Beneficial and adverse effects of dam construction in canal tannery wastewater effluent with a high content of chromium in Hazaribagh, Bangladesh.

BACKGROUND: Blockage to divide downstream canals into upstream canals, into which tannery wastewater including a high concentration of trivalent chromium [Cr(III)] is directly discharged, has been constructed in Hazaribagh, a tannery built-up area in Bangladesh. However, there has been no study to verify the environmental significance of blockage construction for water pollution of Cr in nature. METHODS: Consecutive fixed area monitoring for a total of 164 water samples collected outside and inside Hazaribagh from 2014 to 2023 was carried out to clarify the effects of stagnant and flowable canal water in the presence or absence of blockage on Cr(III) and hexavalent Cr [Cr(VI)] concentrations. RESULTS: Since pollution of Cr(III) and Cr(VI) in Buriganga River (outside Hazaribagh) was not serious, this study then focused on their pollution in canal water (inside Hazaribagh) in the nonblockage period, blockage construction period and blockage destruction period. As expected, the mean Cr(III) concentration in downstream canal water samples in the blockage construction period was more than 98% lower than that in the upstream canal water samples in the same period, while the concentrations were comparable in downstream and upstream canal water samples in the nonblockage period and blockage destruction period. Unexpectedly, the mean concentration of Cr(VI) in the upstream canal water samples in the blockage construction period was 38.6-fold and 3.3-fold higher than that in the downstream canal water samples and the Cr(VI) guideline value by the US-EPA, respectively. CONCLUSION: This study demonstrated for the first time not only a merit of decreased Cr(III) pollution but also a demerit of increased Cr(VI) pollution in stagnant water derived from blockage construction in natural environments. This bitter lesson obtained by the enclosure of Cr(III)-polluted water is globally applicable for water pollution of Cr(III), which is used in various industries including the leather industry.

A Novel Approach for Designing a Sub-Bandgap in CuGa(S,Te)2 Thin Films Assisted with Numerical Simulation of Solar Cell Devices for Photovoltaic Application.

As a well-explored chalcopyrite material, copper gallium sulfide CGS has been considered a potential material for solar cell absorber layers. However, its photovoltaic attributes still require to be improved. In this research, a novel chalcopyrite material, copper gallium sulfide telluride CGST, has been deposited and verified as a thin film absorber layer to fabricate high-efficiency solar cells by experimental testing and numerical simulations. The results display the intermediate band formation in CGST with incorporation of Fe ions. Electrical studies showed enhancement in mobility from 1.181 to 1.473 cm2 V-1 s-1 and conductivity from 2.182 to 5.952 S cm-1 for pure and 0.08 Fe-substituted thin films. The I-V curves display the photoresponse and ohmic nature of the deposited thin films, and the maximum photoresponsivity (0.109 A W-1) was observed for 0.08 Fe-substituted films. Theoretical simulation of the prepared solar cells was carried out using SCAPS-1D software, and the obtained efficiency displayed an increasing trend from 6.14 to 11.07% as the Fe concentration increased from 0.0 to 0.08. This variation in efficiency is attributed to the decrease in bandgap (2.51-1.94 eV) and the formation of an intermediate band in CGST with Fe substitution, which is evidenced in UV-vis spectroscopy. The above revealed results open the way to 0.08 Fe-substituted CGST as a promising candidate as a thin film absorber layer in solar photovoltaic technology.

Unexpected associations of long-term and excessive exposure to trivalent chromium with hypertension and glycosuria in male tannery workers.

Serious health hazards including renal, skin and hearing disorders have been reported in Bangladeshi tannery workers (TWs) who were chronically exposed to a large amount of trivalent chromium [Cr(III)]. However, the effects of Cr(III) exposure on the prevalence of hypertension and the prevalence of glycosuria in TWs remain unknown. Since the Cr level in toenails is an established marker reflecting long-term exposure to Cr(III) in humans, the associations of Cr levels in toenails with the prevalence of hypertension and the prevalence of glycosuria in male tannery and non-tannery office workers (non-TWs) in Bangladesh were investigated in this study. The mean toenail Cr level in non-TWs (0.5 µg/g, n = 49) was comparable to that in the general population reported previously. Mean Cr levels in TWs with a low toenail Cr level (5.7 µg/g, n = 39) and those with a high toenail Cr level (298.8 µg/g, n = 61) were >10-fold and >500-fold higher, respectively, than that in non-TWs. Our univariate and multivariate analyses indicated that the prevalence of hypertension and the prevalence of glycosuria in TWs with a high toenail Cr level, but not in TWs with a low toenail Cr level, were significantly lower than those in non-TWs. This study showed for the first time that long-term and excessive exposure to Cr(III) that is more than >500-fold but not >10-fold higher than the usual exposure level could decrease the prevalence of hypertension and the prevalence of glycosuria in TWs. Thus, this study revealed unexpected effects of exposure to Cr(III) on health.

