Hair selenium as a monitoring tool for occupational exposures in relation to clinical profile

A county-level spatial epidemiological study of hair selenium and Keshan disease

Background

No spatial analysis of hair selenium and Keshan disease (KD) on a nationwide county-level has been performed. Selenium deficiency is a recognized environmental risk factor for KD. Hair selenium is one of the recognized biomarkers of selenium nutrition. This study aimed to perform a geographically precise and visualized assessment of the achievement of KD prevention and control at the level of selenium nutrition in terms of etiology.

Methods

A spatial ecological study was conducted. The hair selenium content of the residents was assayed using an atomic fluorescence spectrometer. The spatial analysis was performed using ArcGIS.

Results

The median of the hair selenium levels of the 3,028 participants in the 1,174 counties was 0.38 mg/kg, and the content of inhabitants in KD endemic counties was significantly lower than that in KD non-endemic counties (0.34 vs. 0.39 mg/kg, z = −10.03, P < 0.0001). The proportion of Se-deficient and Se-marginal counties in KD endemic counties was significantly higher than that in KD non-endemic counties (59.4 vs. 29.0%, z = −7.45, P < 0.0001). The global autocorrelation analysis was not statistically significant (Moran's I = 0.0005, P = 0.68). Local autocorrelation analysis identified 174 low-low clusters of hair selenium levels, 83 (47.7%) of which are KD endemic counties located in KD endemic provinces of Henan, Gansu, Shaanxi, Inner Mongolia, Jilin, and Heilongjiang. The hair selenium featured a positive correlation with per capita GDP (rs = 0.20, P < 0.0001).

Conclusion

The median of the hair selenium levels of inhabitants living in KD endemic counties was significantly lower than that in KD non-endemic counties. All the 83 KD endemic counties with low-low clusters of hair selenium levels should be prioritized in KD precision prevention and control. These findings are geographically precise and visualized evidence of the assessment of the effectiveness of KD prevention and control at the level of selenium nutrition in terms of etiology.

Effect of environmental toxicants on neuronal functions

In the last few years, neurodegenerative diseases like Alzheimer's disease (AD) and Parkinson's disease (PD) have attracted attention due to their high prevalence worldwide. Environmental factors may be one of the biggest reasons for these diseases related to neuronal dysfunctions. Most of neuronal disorders are strongly associated with pre- and postnatal exposure to environmental toxins released from industries. Some of the neurotoxic metals such as lead, aluminum, mercury, manganese, cadmium, and arsenic as well as some pesticides and metal-based nanoparticles have been involved in AD and PD due to their ability to produce senile/amyloid plaques and NFTs which are the main feature of these neuronal dysfunctions. Exposure to solvents is also majorly responsible for neurodegenerative disorders. The present review highlights the impact of omnipresent heavy metals with some other neurotoxins on human health and how they give rise to neuronal dysfunctions which in turn causes socio-economic consequences due to increasing pollution worldwide. Graphical abstract.

Evaluation of the status and the relationship between essential and toxic elements in the hair of occupationally exposed workers

Lead poisoning is a common disease in lead-acid battery manufacturing industries. Workers can be also exposed to various toxic elements present as contaminants or used as catalysts to enhance batteries' performances. In the present study, levels of essential and toxic elements and their relationship were assessed by analyzing scalp hair samples of 52 workers in a Pb battery manufacturing plant. The impact of some confounding factors on hair mineral contents was also investigated. For comparative purposes, nonoccupationally exposed subjects were selected as controls. All elements were determined by triple quadrupole ICP-MS. The results indicated significantly higher levels of Pb, Sb, As, and Cd in the hair of workers when compared to controls (p < 0.01). The Spearman correlation test revealed significant correlations between Pb/Cr, Pb/Mn, Pb/Ni, Pb/As, Pb/Se, Pb/Sb, Hg/As, Hg/Sn, Hg/Sb, Sb/Cr, Sb/As, Sb/Se, Sb/Cd, Sb/Sn, Sn/Cr, Sn/As, Sn/Cd, Cd/As, Se/Ni, As/Cr, Ni/Cr, Ni/Mn, and Mn/Cr in the hair of workers and Pb/Cr, Pb/Mn, Pb/Ni, Pb/Cd, Mn/Ni, Mn/Cd, Cd/Ni, As/Ni, Sn/Ni, Sb/Sn, and Hg/Sn in the hair of controls. Multiple linear regression analysis revealed linear dependence including Cr = f(Pb, Ni, Sb), Mn = f(Ni, Sb), Ni = f(Mn, Cr, -Cd) (Cd was negatively correlated, β < 0), As = f(Sn, Sb, Hg), Se = f(Ni); Sn = f(As), Sb = f(As, Mn, -Hg, Sn, Se, -Ni) (Hg and Ni were negatively correlated), Hg = f(As, -Sb, Sn) (Sb was negatively correlated), and Pb = f(Cr). The result of this study can be very useful to explain the interactions between elements or for comparison studies when establishing reference ranges or monitoring elements in workplaces.

