Maximum Contaminant Level Research Articles

Analysis of colloidal activated carbon alternatives for in situ remediation of a large PFAS plume and source area

AbstractThis study evaluated optimal locations for in situ remediation of per‐ and poly‐fluoroalkyl substances (PFAS) in groundwater with colloidal activated carbon (CAC). New Freundlich isotherms for PFAS adsorption to CAC were estimated to illustrate the effect of competitive adsorption with dissolved organic carbon and other PFAS in a groundwater sample. A hypothetical model scenario was constructed based on source area characteristics similar to a site impacted by aqueous film forming foam in South Dakota. Modeling indicates that, even with high PFAS concentrations, CAC would still be capable of maintaining concentrations below proposed maximum contaminant levels in the adsorption zone for at least 30–40 years. Two‐dimensional areal modeling indicates that the future breakthrough of PFAS is likely to occur in the localized core of the plume, and that the corresponding future reinjection of CAC will only need to be conducted over a smaller portion of the original injection footprint. The benefits of implementing a phased remedial approach at PFAS sites are discussed. Source area and mid‐plume CAC treatments are shown to be ineffective at attenuating PFAS concentrations at the downgradient property boundary within a reasonable timeframe when PFAS travel time is relatively slow. Among the CAC alternatives evaluated here, a downgradient CAC permeable reactive barrier has the best performance with respect to protecting downgradient receptors.

Evaluation of sample collection containers for selenium quantification

Naturally occurring concentrations of selenium (Se) are very low: 0.02 µg L-1 in freshwater and 0.01-2 mg kg-1 in soil. Mining operations must discharge water in accordance with the United States Environmental Protection Agency’s established maximum contaminant level and may be required to discharge at even lower limits set by the state. For accurate analysis, sample collection containers and labware must be carefully chosen to prevent changes in composition through interactions between sample and container. Our objective was to assess four materials (glass, silanized glass, polytetrafluoroethylene, and polypropylene) for use in Se quantification. Varying Se stock solutions (0, 10, 25, and 50 µg L-1) were prepared in 0.1 M sodium chloride, delivered to each container, and equilibrated for 6, 12, 24, or 48 hours. Selenium was lost to all containers with the least loss occurring in the silanized-treated glass (1-12% across all concentrations). Silanized glassware is recommended for Se quantification as it improved sample integrity.

Radon concentration in spring water as an indicator of seismic activity: a case study of the Muzaffarabad Fault in Pakistan.

Radon and its progenies found in water indicate the existence of seismically active faults in the region. However, exposure to high levels of radon can also result in radiation-related health risks. This study focuses on radon-based active tectonic studies along the Muzaffarabad Fault in the core of the Hazara-Kashmir Syntaxis (HKS), NW Himalayas, Pakistan. In this study, spring water samples were collected along roadside of Jhelum Valley and in close proximity to the Muzaffarabad Fault in Pakistan using Radon Thoron Monitor (RTM1688-2). The results of the study showed that the radon concentrations in the water samples ranged from 1.895 to 17.097 Bq/l. The study found that the highest radon concentration was observed in the samples collected closest to the fault, while the lowest concentration was observed in the samples collected further away. The statistical analysis between the radon concentration and the distance from the fault showed a strong inverse relationship (R2=0.73). The study also found that 68% of the sampling sites had radon concentrations that exceeded the maximum contamination level (MCL) set by the US Environmental Protection Agency (EPA). The higher radon concentrations in the springs water suggest the probability of earthquake, which in turn poses potential health risks for the local population. The findings suggest that the measurement of radon concentration in water can be used as a tool for identifying seismically active faults in the region.

