Manganese exposure and cognitive deficits: a growing concern for manganese neurotoxicity

Teeth and alveolar bones as tracers of metals and radionuclides in inhabitants of a uranium region

Biodosimetry can define risks in inhabitants of areas with potential contaminants, ensuring environmental protection and living conditions due to toxic and radioactive effects. This study aimed to evaluate metals and radionuclides in dental structures and alveolar bones in residents of a uranium area in Paraíba and Pernambuco, Brazil. Eighty-nine specimens were pulverized, fractionated, and chemically prepared for analysis by EDXRF, FAAS, and ICP-MS. Levels of Ca, Cu, Fe, Si, Mn, Ni, Pb, Sr, Ti, V, Zn, K, Mn, Th, and U were investigated. Higher concentrations were measured for Ca, with an average of 272,986.4 mg kg-1. Ni presented in lower concentrations, with an average of 30.4 mg kg-1. For U, concentrations ranged from 1.5 to 145.0 mg kg-1, with more than 27% of the samples above the reference value of 8.1 μg kg-1. For Th, almost 38% of the results were above the limit of 3.5 μg kg-1. In the bone spicules, the contents of U and Th ranged from 45.1 to 1451.2 μg kg-1 and from 7.5 to 78.4 μg kg-1, in this order. The levels of radionuclides were more expressive for the teeth collected in São José do Sabugi, suggesting contamination through food and water consumption. In the bone spicules, the levels of U were up to 179 times higher than the safety limit. The results indicate a possible risk of contamination with probable induced radiobiological effects.

Airborne Exposure to Pollutants and Mental Health: A Review with Implications for United States Veterans

PURPOSE OF REVIEW

Inhalation of airborne pollutants in the natural and built environment is ubiquitous; yet, exposures are different across a lifespan and unique to individuals. Here, we reviewed the connections between mental health outcomes from airborne pollutant exposures, the biological inflammatory mechanisms, and provide future directions for researchers and policy makers. The current state of knowledge is discussed on associations between mental health outcomes and Clean Air Act criteria pollutants, traffic-related air pollutants, pesticides, heavy metals, jet fuel, and burn pits.

RECENT FINDINGS

Although associations between airborne pollutants and negative physical health outcomes have been a topic of previous investigations, work highlighting associations between exposures and psychological health is only starting to emerge. Research on criteria pollutants and mental health outcomes has the most robust results to date, followed by traffic-related air pollutants, and then pesticides. In contrast, scarce mental health research has been conducted on exposure to heavy metals, jet fuel, and burn pits. Specific cohorts of individuals, such as United States military members and in-turn, Veterans, often have unique histories of exposures, including service-related exposures to aircraft (e.g. jet fuels) and burn pits. Research focused on Veterans and other individuals with an increased likelihood of exposure and higher vulnerability to negative mental health outcomes is needed. Future research will facilitate knowledge aimed at both prevention and intervention to improve physical and mental health among military personnel, Veterans, and other at-risk individuals.

Child and Adolescent Manganese Biomarkers and Adolescent Postural Balance in Marietta CARES Cohort Participants

BACKGROUND

Manganese (Mn) plays a significant role in both human health and global industries. Epidemiological studies of exposed populations demonstrate a dose-dependent association between Mn and neuromotor effects ranging from subclinical effects to a clinically defined syndrome. However, little is known about the relationship between early life Mn biomarkers and adolescent postural balance.

OBJECTIVES

This study investigated the associations between childhood and adolescent Mn biomarkers and adolescent postural balance in participants from the longitudinal Marietta Communities Actively Researching Exposures Study (CARES) cohort.

METHODS

Participants were recruited into CARES when they were 7-9 y old, and reenrolled at 13-18 years of age. At both time points, participants provided samples of blood, hair, and toenails that were analyzed for blood Mn and lead (Pb), serum cotinine, hair Mn, and toenail Mn. In adolescence, participants completed a postural balance assessment. Greater sway indicates postural instability (harmful effect), whereas lesser sway indicates postural stability (beneficial effect). Multivariable linear regression models were conducted to investigate the associations between childhood and adolescent Mn biomarkers and adolescent postural balance adjusted for age, sex, height-weight ratio, parent/caregiver intelligence quotient, socioeconomic status, blood Pb, and serum cotinine.

RESULTS

CARES participants who completed the adolescent postural balance assessment (n = 123 ) were 98% White and 54% female and had a mean age of 16 y (range: 13-18 y). In both childhood and adolescence, higher Mn biomarker concentrations were significantly associated with greater adolescent sway measures. Supplemental analyses revealed sex-specific associations; higher childhood Mn biomarker concentrations were significantly associated with greater sway in females compared with males.

DISCUSSION

This study found childhood and adolescent Mn biomarkers were associated with subclinical neuromotor effects in adolescence. This study demonstrates postural balance as a sensitive measure to assess the association between Mn biomarkers and neuromotor function. https://doi.org/10.1289/EHP13381.

Improving the Sensitivity of a Mn(II)-Specific DNAzyme for Cellular Imaging Sensor through Sequence Mutations

Detection of Mn2+ in living cells is important in understanding the roles of Mn2+ in cellular processes and investigating its potential implications in various diseases and disorders. Toward this goal, we have previously selected a Mn2+-specific 11-5 DNAzyme through an in vitro selection method and converted it into a fluorescence sensor for intracellular Mn2+ sensing. Despite the progress, the nucleotides responsible for the activity are unclear, and the performance of the DNAzyme needs to be improved in order for more effective applications in biological systems. To address these issues, we herein report site-specific mutations within the catalytic domain of the selected 11-5 DNAzyme. As a result, we successfully identified a variant DNAzyme, designated as Mn5V, which exhibited a twofold increase in activity compared to the original 11-5 DNAzyme. Importantly, Mn5V DNAzyme maintained its high selectivity for Mn2+ over other competing metal ions. Upon the addition of Mn2+, Mn5V DNAzyme exhibited a higher fluorescence signal within the tumor cells compared to that of the 11-5 DNAzyme. This study therefore provides a better understanding of how the DNAzyme functions and a more sensitive probe for investigating Mn2+ in biological systems.

Probabilistic risk assessment for determining nonessential metals in commercial infant formula products in Taiwan

During the early months of life, infant formula plays a crucial role as a primary source of both food and essential nutrients for infants, serving as a replacement for or supplement to breast milk. However, nonessential metals in infant formulas are a concern because infants are highly vulnerable to chemical exposure. The aim of this study was to investigate infant exposure to nonessential metals in infant formula products in Taiwan and assess the associated health risks. In this study, concentrations of arsenic (As), barium (Ba), cadmium (Cd), manganese (Mn), lead (Pb), and vanadium (V) in 45 formula products for 0-1-year-old infants were determined by inductively coupled plasma mass spectrometry. The mean As, Ba, Cd, Mn, Pb, and V concentrations were 6.42, 280, 3.72, 1425, 20.4, and 21.9 µg/kg, respectively. According to our probabilistic simulation of the estimated daily intake of metals, the proportion of hazard quotients exceeding one was 7.69% for As and 3.29% for Mn, and that of hazard index (HI) values exceeding 1 was >17% for metals. Arsenic had the largest HI contribution (46.9%), followed by Mn (22.3%) and Pb (12.7%). The nonessential metals content in infant formula raises potential noncarcinogenic health concerns for infants in Taiwan. Therefore, regulations for nonessential metals must be imposed on related food products in Taiwan, with a particular focus on As and Mn.

Prenatal manganese biomarkers and operant test battery performance in Mexican children: Effect modification by child sex

BACKGROUND

Manganese (Mn) is essential to healthy neurodevelopment, but both Mn deficiency and over-exposure have been linked to prefrontal cortex (PFC) impairments, the brain region that regulates cognitive and neurobehavioral processes responsible for spatial memory, learning, motivation, and time perception. These processes facilitated by attention, inhibitory control, working memory, and cognitive flexibility are often sexually dimorphic and complex, driven by multiple interconnected neurologic and cognitive domains.

OBJECTIVE

We investigated the role of child sex as an effect modifier of the association between prenatal Mn exposure and performance in an operant testing battery (OTB) that assessed multiple cognitive and behavioral functional domains.

METHODS

Children (N = 575) aged 6-8 years completed five OTB tasks. Blood and urinary Mn measurements were collected from mothers in the 2nd and 3rd trimesters. Multiple regression models estimated the association between Mn biomarkers at each trimester with OTB performance while adjusting for socio-demographic covariates. Covariate-adjusted weighted quantile sum (WQS) regression models were used to estimate the association of a Mn multi-media biomarker (MMB) mixture with OTB performance. Interaction terms were used to estimate modification effect by child sex.

