Coverage intervals for trace elements in human scalp hair are site specific

Microchemistry of Single Hair Strands Below and Above the Scalp: Impacts of External Contamination on Cuticle and Cortex Layers

External contamination of hair is the most significant challenge to it becoming an accepted matrix for monitoring endogenous metal exposure and nutritional deficiency. Here we use laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) to quantify elemental concentrations in hair strands below and above the scalp in the cuticle and cortex layers to determine the extent of external contamination in a reference population. Evidence of hair strand contamination occurred for barium, calcium, iron, magnesium, and strontium in both the outer cuticle and the inner cortex layers, with increasing concentrations from root to tip. Aluminum, boron, copper, lead, and manganese showed significant contamination in the cuticle layer only, suggesting some protection of the inner cortex. Phosphorus and potassium decreased outside the scalp suggesting loss by washing, while chromium, mercury, selenium, sodium, titanium, and zinc showed no evidence of loss or external contamination above the scalp. The results clearly show that for most elements, hair chemistry above the scalp is unreliable for use in interpretation of endogenous exposures or deficiencies, and that the below-scalp portion provides a more accurate monitoring tool. This is the first paper to provide a reference range of elemental hair chemistry that is not impacted by the external environment.

Spatial distribution, impact factors, and potential health implications of trace elements in human hair from capital residents in China

We analyzed the levels, spatial distribution, impact factors, source apportionment, and potential health implications of trace elements (V, Zn, Cu, Mn, Ni, Mo, and Co) in 1202 human hair samples of urban residents aged 4-55 from 29 cities in China. The median values of seven trace elements in hair were found in the following increasing order: Co (0.02 μg/g) < V (0.04 μg/g) < Mo (0.05 μg/g) < Ni (0.32 μg/g) < Mn (0.74 μg/g) < Cu (9.63 μg/g) < Zn (157 μg/g). The spatial distribution of these trace elements in the hair from the six geographical subdivisions varied depending on the exposure sources and impact factors. Principal component analysis (PCA) revealed that Cu, Zn, and Co in the hair samples of urban residents were primarily derived from food, whereas V, Ni, and Mn were attributed to industrial activities and food. Majority of the hair samples (up to 81%) from North China (NC) exceeded the recommended value for V content, whereas up to 59.2%, 51.3%, and 31.6% samples from Northeast China (NE) exceeded the recommended values for Co, Mn, and Ni contents, respectively. The levels of Mn, Co, Ni, Cu, and Zn were significantly higher in female hair than those in male hair, whereas the levels of Mo were higher in male than in female hair (p < 0.01). Furthermore, significantly higher Cu/Zn ratios were observed in the hair of male residents than those in the female residents (p < 0.001), indicating a higher health risk for male residents.

Potentially toxic elements in human scalp hair around China's largest polymetallic rare earth ore mining and smelting area

There is a growing concern about human health of residents living in areas where mining and smelting occur. In order to understand the exposure to the potentially toxic elements (PTEs), we here identify and examine the cadmium (Cd), chromium (Cr), copper (Cu), manganese (Mn), nickel (Ni), lead (Pb) and zinc (Zn) in scalp hair of residents living in the mining area (Bayan Obo, n = 76), smelting area (Baotou, n = 57) and a reference area (Hohhot, n = 61). In total, 194 hair samples were collected from the volunteers (men = 87, women = 107) aged 5-77 years old in the three areas. Comparing median PTEs levels between the young and adults, Ni levels were significantly higher in adults living in the smelting area while Cr was highest in adults from the mining area, no significant difference was found for any of the elements in the reference area. From the linear regression model, no significant relationship between PTEs concentration, log₁₀(PTEs), and age was found. The concentrations of Ni, Cd, and Pb in hair were significantly lower in the reference area when compared to both mining and smelting areas. In addition, Cu was significantly higher in the mining area when compared to the smelting area. Factor analysis (FA) indicated that men and women from the smelting area (Baotou) and mining area (Bayan Obo), respectively, had different underlying communality of log10(PTEs), suggesting different sources of these PTEs. Multiple factor analysis quantilized the importance of gender and location when combined with PTEs levels in human hair. The results of this study indicate that people living in mining and/or smelting areas have significantly higher PTEs (Cu, Ni, Cd, and Pb) hair levels compared to reference areas, which may cause adverse health effects. Remediation should therefore be implemented to improve the health of local residents in the mining and smelting areas.