Environmental Assessment and Monitoring of Heavy Metals in New York City Potable Water Systems: Case Study at Medgar Evers College, Correlation Analysis, and Public Health Impacts

Reinforced by this study, New York City has one of the cleanest water systems in the world. Medgar Evers College (MEC) serves 7000 students/1050 faculty/staff. Given that: (1) students/faculty/staff spend 20–30% of their daily time there; (2) potable water sources must abide by the EPA’s maximum contamination levels (MCLs); and (3) a detrimental impact on human health arises from violations to EPA’s water quality mandates, we quantified the abundance of 27 heavy metals (96 samples, N = 3) using MEC as a case study. Water was collected from all potable water sources, following EPA protocols for sample-matrix preparation, collection, and wet-chemical analysis. Linear polyethylene containers/caps were used to prevent sample contamination while the water samples were spiked with HNO3 (aq) for preservation. Heavy metal concentrations were quantified using New Jersey’s Meadowlands Environmental Research Institute’s Inductively Coupled Plasma-Mass Spectrometer (ICP-MS, Agilent 7700X) in no gas, and He flow modes. Ninety-five percent of sample concentration relative standard deviations (RSDs) reveal four distinct regions: (1) where one mode is more precise than the other, and sample data exhibit very good to excellent precision, RSD ≤ 15%; (2) despite being at low concentrations, measurements exhibit good to excellent precision, RSD ≤ 20%; (3) species concentrations ≥0.1 ppb very good to excellent precision is shown, RSD ≤ 15%; and (4) species at concentrations ≤ 10−3 ppb display fair to very poor precision, RSD ≥ 30%. All heavy metals complied with their respective EPA MCLs (except Fe). Over 90% of Fe sample concentrations were enhanced by up to about 30×. Two samples exhibited [Pb] = 13.7 (No gas mode, RSD = 3.32%) and 14.8 ppb (He mode, RSD = 0.75%), which is close to the EPA Primary MCL, 15 ppb. Based on EPA/WHO end-member equations, we estimate a 1/103 to 1/108 chance of cancer attainment from long-term exposure to the range of concentrations of heavy metals measured in this study.

Evaluation of the Radon Levels in the Groundwater Wells of Qatar: Radiological Risk Assessment

The objective of this work is to give a holistic overview of the groundwater quality in Qatar in terms of its radon levels and provide a radiological risk assessment of elevated radon levels on human health. This study covered the analysis of groundwater collected from various locations throughout Qatar and maps using ArcGIS followed by a radiological risk assessment of radon in Qatar. There is no extensive study reported to investigate radon activity levels in groundwater across Qatar and their health effects. The radon level measurements of the Qatari groundwater ranged between 2.7 ± 0.2 and 60.7 ± 13.4 Bq/L with a mean value of 20.6 Bq/L, which is greater than the US EPA’s maximum contamination level (11 Bq/L). About 65% of the studied samples exceeded the US EPA’s MCL guidelines. The mean total annual effective dose due to radon inhalation and ingestion was 0.056 mSv/y, which is below the WHO reference level of 0.1 mSv/y. The radon radiological risk study through inhalation and ingestion clearly revealed that the contribution of the inhalation dose was higher than the ingestion dose.

Elevated parkinsonism pathological markers in dopaminergic neurons with developmental exposure to atrazine

Atrazine (ATZ) is one of the most used herbicides in the US and a known endocrine disruptor. ATZ is frequently detected in drinking water, especially in Midwestern regions of the United States, exceeding the EPA regulation of maximum contamination level (MCL) of 3 ppb. Epidemiology studies have suggested an association between ATZ exposure and neurodegeneration. Less, however, is known about the neurotoxic mechanism of ATZ, particularly for exposures at a developmental stage. Here, we exposed floor plate progenitors (FPPs) derived from human induced pluripotent stem cells (hiPSCs) to low concentrations of ATZ at 0.3 and 3 ppb for two days followed by differentiation into dopaminergic (DA) neurons in ATZ-free medium. We then examined the morphology, activity, pathological protein aggregation, and transcriptomic changes of differentiated DA neurons. We observed significant decrease in the complexity of neurite network, increase of neuronal activity, and elevated tau- and α-synuclein (aSyn) pathologies after ATZ exposure. The ATZ-induced neuronal changes observed here align with pathological characteristics in Parkinson's disease (PD). Transcriptomic analysis further corroborates our findings; and collectively provides a strong evidence base that low-concentration ATZ exposure during development can elicit increased risk of neurodegeneration.