RESULTS

Higher blood Mn exposure was associated with better response rates (more motivation) on the progressive ratio task and higher overall accuracy on the delayed matching-to-sample task. In the WQS models, the MMB mixture was associated with better response rates (more motivation) on the progressive ratio task. Additionally, for the linear and WQS models, we observed a modification effect by child sex in the progressive ratio and delayed matching-to-sample tasks. Higher prenatal Mn biomarker levels were associated with improved task performance for girls and reduced performance in boys.

CONCLUSION

Higher prenatal blood Mn concentrations and the MMB mixture predicted improved performance on two of five operant tasks. Higher prenatal Mn concentrations regulated executive functions in children in a sexually dimorphic manner. Higher prenatal Mn exposure is associated with improved performance on spatial memory and motivation tasks in girls, suggesting that Mn's nutritional role is sexually dimorphic, and should be considered when making dietary and/or environmental intervention recommendations.

Trace Elements Levels in Major Depressive Disorder-Evaluation of Potential Threats and Possible Therapeutic Approaches

The multifactorial etiology of major depressive disorder (MDD) includes biological, environmental, genetic, and psychological aspects. Recently, there has been an increasing interest in metallomic studies in psychiatry, aiming to evaluate the role of chosen trace elements in the MDD etiology as well as the progression of symptoms. This narrative review aims to summarize the available literature on the relationship between the concentration of chosen elements in the serum of patients with MDD and the onset and progression of this psychiatric condition. The authors reviewed PubMed, Web of Science, and Scopus databases searching for elements that had been investigated so far and further evaluated them in this paper. Ultimately, 15 elements were evaluated, namely, zinc, magnesium, selenium, iron, copper, aluminium, cadmium, lead, mercury, arsenic, calcium, manganese, chromium, nickel, and phosphorus. The association between metallomic studies and psychiatry has been developing dynamically recently. According to the results of current research, metallomics might act as a potential screening tool for patients with MDD while at the same time providing an assessment of the severity of symptoms. Either deficiencies or excessive amounts of chosen elements might be associated with the progression of depressive symptoms or even the onset of the disease among people predisposed to MDD.

Select micronutrients for the preterm neonate

If premature neonates are not provided with adequate nutrition, they will quickly become deficient because of increased requirements and a lack of nutrient stores to achieve adequate growth. The provision of many of the recommended micronutrients for pediatric and adult patients is challenging in premature neonates because of the limited data surrounding the true needs of premature neonates and the difficulty in assessing adequate serum levels of these nutrients in this patient population. Parenteral and enteral nutrition shortages further complicate providing adequate micronutrients to premature neonates. This review will discuss select micronutrients and their importance to the preterm neonate, with special emphasis on micronutrients with limited evidence and more challenging supplementation and repletion strategies.

The Role of Oxidative Stress in Manganese Neurotoxicity: A Literature Review Focused on Contributions Made by Professor Michael Aschner

This literature review focuses on the evidence implicating oxidative stress in the pathogenesis of manganese neurotoxicity. This review is not intended to be a systematic review of the relevant toxicologic literature. Instead, in keeping with the spirit of this special journal issue, this review highlights contributions made by Professor Michael Aschner's laboratory in this field of study. Over the past two decades, his laboratory has made significant contributions to our scientific understanding of cellular responses that occur both in vitro and in vivo following manganese exposure. These studies have identified molecular targets of manganese toxicity and their respective roles in mitochondrial dysfunction, inflammation, and cytotoxicity. Other studies have focused on the critical role astrocytes play in manganese neurotoxicity. Recent studies from his laboratory have used C. elegans to discover new facets of manganese-induced neurotoxicity. Collectively, his body of work has dramatically advanced the field and presents broader implications beyond metal toxicology.

A Highly Selective Mn(II)-Specific DNAzyme and Its Application in Intracellular Sensing

Manganese is an essential trace element in the human body that acts as a cofactor in many enzymes and metabolisms. It is important to develop methods to detect Mn²⁺ in living cells. While fluorescent sensors have been very effective in detecting other metal ions, Mn²⁺-specific fluorescent sensors are rarely reported due to nonspecific fluorescence quenching by the paramagnetism of Mn²⁺ and poor selectivity against other metal ions such as Ca²⁺ and Mg²⁺. To address these issues, we herein report in vitro selection of an RNA-cleaving DNAzyme with exceptionally high selectivity for Mn²⁺. Through converting it into a fluorescent sensor using a catalytic beacon approach, Mn²⁺ sensing in immune cells and tumor cells has been achieved. The sensor is also used to monitor degradation of manganese-based nanomaterials such as MnOx in tumor cells. Therefore, this work provides an excellent tool to detect Mn²⁺ in biological systems and monitor the Mn²⁺-involved immune response and antitumor therapy.

Dietary Trace Elements and the Pathogenesis of Neurodegenerative Diseases

Trace elements such as iron (Fe), zinc (Zn), copper (Cu), and manganese (Mn) are absorbed from food via the gastrointestinal tract, transported into the brain, and play central roles in normal brain functions. An excess of these trace elements often produces reactive oxygen species and damages the brain. Moreover, increasing evidence suggests that the dyshomeostasis of these metals is involved in the pathogenesis of neurodegenerative diseases, including Alzheimer's disease, prion diseases, and Lewy body diseases. The disease-related amyloidogenic proteins can regulate metal homeostasis at the synapses, and thus loss of the protective functions of these amyloidogenic proteins causes neurodegeneration. Meanwhile, metal-induced conformational changes of the amyloidogenic proteins contribute to enhancing their neurotoxicity. Moreover, excess Zn and Cu play central roles in the pathogenesis of vascular-type senile dementia. Here, we present an overview of the intake, absorption, and transport of four essential elements (Fe, Zn, Cu, Mn) and one non-essential element (aluminum: Al) in food and their connections with the pathogenesis of neurodegenerative diseases based on metal-protein, and metal-metal cross-talk.

L-carnitine attenuates acoustic startle reflex dysfunction in adult male rats exposed to mancozeb

The fungicide mancozeb increases oxygen-free radicals in the central nervous system. As an antioxidant, L-carnitine protects DNA and cell membranes from damage caused by oxygen-free radicals. The present study investigated how L-carnitine affected the acoustic startle response (ASR) in rats exposed to mancozeb. In this experimental study, male Wistar rats were gavaged orally with mancozeb (500, 1000, and 2000 mg/kg), L-carnitine (100, 200, and 400 mg/kg), or L-carnitine (200 mg/kg) + mancozeb (500 mg/kg) three times in 1 week. In the sham group, saline (0.9%, 10 mL/kg) was gavaged at a volume equivalent to that of the drugs. The control group did not receive any treatment. The results showed that locomotor activity and the percentage of prepulse inhibition in the mancozeb groups decreased compared to the sham group while these parameters increased in the L-carnitine group (200 mg/kg) compared to sham rats. In conclusion, mancozeb may increase the risk factor for cognitive diseases such as schizophrenia in people exposed to it while pretreatment with L-carnitine can attenuate the toxic effect.

Light-independent anaerobic microbial oxidation of manganese driven by an electrosyntrophic coculture

Anaerobic microbial manganese oxidation (AMMO) has been considered an ancient biological metabolism for Mn element cycling on Archaean Earth before the presence of oxygen. A light-dependent AMMO was recently observed under strictly anoxic conditions, providing a new proxy for the interpretation of the evolution of oxygenic photosynthesis. However, the feasibility of biotic Mn(II) oxidation in dark geological habitats that must have been abundant remains unknown. Therefore, we discovered that it would be possible to achieve AMMO in a light-independent electrosyntrophic coculture between Rhodopseudomonas palustris and Geobacter metallireducens. Transmission electron microscopy analysis revealed insoluble particle formation in the coculture with Mn(II) addition. X-ray diffraction and X-ray photoelectron spectroscopy analysis verified that these particles were a mixture of MnO2 and Mn3O4. The absence of Mn oxides in either of the monocultures indicated that the Mn(II)-oxidizing activity was induced via electrosyntrophic interactions. Radical quenching and isotopic experiments demonstrated that hydroxyl radicals (•OH) produced from H2O dissociation by R. palustris in the coculture contributed to Mn(II) oxidation. All these findings suggest a new, symbiosis-dependent and light-independent AMMO route, with potential importance to the evolution of oxygenic photosynthesis and the biogeochemical cycling of manganese on Archaean and modern Earth.

Neurocognitive function in adult residents of a mining district in Mexico after reducing manganese exposure: Follow-up after 11 years

BACKGROUND

Little is known about the neurotoxic effects of chronic exposure to airborne Mn once exposure has been reduced. The environmentally exposed and the reference adult populations evaluated in 2002 were followed, after an environmental management program (EMP) was implemented to reduce the exposure in a mining district in Mexico.