Levels of trace elements in human hair samples of adolescents living near petrochemical plants

The aim of the study is a comparative analysis to investigate human hair metal profiles of adolescents residing near petrochemical plants (Sicily, Italy). We selected the small town of Augusta, Gela, and Pace del Mela, and a control area made up of the towns characterized by low anthropogenic activity. Twenty trace elements were measured in samples of scalp hair from adolescents (11-14 years old) of both genders. Hair samples were cleaned using a rigorous cleaning method, mineralized, and processed for analyses by inductively coupled plasma-mass spectrometry (ICP-MS). In industrial sites, zinc was always the most abundant element, ranging from186 to 217 μg g^-1. Following zinc, the elements Al, Ba, Cu, Fe, and Sr were in the range 1-20 μg g^-1. The remaining elements had concentrations < 1 μg g^-1. The comparison with adolescents living in suburban area highlighted that As, Ba, Mn, Sr, U, and V have the highest median concentrations in an industrial location. An industrial factor (As, Mn, Sr, U, and V) and an urban factor (Cd, Cr, Cu, Mo, Ni, and Sb) were distinguished by the multivariate statistical analysis between a cohort residing in urban and industrial areas. Statistically significant differences (Kruskal-Wallis test, p < 0.05) between the genders were found for Ba, Mn, Ni, Sr, and V in all industrial sites with median concentrations higher in females' hair than males'. The data confirm that the study areas are heavily affected by industrial and urban emissions of metals and metalloids, representing a potential hazard to the local population.

Sex determination of mummies through multi-elemental analysis of head hair using electrothermal vaporization coupled to inductively coupled plasma optical emission spectrometry

Sex determination of human remains is of great archaeological significance, as it provides a more complete picture of social and familial structures within ancient societies. Typically performed through examination of bones in the pelvic region, accurate sex determination can be exceedingly challenging in the absence of a sufficiently preserved skeleton. Here, a method for sex determination in living humans, involving measurement of magnesium, strontium, sulfur, and zinc in head hair along with multivariate statistics, was applied for the first time to hair collected from 500 year-old mummies originating from Peru. Hair samples were washed in doubly deionized water, dried, and ground prior to analysis via electrothermal vaporization coupled to inductively coupled plasma optical emission spectrometry; only 2 mg of hair is required for analysis. Point-by-point internal standardization was performed with Ar i 430.010 nm to compensate for sample loading effects on the plasma. Peak areas were integrated and mass corrected before being used in combination with multivariate analysis. Although principal component analysis provided insufficient separation between the sexes, linear discriminant analysis (LDA) was highly effective for sex determination. Using mummy hair as the LDA model enabled accurate sex prediction of the mummies, showing that, despite the age of the hair, the samples still contain the necessary elemental information for sex determination. For accurate sex determination of mummies using hair collected from living humans, magnesium had to be replaced by sodium due to significant differences in dietary habits. With this simple modification, hair from living humans in North America could be used to successfully predict the sex of individuals who lived more than 500 years ago in Peru. This work paves the way for broader use of non-skeletal sex determination methods within the field of archaeology, filling a significant gap.

Multi-elemental analysis of hair from living humans allows for accurate, non-skeletal sex determination of 500 year-old mummified individuals.

Biomonitoring of Trace Elements in Hair of Schoolchildren Living Near a Hazardous Waste Incinerator-A 20 Years Follow-Up

Since 1998, a monitoring program is periodically performed to assess the environmental and human health impact of air chemicals potentially emitted by a hazardous waste incinerator (HWI) located in Constantí (Catalonia, Spain). In 2017, samples of hair were collected from 94 schoolchildren (aged 10-13 years) living nearby and the levels of 11 trace elements (As, Be, Cd, Cr, Hg, Mn, Ni, Pb, Sn, Tl and V) were determined. The concentrations showed the following descending order: Pb > Hg > Ni > Sn > Mn > Cr. In turn, As, Be and Tl were not detected, while Cd and V were found only in a few samples. Some metal levels were significantly, positively correlated. Some significant differences were also noticed according to the gender and the specific zone of residence. Finally, the levels of trace elements showed fluctuations through time. Cr and Pb showed a significant decrease in comparison to the concentrations obtained in the baseline study (1998). According to the current results, metal emissions from the HWI are not relevant in terms of human health impact since their levels were similar and even lower than those reported in other contaminated areas.