Heme protein identified from scaly-foot gastropod can synthesize pyrite (FeS2) nanoparticles.

The scaly-foot gastropod (Chrysomallon squamiferum), which lives in the deep-sea zone of oceans around thermal vents, has a black shell and scales on the foot. Both the black shell and scales contain iron sulfide minerals such as greigite (Fe3S4) and pyrite (FeS2). Although pyrite nanoparticles can be used as materials for solar panels, it is difficult to synthesize stable and spherical nanoparticles in vitro. In this study, we extracted organic molecules that interact with nano-pyrite from the shell of the scaly-foot gastropod to develop a low-cost, eco-friendly method for pyrite nanoparticles synthesis. Myoglobin (csMG), a heme protein, was identified in the iron sulfide layer of the shell. We purified recombinant csMG (r-csMG) and demonstrated that r-csMG helped in the conversion of ferric ions, sulfide ions and sulfur into spherical shaped pyrite nanoparticles at 80°C. To reduce the effort and cost of production, we showed that commercially available myoglobin from Equus caballus (ecMG) also induced the in vitro synthesis of pyrite nanoparticles. Using structure-function experiments with digested peptides, we highlighted that the amino acid sequence of r-csMG peptides controlled the spherical shape of the nanoparticle while the hemin molecules, which the peptides interacted with, maintained the size of nanoparticles. Synthesized pyrite nanoparticles exhibited strong photoluminescence in the visible wavelength region, suggesting its potential application as a photovoltaic solar cell material. These results suggest that materials for solar cells can be produced at low cost and energy under eco-friendly conditions. STATEMENT OF SIGNIFICANCE: Pyrite is a highly promising material for photovoltaic devices because of its excellent optical, electrical, magnetic, and transport properties and high optical absorption coefficient. Almost all current pyrite synthesis methods use organic solvents at high temperature and pressure under reducing conditions. Synthesized pyrite nanoparticles are unstable and are difficult to use in devices. The scaly-foot gastropod can synthesize pyrite nanoparticles in vivo, meaning that pyrite nanoparticles can be generated in an aqueous environment at low temperature. In this study, we demonstrated the synthesis of pyrite nanoparticles using a heme protein identified in the iron sulfide layer of the scaly-foot gastropod shell. These results exemplify how natural products in organisms can inspire the innovation of new technology.

Decreased hearing levels at frequencies for understanding speech in tannery workers exposed to a high level of trivalent chromium in Bangladesh.

Hexavalent chromium [Cr(VI)], which has a strong corrosive effect, has been reported to cause perforation of the eardrum. Trivalent chromium [Cr(III)] also has a weak corrosive effect. However, there has been no study on the effects of exposure to Cr, either Cr(VI) or Cr(III), on hearing levels in animals or humans. In this study, the effect of Cr(III) exposure on hearing levels was determined in a human study. Then the reproducibility of the results obtained in the human study and the etiology were investigated in an animal study. The mean levels of total chromium (t-Cr) in hair and toenails from 100 Bangladeshi tannery workers were >20-fold and >360-fold higher, respectively, than those in hair and toenails from 49 Bangladeshi non-tannery workers (office workers). Multivariate analysis revealed decreases of hearing levels (DHLs) at 1 k and 4 k Hz, frequencies that are crucial for understanding language, but not at 8 k and 12 k Hz, in the tannery workers. Since >99.99% of t-Cr in the wastewater that the workers were in direct contact with in the tanneries was Cr(III), the epidemiological results suggest Cr(III)-mediated DHLs in the tannery workers. The results of animal experiments in this study further showed that treatment with eardrops but not intraperitoneal injection with the same amount of Cr(III) that tannery workers might be exposed to resulted in DHL with a damaged eardrum in mice. Previous studies suggested that Cr(III) can directly reach the eardrums of tannery workers via droplets in the air. Cr(III) could also reach the eardrum via picking an ear canal with a finger contaminated with tannery wastewater including Cr(III). Taken together, the results of both human and animal studies suggest the risk of DHLs caused by damage of the eardrum through external exposure to Cr(III) via the ear canal.