OBJECTIVE

The aim of this study was to compare the association between exposure to Mn and neurocognitive performance in environmentally exposed and reference groups of adults before and after EMP implementation.

METHODS

In 2013, the same battery of neurocognitive tests used in the initial study (2002) was applied to 58 adults exposed to airborne Mn and 30 adults from the reference community. A cumulative exposure index (CEI) was estimated for the study population before and after the EMP. Categorical outcomes were analyzed using logistic regression, and the resulting ORs were compared between studies. Continuous outcomes were analyzed using linear regression. All models were adjusted for age, years of education, socioeconomic status and blood lead levels.

RESULTS

Exposed adults from the post-EMP study showed an improvement in fine motor and verbal regulation of motor skills (OR < 1) compared to the exposed adults from the pre-EMP study (OR > 1). In both pre- and post-studies, the exposed adults showed a deterioration in their dynamic organization of motor activity compared to the reference group (p < 0.05); however, they showed no significant change in attention and working-memory performance.

DISCUSSION

After four years of a significant reduction in airborne Mn levels resulting from EMP implementation, chronically exposed adults showed an improvement in fine motor and verbal regulation of motor skills; however, the remaining areas of their motor and cognitive functions remained impaired.

Tap Water Consumption Is Associated with Schoolchildren’s Cognitive Deficits in Afghanistan

Environmental influence on intelligence quotient (IQ) is poorly understood in developing countries. We conducted the first cross-sectional investigation to assess the role of socio-economic and environmental factors on schoolchildren’s IQ in Jalalabad, Afghanistan. A representative sample of 245 schoolchildren aged 7–15 was randomly selected in five schools. Children’s records included: non-verbal IQ TONI-1 scale, body mass index, socio-economic status, and further environmental indicators (water supply, proximity to a heavy-traffic road, use of surma traditional cosmetics). The mean age of the children was 11.7 years old (±2.0 years), and 70.2% and 29.8% were male and female, respectively. The children’s mean IQ was 83.8 (±12.6). In total, 37 (14.9%) of the children were overweight, 78 (31.5%) were living below the USD 1.25 poverty line, 133 (53.6%) used tap water supply, 76 (30.6%) used surma, and 166 (66.9%) were exposed to heavy road traffic. The children’s IQ was significantly and independently lowered by tap water use (−3.9; 95% CI [−7.1; −0.6]) and by aging (−1.4; 95% CI [−2.2; −0.6]), as revealed in multivariate analysis, independently of gender, socio-economic status, exposure to heavy road traffic, overweight status, and surma use. Lower IQ among older children is possibly attributed to chronic stress experienced by adolescents due to living conditions in Afghanistan. While using tap water prevents fecal peril, it may expose children to toxic elements such as lead which is known to lower their intellectual development.

Indirect mediators of systemic health outcomes following nanoparticle inhalation exposure

The growing field of nanoscience has shed light on the wide diversity of natural and anthropogenic sources of nano-scale particulates, raising concern as to their impacts on human health. Inhalation is the most robust route of entry, with nanoparticles (NPs) evading mucociliary clearance and depositing deep into the alveolar region. Yet, impacts from inhaled NPs are evident far outside the lung, particularly on the cardiovascular system and highly vascularized organs like the brain. Peripheral effects are partly explained by the translocation of some NPs from the lung into the circulation; however, other NPs largely confined to the lung are still accompanied by systemic outcomes. Omic research has only just begun to inform on the complex myriad of molecules released from the lung to the blood as byproducts of pulmonary pathology. These indirect mediators are diverse in their molecular make-up and activity in the periphery. The present review examines systemic outcomes attributed to pulmonary NP exposure and what is known about indirect pathological mediators released from the lung into the circulation. Further focus was directed to outcomes in the brain, a highly vascularized region susceptible to acute and longer-term outcomes. Findings here support the need for big-data toxicological studies to understand what drives these health outcomes and better predict, circumvent, and treat the potential health impacts arising from NP exposure scenarios.

Risk evaluation of occupational exposure of southern Brazilian flower farmers to pesticides potentially leading to cholinesterase inhibition and metals exposure

This work presents a frequency matched observational study comparing flower farmers exposed to pesticides and unexposed individuals as controls. All subjects were interviewed before plasma and urine collection. Manganese and Zinc were measured in theses samples by using dynamic reaction cell inductively coupled mass spectrometry. Cholinesterase activity was analyzed through spectrophotometry by using a modified version of the Ellman method. Seventy-eight percent of subjects reported occupational contact with pesticides, from which 37% reported exposure for over 9 years. Flower farms farmers had increased odds of having headache and irritability, respectively, by factors of 6.2 and 2.4 than the control subjects. While the odds of exposed subjects to have insomnia was smaller than control subjects by a factor of 0.34. Exposure to pesticides had a significant effect regarding the plasmatic plasma and urinary manganese levels and whole blood cholinesterase activity (p < 0.05). High levels of plasma and urinary manganese, as well as cholinesterase inhibition in whole blood, were evident in the flower farmers who participated in the study.

Role of Environmental Toxicants on Neurodegenerative Disorders

Neurodegeneration leads to the loss of structural and functioning components of neurons over time. Various studies have related neurodegeneration to a number of degenerative disorders. Neurological repercussions of neurodegeneration can have severe impacts on the physical and mental health of patients. In the recent past, various neurodegenerative ailments such as Alzheimer’s and Parkinson’s illnesses have received global consideration owing to their global occurrence. Environmental attributes have been regarded as the main contributors to neural dysfunction-related disorders. The majority of neurological diseases are mainly related to prenatal and postnatal exposure to industrially produced environmental toxins. Some neurotoxic metals, like lead (Pb), aluminium (Al), Mercury (Hg), manganese (Mn), cadmium (Cd), and arsenic (As), and also pesticides and metal-based nanoparticles, have been implicated in Parkinson’s and Alzheimer’s disease. The contaminants are known for their ability to produce senile or amyloid plaques and neurofibrillary tangles (NFTs), which are the key features of these neurological dysfunctions. Besides, solvent exposure is also a significant contributor to neurological diseases. This study recapitulates the role of environmental neurotoxins on neurodegeneration with special emphasis on major neurodegenerative disorders such as Alzheimer’s and Parkinson’s disease.

Impacts of a perinatal exposure to manganese coupled with maternal stress in rats: Tests of untrained behaviors

Manganese (Mn), an element that naturally occurs in the environment, has been shown to produce neurotoxic effects on the developing young when levels exceed physiological requirements. To evaluate the effects of this chemical in combination with non-chemical factors pregnant Long-Evans rats were treated with 0, 2, or 4 mg/mL Mn in their drinking water from gestational day (GD) 7 to postnatal day (PND) 22. Half of the dams received a variable stress protocol from GD13 to PND9, that included restraint, small cage with reduced bedding, exposure to predator odor, intermittent intervals of white noise, lights on for 24 h, intermittent intervals of lights on during dark cycle and cages with grid floors and reduced bedding. One male and one female offspring from each litter were tested to assess untrained behavior. Ultrasonic vocalizations (USV) were recorded from PND13 pups while they were isolated from the litter. Locomotor activity (MA) was measured in figure-eight mazes at PND 17, 29, and 79 (different set of rats at each time point). Social approach (SA) was tested at PND48. Acoustic startle response (ASR) and pre-pulse inhibition (PPI) were measured starting at PND58. At PND53 a sweetness preference for a chocolate flavored milk solution was assessed. There were sex related differences on several parameters for the USVs. There was also a Mn by stress by sex interaction with the females from the 4 mg/mL stressed dams having more frequency modulated (FM) call elements than the 4 mg/mL non-stressed group. There was an effect of Mn on motor activity but only at PND29 with the 2 mg/mL group having higher counts than the 0 mg/mL group. The social approach test showed sex differences for both the habituation and test phase. There was an effect of Mn, with the 4 mg/mL males having a greater preference for the stimulus rat than did the 0 mg/mL males. There was also a stress by sex interaction. The ASR and PPI had only a sex effect. Thus, with only the FM call elements having a Mn by stress effect, and the PND29 MA and SA preference index having a Mn effect but at different doses requires further investigation.