Low internal exposure and absence of adverse effects in workers exposed to high air levels of inorganic selenium

Selenium is an essential trace element for humans, but adverse health effects may occur after elevated intake. The margin between it is small. This study aimed to assess external and internal exposure in workers of a selenium-processing plant, in which elemental and inorganic selenium occurred. Selenium was analyzed in the form of the selenium concentration in plasma (Se-P), in erythrocytes (Se-RBC) and in personal air samples (Se_total-Air) of 17 exposed workers. Internal exposure was compared to 20 controls without occupational selenium exposure. For potential effects, glucose, HbA1c, proinsulin, prothrombin time and GPX were determined. Se_total-Air had a maximum of 2394 μg/m³ (median 319 μg/m³), containing a small water-soluble fraction (median 12.7 μg/m³, range 0.07-975 μg/m³). Se-P of the exposed ranged from 62 to 123 μg/L (median 105 μg/L), whereas the median of Se-RBC was 63.4 μg/L blood (range 51.9-92.7 μg/L). Both were significantly higher than the controls. No significant difference was found for the effect parameters. Biological effect monitoring of employees occupationally exposed to very high levels of selenium and inorganic selenium compounds did not show any indication of adverse health effects. The moderate increase of the internal selenium exposure compared to the high ambient exposure to selenium and its compounds suggests an efficient air protection or an extremely low resorption of elemental and inorganic species of selenium via inhalation.

Selenium neurotoxicity in humans: bridging laboratory and epidemiologic studies

Selenium is a metalloid of considerable interest in the human from both a toxicological and a nutritional perspective, with a very narrow safe range of intake. Acute selenium intoxication is followed by adverse effects on the nervous system with special clinical relevance, while the neurotoxicity of long-term overexposure is less characterized and recognized. We aimed to address this issue from a public health perspective, focusing on both laboratory studies and the few epidemiologic human studies available, with emphasis on their methodological strengths and limitations. The frequently overlooked differences in toxicity and biological activity of selenium compounds are also outlined. In addition to lethargy, dizziness, motor weakness and paresthesias, an excess risk of amyotrophic lateral sclerosis is the effect on the nervous system which has been more consistently associated with chronic low-level selenium overexposure, particularly to its inorganic compounds. Additional research efforts are needed to better elucidate the neurotoxic effects exerted by selenium overexposure.

The occurrence and incorporation of copper and zinc in hair and their potential role as bioindicators: a review

This article reviews evidence that suggests Cu and Zn concentrations are not altered significantly by exogenous processes and may be useful in applications of hair analysis. The review attempts to identify what Cu and Zn concentrations may actually indicate biogenically and investigates the mechanisms by which they are incorporated into hair. Associations with specific hair components are proposed and avenues for development as a bioindicator are identified. Areas of research that offer promise in application or confirming the use of Cu and Zn are also indicated. Correlations and relationships with other health disorders are reviewed. Endogenous blood concentrations may also explain alterations in hair structure relating to breast cancer.

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.

Recent developments in selenium metabolism and chemical speciation: a review

The biological roles of selenium and its mode of action have only recently begun to be revealed. To date, the major functions of selenium can be attributed to its antioxidative properties and its role in the regulation of thyroid hormone metabolism, cell growth and eicosanoid biosynthesis. The unusual feature of selenoprotein synthesis is that selenocysteine insertion is specified by the stop UGA codon. A number of selenocysteine-specific gene products and a stem-loop structure in the 3' untranslated region are required for selenocysteine biosynthesis and the decoding of UGA codons in the open reading frame of the mRNA. The major biological functions of selenium are achieved through its redox activity when present as selenocysteine at the active sites of selenoproteins and these proteins are selenium-dependent since replacement with the sulphur analogue cysteine causes loss of enzyme activity. Both organic and inorganic forms of selenium may be utilised by the body, with the selenoamino acids showing greatest bioavailability. Knowledge of the biochemistry of the element coupled with appropriate techniques for the study of the distribution of selenium species in health and disease could help to identify sensitive markers of selenium status.