Redistribution of potentially toxic elements in the hydrosphere after the relocation of a group of tanneries.

Simultaneous relocation of a group of pollutant sources in a heavily polluted area is a rare event. Such a relocation has been implemented in Hazaribagh, a tannery built-up area with heavy pollution, in Bangladesh. This provides a valuable opportunity to compare the changes in environmental conditions associated with the relocation of multiple putative sources. Our environmental monitoring for a period of 6 years at the stationary areas centered on Hazaribagh geographically revealed trivalent [Cr(III)], hexavalent [Cr(VI)] chromium, lead, iron, and manganese as tannery-related elements after the legal deadline for tannery relocation. The median Cr(III) level in canal water, into which wastewater from tanneries was directly discharged, after the relocation was 97% lower of that before the relocation, indicating a beneficial effect of the relocation. In contrast, the median Cr(VI) level in water samples just after the relocation and 2 years after the relocation were approximately 5-fold and 30-fold higher, respectively, than those before the relocation. These results indicate not only a harmful effect of the relocation but also the possibility of conversion from Cr(III) to Cr(VI) in nature. Although the health hazard indexes considering all of the tannery-related elements in all of the canal water samples before the relocation exceeded the safety thresholds, the percentages of samples in which the indexes exceeded their safety thresholds after the relocation decreased by 32.5%-45.0%. Treatment with our patented hydrotalcite-like compound consisting of magnesium and iron (MF-HT) resulted in decreases in the health hazard indexes in all of the water samples in which the indexes exceeded their safety thresholds to levels lower than their thresholds. Thus, this study shows the double-edged effects associated with the relocation and a potential solution.

Co-deposition of MoS2films by reactive sputtering and formation of tree-like structures.

Transition metal dichalcogenides (TMDCs) are versatile layered materials with potential applications ranging from optoelectronic devices to water splitting. Top-down fabrication methods such as exfoliation are not practical for a large-scale production of high-quality devices: a bottom-up approach such as sputtering, a low-temperature deposition method, is more suitable. However, due to its anisotropic nature, the growth mechanism of molybdenum disulfide (MoS2) via sputtering is complex and remains to be investigated in detail. In this paper, we study the growth of MoS2 films co-deposited by using a sulfur (S) hot-lip cell and a molybdenum (Mo) sputtering target via reactive sputtering. The impact of S partial pressure on the structure and morphology of MoS2films was systematically characterized, and it was observed that the growth is dominated by vertically-oriented sheets with horizontal branches, resulting in a tree-like structure. The growth front of the structures is ascribed to the anisotropic incorporation of adatoms with regards to the orientation of MoS2.

Clinical spectrum and predictors of severity of dengue among children in 2019 outbreak: a multicenter hospital-based study in Bangladesh.

BACKGROUND: The mosquito-borne arboviral disease dengue has become a global public health concern. However, very few studies have reported atypical clinical features of dengue among children. Because an understanding of various spectrums of presentation of dengue is necessary for timely diagnosis and management, we aimed to document the typical and atypical clinical features along with predictors of severity among children with dengue during the largest outbreak in Bangladesh in 2019. METHODS: We conducted a cross-sectional study between August 15 and September 30, 2019. in eight tertiary level hospitals in Dhaka city. Children (aged < 15 years) with serologically confirmed dengue were conveniently selected for data collection through a structured questionnaire. Descriptive, inferential statistics, and multivariable logistic regression were used to analyze data. RESULTS: Among the 190 children (mean age 8.8 years, and male-female ratio 1.22:1) included in the analysis, respectively 71.1 and 28.9% children had non-severe and severe dengue. All children had fever with an average temperature of 103.3 ± 1.2 F (SD). Gastrointestinal symptoms were the most common associated feature, including mostly vomiting (80.4%), decreased appetite (79.5%), constipation (72.7%), and abdominal pain (64.9%). Mouth sore, a less reported feature besides constipation, was present in 28.3% of children. Atypical clinical features were mostly neurological, with confusion (21.3%) being the predominant symptom. Frequent laboratory abnormalities were thrombocytopenia (87.2%), leucopenia (40.4%), and increased hematocrit (13.4%). Age (AOR 0.86, 95%CI 0.75-0.98, p = 0.023), mouth sore (AOR 2.69, 95%CI 1.06-6.96, p = 0.038) and a decreased platelet count (< 50,000/mm3) with increased hematocrit (> 20%) (AOR 4.94, 95%CI 1.48-17.31, p = 0.01) were significant predictors of severity. CONCLUSIONS: Dengue in children was characterized by a high severity, predominance of gastrointestinal symptoms, and atypical neurological presentations. Younger age, mouth sores, and a decreased platelet with increased hematocrit were significant predictors of severity. Our findings would contribute to the clinical management of dengue in children.