Age-dependent Radiological Risk Assessment of Radon (222Rn) in Samples of Commercial Bottled Water from Benin City, Nigeria

Radon inhalation as well as ingestion through the use of water has a high potential of causing serious harm to sensitive cells and organs of the body when absorbed into the bloodstream. Therefore, this study aimed to assess the radiological health damage caused by radon in drinking bottled water available in Benin City, Edo State, Nigeria. Radon concentration was measured using a RAD7 electronic radon detector. The mean activity concentration radon is 137.18 ± 0.25 mBq/L. This mean value is slightly higher than 0.1 Bq/L recommended by the Standard Organisation of Nigeria but lower than the maximum contaminant level (MCL) of 11.1 Bq/L set by the United States Environmental Protection Agency and 100 Bq/L set by the World Health Organisation (WHO) for consumption of radon in drinking water. The mean total annual effective dose is 1.07±1.91 (\(\mu\)Sv/y) for infants, 0.61±1.09 (\(\mu\)Sv/y) for children, and 0.70±1.24 (\(\mu\)Sv/y) for adults. The computed annual effective dose to the public by inhalation and ingestion radon through the use of bottled water in the study areas are lower than the 0.1 mSv/y limit recommended by WHO. The estimated average for the age group excess lifetime cancer risk are 3.21 ± 5.71, 1.836 ± 3.26, 2.086 ± 3.71 (x 10-6) for infants, children and adults respectively. These values are below the world average permissible levels. Hence, consumption of the water examined poses no serious health risk to consumers.

Influence of iron, phosphate, and silicate on arsenic removal from groundwater using a low-cost ceramic filter.

The ceramic filter amended with iron (Fe) has proven to be a potential low-cost method for arsenic (As) removal from groundwater. The presence of Fe, phosphate (P), and silicate (Si) significantly affects the As removal efficiency of the ceramic filter, which has not been passably investigated. The present research aimed to examine the effect of Fe, P, and (or) Si presence as single or in combination on As (III) removal from synthetics groundwater by a low-cost iron amended ceramic filter (IACF). Laboratory-scale filtration experiments at different compositions of Fe, P, Si, and As (III) were conducted by the IACF fabricated with a ceramic candle and iron netting box. Fe (II) in synthetic groundwater positively impacted As (III) removal. At a concentration of 2mg/L of Fe (II), the As levels in the effluent decreased to less than the maximum contamination level (MCL) of 50 μg/L. Groundwater P concentration needed less than 3mg/L or Si concentrations required less than 35 mg/L to effectively reduce As (III) to below the MCL at 5mg/L of groundwater Fe (II). The cumulative effect of P and Si on As removal was found to be more significant than distinct contributions. The presence of 2mg/L P and 35 mg/L or higher Si in the groundwater cumulatively reduced the As removal performance from 92% to 63%, and the MCL was not met. The negative impact of P and Si on As (III) removal followed the order of (P + Si) > P > Si. P competed with As for adsorption sites during the process, while Si inhibited the Fe release and floc formation, significantly reducing As removal performance. The study findings can potentially contribute to optimizing IACF as a low-cost method for As removal from groundwater.

Toxic metal mixtures in private well water and increased risk for preterm birth in North Carolina

BackgroundPrenatal exposure to metals in private well water may increase the risk of preterm birth (PTB) (delivery < 37 weeks’ gestation). In this study, we estimated associations between arsenic, manganese, lead, cadmium, chromium, copper, and zinc concentrations in private well water and PTB incidence in North Carolina (NC).MethodsBirth certificates from 2003–2015 (n = 1,329,071) were obtained and pregnancies were assigned exposure using the mean concentration and the percentage of tests above the maximum contaminant level (MCL) for the census tract of each individuals’ residence at the time of delivery using the NCWELL database (117,960 well water tests from 1998–2019). We evaluated associations between single metals and PTB using adjusted logistic regression models. Metals mixtures were assessed using quantile-based g-computation.ResultsCompared with those in other census tracts, individuals residing in tracts where > 25% of tests exceeded the MCL for lead (aOR 1.10, 95%CI 1.02,1.18) or cadmium (aOR 1.11, 95% CI 1.00,1.23) had an increased odds of PTB. Conversely, those residing in areas with > 25% MCL for zinc (aOR 0.77 (95% CI: 0.56,1.02) and copper (aOR 0.53 (95% CI: 0.13,1.34)) had a reduced odds of PTB. A quartile increase in the concentrations of a mixture of lead, cadmium, and chromium was associated with a small increased odds for PTB (aOR 1.02, 95% CI 1.01, 1.03). This metal mixture effect was most pronounced among American Indian individuals (aOR per quartile increase in all metals: 1.19 (95% CI 1.06,1.34)).ConclusionsIn a large study population of over one million births, lead and cadmium were found to increase the risk of PTB individually and in a mixture, with additional mixtures-related impacts estimated from co-exposure with chromium. This study highlights critical racial and ethnic health disparities in relation to private well water thereby emphasizing the urgent need for improved private well water quality to protect vulnerable populations.