Drinking Water Quality and Public Health in the Kathmandu Valley, Nepal: Coliform Bacteria, Chemical Contaminants, and Health Status of Consumers

Residents of Nepal’s Kathmandu Valley draw drinking water from tube wells, dug wells, and stone spouts, all of which have been reported to have serious water quality issues. In this study, we analyzed drinking water samples from 35 tube wells, dug wells, stone spouts, and municipal tap water for bacterial and chemical contaminants, including total and fecal coliform, aluminum, arsenic, barium, beryllium, boron, cadmium, cobalt, chromium, copper, fluoride, iron, mercury, manganese, molybdenum, nickel, lead, antimony, selenium, thallium, uranium, vanadium, and zinc. We also asked a sampling of households who used these specific water sources to rate the taste of their water, list any waterborne diseases they were aware of, and share basic health information about household members. This survey provided us with information from 146 households and 603 individuals. We found widespread bacterial contamination of water sources, with 94% of sources having detectable total or fecal coliform. Nepal Drinking Water Quality Standards and World Health Organization (WHO) Drinking-Water Guidelines or health-based values were exceeded for aluminum (max = 0.53 mg/L), arsenic (max = 0.071 mg/L), iron (max = 7.22 mg/L), and manganese (max = 3.229 mg/L). The distribution of water sources with high arsenic, iron, and manganese appeared to be associated with floodplain deposits. Mixed effects logistic regression models were used to examine the interactions between social factors and water contaminants and their effects on household members’ health. Consumers of water sources with both high and low concentrations of manganese were less likely to have a positive attitude towards school than those whose water sources had moderate concentrations of manganese. Social factors, especially education, played a large role in predicting individual health outcomes. Household taste ratings of drinking water were not correlated with iron or manganese concentrations, suggesting that WHO’s reliance on aesthetic criteria for these contaminants instead of formal drinking-water guidelines may not be sufficient to protect public health.

PI3K/Akt Signaling Pathway Ameliorates Oxidative Stress-Induced Apoptosis upon Manganese Exposure in PC12 Cells

Manganese (Mn)-induced neurotoxicity has aroused public concerns for many years, but its precise mechanism is still poorly understood. Herein, we report the impacts of the phosphatidylinositol 3-kinase/protein kinase B (PI3K/Akt) signaling pathway in mediating neurological effects induced by manganese sulfate (MnSO₄) exposure in PC12 cells. In this study, cells were treated with MnSO₄ for 24 h in the absence or presence of LY294002 (a special inhibitor of PI3K). We investigated cell viability and apoptosis signals, as well as levels of superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), catalase (CAT), and malondialdehyde (MDA). The mRNA levels of B-cell lymphoma 2 (Bcl-2), Bcl-2-associated X protein (Bax), and Caspase-3 were also quantified through real-time quantitative PCR (RT-qPCR); protein levels of serine/threonine protein kinase (Akt) and forkhead box O3A (Foxo3a) were determined by western blot. Increasing of MnSO₄ doses led to decreased SOD, GSH-Px, and CAT activities, while the level of MDA was upregulated. Moreover, cell apoptosis was significantly increased, as the mRNA of Bcl-2 and Caspase-3 was significantly decreased, while Bax mRNA was increased. Phosphorylated Akt (p-Akt) and Foxo3a (p-Foxo3a) were upregulated in a dose-dependent manner. In addition, LY294002 pretreatment reduced the activity of SOD, GSH-Px, and CAT but elevated MDA levels. Meanwhile, LY294002 pretreatment also increased cell apoptosis given the upregulated Bax and Caspase-3 mRNAs and decreased Bcl-2 mRNA. In summary, the PI3K/Akt signaling pathway can be activated by MnSO₄ exposure and mediate MnSO₄-induced neurotoxicity.

Association between blood metals mixtures concentrations and cognitive performance, and effect modification by diet in older US adults

Background:

Chronic exposure to heavy metals has been associated with adverse neurological outcomes in older adults. Inflammatory processes are suspected as an underlying pathway by which metals exert their neurotoxicity. In parallel, a diet rich in antioxidant and anti-inflammatory components may protect against chronic inflammation.

Objectives:

We examined the associations of blood concentrations of lead, cadmium, and manganese as a mixture with cognitive performance in older US adults and potential modification of these associations by diet as measured by the Healthy Eating Index 2015 (HEI-2015) and the Adapted Dietary Inflammatory Index (ADII).

Methods:

We used data on 1,777 adults ≥60 years old from the US National Health and Nutrition Examination Survey (NHANES; 2011–2014). We derived the ADII and the HEI-2015 from two nonconsecutive 24-hour diet recalls. Cognitive performance was measured by the Consortium to Establish a Registry for Alzheimer’s Disease (CERAD) Word Learning subtest, the animal fluency test, and the Digit Symbol Substitution Test (DSST). We also constructed a composite z-score reflecting overall cognitive performance. We used quantile g-computation to evaluate the joint associations of a mixture of metals with cognitive performance test scores. We also evaluated effect modification by sex and diet quality indices using Cochran Q tests.

Results:

The median (interquartile range) of blood metals were 0.38 μg/L (0.35), 14.70 μg/L (11.70), and 8.74 μg/L (4.06) for cadmium, lead, and manganese, respectively. Increasing blood concentrations of all metals by one quartile was associated with a decrease in overall cognitive performance (–0.04; 95% confidence interval [CI] = –0.09, 0.02), CERAD (–0.04; 95% CI = –0.12, 0.03), animal fluency (–0.02; 95% CI, –0.11, 0.06), and DSST (–0.05; 95% CI = –0.11, 0.02) test scores. These associations were more pronounced in adults with high pro-inflammatory or low-diet quality and null or positive though imprecise associations in participants with a high anti-inflammatory. These associations also varied by sex with inverse associations in men and positive associations in women.

Conclusions:

Our findings suggest that adherence to an antioxidant and anti-inflammatory diet may prevent blood metals adverse cognitive effects among older adults. If confirmed, strategies based on diet could provide a potential complementary and efficient approach to counteract effects of environmental pollutants.

Risks to children from inhalation of aerosolized aqueous manganese emitted from ultrasonic humidifiers can be greater than for corresponding ingestion

The essential trace element manganese (Mn) can cause neurotoxicity with inhalation acknowledged as a more severe health and cognition threat than ingestion.

METHODS

Over a range of aqueous Mn concentrations present in tap water, this research characterizes exposures and risks for adults and 0.25, 1, 2.5, and 6 yr old children who ingest the water and inhale respirable particles produced by a room-sized ultrasonic humidifier filled with the same water. Aqueous Mn concentrations evaluated included 50 µg/L USEPA esthetic guideline, 80 µg/L WHO infant guideline, and 120 µg/L Canadian regulatory level. Airborne-particle-bound Mn concentrations were generated for water filling an ultrasonic humidifier under four realistic room conditions (33 m³ small or 72 m³ large) with varying ventilation rates from 0.2/h -1.5/h. Average daily doses (ADD) and reference intake doses were calculated for ingestion and 8-h inhalation of humidified air. Hazard quotients (HQ) compared the intake doses and reference doses. Multi-path particle dosimetry (MPPD) model quantified the particle deposition and deposited dose in children's and adults' respiratory tracts.

RESULTS

At only 11 µg/L Mn, the resulting humidified air Mn exceeds USEPA's reference concentration of 0.05 µg/m³ Mn in small room with low, energy-efficient ventilation. Inhalation ADD are 2 magnitudes lower than ingestion ADD for identical water Mn concentrations and daily exposure frequency. Even so, ingestion HQs are approximately 0.2 but inhalation risk is significant (HQ>1) for children and adults when breathing Mn-humidified air under most small room conditions at 50, 80 or 120 µg/L Mn. MPPD model indicates inhaled Mn deposits in head and pulmonary regions, with greater Mn dose deposits in children than adults.

CONCLUSION

Inhalation of Mn-particles produced from ultrasonic humidifiers can pose greater risks than ingestion at the same water concentration, especially for children. Aqueous Mn concentration and room size influence risks. Limiting manganese exposures and setting regulations requires consideration of both ingestion and inhalation of water.

Manganese Intoxication Recovery and the Expression Changes of Park2/Parkin in Rats

Occupational overexposure to manganese (Mn) produces Parkinson's disease-like manganism. Acute Mn intoxication in rats causes dopaminergic neuron loss, impairment of motor activity and reduction of the expression of Park2/Parkin. The expression of Park2/Parkin is also reduced. Whether these changes are reversible after cessation of Mn exposure is unknown, and is the goal of this investigation. Adult male rats were injected with Mn²⁺ at doses 1 mg/kg and 5 mg/kg in the form of MnCl₂·4H₂O, every other day for one-month to produce acute Mn neurotoxicity. For a half of rats Mn exposure was suspended for recovery for up to 5 months. Mn neurotoxicity was evaluated by the accumulation of Mn in blood and brain, behavioral activities, dopaminergic neuron loss, and the expression of Park2/Parkin in the blood cells and brain. Dose-dependent Mn neurotoxicity in rats was evidenced by Mn accumulation, rotarod impairments, reduction of tyrosine hydroxylase (TH)-positive neurons in the substantia nigra, decreased level of Park2 mRNA in the blood and brain, and decreased Parkin protein in the brain. After cessation of Mn exposure, the amount of Park2 mRNA in the blood started to increase one month after the recovery. After 5-month of recovery, blood and brain Mn returned to normal, rotarod activity recovered, the reduction of TH-positive dopaminergic neurons ameliorated, and the level of Park2 mRNA in the blood and Park2/Parkin in the midbrain and striatum were returned to the normal. Mn neurotoxicity in rats is reversible after cessation of Mn exposure. The level of Park2 mRNA in the blood could be used as a novel biomarker for Mn exposure and recovery.

