Factors determining percutaneous metal absorption

Metal(loid) speciation in dermal bioaccessibility extracts from contaminated soils and permeation through synthetic skin

Dermal exposure to metal(loid)s from contaminated soils can contribute to health risk. Metal(loid) speciation will influence their bioaccessibility in sweat and subsequent permeation across the skin. Therefore, the speciation of the bioaccessible fraction of metal(loid)s in two synthetic sweat formulations (sweat A (pH 6.5) and B (pH 4.7)) was assessed using chemical equilibrium modelling (Visual MINTEQ). Permeation through synthetic skin and the influence of sebum in the permeation of As, Cr, Cu, Ni, Pb, and Zn were also investigated using Franz cells. Following dermal bioaccessibility tests for five Chromated Copper Arsenate (CCA)-contaminated soils and one certified soil (SQC001), mean metal(loid) bioaccessibility (%) was higher in sweat B (2.33-18.8) compared to sweat A (0.12-7.53). Arsenic was almost entirely found as As(V) in both sweats. In sweat A, comparable concentrations of Cr(III) and Cr(VI) were found whereas in sweat B, Cr was primarily present as Cr(III). Copper was primarily found as Cu2+. Bioaccessible Cr extracted from nearly all soils permeated through the Strat-M membrane when it was coated with sebum. The Cr permeation coefficient (Kp) ranged between 0.004 and 0.13 cm/h and the Kp for Cu was higher (0.024-0.52 cm/h). As, Ni, Pb, and Zn did not permeate the synthetic skin.

In vitro skin permeation of potassium hexachloroplatinate and a comparison with potassium tetrachloroplatinate

Halogenated platinum salts are known respiratory sensitizers in the workplace, and occupational exposure to platinum via the respiratory system and skin has been reported. The aim of this study was to compare the permeability and skin retention of potassium hexachloroplatinate to previously published data of potassium tetrachloroplatinate. Experiments were performed using female Caucasian skin and Franz diffusion cells with the application of 0.3mg Pt/mL in the donor solution for 24-hours. After 8-hours of exposure, 1.87ng/cm² of Pt was detected in the receptor solution with exposure to potassium hexachloroplatinate, whereas 0.47ng/cm² was detected with exposure to potassium tetrachloroplatinate. After 24-hours of exposure the Pt retention in the skin was 1861.60ng/cm² and 1486.32ng/cm² with exposure to potassium hexa- and tetrachloroplatinate respectively. The faster rate of Pt permeation from exposure to potassium hexachloroplatinate was confirmed by the flux and permeability coefficient values. The results indicate a higher permeability and skin retention of Pt when exposed to potassium hexachloroplatinate, confirming a higher risk associated with occupational exposure to this platinum compound relative to potassium tetrachloroplatinate.

The Toxicological Risk Assessment of Dermal Exposure of Patients Exposed to Lead and Cadmium Due to Application of Ointments with Marjoram Herb Extract (Majoranae herbae extractum)

Potential heavy metal impurities (HMI) in pharmaceuticals/pharmaceutical products/drugs based on plant raw materials (e.g., herbs) are an important problem in the pharmaceutical industry; however, there is a lack of scientific articles on the comprehensive toxicological risk assessment of HMI in ointment applied dermally. To make the appropriate toxicological risk assessment, we consider: (1) the raw results of the levels of lead and cadmium in the ointments (metal per kg of mass), (2) one-time administration of the applied ointment, (3) daily exposure of Pb and Cd in the applied ointments according to the maximum daily dose of applied pharmaceuticals, including transcutaneous penetration, (4) human health risk assessment based on the USEPA model, and 5) the margin of exposure (MoE). The raw results indicated that lead (7.05-101.78 µg/kg) and cadmium (0.32-0.81 µg/kg) were present in all samples. The levels of analyzed HMI (independently of the producer and declared composition) were similar. Pb and Cd contamination associated with daily doses met the standards of the ICH Q3D (R2) guide on elemental impurities in pharmaceuticals, including the cutaneous route of administration. Taking into account the daily amount of lead and cadmium (ointment, ug/day) the results were satisfactory, confirming the safety of marjoram herb extract ointments available in Polish pharmacies according to the ICH guideline Q3D (R2) on elemental impurities. The HQ values obtained for Pb and Cd in all samples were less than 1; therefore, exposure to these HMI would not cause a health risk based on the USEPA model strategy. Furthermore, the obtained values of MoE for Pb and Cd in ointments were above 100, so exposure to these elements would not cause a health risk based on the MoE-based strategy. The original contribution of this work is that this is the first study on the triple approach strategy to evaluate the safety of heavy metal impurities in traditional herbal medicinal products applied dermally in solid form (ointments with marjoram herb extract). The research is novel and has not been previously published; The proposed procedure includes transcutaneous penetration of heavy metal (Pb and Cd) impurities described for the first time in the literature.