Analysis of gut bacteriome of in utero arsenic-exposed mice using 16S rRNA-based metagenomic approach.

Approximately 200 million people worldwide are affected by arsenic toxicity emanating from the consumption of drinking water containing inorganic arsenic above the prescribed maximum contaminant level. The current investigation deals with the role of prenatal arsenic exposure in modulating the gut microbial community and functional pathways of the host. 16S rRNA-based next-generation sequencing was carried out to understand the effects of in utero 0.04 mg/kg (LD) and 0.4 mg/kg (HD) of arsenic exposure. This was carried out from gestational day 15 (GD-15) until the birth of pups to understand the alterations in bacterial diversity. The study focused on gestational exposure to arsenic and the altered gut microbial community at phyla and genus levels, along with diversity indices. A significant decrease in firmicutes was observed in the gut microbiome of mice treated with arsenic. Functional analysis revealed that a shift in genes involved in crucial pathways such as insulin signaling and non-alcoholic fatty liver disease pathways may lead to metabolic diseases in the host. The present investigation may hypothesize that in utero arsenic exposure can perturb the gut bacterial composition significantly as well as the functional pathways of the gestationally treated pups. This research paves the way to further investigate the probable mechanistic insights in the field of maternal exposure environments, which may play a key role in epigenetic modulations in developing various disease endpoints in the progeny.

Removal of copper contamination from simulated wastewater using chitosan and shrimp waste: Equilibrium analysis

This study addressed copper removal from aqueous solution using unprocessed shrimp tail shell waste (STW) with comparison to removal by chitosan derived from shrimp shell. The use of a copper ion selective electrode enabled continuous copper concentration measurement and determination of the STW mass-time relationship needed to achieve the USEPA Maximum Contaminant Level for copper as a function of adsorbent dose. Copper removal using chitosan produced a blue solid without surface morphology changes, consistent with an adsorption or ion exchange mechanism. Calcium carbonate in the STW was essential for copper removal by the formation of a green copper-containing deposit primarily on the exposed edges of the ground shrimp solids and an increase in calcium concentration and pH in the treated solution. The systems reached equilibrium over several days. Equilibrium data were fitted to the Freundlich, Langmuir, Temkin, Sips, and B-E-T isotherms and the Freundlich model fit the data well. Raw STW, cooked STW, and chitosan with particle sizes ranging from 425 to 850 µm gave a maximum copper loading of 184 mg/g, 170 mg/g, and 129 mg/g, respectively. Both raw and cooked STW had higher copper capacities than commercial chitosan and provide a low cost and environmentally friendly adsorbent. Comparison of small particle size (< 425 µm) adsorbents after six hours showed that raw STW had double the copper loading of chitosan. Small STW achieved greater than 97.4% copper removal from a 50 mg/L copper solution and reached the MCL in less than one hour for 1.5 g/L loadings.