Assessment of Gender Effects and Reference Values of Mane Hair Trace Element Content in English Thoroughbred Horses (North Caucasus, Russia) Using ICP-DRC-MS

The objective of the present study was assessment of gender differences in hair trace element content in English Thoroughbred horses (North Caucasus, Russia) using ICP-DRC-MS and calculation of the reference values. Trace element content in mane hair of 190 stallions and 94 mares (3-7 years old) bred in North Caucasus (Russia) was assessed using inductively coupled plasma mass spectrometry. Mane hair Co, Cr, Mn, Li, Si, and Sr levels in mares exceeded those in stallions by 77%, 63%, 64%, 42%, 39%, and 64%, respectively. Hair Fe and Si content was nearly twofold higher in female horses as compared to the males. Only hair Zn content was 5% higher in stallions as compared to mares. In addition, mares were characterized by 63%, 65%, 29%, and 40% higher levels of As, Pb, Sn, and Ni levels in hair as compared to the respective values in stallions. In turn, hair Al and Hg were more than twofold higher in mares than in stallions. The reference intervals of mane hair content (μg/g) for Co (0.006-0.143), Cr (0.028-0.551), Cu (4.17-6.84), Fe (10.11-442.2), I (0.026-3.69), Mn (0.551-12.55), Se (0.108-0.714), Zn (97.43-167), Li (0.011-0.709), Ni (0.060-0.589), Si (0.665-29.12), V (0.006-0.584), Al (1.98-168.5), As (0.006-0.127), Cd (0.002-0.033), B (0.494-16.13), Pb (0.018-0.436), Sn (0.002-0.144), Sr (1.0-9.46), and Hg (0.0018-0.017) in the total cohort of horses were estimated using the American Society for Veterinary Clinical Pathology Quality Assurance and Laboratory Standard Guidelines. The reference intervals were also estimated for stallions and mares bred in North Caucasus (Russia) and may be used for interpretation of the results of hair trace element analysis in horses.

Statistical resolutions for large variabilities in hair mineral analysis

Measuring biomaterials is usually subject to error. Measurement errors are classified into either random errors or biases. Random errors can be well controlled using appropriate statistical methods. But, biases due to unknown, unobserved, or temporary causes, may lead to biased conclusions. This study describes a verification method to examine whether measurement errors are random or not and to determine efficient statistical methods.

A number of studies have dealt with associations between hair minerals and exposures such as health, dietary or environmental conditions. Most review papers, however, emphasize the necessity for validation of hair mineral measurements, since large variations can cause highly variable results. To address these issues, we answer the following questions:

How can we ascertain the reliability of measurements?

How can we assess and control the variability of measurements?

How do we efficiently determine associations between hair minerals and exposures?

How can we concisely present the reference values?

Since hair minerals all have distinctive natures, it would be unproductive to examine each mineral individually to find significant and consistent answers that apply to all minerals. To surmount this difficulty, we used one simple model for all minerals to explore quantitative answers. Hair mineral measurements of six-year-old children were analyzed based on the statistical model. The analysis verified that most of the measurements were reliable, and their inter-individual variations followed two-parameter distributions. These results allow for sophisticated study designs and efficient statistical methods to examine the effects of various kinds of exposures on hair minerals.

Assessment of hair metal levels in aluminium plant workers using scalp hair ICP-DRC-MS analysis