Risk of Exposure to Trace Elements through the Application of Facial Makeup Powders

The study aimed to ascertain the levels of trace elements present in the face powders marketed in Ghana. Fifteen different brands of facial makeup powders were purchased from a local market in Ghana. The samples were analyzed using an X-ray fluorescence (XRF) analyzer to determine the concentrations of 16 elements (Pb, As, Hg, Zn, Fe, Mn, Cr, Ti, Cu, Ni, Co, Sb, Cd, Ag, Sn, and Au). The contents of the trace elements were ordered in the following descending order according to the maximum concentrations: Fe > Zn > Ti > Mn > Cr > Hg > As > Pb > Cu, Ni, Co, Sb, Cd, Ag, Sn, and Au. Pearson correlation statistics showed strong positive relationships between Pb and Zn (r = 0.71), Pb and Cr (r = 0.57), Hg and Zn (r = 0.63), Hg and Fe (r = 0.73), Hg and Cr (r = 0.61), Zn and Fe (r = 0.69), Zn and Cr (r = 0.88), Fe and Cr (r = 0.67), and Fe and Ti (r = 0.62). Except for Pb and Cr, all the other elements had their margin of safety (MOS) values less than 100. The hazard indices (HIs) for Pb, Mn, Cr, and Ti were less than 1, indicating no risk. However, the HIs for As, Hg, Zn, and Fe were more than 1, indicating a potential risk of usage in adults. As a result, using face powders could put users at risk of exposure to trace elements. Dermal exposure to trace elements from cosmetics resulted in a lifetime cancer risk (LCR) that was higher than what was considered tolerable (LCR >10−6) due to the presence of Pb, As, and Cr. Mercury was identified as a potential skin sensitizer in the cosmetic samples examined by an exposure-based sensitization quantitative risk assessment (SQRA).

Transdermal permeation of inorganic cerium salts in intact human skin

The stratum corneum protects the body against external agents, such as metals, chemicals, and toxics. Although it is considered poorly permeable to them, comprising the major barrier to the permeation of such substances, it may become a relevant gate of entry for such molecules. Cerium (Ce) is a lanthanide that is widely used in catalytic, energy, biological and medicinal applications, owing to its intrinsic structural and unique redox properties. Cerium salts used to produce cerium oxide (CeO₂) nanostructures can potentially come into contact with the skin and be absorbed following dermal exposure. The objective of this study was to investigate the percutaneous absorption of three inorganic Ce salts: cerium (III) chloride (CeCl₃); cerium (III) nitrate (Ce(NO₃)₃) and ammonium cerium (IV) nitrate (Ce(NH₄)₂(NO₃)₆), which are commonly adopted for the synthesis of CeO₂ using in vitro - ex vivo technique in Franz diffusion cells. The present work shows that Ce salts cannot permeate intact human skin, but they can penetrate significantly in the epidermis (up to 0.29 μg/cm²) and, to a lesser extent in dermis (up to 0.11 μg/cm²). Further studies are required to evaluate the potential effects of long-term exposure to Ce.

Assessment of dermal absorption of beryllium and copper contained in temple tips of eyeglasses

Dermal exposure to hazardous substances such as chemicals, toxics, metallic items and other contaminants may present substantial danger for health. Beryllium (Be) is a hazardous metal, especially when inhaled and/or in direct contact with the skin, associated with chronic beryllium disease (CBD) and Be sensitization (BeS). The objective of this study was to investigate the percutaneous penetration of beryllium and copper contained in metallic items as eyeglass temple tips (specifically BrushCAST® Copper Beryllium Casting Alloys containing Be 0.35 < 2.85%; Cu 95.3-98.7%), using Franz diffusion cells. This work demonstrated that the total skin absorption of Cu was higher (8.86%) compared to Be (4.89%), which was expected based on the high percentage of Cu contained in the eyeglass temple tips. However, Be accumulated significantly in the epidermis and dermis (up to 0.461 µg/cm²) and, to a lesser extent, in the stratum corneum (up to 0.130 µg/cm²) with a flux of permeation of 3.52 ± 4.5 µg/cm²/hour and lag time of 2.3 ± 1.3 h, after cutaneous exposure of temple tip into 1.0 mL artificial sweat for 24 h. Our study highlights the importance of avoiding the use of Be alloys in items following long-term skin contact.

Rapid Review of Dermal Penetration and Absorption of Inorganic Lead Compounds for Occupational Risk Assessment

Lead (Pb) exposure continues to be a significant public health issue in both occupational and non-occupational settings. The vast majority of exposure and toxicological studies have focused on effects related to inhalation and gastrointestinal exposure routes. Exposure to inorganic Pb compounds through dermal absorption has been less well studied, perhaps due to the assumption that the dermal pathway is a minor contributor to aggregate exposures to Pb compounds. The aim of this rapid review was to identify and evaluate published literature on dermal exposures to support the estimation of key percutaneous absorption parameters (Kp, flux, diffusion rate) for use in occupational risk assessment. Eleven articles were identified containing information from both in vitro and in vivo systems relevant to percutaneous absorption kinetics. These articles provided 24 individual study summaries and information for seven inorganic Pb compounds. The vast majority of study summaries evaluated (n = 22, 92%) reported detectable amounts of dermal absorption of inorganic Pb. Data were identified for four Pb compounds (Pb acetate, Pb nitrate, Pb oxide, and Pb metal) that may be sufficient to use in evaluating physiologically based pharmacokinetic models. Average calculated diffusion rates for the pool of animal and human skin data ranged from 10-7 to 10-4 mg cm-2 h-1, and Kp values ranged from 10-7 to 10-5 cm h-1. Study design and documentation were highly variable, and only one of the studies identified was conducted using standard test guideline-compliant methodologies. Two studies provided quality estimates on the impacts of dermal absorption from water-insoluble Pb compounds on blood Pb levels. These two studies reported that exposures via dermal routes could elevate blood Pb by over 6 µg dl-1. This estimation could represent over 100% of 5 µg dl-1, the blood Pb associated with adverse health effects in adults. The utility of these estimates to occupational dermal exposures is limited, because the confidence in the estimates is not high. The literature, while of limited quality, overall strongly suggests inorganic Pb has the potential for dermal uptake in meaningful amounts associated with negative health outcomes based on upper bound diffusion rate estimates. Future standard test guideline-compliant studies are needed to provide high-confidence estimates of dermal uptake. Such data are needed to allow for improved evaluation of Pb exposures in an occupational risk assessment context.