(Invited) Insights on Decentralized Electrochemical Reduction of Nitrate

Ammonia is a chemical commodity with demonstrated global importance given its clear food-energy-water nexus. Ammonia large-scale production relies on the Haber-Bosch process which employs hydrogen and nitrogen as reagents under high pressure (10 MPa) and high temperature (500 °C). This process is responsible for more than ~180 million tons of ammonia production per year to satisfy industrial and agricultural needs. Sustaining the ammonia production through the Haber-Bosch process has a huge carbon footprint as sustainability toll. The Haber-Bosch process generates over 450 million tons of CO2 annually, which represents almost 1.5 % of global emissions per year. The fossil fuel reliance of this high energy demand process of ammonia synthesis defines the world economy in many ways. For instance, recent cost increase on ammonia production has had a direct impact on food price inflation worldwide. Ammonia shortage has different causes such as geopolitical conflicts around the world, and increased natural gas price, among others. Thus, a fossil fuel-free green chemical synthesis alternative is required to alleviate the ammonia demand while diminishing the carbon footprint.Agriculture is strongly dependent on ammonia-based fertilizers generating a nitrogen-imbalance in the environment due to N-species (e.g., NO3 -, NO2 -, NH4 +) runoff to ground and surface water. Among these N-species, high concentrations of nitrate and nitrite are highlighted as frequent water quality violations in the US. Concentrations way above the regulated maximum contaminant levels (MCL) of 10 mg L-1 for NO3 --N and 1 mg L-1 for NO2 --N are commonly found in many water resources. Implementation of electrochemical reduction of nitrate (ERN) to produce ammonia can address environmental pollution while producing ammonia under mild conditions with less carbon footprint. The ERN process can become a decentralized ammonia production system alleviating needs at small and even medium scale production. Selectively reducing nitrate towards ammonia has gained attention due to several advantages respect to direct N2 gas reduction such as higher solubility and lower energy barrier. This electrochemically driven process can be coupled with renewable energy systems and therefore holds the promise to enable fossil-free ammonia production off-grid.The mechanisms for electrochemical conversion of nitrate to nitrogen gas are highly complex, involving numerous reactions, products and stable intermediates (e.g., ammonia, nitrite, hydrazine, hydroxylamine, nitric oxide, nitrous oxide) spanning the many nitrogen oxidation states (from -III up to +V). Controlling the reaction selectivity of a complex mechanisms that involve different charge transfer and chemical reactions (e.g., hydrogenation) is challenging. This invited presentation aims to showcase some of the advances in terms of electrode engineering design to steer selectivity towards ammonia production as well as some of the challenges that will be faced when translating lessons learnt towards application under real environmental samples.

Cellulose/amylose derivatives bearing bulky substituents as reversible fluorescent sensors for detection of Fe3+

Two novel cellulose and amylose derivatives bearing bulky tris(2-benzothienylformate) pendants (Cel-3 and Amy-3) were expeditiously prepared by one-step esterification. The fluorescent sensing performance of six polysaccharide derivatives, including Cel-3/Amy-3, and other four previously prepared benzothienyl- or benzofuranyl-phenylcarbamates of cellulose and amylose (Cel-1/Amy-1, Cel-2/Amy-2), were carefully evaluated using eight metal ions, including Co2+, K+, Na+, Li+, Hg2+, Ni2+, Ca2+ and Fe3+. All six derivatives exhibited excellent fluorescence quenching property to Fe3+ ions with high sensitivity and selectivity. Especially, the limit of detection of Amy-2 with benzofuranylphenylcarbamates for Fe3+ was 3.0 μM, much lower than the maximum contaminant level for Fe3+ in the drinking water. Additionally, the six bulky derivatives displayed the interesting fluorescence “turn-off” and “turn-on” observation, indicating a desirable reversibility for Fe3+ detection. The high anti-interference ability was also observed for detection of Fe3+ on the benzothienyl/benzofuranyl derivatives of cellulose and amylose in the combined system containing Co2+, K+, Na+, Li+, Hg2+, Ni2+ and Ca2+. It suggested that the obtained polysaccharide derivatives with bulky chromophores possessed good potentials for detection of Fe3+ as high-efficient fluorescent sensors in diverse applications. The sensing mechanism for detection of Fe3+ was further proposed based on the Stern-Volmer plots and fluorescence titration analysis.