Development of an efficient remediation system with a low cost after identification of water pollutants including phenolic compounds in a tannery built-up area in Bangladesh.

Water pollution caused by tannery wastewater is an important issue in developing countries. Most studies have focused on inorganic chemicals represented by chromium as a tannery-related main pollutant. This is the first study in which pollution of water by tannery-related organic chemicals was assessed by a combination of qualitative and quantitative analyses. Our quantitative analysis showed that the maximum concentration of total phenolic compounds (phenols), consisting of phenol, bisphenol F, p-cresol and chlorocresol, in canal water in a tannery built-up area in Bangladesh was >67-fold higher than the Environmental, Health and Safety (EHS) guideline value. Mapping of our results indicated tanneries as the sources of phenols pollution. Our original depurative, a hydrotalcite-like compound consisting of magnesium and iron (MF-HT), could adsorb all kinds of phenols and exhibited the highest phenol adsorption ability (115.8 mg/g) among reported hydrotalcite-like compounds. The levels of phenols in canal water samples were reduced to levels below the guideline value by using MF-HT with assistance of a photocatalytic reaction. Moreover, the mean level of chromium (112.2 mg/L) in canal water samples was decreased by 99.7% by using the depurative. Thus, the depurative has the potential for solving the problem of tannery-related water pollution by phenols and chromium.

Increased levels of renal damage biomarkers caused by excess exposure to trivalent chromium in workers in tanneries.

BACKGROUND: The process for leather material production is carried out in developing countries using a large amount of trivalent chromium [Cr(III)]. Assesment of health risks for millions of workers in tanneries worldwide that are highly polluted with Cr(III) is needed. METHODS: Levels of total Cr and its chemical species in wastewater samples from tannery built-up areas of Bangladesh were investigated. Cr-mediated renal damage was assessed in 100 male tannery workers by epidemiological analysis consisting of questionnaires and measurements of levels of urinary Cr and urinary renal damage markers [urinary levels of total protein and kidney injury molecule-1 (KIM-1)]. RESULTS: High levels of total Cr (mean ± standard deviation = 1,908,762 ± 703,450 µg/L) were detected in wastewater samples from 13 sites of tanneries. More than 99.99% of total Cr in the wastewater was Cr(III), indicating that workers in the tanneries were exposed to large concentrations of Cr(III). Cr levels (mean ± standard, 2.89 ± 4.23 µg/g creatinine) in urine samples from the workers in tanneries were >24-fold higher than the levels in a general population previously reported. Multivariate analysis showed significant correlations between urinary levels of Cr and urinary levels of renal damage biomarkers. Nagelkerke Pseudo R2 values also showed that Cr level is the strongest contributor to the levels of renal damage biomarkers in the workers. CONCLUSION: Our results newly suggest that excess exposure to Cr(III) could be a risk for renal damage in humans.

Hearing loss in humans drinking tube well water with high levels of iron in arsenic-polluted area.

Well water for drinking with increased levels of iron in arsenic-polluted areas has been reported worldwide. Oral exposure to arsenic has been shown to be associated with hearing loss, while there is no evidence for an association between excessive exposure to iron and hearing loss in humans. In this study, we determined iron and arsenic levels in biological samples and hearing levels by pure tone audiometry (PTA) in subjects in a control area and an arsenic-polluted area in Bangladesh. The iron level in well water in the arsenic-polluted area was significantly higher than that in piped supply water in the control area. Subjects in the polluted area (n = 109), who had higher iron and arsenic levels in hair and toenails than those in subjects in the control area (n = 36), had an increased risk of hearing loss at 8 kHz and 12 kHz after adjustments for age, gender, smoking and BMI. Significant associations of the exposure group with hearing loss at 8 kHz and 12 kHz remained after further adjustment for arsenic levels in toenails and hair. Thus, this pilot study showed that excessive exposure to iron via drinking water is a potential risk for hearing loss in humans.