Insight into synergies between Acinetobacter sp. AL-6 and pomelo peel biochar in a hybrid process for highly efficient manganese removal

The manganese contamination of groundwater is a global issue that needs to be solved urgently. In this study, a hybrid process between pomelo peel biochar(BC) and Acinetobacter sp. AL-6 (strain AL-6) was established to remove manganese from water. The results showed that microbe-biochar composite had removed 98.19% of manganese (800 mg L^-1) within 48 h. Compared with two separate systems (biochar, strain AL-6), the co-system (strain AL-6 and BC composite) had an excellent synergy effect on manganese removal. The average removal rate of manganese in the synergistic system was 14.08 mg L^-1 h^-1, which was 6.41 times higher than strain AL-6, 3.45 times higher than biochar, and even at 2.24 times their sum. In addition, the scanning electron microscope (SEM) and the bioassay indicated that many strains were attached to biochar and had vigorous biological activity. The FTIR results showed that the functional groups of OH, CO, CO, CH₂, and CH played a vital role in removing manganese. And the correlation analysis shows that biochar with strains AL-6 has a highly synergistic effect on manganese removal. Meanwhile, the composite material can maintain excellent manganese removal efficiency under different pH conditions. Besides, in the sequence batch reactor (SBR) inoculating with the microbe-biochar composite, more than 96% of manganese was removed, which far exceeded the treatment efficiency of free bacteria in the SBR. Hence, biochar-immobilized AL-6 has great potential and can be applied to degrade manganese polluted wastewater.

Physiological mechanisms of the tolerance response to manganese stress exhibited by Pinus massoniana, a candidate plant for the phytoremediation of Mn-contaminated soil

Manganese (Mn) pollution in soil, especially around mining areas, is a serious environmental problem worldwide. Generally, plant remediation technology needs to select species with high Mn tolerance, and exploring the Mn tolerance mechanism of tree species with high ecological and economic benefits is of considerable significance for the effective identification and efficient utilization of Mn phytoremediation species. Masson pine (Pinus massoniana) is one of the main afforestation tree species, exhibiting high ecological and economic value in subtropical areas and also a plant with high Mn accumulation. To reveal the mechanisms governing the tolerance of this species for Mn stress, the morphological, physiological, and biochemical responses of seedlings grown in sand cultures under different Mn stress (0.0009~30 mmol·L^-1) were analyzed. The results showed that despite the chlorosis of leaves under high Mn stress (30 mmol·L^-1), the height of plant seedling, the diameter of ground and the root morphology was not significantly inhibited (p < 0.05), and a high level of Mn accumulated (translocation factor = 1.10). With increasing Mn concentration, malondialdehyde (MDA), soluble protein, and soluble sugar increased, and superoxide dismutase (SOD) and catalase (CAT) increased at first and later decreased. Under Mn stress, net photosynthetic rate, transpiration rate, stomatal conductance, total chlorophyll, chlorophyll a, and carotenoids increased first and subsequently decreased, and intercellular CO₂ concentration and chlorophyll b decreased, but chlorophyll fluorescence characteristics did not change significantly. Taken together, these results indicate that Masson pine can tolerate Mn stress by increasing its antioxidant enzyme activity and non-enzyme metabolite content. In addition, Masson pine can maintain photosynthesis by changing its gas exchange parameters, photosynthetic pigment content, and chlorophyll fluorescence, which is another important mechanism for coping with high Mn concentrations in the environment. In conclusion, the above results show that Masson pine can be effectively used for phytoremediation of Mn-contaminated soil.

Manganese in potable water of nine districts, Bangladesh: human health risk

Safe drinking water is directly linked to good human health. An excessive amount of manganese (Mn) in drinking water supplies causes people show symptoms of neurotoxicity. In this study, the level of Mn in potable water sourced from tube wells located in 9 (nine) districts of Bangladesh was monitored. In total, 170 (one hundred and seventy) water samples were collected and Mn was quantified by atomic absorption spectroscopy (AAS). The levels of Mn found in the tube well water samples of Sirajganj, Meherpur, Chuadanga, Jhenaidah, Magura, Faridpur, Jashore, Satkhira, and Khulna were 0.37-1.86, 0.10-4.11, 0.30-0.76, 0.26-0.94, 0.01-0.18, 0.21-1.78, 0.08-1.23, 0.05-0.27, and 0.01-2.11 mg/L, respectively. Results revealed that Mn level was beyond the highest contaminated levels of 0.1 mg/L and 0.4 mg/L, which are recommended by Bangladesh Drinking Standard (BDS) and World Health Organization (WHO), respectively. The maximum Mn contaminated level reached up to 4.11 mg/L (mean, 0.53 mg/L). The Mn level in tube well water exceeded 51.1% and 75.9% set by the recommended value of WHO and BDS, respectively. Furthermore, the calculated hazard quotient (HQ) value for Mn was observed to be greater than unity, indicating both children and adults risked potential non-carcinogenic health issues. The water supply authorities should take steps to provide Mn-free drinking water for communities.

Interaction of Blood Manganese Concentrations with GSTT1 in Relation to Autism Spectrum Disorder in Jamaican Children

Using data from 266 age- and sex-matched pairs of Jamaican children with autism spectrum disorder (ASD) and typically developing (TD) controls (2-8 years), we investigated whether glutathione S-transferase theta 1 (GSTT1) modifies the association between blood manganese concentrations (BMC) and ASD. After adjusting conditional logistic regression models for socioeconomic status and the interaction between GSTT1 and GSTP1 (glutathione S-transferase pi 1), using a recessive genetic model for GSTT1 and either a co-dominant or dominant model for GSTP1, the interaction between GSTT1 and BMC was significant (P = 0.02, P = 0.01, respectively). Compared to controls, ASD cases with GSTT1-DD genotype had 4.33 and 4.34 times higher odds of BMC > 12 vs. ≤ 8.3 μg/L, respectively. Replication in other populations is warranted.

Short Report: Using Targeted Urine Metabolomics to Distinguish Between Manganese Exposed and Unexposed Workers in a Small Occupational Cohort

Objectives: Despite the widespread use of manganese (Mn) in industrial settings and its association with adverse neurological outcomes, a validated and reliable biomarker for Mn exposure is still elusive. Here, we utilize targeted metabolomics to investigate metabolic differences between Mn-exposed and -unexposed workers, which could inform a putative biomarker for Mn and lead to increased understanding of Mn toxicity. Methods: End of shift spot urine samples collected from Mn exposed (n = 17) and unexposed (n = 15) workers underwent a targeted assay of 362 metabolites using LC-MS/MS; 224 were quantified and retained for analysis. Differences in metabolite abundances between exposed and unexposed workers were tested with a Benjamini-Hochberg adjusted Wilcoxon Rank-Sum test. We explored perturbed pathways related to exposure using a pathway analysis. Results: Seven metabolites were significantly differentially abundant between exposed and unexposed workers (FDR ≤ 0.1), including n-isobutyrylglycine, cholic acid, anserine, beta-alanine, methionine, n-isovalerylglycine, and threonine. Three pathways were significantly perturbed in exposed workers and had an impact score >0.5: beta-alanine metabolism, histidine metabolism, and glycine, serine, and threonine metabolism. Conclusion: This is one of few studies utilizing targeted metabolomics to explore differences between Mn-exposed and -unexposed workers. Metabolite and pathway analysis showed amino acid metabolism was perturbed in these Mn-exposed workers. Amino acids have also been shown to be perturbed in other occupational cohorts exposed to Mn. Additional research is needed to characterize the biological importance of amino acids in the Mn exposure-disease continuum, and to determine how to appropriately utilize and interpret metabolomics data collected from occupational cohorts.