Human exposure to toxic elements through facial cosmetic products: Dermal risk assessment

Facial cosmetics are the most commonly consumed product, mainly by the women from all over the world irrespective of their age. The facial cosmetics may be contaminated with several toxic elements, which can get absorb on to the facial skin and migrate to the blood vessels. Hence the absorbed toxic elements can cause further adverse effects on the human body. The present study aims to assess the toxic element contents (arsenic, lead, nickel, mercury, and cadmium) in commonly consumed facial cosmetics (face powder, foundation, lightening creams, moisturizer, eye shadow, lipsticks, eyeliner, blush, mascara, sunscreen) and to carry out the risk assessment through different methods. The dermal risk was evaluated as SED, NOAEL, MoS, HQ and ILCR, which is linked with the exposure of selected toxic elements. The total CDDE for all selected elements in facial cosmetic products was found in increasing order as follow: face powder > foundation > lightening creams > moisturizer > eye shadow > lipsticks > eyeliner > blush > mascara > sunscreen. The HQ and HI values for selected elements were found to be < 1 in all facial cosmetics. Whereas the probable MoS of selected toxic elements in all facial cosmetics except eyeliner were found to be 3-4 folds lower than the minimum value of 100 regulated by the WHO.

Influence of repeated contacts on the transfer of elemental metallic lead between compartments in an integrated conceptual model for dermal exposure assessment

Transfer of contaminants to and from the skin surface has been postulated to occur through a number of different pathways and compartments including: object(s)-to-skin, skin-to-skin, skin-to-clothing, skin-to-gloves, air-to-skin, skin-to-lips, and skin-to-saliva. However, many identified transfer pathways have been only minimally examined to determine the potential for measurable transfer. The purpose of this study was to quantitatively evaluate repeated transfer between different compartments using elemental metallic lead (Pb) in the solid form using a series of systematic measurements in human subjects. The results demonstrated that some transfer pathways and compartments are significantly more important than others. Transfer of Pb could not be measured from skin to cotton clothing or skin to laminate countertop surfaces. However, transfer was consistently measured for skin-to-skin and between the skin and the surface of nitrile gloves, suggesting the potential for significant transfer to or from these compartments in real-world exposure scenarios, and the importance of these pathways. With repeated contacts, transfer increased non-linearly between 1 and 5 contacts, but appeared to approach a steady state distribution among the compartments within 10 contacts. Consistent with other studies, relative to 100% transfer for a single contact, the quantitative transfer efficiency decreased with repeated contacts to 29% after 5 contacts and 11-12% after 10 contacts; for skin-to-skin transfer measurements, transfer efficiency after either 5 or 10 contacts was approximately 50% of the single contact transfer. These data are likely to be useful for refining current approaches to modeling of repeated contacts for dermal exposure and risk assessment.

Metal Content in Textile and (Nano)Textile Products

Metals, metallic compounds, and, recently, metallic nanoparticles appear in textiles due to impurities from raw materials, contamination during the manufacturing process, and/or their deliberate addition. However, the presence of lead, cadmium, chromium (VI), arsenic, mercury, and dioctyltin in textile products is regulated in Europe (Regulation 1907/2006). Metal determination in fabrics was performed by inductively coupled plasma-mass spectrometry (ICP-MS) after microwave-assisted acid digestion. The ICP-MS procedure has been successfully validated; relative standard deviations were up to 3% and analytical recoveries were within the 90-107% range. The developed method was applied to several commercial textiles, and special attention has been focused on textiles with nanofinishing (fabrics prepared with metallic nanoparticles for providing certain functionalities). Arsenic content (in textile T4) and lead content (in subsamples T1-1, T1-2, and T3-3) were found to exceed the maximum limits established by the European Regulation 1907/2006. Although impregnation of yarns with mercury compounds is not allowed, mercury was quantified in fabrics T1-2, T5, and T6. Further speciation studies for determining hexavalent chromium species in sample T9 are necessary (hexavalent chromium is the only species of chromium regulated). Some textile products commercialised in Europe included in this study do not comply with European regulation 1907/2006.