Chromium-mediated hyperpigmentation of skin in male tannery workers in Bangladesh.

Since tannery workers in developing countries are chronically exposed to high levels of chromium (Cr), there are serious concerns about health problems. However, there has been limited study in which Cr levels were measured in tannery workers, who are chronically exposed to Cr. Our preliminary inspection showed that there was hyperpigmented skin in tannery workers. We therefore investigated the correlation between skin pigmentation levels digitally evaluated as L* values by using a reflectance spectrophotometer and Cr levels in skin appendages in 100 male tannery workers and in 49 male non-tannery workers in Bangladesh. Digitalized skin pigmentation levels of the face and feet in addition to Cr levels in hair and toenails in tannery workers were significantly higher than those in non-tannery workers in our univariate analysis. Spearman's rank correlation coefficient analysis showed significant correlation between duration of tannery work (years) and Cr levels in hair (r = 0.62) and toenails (r = 0.61). Our multivariate analysis also showed that Cr levels in hair and toenails were significantly correlated with digitalized skin pigmentation levels of the face and feet in addition to duration of tannery work in all participants. Thus, our results showed the development of hyperpigmented skin in tannery workers. Our results also suggested that hyperpigmented skin could be a useful diagnostic marker for chronic exposure to Cr. Furthermore, cutaneous L* value might be a convenient marker for detection of chronic Cr poisoning, since the digitalized values enable objective evaluation of skin pigmented levels by general people as well as dermatologists.

A rare variety of congenital adrenal hyperplasia with mosaic Klinefelter syndrome: a unique combination presenting with ambiguous genitalia and sexual precocity

Congenital adrenal hyperplasia (CAH) due to the three-beta-hydroxysteroid-dehydrogenase (3ß-HSD) enzyme deficiency is a rare autosomal recessive disorder presenting with sexual precocity in a phenotypic male. Klinefelter syndrome (KS) is the most common sex chromosome aneuploidy presenting with hypergonadotropic hypogonadism in a male. However, only a handful of cases of mosaic KS have been described in the literature. The co-existence of mosaic KS with CAH due to 3ß-HSD enzyme deficiency portrays a unique diagnostic paradox where features of gonadal androgen deficiency are masked by simultaneous adrenal androgen excess. Here, we report a 7-year-old phenotypic male boy who, at birth presented with ambiguous genitalia, probably a microphallus with penoscrotal hypospadias. Later on, he developed accelerated growth with advanced bone age, premature pubarche, phallic enlargement and hyperpigmentation. Biochemically, the patient was proven to have CAH due to 3ß-HSD deficiency. However, the co-existence of bilateral cryptorchidism made us to consider the possibility of hypogonadism as well, and it was further explained by concurrent existence of mosaic KS (47,XXY/46,XX). He was started on glucocorticoid and mineralocorticoid replacement and underwent right-sided orchidopexy on a later date. He showed significant clinical and biochemical improvement on subsequent follow-up. However, the declining value of serum testosterone was accompanied by rising level of FSH thereby unmasking hypergonadotropic hypogonadism due to mosaic KS. In future, we are planning to place him on androgen replacement as well. Learning points: •• Ambiguous genitalia with subsequent development of sexual precocity in a phenotypic male points towards some unusual varieties of CAH. •• High level of serum testosterone, adrenal androgen, plasma ACTH and low basal cortisol are proof of CAH, whereas elevated level of 17-OH pregnenolone is biochemical marker of 3ß-HSD enzyme deficiency. •• Final diagnosis can be obtained with sequencing of HSD3B2 gene showing various mutations. •• Presence of bilateral cryptorchidism in such a patient may be due to underlying hypogonadism. •• Karyotyping in such patient may rarely show mosaic KS (47,XXY/46,XX) and there might be unmasking of hypergonadotropic hypogonadism resulting from adrenal androgen suppression from glucocorticoid treatment.

Arsenic level in toenails is associated with hearing loss in humans.