The objective of the present study was to assess the level of aluminium and toxic metals in hair of workers occupationally exposed to aluminium. 124 employees of the aluminium plant working in the hydrometallurgical (n = 43) and sintering units (n = 41), as well as 40 occupationally nonexposed controls were examined. Hair aluminium (Al), arsenic (As), beryllium (Be), cadmium (Cd), mercury (Hg), nickel (Ni), lead (Pb), and tin (Sn) content was assessed using inductively-coupled plasma mass spectrometry. The obtained data demonstrate that aluminium plant workers had significantly higher levels of hair Al (28.8 (15.4-58.6) vs 7.8 (4.3-14.2) μg/g, p < 0.001), Cd (0.053 (0.032 - 0.095) vs 0.025 (0.014 - 0.043) μg/g, p < 0.001) and Pb (0.672 (0.299-1.310) vs 0.322 (0.170 - 0.609) μg/g, p = 0.012) than the controls, respectively. Further analysis demonstrated that persons involved in different technological processes were characterized by distinct hair metal profiles. Hair Al, Be, Cd, Ni, Pb, and Sn levels in men working in the sintering unit of the aluminium plant exceeded the respective control values. In turn, workers of the hydrometallurgical unit were characterized by more than 2-fold higher levels of Al and Cd in hair as compared to the controls. The results of the present study demonstrate that workers of the aluminium plant are characterized by increased risk of Al as well as As, Cd, Pb, and Sn exposure.

Effects of sex on the levels of metals and metalloids in the hair of a group of healthy Spanish adolescents (13 to 16 years old)

Human biomonitoring can be a reliable tool to protect the health of the citizens of major urban environments. Human hair may be an invaluable specimen to determine chronic exposure to any environmental contaminant in an individual, especially in the young population. However, different factors including a lack of studies that have established reference values for metals and metalloids (trace elements) in human scalp hair make the use of this matrix controversial. A monitoring study was performed to establish possible normal or tentative reference values of Al, As, Be, Cd, Cr, Cu, Hg, Mn, Pb, Sn, Ti, Tl and Zn in adolescents' (aged 13-16) hair who have lived since birth in Alcalá de Henares, Madrid region (Spain). Strict inclusion criteria were followed to study the effect of sex on the hair metal content, and the levels of the above contaminants were also studied in park topsoils from Alcalá de Henares. Scalp hair samples were collected from 96 healthy adolescents (28 boys and 68 girls), and reference values were calculated following the recommendations of the International Union of Pure and Applied Chemistry. The levels of Cd, Cu, Pb, Sn and Zn in hair of adolescents from Alcalá de Henares show a sex dependency, being significantly higher in female participants. Sex should be a factor taken into account when developing future reference values and hair metal content. Soil metal contamination was not correlated with the levels found in hair. To conclude, the values of metals and metalloids here analysed and discussed could be considered as tentative reference values for Spanish adolescents aged 13-16 years living in the Madrid region, and may be used to identify the level of exposure of adolescents in this Spanish region to the various metals and metalloids.

Reference levels of trace elements in hair samples from children and adolescents in Madrid, Spain

INTRODUCTION

Hair samples are used as a tool to evaluate environmental exposure to contaminants and metabolic status in the individual. However, the use of human hair is controversial, mainly because of the lack of well-defined reference levels. In the case of Spain, very few biomonitoring studies have investigated these issues in infants, children or adolescents.

OBJECTIVE

To establish reference levels for trace elements in children and teenagers in Madrid, Spain.

MATERIAL AND METHODS

Inductively coupled plasma mass spectrometry (ICP-MS) was used to measure Al, As, Ag, Ba, Bi, Cd, Cr, Co, Cu, Fe, Mn, Mo, Ni, Pb, Se, Sr, Tl and Zn levels in hair samples from 648 healthy children and adolescents (253 boys and 395 girls) between April 2008 and December 2009.

RESULTS

Median levels were as follows: Al 18.5μg/g, As 0.07μg/g, Ag 196ng/g, Ba 0.5μg/g, Bi 0.01μg/g, Cd 18.3ng/g, Cr 0.4μg/g, Co 14.5ng/g, Cu 25.7μg/g, Fe 15.5μg/g, Mn 328ng/g, Mo 0.04μg/g, Ni 0.5μg/g, Pb 0.70μg/g, Se 0.5μg/g, Sr 1.29μg/g, Tl 0.28ng/g and Zn 121μg/g.

DISCUSSION AND CONCLUSION

The values of trace elements here described could be considered as possible reference ranges for hair samples from children and adolescents aged 0-18 years living in the Madrid region (central Spain). These values could also be selected as a preliminary screening tool to assess exposure sources and to generate information needed to develop prevention strategies and likewise could be a complement to other diagnostic procedures.