Percutaneous metals absorption following exposure to road dust powder

The skin constitutes a protective barrier to external physical and chemical aggressions. Although it is constantly exposed to various xenobiotics, it is generally considered poorly permeable to them, as for example metal ions, becoming unfortunately an entry route of such substances. Metals may penetrate inside the skin inducing more or less local effects such as skin sensitization and potential metals diffusion into the bloodstream. The objective of the study was to investigate the percutaneous penetration of metals in vitro - ex vivo in Franz cell with intact as well damaged skin applying a road dust powder. Moreover, porcine and human skins were compared. This study demonstrated that, after the application of a road dust powder on the skin, metals can penetrate and permeate this cutaneous membrane. From this experimental analysis, in intact skin lead (Pb) achieved the highest skin absorption in both human and porcine skin, while skin absorption profile of cobalt (Co) was the lowest in human skin than the one in porcine model. The concentrations of Ni present in receiving solution were higher compared to other metals in all experiments performed. The present work, definitely shows that metals permeation through damaged skin is accelerated than intact skin, as a result of the weaker cutaneous barrier function. According to published data, pig skin appeared as a suitable model for human skin. Our results confirmed that skin absorption of metals can be relevant in environmental exposures.

Aluminium in cosmetics and personal care products

Usage of inorganic ingredients like aluminium salts in cosmetics and personal care products has been a concern for producers and consumers. Although aluminium is used to treat hyperhidrosis, some worries have been raised about aluminium's role in breast cancer, breast cyst and Alzheimer's disease. The human population is exposed to aluminium from vaccines, diet, and drinking water, but the frequent use of aluminium-based cosmetics might add additional local exposure. This paper reviews literature to determine if aluminium-based products may pose potential harm to the body. The dermal absorption of aluminium is not widely understood. It is not yet known whether aluminium can travel from the skin to brain to cause Alzheimer's disease. Aluminium may cause gene instability, alter gene expression or enhance oxidative stress, but the carcinogenicity of aluminium has not been proved yet. Until now, epidemiological researches were based on oral information, which lacks consistency, and the results are conflicting. Future studies should target real-life-based long-time exposure to antiperspirants and other aluminium-containing cosmetics and personal care products.

Skin permeation of nickel, cobalt and chromium salts in ex vivo human skin, visualized using mass spectrometry imaging

Skin permeation and distribution of three of the most common skin sensitizers was investigated using a previously developed animal-free exposure method combined with imaging mass spectrometry. Nickel, cobalt, and chromium (III) salts were dissolved in a buffer and exposed to human skin ex vivo, to be analyzed using time of flight secondary ion mass spectrometry (ToF-SIMS). Our findings demonstrate that metal haptens mainly accumulated in the stratum corneum, however all three metal sensitizers could also be detected in the epidermis. Cobalt and chromium (III) species penetrated into the epidermis to a larger extent than nickel species. The degree of penetration into the epidermis is suggested to be affected by the sensitization potency of the metal salts, as well as their speciation, i.e. the amount of the respective metal present in the solution as bioaccessible and solubilised ions. Our method provided permeation profiles in human skin for known sensitizers, on a level of detail that is not possible to achieve by other means. The findings show that the permeation profiles are different, despite these sensitizers being all metal ions and common causes of contact allergy. Studying skin uptake by only considering penetration through the skin might therefore not give accurate results.

Comparison of Synthetic Sweat and Influence of Sebum in the Permeation of Bioaccessible Metal(loid)s from Contaminated Soils through a Synthetic Skin Membrane

Dermal exposure to metal(loid)s from contaminated soils has received less attention than oral and inhalation exposure. Still, it can be a relevant pathway for some contaminants. Comparison of synthetic sweats (donor solutions), the influence of sebum, and the characterization of diffusion parameters through a synthetic membrane (acting as skin surrogate) in the permeation of metal(loid)s (As, Cr, Cu, Ni, Pb, and, Zn) from polluted soils is missing. The dermal bioaccessibility tests were performed using two sweat compositions [EN 1811, pH 6.5 (sweat A) and NIHS 96-10, pH 4.7 (sweat B)]. Diffusion parameters of soluble metal(loid)s using the Franz cell methodology were calculated using the Strat-M membrane. The influence of synthetic sebum in the permeation of metal(loid)s was also investigated. The metal(loid) bioaccessibility percentage was higher for sweat B (pH 4.7) compared to sweat A (pH 6.5), attributed to lower pH of sweat B. Among the six elements tested, only chromium and copper permeated the membrane. Permeation coefficient (K_p) was higher for chromium in sweat A (0.05-0.11 cm h^-1) than sweat B (0.0007-0.0037 cm h^-1) likely due to a higher pH and thus more permeable Cr species. The presence of sebum increased lag times for copper permeation. Additional studies regarding speciation of metal(loid)s following extractions in synthetic sweat and comparison of synthetic membrane Strat-M and human skin in the permeation of metal(loid)s are recommended.

Inorganic ions in the skin: Allies or enemies?

Skin constitutes a barrier protecting the organism against physical and chemical factors. Therefore, it is constantly exposed to the xenobiotics, including inorganic ions that are ubiquitous in the environment. Some of them play important roles in homeostasis and regulatory functions of the body, also in the skin, while others can be considered dangerous. Many authors have shown that inorganic ions could penetrate inside the skin and possibly induce local effects. In this review, we give an account of the current knowledge on the effects of skin exposure to inorganic ions. Beneficial effects on skin conditions related to the use of thermal spring waters are discussed together with the application of aluminium in underarm hygiene products and silver salts in treatment of difficult wounds. Finally, the potential consequences of dermal exposure to topical sensitizers and harmful heavy ions including radionuclides are discussed.

Can the Reactivity to Chromate Be Changed in Patch Testing Using a Barrier Cream?