Adsorption of Mn2+ from Aqueous Solution Using Manganese Oxide-Coated Hollow Polymethylmethacrylate Microspheres (MHPM)

Results of investigation on adsorption of Mn2+ from aqueous solution by manganese oxide-coated hollow polymethylmethacrylate microspheres (MHPM) are reported here. This is the first report on Mn-coated hollow polymer as a substitute for widely used materials like green sand or MN-coated sand. Hollow polymethylmethacrylate (HPM) was prepared by using a literature procedure. Manganese oxide (MnO) was coated on the surface of HPM (MHPM) by using the electroless plating technique. The HPM and MHPM were characterized by using optical microscopy (OM), scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and thermogravimetric analysis (TGA). Optical and scanning micrographs were used to monitor the surface properties of the coated layer which revealed the presence of MnO on the surface of HPM. TGA showed the presence of 4-5% of MnO in MHPM. Adsorption isotherm studies were carried out as a function of pH, initial ion concentration, and contact time, to determine the adsorption efficiency for removal of Mn2+ from contaminated water by the synthesized MHPM. The isotherm results showed that the maximum adsorption capacity of MnO-coated HPM to remove manganese contaminants from water is 8.373 mg/g. The obtained ${\text{R}}^2$ values of Langmuir isotherm and Freundlich isotherm models were 1 and 0.87, respectively. Therefore, ${\text{R}}^2$ magnitude confirmed that the Langmuir model is best suited for Mn2+ adsorption by a monolayer of MHPM adsorbent. The material developed shows higher adsorption capacity even at a higher concentration of solute ions, which is not usually observed with similar materials of this kind. Overall findings indicate that MHPM is a very potential lightweight adsorbent for removal of Mn2+ from the aqueous solution because of its low density and high surface area.

Evaluate the adverse impact of metal oxide on workers of different age groups that engage with gas metal arc welding process: health risk assessment

Immense epidemiological studies have been indicated about adverse effects of the welding fumes on the health of the welders, especially respiratory problems and other physiological disorders. The different types of welding mechanisms produce aerosols/fumes that contain different metals including chromium (Cr) and manganese (Mn). In the present study, the welders of two age groups (adolescents and adults) were selected; simultaneously the age-matched adolescents and adults belong to nonindustrial area as referents/control subjects. Biological samples (scalp hair) were collected from welders and referents, along with analyzed for Cr and Mn by electrothermal atomic absorption spectrometer, prior to acid digestion. To evaluate the occupational exposure on the health of the workers, the clinical features and biochemical parameters of selected population (exposed and non-exposed age-matched groups) were also carried out. The resulted data indicated that the concentrations of Mn and Cr were significantly higher in scalp hair samples of welders as compared to referent subjects (p < 0.01), verifying the absorption/exposure of both metals produced in welding fumes. The high prevalence of anemia and stomach disorder was observed in adolescent than adult welding workers. The incidence of asthma and related symptoms was elevated in adult welders than in younger boys. The neurological problems were particularly observed in aged welders > 50 years, might be due to long time exposure of welding fumes contains different toxicant especially Mn in ill ventilation system of workshops.

A Review on the Environmental Exposure to Airborne Manganese, Biomonitoring, and Neurological/Neuropsychological Outcomes

The occupational exposure to airborne manganese (Mn) has been linked for decades with neurological effects. With respect to its environmental exposure, the first reviews on this matter stated that the risk posed to human health by this kind of exposure was still unknown. Later, many studies have been developed to analyze the association between environmental Mn exposure and health effects, most of them including the measure of Mn in selected human biomarkers. This review aims at collecting and organizing the literature dealing with the environmental airborne Mn exposure (other routes of exposure were intentionally removed from this review), the biomonitoring of this metal in different body matrices (e.g., blood, urine, nails, hair), and the association between exposure and several adverse health effects, such as, e.g., neurocognitive, neurodevelopmental, or neurobehavioral outcomes. From the different exposure routes, inhalation was the only one considered in this review, to take into account the areas influenced by industrial activities closely related to the Mn industry (ferromanganese and silicomanganese plants, Mn ore mines, and their processing plants) and by traffic in countries where a fuel additive, methylcyclopentadienyl manganese tricarbonyl (MMT), has been used for years. In these areas, high air Mn levels have been reported in comparison with the annual Reference Concentration (RfC) given by the US EPA for Mn, 50 ng/m³. This review was performed using Scopus and MEDLINE databases with a keyword search strategy that took into account that each valid reference should include at least participants that were exposed to environmental airborne Mn and that were subjected to analysis of Mn in biomarkers or subjected to neurological/neuropsychological tests or both. Overall, 47 references matching these criteria were included in the discussion. Most of them report the measure of Mn in selected biomarkers (N = 43) and the assessment of different neurological outcomes (N = 31). A negative association is usually obtained between Mn levels in hair and some neurological outcomes, such as cognitive, motor, olfactory, and emotional functions, but not always significant. However, other biomarkers, such as blood and urine, do not seem to reflect the chronic environmental exposure to low/moderate levels of airborne Mn. Further studies combining the determination of the Mn exposure through environmental airborne sources and biomarkers of exposure and the evaluation of at least cognitive and motor functions are needed to better understand the effects of chronic non-occupational exposure to airborne Mn.

Characterization of ambient PM1 at a suburban site of Agra: chemical composition, sources, health risk and potential cytotoxicity

The present study was conducted at a University campus of Agra to determine concentrations of crustal and trace elements in submicron mode (PM₁) particles to reveal sources and detrimental effects of PM₁-bound metals (Cr, Cd, Mn, Zn, As, Co, Pb, Cu and Ni) in samples collected in the foggy (1 December 2016-17 January 2017) and non-foggy periods (1 April 2016-30 June 2016). Samples were collected twice a week on preweighed quartz fibre filters (QM-A 47 mm) for 24 h using Envirotech APM 577 (flow rate 10 l min^-1). Mass concentration of PM₁ was 135.0 ± 28.2 and 54.0 ± 18.5 µg/m³ during foggy and non-foggy period, respectively; crustal and trace elements were 13 and 4% during foggy and 11 and 3% in the non-foggy period. Source identification by PCA (principal component analysis) suggested that biomass burning and coal combustion was the prominent sources in foggy period followed by resuspended soil dust, industrial and vehicular emission, whereas in non-foggy period resuspended soil dust was dominant followed by biomass burning and coal combustion, industrial and vehicular emissions. In both episodes, Mn has the highest Hq (hazard quotient) value and Cr has the highest IlcR (Incremental Lifetime Cancer Risk) value for both adults and children. In vitro cytotoxicity impact on macrophage (J774) cells was also tested using MTT assay which revealed decreasing cell viability with increasing particle mass.

GLP-1 mimetics and cognition

Glucagon-like peptide-1 (GLP-1) receptor agonists are a class of antidiabetic drugs that improve the glycaemia via several molecular pathways. Recent evidence suggest that they also have additional effects modulating pathophysiologic pathways included in cognitive disorders. Since some forms of cognitive dysfunction such as Alzheimer's disease are more common among diabetic patients than in the normal population, antidiabetic drugs that have neuroprotective effects affording protection for cognitive disorders would be of benefit. Therefore, we reviewed the pharmacologic effects of GLP-1 analogues and found that they may have the additional benefit of improving cognitive performance via at least eight molecular mechanisms.

Hypermanganesemia Induced Chorea and Cognitive Decline in a Tea Seller

Background

Manganese associated neurotoxicity and neurodegeneration is quite rare yet established neurological disorder. This neurotoxic element has predilection for depositing in basal ganglia structures, manifesting mainly as parkinsonian and dystonic movement disorders with behavioral abnormalities.

Case report

We report a 40-year-old man who presented with a subacute onset bilateral, asymmetric hyperkinetic movement disorder (predominantly left sided chorea) with multi-domain cognitive impairment, dysarthria, and generalized rigidity. Clinical history and examination yielded multiple differential diagnoses including deposition and metabolic disorders, autoimmune and paraneoplastic encephalitis involving basal ganglia, and neurodegenerative disorders with chorea and cognitive impairment. However, magnetic resonance imaging was suggestive of paramagnetic substance deposition, which came out to be manganese after laboratory investigations. History, clinical examinations, and investigation results pointed towards a diagnosis of acquired hypermanganesemia due to over-ingestion of manganese containing substance (i.e., black tea). He was treated symptomatically and with chelation therapy (calcium disodium edetate). At the sixth month of follow-up, complete resolution of chorea, dysarthria and partial amelioration of rigidity were observed. His cognitive decline and behavioral abnormalities improved.

Discussion

This is probably the first reported case of acquired hypermanganesemia that presented as a combination of asymmetric chorea and cognitive dysfunction with atypical imaging characteristics. The clinical picture mimicked that of Huntington's disease. We highlight the potential deleterious effects of an apparently "benign" non-alcoholic beverage (i.e., black tea) on cerebral metabolism.

