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

The interaction between metals and catecholamines: oxidative stress, DNA damage, and implications for human health

The interaction between metals and catecholamines plays a pivotal role in the generation of reactive oxygen species (ROS), leading to oxidative stress and DNA damage. ROS are linked to several diseases, including neurodegenerative disorders such as Parkinson's and Alzheimer's diseases. This review examines how essential metals (iron, copper, zinc, manganese) and a few non-essential metal(loid)s (mercury, chromium, arsenic, aluminum, cadmium, and nickel) contribute to oxidative stress in the presence of catecholamines. In the presence of metals, catecholamines can cause oxidative DNA modification, possibly resulting in cell apoptosis, by taking part in redox reactions and oxidizing to the corresponding aminochrome with simultaneous ROS production. Essential metals are vital for physiological functions, but imbalances in their homeostasis can be harmful. Furthermore, non-essential metals, commonly encountered through environmental or occupational exposure, can exhibit significant toxicity. Previous studies on catecholamine-induced oxidative stress focused on copper and iron, but this review emphasizes the need to investigate other neurotoxic metals and expand existing knowledge on the interactions between metals, catecholamines, and DNA damage. Results from such research could help prioritizing the development of new assessment methods associated with adverse outcome pathways, to reliably predict harmful effects on human health, aiding in the development of therapeutical strategies. The present work will help to shed light on the interplay of metals, catecholamines, and DNA damage in different diseases hopefully fostering new research in this still understudied topic. Future research should investigate the molecular mechanisms through which these metals affect neuronal health and contribute to disease pathogenesis.

Alleviating effect of intranasal zinc on symptoms of allergic rhinitis

Background

There is no information about the clinical implications and kinetics of zinc (Zn) in the nasal cavity, a center of allergic inflammation, and serum in subjects with allergic rhinitis (AR).

Objective

Effects of intranasal Zn on symptoms before and after allergen provocation were investigated in humans and mice with or without AR.

Methods

The first clinical follow-up study for Zn levels in nasal epithelial lining fluid (ELF) and serum was conducted in 57 control subjects and 44 patients with Japanese cedar pollinosis (JCP), a representative seasonal AR, from preseason to season. The clinical implications and kinetics of Zn levels in ELF and serum were further investigated in model mice with JCP.

Results

This clinical study showed that the Zn level in nasal ELF from patients with JCP was increased after pollen exposure and became significantly higher than that in nasal ELF from controls in the JCP season. Conversely, the serum Zn level in patients was decreased after pollen exposure and became significantly lower than that in the controls in the JCP season. To further investigate the clinical implication of Zn level, model mice that mimicked the kinetics of intranasal and serum Zn levels as well as the symptoms in patients with JCP were established. The mouse interventional study showed that the symptoms of mice with provocative JCP were significantly improved by treatment with the putative human-equivalent dose of Zn. The relative number of mucin-secreting goblet cells, a sign of provocative allergic rhinitis, in the mice was decreased by intranasal treatment with Zn.

Conclusion

The study's behavioral and pathologic results indicate that an increased level of intranasal Zn can alleviate symptoms of AR.

Elevated level of urinary tellurium is a potential risk for increase of blood pressure in humans and mice

BACKGROUND

People worldwide are routinely exposed to tellurium mainly via dietary ingestion. There has been no study to clarify the contribution of tellurium to blood pressure in humans or animals.

METHODS

In this cross-sectional study conducted in a general population of 2592 residents in Japan, the associations of urinary tellurium levels with blood pressure and prevalence of hypertension were investigated. The potential sources of tellurium were also investigated. An interventional study in mice confirmed the effect of tellurium exposure on blood pressure.

RESULTS

Linear and logistic regression analyses with consideration of confounders including urinary sodium-potassium ratio showed significant positive associations of urinary tellurium level with prevalence of hypertension and blood pressure. Cereals/beans and vegetables/fruits were determined to be potential dietary sources of tellurium exposure. Intermediary analysis suggested that increased intake of cereals/beans, but not that of vegetables/fruits, is positively associated with the tellurium-mediated risk of hypertension. Correspondingly, the mouse study showed that exposure to a putative human-equivalent dose of tellurium via drinking water increased blood pressure with an elevated level of urinary tellurium. The temporally increased blood pressure was decreased to the normal level by a break of tellurium exposure with a reduced level of urinary tellurium.