Arsenic (As) pollution in drinking water is a worldwide health risk for humans. We previously showed hearing loss in young people who live in areas of As-polluted drinking water and in young mice orally treated with As. In this study, we epidemiologically examined associations between As levels in toenails and hearing in 145 Bangladeshi aged 12-55 years in 2014. Levels of As in toenails, but not those in urine, were shown to be significantly correlated with hearing loss at 4 kHz [odds ratio (OR) = 4.27; 95% confidence interval (CI): 1.51, 12.05], 8 kHz (OR = 3.91; 95% CI: 1.47, 10.38) and 12 kHz (OR = 4.15; 95% CI: 1.55, 11.09) by multivariate analysis with adjustments for age, sex, smoking and BMI. Our experimental study further showed a significant association between As levels in inner ears and nails (r = 0.8113, p = 0.0014) in mice orally exposed to As, suggesting that As level in nails is a suitable index to assess As level in inner ears. Taken together, the results of our study suggest that As level in nails could be a convenient and non-invasive biomarker for As-mediated hearing loss in humans.

Impairment of extra-high frequency auditory thresholds in subjects with elevated levels of fasting blood glucose.

This study was performed to assess whether there is an association between elevated Fasting Blood Glucose (FBG) and hearing impairment in Bangladeshi population. A total of 142 subjects (72 with elevated FBG; 70 control) were included in the study. The mean auditory thresholds of the control subjects at 1, 4, 8 and 12 kHz frequencies were 6.35 ± 0.35, 10.07 ± 0.91, 27.57 ± 1.82, 51.28 ± 3.01 dB SPL (decibel sound pressure level), respectively and that of the subjects with elevated FBG were 8.33 ± 0.66, 14.37 ± 1.14, 38.96 ± 2.23, and 71.11 ± 2.96 dB, respectively. The auditory thresholds of the subjects with elevated FBG were significantly (p < 0.05) higher than the control subjects at all the above frequencies, although hearing impairment was most evidently observed at an extra-high (12 kHz) frequency. Subjects with a long duration of diabetes (>10 years) showed significantly (p < 0.05) higher level of auditory thresholds at 8 and 12 kHz, but not at 1 and 4 kHz frequencies, compared to subjects with shorter duration of diabetes (≤10 years). In addition, based on the data of odds ratio, more acute impairment of hearing at the extra-high frequency was observed in diabetic subjects of both older (>40 years) and younger (≤40 years) age groups compared to the respective controls. The binary logistic regression analysis showed a 5.79-fold increase in the odds of extra-high frequency hearing impairment in diabetic subjects after adjustment for age, gender and BMI. This study provides conclusive evidence that auditory threshold at an extra-high frequency could be a sensitive marker for hearing impairment in diabetic subjects.

Material challenges for solar cells in the twenty-first century: directions in emerging technologies.

Photovoltaic generation has stepped up within the last decade from outsider status to one of the important contributors of the ongoing energy transition, with about 1.7% of world electricity provided by solar cells. Progress in materials and production processes has played an important part in this development. Yet, there are many challenges before photovoltaics could provide clean, abundant, and cheap energy. Here, we review this research direction, with a focus on the results obtained within a Japan-French cooperation program, NextPV, working on promising solar cell technologies. The cooperation was focused on efficient photovoltaic devices, such as multijunction, ultrathin, intermediate band, and hot-carrier solar cells, and on printable solar cell materials such as colloidal quantum dots.

Manganese in toenails is associated with hearing loss at high frequencies in humans.

PURPOSE: Elevated hearing thresholds from high frequencies are known to be one of the hallmarks of age-related hearing loss. Our recent study showed accumulation of manganese (Mn) in inner ears resulting in acceleration of age-related hearing loss in mice orally exposed to Mn. However, there is no evidence showing an association between Mn in non-invasive biological samples and hearing loss in humans evaluated by pure tone audiometry (PTA). In this study, we evaluated Mn in non-invasive biological samples as a possible biomarker for hearing loss in humans. MATERIALS AND METHODS: We determined hearing levels by PTA and Mn levels in toenails, hair and urine with an inductively coupled plasma mass spectrometer (ICP-MS) in 145 healthy subjects in Bangladesh. RESULTS: Multivariable analyses showed that Mn levels in toenails, but not in hair and urine samples, were significantly associated with hearing loss at 8 kHz and 12 kHz. Moreover, our experimental study showed a significant correlation between Mn levels in inner ears and nails, but not hair, in mice orally exposed to Mn. CONCLUSIONS: The results provide novel evidence that Mn in toenails is a possible biomarker for hearing loss at high frequencies in humans.