Sodium Para-aminosalicylic Acid Reverses Changes of Glutamate Turnover in Manganese-Exposed Rats

Sodium para-aminosalicylic acid (PAS-Na) has been used to treat patients with manganism, a neurological disease caused by manganese (Mn) toxicity, although the exact molecular mechanisms are yet unclear. The present study aims to investigate the effect of PAS-Na on glutamate (Glu) turnover of Mn-exposed rats. The results showed that Mn concentrations in the hippocampus, thalamus, striatum, and globus pallidus were increased in Mn-exposed rats. Moreover, the results also demonstrated that subacute Mn exposure (15 mg/kg for 4 weeks) interrupted the homeostasis of Glu by increasing Glu levels but decreasing glutamine (Gln) levels in the hippocampus, thalamus, striatum, and globus pallidus in male Sprague-Dawley rats. These effects lasted even after Mn exposure had been ceased for a period of 6 weeks. Meanwhile the main Glu turnover enzymes [Gln synthetase (GS) and phosphate-activated glutaminase (PAG)] and transporters [Glu/aspartate transporter (GLAST) and Glu transporter-1 (GLT-1)] were also affected by Mn treatment. Additionally, PAS-Na treatment recovered the aforementioned changes induced by Mn. Taken together, these results indicate that Glu turnover might be involved in Mn-induced neurotoxicity. PAS-Na treatment could promote Mn excretions and recover the changes in Glu turnover induced by Mn, and a prolonged PAS-Na treatment may be more effective.

Chronic exposure to heavy metals from informal e-waste recycling plants and children's attention, executive function and academic performance

E-waste contains valuable metals that require appropriate waste management plans. However, rudimentary e-waste processing methods are a source of heavy metals environmental pollution. This study has characterised concentrations of heavy metals in soil (n = 10), water (n = 10) and hair (n = 44) of children in areas surrounding Jakarta (Indonesia), where e-waste is being or has been conducted in the past, and in a reference unexposed site. Chronic exposure to Mn, Pb, Hg, As and Cd and its associations with attention and executive function, characterised with the Trail Making Test (TMT), along with academic performance scores was conducted using multivariate regression analysis. Models were adjusted for age, gender, parental education, environmental tobacco smoke and residential traffic. Lead (3653 ± 3355 mg/kg), cadmium (3.4 ± 0.9 mg/kg) and mercury (15.2 ± 28.5 mg/kg) concentrations from soil and manganese concentrations in water (1.43 ± 0.64 mg/L) in the exposed sites were higher than current regulations. Heavy metal concentrations in hair of children living near e-waste facilities was higher than for children living in non-exposed areas (Pb: 0.155 ± 0.187 vs 0.0729 ± 0.08 mg/g; Mn: 0.130 ± 0.212 vs 0.018 ± 0.045 mg/g; Hg: 0.008 ± 0.0042 vs 0.002 ± 0.0011 mg/g) suggesting chronic exposure to heavy metals. Manganese exposure was associated with worse cognitive performance in the domains of attention (TMT-A score: 66 s, 95% CI 0.09, 132), executive function (TMT-B score: 105 s, 95% CI 11.5, 198) and social sciences (-29%, 95% CI -54, -4.7) (per unit of Mn in hair mg/g). These results suggest that informal e-waste activities contribute to local heavy metal soil contamination, and could be an important source of metal exposure to children living in the vicinity of these facilities with putative impacts on their cognitive performance. E-waste management regulation and remediation programmes should be implemented to reduce environmental pollution and associated health effects.

Children's environmental health based on birth cohort studies of Asia (2) - air pollution, pesticides, and heavy metals

The life style and child raising environment in Asia are quite different compared with Western countries. Besides, the children's environmental threats and difficulties in conducting studies could be different. To address children's environmental health in Asia area, the Birth Cohort Consortium of Asia (BiCCA) was co-established in 2011. We reviewed the mercury, polychlorinated biphenyls, perfluoroalkyl substances, phthalates, and environmental tobacco smoke in pervious based on birth cohort studies in Asia. The aim of this study was to summarize the traditional environmental pollution and the target subjects were also based on the birth cohort in Asia area. Environmental pollutants included air pollutants, pesticides focusing on organochlorine pesticides, diakylphosphates, and pyrethroid, and heavy metals including lead, arsenic, cadmium, manganese, vanadium, and thallium. Fetal growth and pregnancy outcomes, childhood growth and obesity, neurodevelopment and behavioral problems, and allergic disease and immune function were classified to elucidate the children's health effects. In total, 106 studies were selected in this study. The evidences showed air pollution or pesticides may affect growth during infancy or childhood, and associated with neurodevelopmental or behavioral problems. Prenatal exposure to lead or manganese was associated with neurodevelopmental or behavioral problems, while exposure to arsenic or cadmium may influence fetal growth. In addition to the harmonization and international collaboration of birth cohorts in Asia; however, understand the whole picture of exposure scenario and consider more discipline in the research are necessary.

Blood manganese levels during pregnancy and postpartum depression: A cohort study among women in Mexico

BACKGROUND

Occupational studies have shown an association between elevated Mn exposure and depressive symptoms. Blood Mn (BMn) naturally rises during pregnancy due to mobilization from tissues, suggesting it could contribute to pregnancy and postpartum depressive symptoms.

OBJECTIVES

To assess the association between BMn levels during pregnancy and postpartum depression (PPD), creating opportunities for possible future interventions.

METHODS

We studied 561 women from the reproductive longitudinal Programming Research in Obesity, Growth, Environment, and Social Stressors (PROGRESS) cohort in Mexico City. BMn was measured at the 2^nd and 3^rd trimesters, as well as delivery. The Edinburgh Postnatal Depression Scale (EPDS) was used to assess PPD symptoms at 12-months postpartum. We used a generalized linear model assuming a Poisson distribution to assess the association between BMn levels and PPD, with adjustments for age, stress and depressive symptoms during pregnancy, education, socioeconomic status, and contemporaneous blood lead levels.

RESULTS

The mean ± standard deviation (SD) EPDS score at 12-months postpartum was 6.51 ± 5.65, and 17.11% of women met the criteria for possible PPD (score ≥ 13). In adjusted models, BMn during the 3^rd trimester (β: 0.13, 95% CI: 0.04-0.21) and BMn levels averaged at the 2^nd and 3rd trimester (β: 0.14, 95% CI: 0.02-0.26) had a positive association with EPDS scores at 12 months postpartum. BMn at the 2^nd trimester (β: 0.07, 95% CI: -0.09-0.22) and delivery (β: 0.03, 95% CI: -0.04-0.10) had a non-significant positive association with EPDS scores at 12-months postpartum. Stress and depressive symptoms during pregnancy was associated with higher EPDS scores at 12-months postpartum in all of the adjusted models but were only significant when either BMn during 3^rd trimester or BMn averaged across 2^nd and 3^rd trimester was assessed as the exposure.

DISCUSSION

Our results demonstrate that elevated BMn levels during pregnancy predict PPD symptoms and could be a potential pathway for intervention and prevention of PPD.

Manganese levels in infant formula and young child nutritional beverages in the United States and France: Comparison to breast milk and regulations

Exposure to high levels of manganese (Mn) in children has recently been associated with adverse neurodevelopmental effects. Current infant formula regulations for Mn content were set between 1981 (United States), 2006 (European Union, France), and 2007 (Codex Alimentarius) prior to the publication of much of the growing body of research on the developmental neurotoxicity of Mn. In this study, we sought to measure the concentrations of Mn in some infant formulas and young child nutritional beverages available on the United States (US) and French markets using ion beam analysis by particle induced X-ray emission (PIXE) spectrometry and then compare the analytical results to concentrations reported in the literature for breast milk and applicable infant formula regulations and guidelines. We were particularly interested in measuring Mn concentrations in product types for which there is very little data from previous surveys, especially soy-based, rice-based, goat-milk based, chocolate-flavored, and nutritional beverages for young children that are not regulated as infant or follow-on formulas (e.g. “toddler formulas” and “toddler powders”). We purchased 44 infant formulas and young child nutritional beverage products in the US and France with varying protein sources (cow-milk, goat-milk, soy, rice) labelled for birth to 3 years. We selected these samples using maximum variation sampling to explore market extremes to facilitate comparisons to regulatory limits. Since this sampling method is non-probabilistic, other inferences cannot be made beyond this set of samples to the overall markets. We used ion beam analysis to measure the concentrations of Mn in each product. The range of measured Mn concentrations in the products is 160–2,800 μg/L, substantially higher than the 3–6 μg/L mean Mn concentration reported in human breast milk. All products satisfied national and Codex Alimentarius Commission (CAC) international standards for minimum Mn content in infant formulas; however, 7/25 of the products purchased in the US exceeded the CAC Guidance Upper Level of 100 μg Mn/kcal for infant formula.