BACKGROUND

The persistent, difficult-to-treat, allergic contact dermatitis from hexavalent chromium in European construction workers has diminished significantly since the legislative measurements that came into force in January 2005. However, sensitization to hexavalent chromium continues to be a problem. Barrier creams have been tried for various allergens with divergent results.

OBJECTIVE

The aim of the study was to investigate the protective capacity of barrier cream candidates against hexavalent chromium in a patch test situation.

METHODS

An experimental study was performed to investigate the reductive properties of glutathione and iron sulfate on the patch test reactivity in chromium-allergic individuals when exposed to hexavalent chromium. In this study, we also investigated the protective properties of a commercially available barrier cream.

CONCLUSIONS

A higher number of volunteers (16/18) showed reactions on the skin treated with the commercially available barrier cream, compared with the untreated skin (13/18) on test reading day 3/4 or day 7. The skin treated with petrolatum or Essex cream showed fewer and less prominent allergic reactions than the skin treated with the commercially available barrier cream.

Safety of Nanoclay/Spring Water Hydrogels: Assessment and Mobility of Hazardous Elements

The presence of impurities in medicinal products have to be controlled within safety limits from a pharmaceutical quality perspective. This matter is of special significance for those countries and regions where the directives, guidelines, or legislations, which prescribe the rules for the application of some products is quite selective or incomplete. Clay-based hydrogels are quite an example of this matter since they are topically administered, but, in some regions, they are not subjected to well-defined legal regulations. Since hydrogels establish an intimate contact with the skin, hazardous elements present in the ingredients could potentially be bioavailable and compromise their safety. The elemental composition and mobility of elements present in two hydrogels have been assessed. Sepiolite, palygorskite, and natural spring water were used as ingredients. The release of a particular element mainly depends on its position in the structure of the hydrogels, not only on its concentration in each ingredient. As a general trend, elements' mobility reduced with time. Among the most dangerous elements, whose presence in cosmetics is strictly forbidden by European legal regulations, As and Cd were mobile, although in very low amounts (0.1 and 0.2 μg/100 g of hydrogel, respectively). That is, assuming 100% bioavailability, the studied hydrogels would be completely safe at normal doses. Although there is no sufficient evidence to confirm that their presence is detrimental to hydrogels safety, legally speaking, their mobility could hinder the authorization of these hydrogels as medicines or cosmetics. In conclusion, the present study demonstrates that hydrogels prepared with sepiolite, palygorskite, and Alicún spring water could be topically applied without major intoxication risks.

Mercury Exposure and Health Problems of the Students Using Skin-Lightening Cosmetic Products in Makassar, South Sulawesi, Indonesia

Despite legal and safety issues, skin-lightening cosmetic products—including hazardous mercury-containing cosmetics—are in increasing demand in Indonesia. Perceptions of beauty may result in desires to have lighter skin tones, regardless of the safety of these cosmetics, which block the production of melanin and thus lighten skin tone. This study investigated Hg exposure of students using skin-lightening cosmetics and assessed the health issues. A total of 105 female students were given a questionnaire regarding their use of cosmetics; a further 43 students formed a non-cosmetic-user control group. Their scalp hair and cosmetic products were analyzed by particle-induced X-ray emission (PIXE) spectroscopy. The geometric-mean hair Hg concentration for the cosmetics-using students was 6.7 µg g−1—three times that of the control group (2.3 µg g−1). Of twenty-seven cosmetic samples were analyzed, twenty had Hg concentrations of 0.12–7834.4 µg g−1 (mean 554.6 µg g−1), and seven had no detectable Hg. The hair Hg concentrations exhibited a statistically significant correlation with cosmetic Hg concentration. The health assessments indicated only rigidity & ataxia and irregular eye movement were prevalent in the cosmetic-using students with less than 7% occurrences.

Chronic Copper Exposure Induces Hypospermatogenesis in Mice by Increasing Apoptosis Without Affecting Testosterone Secretion

Chronic copper exposure impaired spermatogenesis in adult male mice. The aim of this study was to determine whether chronic copper exposure can induce apoptosis of testicular cell and hypospermatogenesis via disturbing testosterone synthesis in adult male mice. In the present study, sixty CD-1 male mice were randomly divided into four groups, and were continuously administered for 8 weeks by oral gavage with copper sulfate at a dose of 0, 25, 100, and 150 mg/kg/day, respectively. We determined the content of serum and testicular copper, testicular coefficient, testicular histopathology, sperm count and motility, the mRNA and protein levels of Caspase-3, Bax, and Bcl-2, Leydig cell count, testosterone content, testosterone synthetase, and testosterone synthesis-related genes. The results showed that the copper levels in serum increased in a dose-dependent manner, and the copper levels in testes were significantly related to serum copper levels. Male mice given copper sulfate 100 and 150 dosage groups showed significant decreased in sperm motility and sperm number as well as increased in testes damage, and there was no significant change in testicular coefficient in the four groups. The mRNA levels of Bcl-2 decreased and Caspase-3 increased in 150 dosage group, and Bax increased in two higher dosage groups. Meanwhile, Caspase-3 and Bax proteins increased in 150 dosage group, and Bcl-2 protein decreased in three copper treatment groups. Nevertheless, there were no differences on the levels of testosterone content and testosterone synthetase of 3β-HSD, 17β-HSD, 17α-Hyd, and 20α-Hyd, mRNA levels of Cyp11a1, Cyp17a1, and Star, and quantity of Leydig cells in four groups. Overall, these data showed that chronic copper exposure led to copper residues in the testes, and the doses of 100 and 150 mg/kg/day copper sulfate may induce hypospermatogenesis by increasing apoptosis without affecting testosterone secretion.

