0,01; p = 0,882). According to sex and age zinc distribution in the hair was homogenous. The alkaline phosphaase had identical behavior. CONCLUSIONS: zinc deficiency is extremely high in the municipality of João Pessoa.

Concentrations of lead in blood, hair and saliva of German children living in three different areas of traffic density

Lead contents in hair, whole blood and saliva were determined for 245 healthy children (121 male, 124 female, age: 8-10 years) from three residential areas of Düsseldorf (North-Rhine-Westphalia, Germany) with different traffic densities. The geometric mean for the lead content in hair was found to be 0.87 microg/g (range: 0.2-9.9 microg/g) for the entire test group. While the levels of lead in hair in the suburban population were significantly lower than in the two city centre populations, no significant difference concerning the lead content in hair could be detected in the latter. The geometric mean for lead concentration in whole blood amounted to 25.0 microg/l (range: 8.0-154 microg/l). There was no significant difference between the sub-groups. The lead concentrations found in saliva were rather low (range: < 1.5-47.0 microg/l). Of the values, 89% were below the detection limit of 1.5 microg/l. Due to reduced levels of lead in fuel, the present study exposes that the amount of lead in the children examined has further decreased compared to preceding surveys. The correlation between the lead content in hair and the road traffic density was not corroborated by the findings with regard to amounts of lead found in blood, indicating that residual lead from fuel does not result in a substantial burden of lead found in the whole body. In contrast to levels of lead found in blood, levels of lead found in hair may be influenced more by environmental conditions. Saliva is not a suitable material for biological monitoring with respect to lead exposure in children.

Hair-element analysis--still on the fringe

Increasing biological interest in minerals has led to the search for reliable methods to quantify body levels of trace elements and toxic metals. Hair has been a prime candidate because of its ease of collection and the possibility that this body tissue might accurately reflect body loads of these substances. A vast amount of research effort has been expended to explore the value of hair-element analysis. Unfortunately, there are so many confounding factors that influence these measurements that isolated individual results cannot be relied upon. Their current value is in epidemiological studies.

Zinc-catalyzed oxidation of 5-S-cysteinyldopa to 2,2'-bi(2H-1,4-benzothiazine): tracking the biosynthetic pathway of trichochromes, the characteristic pigments of red hair

Trichochromes, the peculiar pigments of red human hair, featuring the Delta(2,2)(')-bi(2H-1,4-benzothiazine) skeleton, are known to arise from cysteinyldopas, mainly the 5-S-isomer (5). However, the mode of formation and the direct precursors have remained largely undefined. To fill this gap, we investigated the oxidation of 5 in air or with chemical and enzymatic agents under biomimetic conditions. In the presence of zinc ions, which occur in epidermal tissues at significant concentrations, the reaction course is diverted toward the formation of a labile 3-carboxy-2H-1,4-benzothiazine intermediate (11), which was identified by direct NMR analysis. Structural formulation was supported by characterization of the analogous compound 13 isolated from oxidation of the model 5-methyl-3-S-cysteinylcatechol (12) after methylation. In the further stages of the oxidation, diastereomeric 2,2'-bi(2H-1,4-benzothiazine) 15 and 14 were obtained from 5 and 12, respectively, the reaction proceeding at a higher rate and to a greater extent in the presence of acids. The dimers were shown to readily convert to each other in the presence of acids. In the case of the methylated dimers 14, a 2,2'-bi(4H-1,4-benzothiazine) intermediate (16) was isolated and characterized. In acidic media, trichochrome C (1a), the most abundant in red human hair, was smoothly formed from aerial oxidation of 15, and under similar conditions, trichochrome-related products (17 and 18) were obtained from 14 prior to or after methylation. The presence of 1a and precursors 5 and 15 was investigated by HPLC analysis of red hair samples following mild proteolytic digestion. On the basis of these data, a likely biosynthetic route to trichochrome pigments of red human hair is depicted.