A comprehensive study including monitoring, assessment of health effects and development of a remediation method for chromium pollution.

Chromium (Cr) pollution caused by wastewater from tanneries is a worldwide environmental problem. To develop a countermeasure, we performed a comprehensive study using Hazaribagh, the tannery area in Dhaka City, Bangladesh, as a model. Our environmental monitoring indicated that the soluble form of Cr, but not barium or arsenic, in Buriganga River is derived from Hazaribagh. Our chemical analysis next showed that Cr, the primary pollutant in canal water at Hazaribagh, consisted of ≤0.7 µM hexavalent Cr [Cr(VI)] and ≤1705 µM trivalent Cr [Cr(III)]. Our biological study then showed that coexposure to Cr(VI) and Cr(III) at possible ratios in canal water at Hazaribagh synergistically promotes transforming activity of human non-tumorigenic HaCaT keratinocytes with activated MEK/ERK and AKT. Our environmental engineering study finally indicated that a magnesium and iron-based hydrotalcite-like compound (MF-HT), our original depurative, can maximally adsorb 9.0 mg/g Cr(VI) and 1041 mg/g Cr(III). Our results suggested the importance of removal of Cr(III) as well as Cr(VI) by showing that Cr(III), which is generally recognized as a chemical with low toxicity, synergistically promoted carcinogenicity of a low level of Cr(VI). Therefore, we propose the use of our original high-efficient and low-cost depurative as a countermeasure to address the worldwide problem of environmental Cr pollution.

Arsenic levels in cutaneous appendicular organs are correlated with digitally evaluated hyperpigmented skin of the forehead but not the sole in Bangladesh residents.

There has been no report showing the effect of arsenic level on digitized skin pigmentation level, a typical diagnostic marker for arsenicosis. Correlations among history of drinking well water, arsenic levels in hair and toenails, and digitalized skin pigmentation levels (L*-value) in sunlight-exposed (forehead) and unexposed (sole) skin areas digitally evaluated by using a reflectance spectrophotometer were examined in 150 residents of Bangladesh. Univariate analysis showed that arsenic levels in hair and toenails of subjects with a history of drinking well water were 10.6-fold and 7.1-fold higher, respectively, than those in subjects without a history of drinking well water. The mean L*-value of foreheads, but not that of soles, in subjects with a history of drinking well water was 1.15-fold lower (more pigmented) than that in subjects without a history of drinking well water. Significant correlations were found between duration of drinking well water and arsenic concentrations in hair (r=0.63; P<0.01) and toenails (r=0.60; P<0.01). Multivariate analysis showed that the arsenic levels in hair and toenails and the duration of drinking well water were strongly correlated with the digitized pigmented level of the forehead but not that of the sole. An increase in the duration of drinking well water may increase hyperpigmentation in the forehead, but not that in the sole, through an increased arsenic level in the human body as shown in cutaneous appendicular organs (hair and toenails).

Oral exposure to arsenic causes hearing loss in young people aged 12-29 years and in young mice.

There is no information on the association between oral exposure to arsenic (As) and hearing loss in humans or mice. In this combined epidemiological study and experimental study, the association of oral exposure to As with hearing loss in people aged 12-29 years and young mice was examined. Subjects in the exposure group (n = 48), who were drinking tube well water contaminated with As, showed significantly higher risks of hearing loss at 4 kHz [odds ratio (OR) = 7.60; 95% confidence interval (CI): 1.56, 57.88], 8 kHz (OR = 5.00; 95% CI: 1.48, 18.90) and 12 kHz (OR = 8.72; 95% CI: 2.09, 47.77) than did subjects in the control group (n = 29). We next performed an experiment in which young mice were exposed to As via drinking water at 22.5 mg/L, which is a much greater concentration than that in human studies. The exposure group showed hearing loss and accumulation of As in inner ears. Ex vivo exposure of the organ of Corti from mice exposed to As significantly decreased the number of auditory neurons and fibers. Thus, our combined study showed that oral exposure to As caused hearing loss in young people and young mice.