Metal nanomaterials: Immune effects and implications of physicochemical properties on sensitization, elicitation, and exacerbation of allergic disease

The recent surge in incorporation of metallic and metal oxide nanomaterials into consumer products and their corresponding use in occupational settings have raised concerns over the potential for metals to induce size-specific adverse toxicological effects. Although nano-metals have been shown to induce greater lung injury and inflammation than their larger metal counterparts, their size-related effects on the immune system and allergic disease remain largely unknown. This knowledge gap is particularly concerning since metals are historically recognized as common inducers of allergic contact dermatitis, occupational asthma, and allergic adjuvancy. The investigation into the potential for adverse immune effects following exposure to metal nanomaterials is becoming an area of scientific interest since these characteristically lightweight materials are easily aerosolized and inhaled, and their small size may allow for penetration of the skin, which may promote unique size-specific immune effects with implications for allergic disease. Additionally, alterations in physicochemical properties of metals in the nano-scale greatly influence their interactions with components of biological systems, potentially leading to implications for inducing or exacerbating allergic disease. Although some research has been directed toward addressing these concerns, many aspects of metal nanomaterial-induced immune effects remain unclear. Overall, more scientific knowledge exists in regards to the potential for metal nanomaterials to exacerbate allergic disease than to their potential to induce allergic disease. Furthermore, effects of metal nanomaterial exposure on respiratory allergy have been more thoroughly-characterized than their potential influence on dermal allergy. Current knowledge regarding metal nanomaterials and their potential to induce/exacerbate dermal and respiratory allergy are summarized in this review. In addition, an examination of several remaining knowledge gaps and considerations for future studies is provided.

Risk of human exposure to metals in some household hygienic products in Nigeria

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Metal content of 27 household hygienic products available in Nigeria was determined.

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SED values for metals in these products were below tolerable intake levels.

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MoS values indicate that they are reasonably safe for human use.

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However, products contained significant amounts of toxic and allergenic metals.

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Effluents from use of products are likely sources of metals to the environment.

This study presents data on the levels and risk of human exposure to Cd, Pb, Cr, Ni, Cu, Co, Mn, Zn and Fe in some popular brands of household hygienic products (HHPs) available in Nigeria. The HHPs were digested with a mixture of HNO₃, HCl and HClO₄ in a ratio of 1:3:1 and the concentrations of the selected metals were quantified by atomic absorption spectrophotometry. The metal concentrations (in μg g⁻¹) in these products ranged from 0.4 to 5.4, <0.09–47.0, <0.12–43.7, <0.06–7.5, <0.12–9.5, <0.06–15.0, <0.09–24.5, 9.0–675 and 62.4–434 for Cd, Pb, Cr, Cu, Co, Ni, Mn, Zn and Fe respectively. The systemic exposure dosages for the metals, arising from the use of these HPPs, were less than their respective provisional tolerable daily intake/recommended dietary allowance values. The household hygienic products are safe to use by humans based on the margin of safety values that were all above 100. However, the products contained significant levels of toxic (Cd and Pb), allergenic (Ni and Cr) and other low toxicity metals (Mn, Zn and Fe), which could be a potential threat to the environment.

Hidden Metals in Several Brands of Lipstick and Face Powder Present on Polish Market

Cosmetics still retain their brilliant effect, but public concern about their toxicity has become a hot issue. Trace amounts of toxic heavy metals can be either intentionally added to cosmetics or present as impurities in the raw materials. We therefore assessed the levels of lead, nickel, copper, zinc and iron in six brands of lipstick and six brands of cosmetic powder that are widely available in local Polish markets. The cosmetics were digested and analyzed for the metals using flame atomic absorption spectrophotometry. Lead and nickel were found in some powders, but none in lipstick samples. This study revealed that the levels of these metals were higher than the specifications reported in the literature data. On the other hand, the copper content was determined at the level of 435 mg/kg in one sample of powder and at 75.92 mg/kg in one lipstick. Iron levels ranged from 0 to 12,168.57 mg/kg depending on the brand of powder or lipstick, and were generally higher in powders. Zinc was detected in the range of 1.73–488.31 mg/kg in all 12 samples. The results lead to the conclusion that constant control of metallic content in lipsticks, powders and other facial cosmetics should be seriously considered.

Effect of transdermal magnesium cream on serum and urinary magnesium levels in humans: A pilot study

Background

Oral magnesium supplementation is commonly used to support a low magnesium diet. This investigation set out to determine whether magnesium in a cream could be absorbed transdermally in humans to improve magnesium status.