CONCLUSIONS

The interdisciplinary approach provided the first evidence that tellurium exposure is a potential risk for increase of blood pressure. Since the human urinary tellurium level in this study is comparable with the levels in general populations in other Asian and European countries in previous studies, exposure to tellurium may be a latent universal risk for hypertension.

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.

Elevated arsenic level in fasting serum via ingestion of fish meat increased the risk of hypertension in humans and mice

Aims

There has been a shortage of human studies to elucidate the association between serum arsenic levels and the prevalence of hypertension. This study multidirectionally investigated associations among arsenic exposure, dietary ingestion, and the risk of hypertension by combined human epidemiological and mouse experimental studies.

Methods and results

This study focused on the total arsenic level in fasting serum, a biomarker of arsenic exposure. Associations among ingestion frequencies of 54 diet items of Japanese food separated into six categories, total arsenic level in fasting serum, and the prevalence of hypertension were investigated in 2709 general people in Japan. Logistic regression analysis demonstrated a dose-dependent association between serum arsenic level and hypertension and a positive association between the ingestion of fish meat and hypertension. Further analysis showed that the latter association was fully mediated by increased fasting serum arsenic levels in humans. Similarly, oral exposure to the putative human-equivalent dose of arsenic species mixture with the same ratios in a common fish meat in Japan increased systolic blood pressure and arsenic levels in fasting serum in mice.

Conclusion

This interdisciplinary approach suggests that fish-meat ingestion is a potential risk factor for arsenic-mediated hypertension. Because the increased consumption of fish meat is a recent global trend, health risks of the increased ingestion of arsenic via fish meat should be further investigated.

Zero waste discharge in tannery industries - An achievable reality? A recent review

In the recent times, more attention is on industrial waste management due to the unaffordable space for dump yards and landfills and the increased charges for waste dumping. Even though the vegan revolution and plant-based meat products are booming, the traditional slaughterhouses and the wastes produced by them continue to be a concern. Waste valorisation is an established procedure striving to create a closed chain process in industries where there is no refuse. Although a highly polluting industry, slaughterhouse industry wastes have been recycled to economically viable leather since ancient times. However, the tannery industry is causing pollution in par with or even more than the slaughterhouses. Effective management of the liquid and solid wastes from the tannery is of utmost concern because of its toxicity. The hazardous wastes generated enter the food chain, causing long term impacts in the ecosystem. Several leather waste transformation processes are widely used in the industries, and they are yielding good products of economic value. However careful exploration into the processes and products of waste valorisation are often ignored as long as the transformed waste product is of higher value than the waste. The most efficient and environmentally friendly waste management technique should convert the refuse into a value-added utilization without any toxic leftovers. Zero waste concept is an extension of the zero liquid discharge concept, where the solid waste is also treated and reused to such an extent that there is no residue to be sent to the landfill. This review initially presents the existing methods for the de-toxification of tannery wastes and examines the possibility of solid waste management within the tannery industry to attain zero waste discharge.

Potential application of a hydrotalcite-like compound for reduction of toxicity to aquatic organisms via rapid and efficient removal of hydrogen sulfide

Hydrogen sulfide (H₂S) is known to have wide ranging toxicities not only as a gas but also as dissolved forms in aquatic environments. The diversity of aquatic organisms can be severely affected by hydrogen sulfide at very low concentrations, indicating the urgent necessity to develop an efficient method for removal of hydrogen sulfide in water. In this study, the removal capacity for hydrogen sulfide of our originally developed hydrotalcite-like compound composed of magnesium and iron (MF-HT) was investigated and its potential application for reduction of toxicity to aquatic organisms was evaluated. The MF-HT experimentally showed a high adsorption capacity of 146.5 mg/g with a fast adsorption equilibrium time of 45 min, both of which are top-class compared with those of other adsorbents previously reported. In fact, removal of hydrogen sulfide (1.2-152.5 mg/L) at an average rate of >97.6% was achieved in groundwater samples (n = 16) by the MF-HT within 60 min. The toxicities of groundwater, indicated by inhibition rate for microalgae (primary producers) and immobilization rate for crustaceans (secondary consumers), were reduced by 96.1% and 82.5% in 2-fold and 4-fold diluted groundwater, respectively, after treatment with the MF-HT for 60 min. These results indicate that MF-HT has an excellent safety record for aquatic organisms. After clarifying the adsorption mechanism, excellent reusability of MF-HT was also confirmed after regeneration using 1 M Na₂CO₃ solution. Considering the efficacy, speed, safety and cost of MF-HT, it could be a novel promising material for solving the problem of hydrogen sulfide pollution in the hydrosphere.