Brief communication: Choice of washing method of hair samples for trace element analysis in environmental studies

Determination of inseparable exogenous and endogenous levels of toxic trace elements such as lead in human scalp hair has been used to understand and assess population exposure to such elements. For any such analysis, washing of the hair samples to remove superficial contamination is the foremost requirement. However, the use of such washing methods prior to elemental analysis removes minute quantities of trace elements from the hair strands. This degree of loss is dependent on the washing method employed. In the present study, the element lead has been determined in human scalp hair after three methods of hair washing. It is apparent that the nonionic detergent-acetone method is best suited for securing valid lead analysis results in human scalp hair.

Urinary levels of metallothioneins and metals in subjects from a semiindustrialized area in Tarragona Province of Spain

The monitoring of heavy metals is important if adverse effects on health are to be avoided. In humans, metallothionein (MT) has been used as a biomonitor for the assessment of cadmium (Cd). In the present study, subjects drawn from the population of Tarragona Province (NE Spain) were investigated. Urinary MT, zinc (Zn), and copper (Cu) concentrations, corrected for creatine concentrations, were determined in 625 samples from healthy subjects aged between 10 and 65 yr. Mean values of MT and Cu in females were higher than those in males, with levels of 29.5 (23.8) vs. 22.7 (24.9) micrograms MT/creatinine (p < 0.001) and 4.8 (6.1) vs 3.4 (4.9) micrograms Cu/g creatinine (p < 0.001). No differences between males and females were observed with respect to urinary Zn: 78.0 (66.4) vs 73.0 (85.5) micrograms/g creatinine, respectively (p = 0.332). Significantly higher MT, Zn, and Cu values were observed in the females aged 15-19 yr and, in the age group of 50-54 yr, only in the Zn and Cu values, when compared with those in males. Significant positive correlations of MT vs Zn and Cu as well as correlations of Zn vs Cu levels were observed in both genders. The present findings confirm the proposed role of MT as a biomonitor of mineral status.

Age- and sex-related differences in zinc and lead levels in human hair

The hair of 1518 healthy subjects between newborn and 70 yr old living in Linfen city and the surrounding rural area in Shanxi province, North China, was analyzed by means of a flame atomic absorption spectrophotometer method in order to determine the concentrations of zinc (Zn) and lead (Pb). The collected samples were subdivided on the basis of age, sex, and place of residence (urban and rural). In female hair, the contents of Zn were higher than in male, but the hair Pb concentrations of males were slightly higher than those of females. Age seems to have a different influence on the two elements. The maximum amount of hair Zn was found generally in newborns. From the baby group (<1 yr) to the puberty group (15-19 yr), Zn levels in hair increased with age, and then Zn levels decreased with age from the puberty group to elderly group (61-70 yr). The hair Pb levels were the lowest in newborns, increased with age from newborn to infant (1-2 yr), and then decreased with age from infant to the elderly. It was shown that the hair Pb and Zn levels were inversely related in various age groups, suggesting that there is possibly antagonism between Pb and Zn in the human body. The results also showed the hair Pb levels of subjects living in the urban area, except for newborns, were higher than those of subjects residing in the rural area. However, no difference between the hair Zn contents of the populations residing in urban and rural areas.

Determination of copper and zinc levels in human hair: influence of sex, age, and hair pigmentation

The Cu and Zn levels of both 607 men (1-85 y old) and 649 women (1-92 y old) were determined by atomic absorption spectrometry. Sex does not influence Cu (14.89 + or - 0.89 mu g/g and 15.26 + or - 0.79 mu g/g hair for males and females, respectively) and Zn contents (200.97 + or - 9.68 mu g/g for men and 209.81 + or - 9.49 mu g/g hair for women). Age influences Cu and Zn concentrations, but only significantly in females: Cu levels decrease over 60 y of age; whereas Zn levels increase significantly from age groups 2-5 to 20-40 years. Hair color influences Cu concentrations in both males and females. In males, white hair contains less Cu than black hair; in females, white hair's Cu levels are significantly lower than those of dark blond, red, light brown, and brown hair. There are no significant differences in Zn concentrations with respect to different hair colors, in either males or females.