Methods and findings

In this single blind, parallel designed pilot study, n = 25 participants (aged 34.3+/-14.8y, height 171.5+/-11cm, weight 75.9 +/-14 Kg) were randomly assigned to either a 56mg/day magnesium cream or placebo cream group for two weeks. Magnesium serum and 24hour urinary excretion were measured at baseline and at 14 days intervention. Food diaries were recorded for 8 days during this period. Mg test and placebo groups’ serum and urinary Mg did not differ at baseline. After the Mg²⁺ cream intervention there was a clinically relevant increase in serum magnesium (0.82 to 0.89 mmol/l,p = 0.29) that was not seen in the placebo group (0.77 to 0.79 mmol/L), but was only statistically significant (p = 0.02)) in a subgroup of non-athletes. Magnesium urinary excretion increased from baseline slightly in the Mg²⁺ group but with no statistical significance (p = 0.48). The Mg²⁺ group showed an 8.54% increase in serum Mg²⁺ and a 9.1% increase in urinary Mg²⁺ while these figures for the placebo group were smaller, i.e. +2.6% for serum Mg²⁺ and -32% for urinary Mg^2+. In the placebo group, both serum and urine concentrations showed no statistically significant change after the application of the placebo cream.

Conclusion

No previous studies have looked at transdermal absorbency of Mg²⁺ in human subjects. In this pilot study, transdermal delivery of 56 mg Mg/day (a low dose compared with commercial transdermal Mg²⁺ products available) showed a larger percentage rise in both serum and urinary markers from pre to post intervention compared with subjects using the placebo cream, but statistical significance was achieved only for serum Mg²⁺ in a subgroup of non-athletes. Future studies should look at higher dosage of magnesium cream for longer durations.

Trial registration

ISRCTN registry ID No. ISRTN15136969

Selected Biomarkers Revealed Potential Skin Toxicity Caused by Certain Copper Compounds

Copper is an essential mineral and plays important roles in skin growth and activity. Copper delivery through skin can provide beneficial effects but its potential to induce skin irritation reactions is often overlooked. Data on dermal toxicity caused by copper compounds is scant. Some recognized in vitro skin toxicity methods are unsuitable for all metal compounds. Here, we employ a keratinocyte-based model and evaluated the skin irritation potential of copper compounds at cellular, genomic and proteomic levels. We determined cell viability and cytotoxicity by using tetrazolium reduction assay and Lactate Dehydrogenase (LDH) assay, performed real-time PCR and protein quantification to assess the expression of biomarkers after treating cells with copper peptide (GHK-Cu), copper chloride (CuCl₂) and copper acetate (Cu(OAc)₂). These copper compounds exhibited different irritancy potentials at the same treatment concentrations. GHK-Cu was not cytotoxic and did not induce any significant change in the expression levels of various skin irritation-related biomarkers. IL-1α and IL-8, HSPA1A and FOSL1 were significantly upregulated following 24-h treatment with CuCl₂ and Cu(OAc)₂ at 58 and 580 μM without concomitant inhibition in cell viability. GHK-Cu has a low potential of inducing skin irritation and therefore provides a safer alternative for the delivery of copper through skin.

Human health risk assessment of lead, manganese and copper from scrapped car paint dust from automobile workshops in Nigeria

The economic downturn in Nigeria and Structural Adjustment Programme led to the flooding of Nigerian market with imported used automobiles. Most of these vehicles needed refurbishing and reworking. The present study is a human health risk assessment of metal exposure resulting from reworking of imported used vehicles in Nigeria. Scrap paint dusts from 56 Japanese made cars were collected from 8 different mechanic villages (workshops A-H] in Southeastern Nigeria. Scrap paints were homogenized, mixed, divided into fine particles and digested by standard method. The filtrates were assayed of lead, manganese and copper with atomic absorption spectrophotometry (AAS). Workshop B has the highest concentration of Pb (4.26 ± 0.93). Manganese in workshops A and F were (3.31 ± 0.85) and (3.04 ± 0.47) respectively and were higher than the levels from workshops C, B, D, G and H. Copper in workshop D (7.11 ± 0.21) was significantly greater than the other workshops. The highest hazard quotient (HQ) through ingestion, inhalation and dermal exposures in adults were 9.44E-05 (workshop B), 4.20E-01 (workshop B) and 1.08E-05 (workshop D) respectively. The highest values for HQ through ingestion, inhalation and dermal in children were 8.82E-04, 7.61E-01 and 2.86E-05 all in workshop B respectively. For children, the highest carcinogenic risk levels were 7.05E-08, 6.09E-05 and 2.29E-10 for ingestion, inhalation and dermal exposures respectively. In adults, the carcinogenic risk levels were 7.55E-09, 3.39E-05 and 8.67E-10 for ingestion, inhalation and dermal exposures respectively. Chronic exposure to scrap car paint dusts may be of significant public health importance in Nigeria as this may add to the body burden of some heavy metals.

Concentrations and exposure risks of some metals in facial cosmetics in Nigeria

The concentrations of nine metals (Cd, Pb, Ni, Cr, Co, Cu, Fe, Mn and Zn) were determined in lip sticks, lip glosses, lip balms, eye pencils, eyeliners, eye shadows, blushes, mascaras and face powders. The study was aimed at providing information on the risk associated with human exposure to metals in these facial cosmetic products. The concentrations of metals in the samples were measured by atomic absorption spectrometry after digestion with a mixture of nitric acid, hydrochloric acid and hydrogen peroxide. The mean concentrations of metals in these facial cosmetics ranged from 3.1 to 8.4 μg g^-1 Cd, 12-240 μg g^-1 Pb, 9.1-44 μg g^-1 Cr, 18-288 μg g^-1 Ni, 1.6-80 μg g^-1 Cu, 7.9-17 μg g^-1 Co, 2.3-28 mg g^-1 Fe, 12-230 μg g^-1 Mn, and from 18 to 320 μg g^-1 Zn. The concentrations of Ni, Cr and Co were above the suggested safe limit of 1 μg g^-1 for skin protection, while Cd and Pb were above the Canadian specified limits. The systemic exposure dosage (SED) values for these metals obtained from the use of these facial cosmetic products were below their respective provisional tolerable daily intake (PTDI)/or recommended daily intake (RDI) values. The margin of safety values obtained were greater than 100 which indicated that the concentrations of the metals investigated in these facial cosmetics do not present considerable risk to the users except in the case of face powders.