Hair from different ethnic groups vary in elemental composition and nitrogen and phosphorus mineralisation in soil

Disposal of hair wastes at landfills causes nitrate leaching to ground water, and use of the waste as fertiliser could be a viable option. This study was to determine elemental composition of major hair types in South Africa and their nitrogen (N) and phosphorus (P) release in soil. Wastes of African, White and Indian hair were obtained from local salons and analysed for carbon (C), N and sulphur (S) with the Leco CNS analyzer, and P, bases, aluminium (Al) and micronutrients, with the ICP. We also conducted an incubation study to determine changes in mineral N and P in soil. Hair wastes were added to soil at increasing rates based on N, incubated at 25 °C with destructive sampling after 0, 28, 56 and 84 days and pH, ammonium-N, nitrate-N and extractable P measured. All data were subjected to analysis of variance. Indian and White hair had higher N than African. White hair had higher C and lower potassium (K) than those of other types. The Fe levels in hair were in the order White > African > Indian, whilst those of Al were African > Indian > White. African hair had higher calcium (Ca), manganese (Mn), zinc (Zn) and cobalt (Co) than the other types. Ammonium-N and nitrate-N releases were in the order: Indian > African > White, especially at higher rates. Ammonium-N increased in the first 28 days and declined thereafter, when nitrate-N increased and pH decreased. The findings implied that hair types differ in elemental composition and nitrogen release in soil, with implications on pollution and soil fertility.

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.

Evaluating the effect of age and area of residence in the metal and metalloid contents in human hair and urban topsoils

Monitoring the levels of trace elements in hair can allow estimating the effects of the geographical location and also can provide a notion of the metal body burden. However, the use of human hair is controversial due to the different confounding factors that could affect the presence of trace elements in hair. As a result, a comprehensive monitoring study was performed in Alcalá de Henares, one of the major cities in the Madrid region, Spain. Trace elements have been monitored in urban topsoils and in human hair of two well-defined and healthy groups of population: children (6-9 years) and adolescents (13-16 years). The city was divided into four areas or zones with different characteristics to assess the possible effect of area of residence and age in the presence of Al, As, Be, Cd, Cr, Cu, Hg, Mn, Pb, Sn, Ti, Tl and Zn in soils and hair. There is no current hypothesis that explains the possible effect of the area of monitoring in the distribution of Be, Cr, Ni, Sn and Ti found in these urban soils, maybe because urban soils receive high disturbance, and there are many factors involved. The presence of most of the trace elements monitored was significantly higher in the hair of the children population, except for Sn and Zn. This could be attributed mainly to dietary habits. Other factors influencing metal content in hair such as environmental factors would have had a minimal effect in the population groups here studied. Finally, none of the levels of trace elements studied in hair were significantly correlated with levels measured in the topsoils of public parks in Alcalá de Henares, with the exception of Pb in adolescent participants.

Penalized linear discriminant analysis and Discrete AdaBoost to distinguish human hair metal profiles: The case of adolescents residing near Mt. Etna

The research focus of the present paper was twofold. First, we tried to document that human intake of trace elements is influenced by geological factors of the place of residence. Second, we showed that the elemental composition of human hair is a useful screening tool for assessing people's exposure to potentially toxic substances. For this purpose, we used samples of human hair from adolescents and applied two robust statistical approaches. Samples from two distinct geological and environmental sites were collected: the first one was characterized by the presence of the active volcano Mt. Etna (ETNA group) and the second one lithologically made up of sedimentary rocks (SIC group). Chemical data were statistically processed by Penalized Linear Discriminant Analysis (pLDA) and Discrete AdaBoost (DAB). The separation between the two groups turned out well, with few overlaps accounting for less than 5%. The chemical variables that better distinguished ETNA group from SIC group were As, Cd, Co, Li, Mo, Rb, Sr, U and V. Both pLDA and DAB allowed us to characterize the elements most closely related to the volcanic contribution (As, U and V) and those (Cd, Co, Li, Mo, Rb and Sr) prevalently influenced by the geology of the area where SIC samples were collected. We conclude that the geological characteristics of the area of residence constitute a key factor in influencing the potential exposure to trace elements. Hair analysis coupled with robust statistical methods can be effectively used as a screening procedure to identify areas at great environmental risk.