Pivotal role of cAMP-PKA-CREB signaling pathway in manganese-induced neurotoxicity in PC12 cells

Manganese (Mn) plays a critical role in individual growth and development, yet excessive exposure can result in neurotoxicity, especially cognitive impairment. Neuronal apoptosis is considered as one of the mechanisms of Mn-induced neurotoxicity. Recent evidence suggests that cAMP-PKA-CREB signaling regulates apoptosis and is associated with cognitive function. However, whether this pathway participates in Mn-induced neurotoxicity is not completely understood. To fill this gap, in vitro cultures of PC12 cells were exposed to 0, 400, 500, and 600 μmol/L Mn for 24 hours, respectively. Another group of cells were pretreated with 10.0 μmol/L rolipram (a phosphodiesterase-4 [PDE4] inhibitor) for 1 hour followed by 500 μmol/L Mn exposure for 24 hours. Flow cytometry, immunofluorescence staining, enzyme-linked immunosorbent assay, and Western blot analysis were used to detect the apoptosis rate, protein levels of PDE4, cAMP signaling, and apoptosis-associated proteins, respectively. We found that Mn exposure significantly inhibited cAMP signaling and protein expression of Bcl-2, while increasing apoptosis rate, protein levels of PDE4, Bax, activated caspase-3, and activated caspase-8 in PC12 cells. Pretreatment of rolipram ameliorated Mn-induced deficits in cAMP signaling and apoptosis. These findings demonstrate that cAMP-PKA-CREB signaling pathway-induced apoptosis is involved in Mn-induced neurotoxicity.

Assessing the contributions of metals in environmental media to exposure biomarkers in a region of ferroalloy industry

Residential proximity to ferroalloy production has been associated with increased manganese exposure, which can adversely affect health, particularly among children. Little is known, however, about which environmental samples contribute most to internal levels of manganese and other ferroalloy metals. We aimed to characterize sources of exposure to metals and evaluate the ability of internal biomarkers to reflect exposures from environmental media. In 717 Italian adolescents residing near ferromanganese industry, we examined associations between manganese, lead, chromium, and copper in environmental samples (airborne particles, surface soil, indoor/outdoor house dust) and biological samples (blood, hair, nails, saliva, urine). In multivariable regression analyses adjusted for child age and sex, a 10% increase in soil Mn was associated with increases of 3.0% (95% CI: 1.1%, 4.9%) in nail Mn and 1.6% (95% CI: -0.2%, 3.4%) in saliva Mn. Weighted-quantile-sum (WQS) regression estimated that higher soil and outdoor dust Mn accounted for most of the effect on nail Mn (WQS weights: 0.61 and 0.22, respectively, out of a total of 1.0). Higher air and soil Mn accounted for most of the effect on saliva Mn (WQS weights: 0.65 and 0.29, respectively). These findings can help inform biomarker selection in future epidemiologic studies and guide intervention strategies in exposed populations.

Reversibility of neuroimaging markers influenced by lifetime occupational manganese exposure

Manganese (Mn) is a neurotoxicant that many workers are exposed to daily. There is limited knowledge about how changes in exposure levels impact measures in magnetic resonance imaging (MRI). We hypothesized that changes in Mn exposure would be reflected by changes in the MRI relaxation rate R1 and thalamic γ-aminobutyric acid (GABAThal). As part of a prospective cohort study, 17 welders were recruited and imaged on two separate occasions approximately two years apart. MRI relaxometry was used to assess changes of Mn accumulation in the brain. Additionally, GABA was measured using magnetic resonance spectroscopy (MRS) in the thalamic and striatal regions of the brain. Air Mn exposure ([Mn]Air) and cumulative exposure indexes of Mn (Mn-CEI) for the past three months (Mn-CEI3M), past year (Mn-CEI12M), and lifetime (Mn-CEILife) were calculated using personal air sampling and a comprehensive work history, while toenails were collected for analysis of internal Mn body burden. Finally, welders' motor function was examined using the Unified Parkinson's Disease Rating Scale (UPDRS). Median exposure decreased for all exposure measures between the first and second scan. ΔGABAThal was significantly correlated with ΔMn-CEI3M (ρ = 0.66, adjusted p = 0.02), ΔMn-CEI12M (ρ = 0.70, adjusted p = 0.006) , and Δ[Mn]Air (ρ = 0.77, adjusted p = 0.002). ΔGABAThal significantly decreased linearly with ΔMn-CEI3M (quantile regression, β = 15.22, p = 0.02) as well as Δ[Mn]Air (β = 1.27, p = 0.04). Finally, Mn-CEILife interacted with Δ[Mn]Air in the substantia nigra where higher Mn-CEILife lessened the ΔR1 per Δ[Mn]Air (F-test, p = 0.005). While R1 and GABA changed with Mn exposure, UPDRS was unaffected. In conclusion, our study shows that effects from changes in Mn exposure are reflected in thalamic GABA levels and brain Mn levels, as measured by R1, in most brain regions.

Assessing children's exposure to manganese in drinking water using a PBPK model

A previously published human PBPK model for manganese (Mn) in infants and children has been updated with Mn in drinking water as an additional exposure source. Built upon the ability to capture differences in Mn source-specific regulation of intestinal uptake in nursing infants who are breast-fed and formula-fed, the updated model now describes the bioavailability of Mn from drinking water in children of ages 0-18. The age-related features, including the recommended age-specific Mn dietary intake, age-specific water consumption rates, and age-specific homeostasis of Mn, are based on the available human data and knowledge of the biology of essential-metal homeostasis. Model simulations suggest that the impact of adding drinking-water exposure to daily Mn exposure via dietary intake and ambient air inhalation in children is not greater than the impacts in adults, even at a drinking-water concentration that is 2 times higher than the USEPA's lifetime health advisory value. This conclusion was also valid for formula-fed infants who are considered at the highest potential exposure to Mn from drinking water compared to all other age groups. Our multi-route, multi-source Mn PBPK model for infants and children provides insights about the potential for Mn-related health effects on growing children and will thereby improve the level of confidence in properly interpreting Mn exposure-health effects relationships in children in human epidemiological studies.

Human DNA Polymerase μ Can Use a Noncanonical Mechanism for Multiple Mn2+-Mediated Functions

Recent research on the structure and mechanism of DNA polymerases has continued to generate fundamentally important features, including a noncanonical pathway involving "prebinding" of metal-bound dNTP (MdNTP) in the absence of DNA. While this noncanonical mechanism was shown to be a possible subset for African swine fever DNA polymerase X (Pol X) and human Pol λ, it remains unknown whether it could be the primary pathway for a DNA polymerase. Pol μ is a unique member of the X-family with multiple functions and with unusual Mn²⁺ preference. Here we report that Pol μ not only prebinds MdNTP in a catalytically active conformation but also exerts a Mn²⁺ over Mg²⁺ preference at this early stage of catalysis, for various functions: incorporation of dNTP into a single nucleotide gapped DNA, incorporation of rNTP in the nonhomologous end joining (NHEJ) repair, incorporation of dNTP to an ssDNA, and incorporation of an 8-oxo-dGTP opposite template dA (mismatched) or dC (matched). The structural basis of this noncanonical mechanism and Mn²⁺ over Mg²⁺ preference in these functions was analyzed by solving 19 structures of prebinding binary complexes, precatalytic ternary complexes, and product complexes. The results suggest that the noncanonical pathway is functionally relevant for the multiple functions of Pol μ. Overall, this work provides the structural and mechanistic basis for the long-standing puzzle in the Mn²⁺ preference of Pol μ and expands the landscape of the possible mechanisms of DNA polymerases to include both mechanistic pathways.

Interactions between 14 Elements in the Human Placenta, Fetal Membrane and Umbilical Cord

The aim of the study was to investigate relationships between the concentrations of macroelements (Ca), microelements (Cr, Cu, Fe, Mn, Mo, Ni, Sn, Sr, V, Zn) and heavy metals (Ag, Cd, Pb) in the placenta, fetal membrane and umbilical cord. ‪Furthermore, we examined relationships between the concentrations of these metals in the studied afterbirths and maternal age, gestational age, placenta parameters (breadth, length, weight) and newborn parameters (length, weight and Apgar score). This study confirms previously reported Zn-Cd, Pb-Cd and Ni-Pb interactions in the placenta. New types of interactions in the placenta, fetal membrane and umbilical cord were also noted. Analysis of the correlations between metal elements in the afterbirths (placenta, fetal membrane and umbilical cord) and biological parameters showed the following relationships: maternal age and Mn (in the fetal membrane); gestational age and Cr, Fe, Zn (in the fetal membrane), Ag and Cu (in the umbilical cord); newborn’s length and Sr (in the placenta), Ag (in the umbilical cord); newborn’s weight and Sr (in the placenta), Cu (in the fetal membrane), Ag (in the umbilical cord); Apgar score and Ca, Cr and Ni (in the umbilical cord); placenta’s length and Cr and Sn (in the fetal membrane), Cu (in the umbilical cord); placenta’s width and Mo, Pb (in the placenta) and placenta weight and Sr (in the placenta), Ag, Fe, Mn (in the fetal membrane). The results show the influence of metals on the placenta, mother and newborn parameters, and the same point indicates the essential trace elements during the course of pregnancy.