In vitro dermal penetration of nickel nanoparticles

Nickel nanoparticles (NiNPs) represent a new type of occupational exposure because, due to the small size/high surface, they can release more Ni ions compared to bulk material. It has been reported a case of a worker who developed sensitization while handling nickel nanopowder without precautions. Therefore there is the need to assess whether the skin absorption of NiNPs is higher compared to bulk nickel. Two independent in vitro experiments were performed using Franz diffusion cells. Eight cells for each experiment were fitted using intact and needle-abraded human skin. The donor phase was a suspension of NiNPs with mean size of 77.7 ± 24.1 nm in synthetic sweat. Ni permeated both types of skin, reaching higher levels up to two orders of magnitude in the damaged skin compared to intact skin (5.2 ± 2.0 vs 0.032 ± 0.010 μg cm(-2), p = 0.006) at 24 h. Total Ni amount into the skin was 29.2 ± 11.2 μg cm(-2) in damaged skin and 9.67 ± 2.70 μg cm(-2) in intact skin (mean and SD, p = 0.006). Skin abrasions lead to doubling the Ni amount in the epidermis and to an increase of ten times in the dermis. This study demonstrated that NiNPs applied on skin surface cause an increase of nickel content into the skin and a significant permeation flux through the skin, higher when a damaged skin protocol was used. Preventive measures are needed when NiNPs are produced and used due to their higher potential to enter in our body compared to bulk nickel.

Microneedle-Mediated Delivery of Copper Peptide Through Skin

PURPOSE

Copper peptide (GHK-Cu) plays an important role in skin regeneration and wound healing. However, its skin absorption remains challenging due to its hydrophilicity. Here we use polymeric microneedle array to pre-treat skin to enhance GHK-Cu skin penetration.

METHODS

Two in vitro skin models were used to assess the capability of microneedles in facilitating skin delivery of GHK-Cu. Histological assay and confocal laser scanning microscopy were performed to characterize and quantify the microconduits created by the microneedles inside skin. Cellular and porcine models were used to evaluate the safety of microneedle-assisted copper peptide delivery.

RESULTS

The depth and percentage of microneedle penetration were correlated with application forces, which in turn influenced the extent of enhancement in the skin permeability of GHK-Cu. In 9 h, 134 ± 12 nanomoles of peptide and 705 ± 84 nanomoles of copper permeated though the microneedle treated human skin, while almost no peptide or copper permeated through intact human skin. No obvious signs of skin irritation were observed with the use of GHK-Cu after microneedle pretreatment.

CONCLUSIONS

It is effective and safe to enhance the skin permeation of GHK-Cu by using microneedles. This approach may be useful to deliver similar peptides or minerals through skin.

Dissolution of the metal sensitizers Ni, Be, Cr in artificial sweat to improve estimates of dermal bioaccessibility

Dermal exposure to sensitizing metals is a serious occupational and public health problem. The usual approach to dermal exposure assessment is to process samples by chemical methods that use reactants to digest the metal particles and quantify the mass. In the case of dermal exposure assessment, these reactants are not representative of the skin surface film liquids and hence, may overestimate bioaccessibility. We hypothesize that the amount and form of sensitizer on a sample that leaches in a biological fluid, as can be estimated using artificial sweat, may be a more relevant metric for assessing health risks. Beryllium metal (Be), nickel metal (Ni), and chromium carbide (Cr3C2) particles were characterized and masses of sensitizing ions were measured using established reactant-assisted digestion procedures and extraction in artificial sweat under physiologically relevant conditions. Chromium ions released into artificial sweat were speciated to understand valence states. The ratios of the fraction of metal dissolved in artificial sweat relative to that dissolved by chemical-specific reactants were 1/2 (Be), 1/108 (Ni), and 1/2500 (Cr). The divalent Be and Ni cations were stable in artificial sweat over time (did not precipitate) whereas hexavalent chromium [Cr(VI)] ions decayed over time. Further analysis using speciated isotope dilution mass spectrometry revealed that the decay of Cr(VI) was accompanied by the formation of Cr(III) in the sweat model. Use of reactant-assisted analytical chemistry to quantify amounts of metal sensitizers on samples could overestimate biologically relevant exposure. In addition to mass, the valence state also influences penetration through the outer stratum corneum of the skin and is an important consideration when assessing exposure to complex sensitizers such as Cr which have multiple valence states with differing penetration efficiencies.

Zinc, its biological role and use in dermatology

This literature review detines the biological role ot zinc in the human body, immune homeostasis and skin physiology as well as pathophysiology ot skin diseases. It describes the current range ot systemic and topical zinc preparations and their pharmacological characteristics. The review also describes skin diseases that may be treated with the use ot zinc preparations on a grounded basis, and discloses the clinical experience ot the use ot these drugs described in the world literature. It sets out certain recommendations tor using zinc preparations in clinical practice.