Molecular contamination control for Exomars 2022 Mission

The ExoMars 2022 integration facility has been built at the Thales Alenia Space Italy in Turin. The facility includes a GBT (Glove Box Train), that is an ISO3 class facility, totally aseptic and characterized by controlled airborne molecular organic contamination. This new facility provides an environment strictly controlled for what concerns cleanliness and contamination, specifically conceived to perform AIT of The Ultra Clean Zone (UCZ) of the ExoMars Rover Analytical Laboratory Drawer.Indeed, standard methods as per ECSS-Q-ST-70-05C and ECSS-Q-ST-70-50C are not suitable for the monitoring of integration facility and Flight H/W. The environment of GBT has been required to be monitored in terms of airborne molecular contamination (AMC) on the basis of ISO 14644-8. The maximum contamination levels allowable on flight H/W after accelerated CO2 snow cleaning and at the end of integration activities are one order of magnitude less than the detection limit of standard FT-IR techniques for molecular contamination.For these reasons a dedicated method has been set up for molecular contamination monitoring. This paper shows the development of Thermal Desoprtion-Gas Cromatography/Mass Spectrometer (TD-GC/MS) method for the monitoring of extremely low organic contamination levels both on air samples and on witnesses representative of the Flight H/W, providing also the most recent results obtained in the frame of ExoMars 2022 UCZ QM and FM AIT Campaign.

Concentration of Phthalate Esters in Bottled Water: A Case Study in Effurun, Delta State, Nigeria

Phthalate esters (PAEs), a group of chemical compounds, are extensively used as additives in plastics. The objective of this study was to determine how much of a few target PAEs have leached into various samples of drinking water packaged in PET bottles in Effurun, Delta State, Nigeria as well as how ambient temperature, sunshine exposure, and cold storage conditions have affected the concentration of PAE. The concentrations of Di-ethyl-phthalate (DEP), di-butyl-phthalates (DBP), benzyl-butyl-phthalate (BBP), di-n-octyl phthalate (DnOP), and Bis-(2-ethyl-hexyl) phthalate (DEHP) were determined in bottled water samples. The concentrations of PAEs were determined using a gas chromatography coupled with a mass sepctroscopy analyzer (GC-MS). Phthalate compound was observed to be in all bottled water placed under different storage conditions; cold storage (CW), ambient storage (AW), and sunlight storage (SLW) for a period of 2, 4, 8, 12 and 16 weeks. However, the greatest leaching effect was observed in PET bottled water placed sunlight conditions for sixteen weeks with concentrations of; DEHP (2.1-11.2) µg/L, DEP (0.98-3.87) µg/L, DBP (2.98-13.8) µg/L. The results from this study indicated that, under various storage conditions, DEP, DBP and DEHP from PET bottles may leach more into the drinking water over a period of time under different storage conditions. The result additionally gave indication that DEHP; a known endocrine disruptor, with anti-androgenic and possible human carcinogen effects, exceeded the 6 µg/L USEPA Maximum Contamination Level (MCL) in drinking water, and also greater than 8 µg/L which is the indicated MCL by the World Health Organization (WHO).

Assessing environmental and radiological impacts and lithological mapping of beryl-bearing rocks in Egypt using high-resolution sentinel-2 remote sensing images

Emerald and other beryls represent a family of the most valuable gemstone around the world and particularly in Egypt. Beryllium (Be) contents in beryl-bearing bedrocks in south Sinai (Wadi Ghazala and Wadi Sedri), and in central and south Eastern Desert of Egypt (Igla area, Zabara-Um Addebaa belt, Homret Akarem, and Homret Mukpid) were investigated in this study. The environmental risk levels of Be, associated major ions, and heavy metals in groundwater nearby to beryl-bearing mineralization were also evaluated. Results showed that Be contents ranged from 1 to 374 ppm in beryl-bearing bedrocks, while in nearby groundwater, Be content has a range of 0.0001–0.00044 mg/L with an average of 0.00032 mg/L, which is within the permissible levels and below (0.004) the U.S. EPA maximum contaminant level (MCL). Most levels of heavy metals (e.g., Be, B, Ni, V, Fe, and Al) in the investigated groundwater of central and south Eastern Desert and south Sinai are within the permissible levels and below their corresponding U.S. EPA MCLs. This study also investigated the radiological risk of natural radionuclides distributed in beryl-bearing bedrocks in the study area using gamma spectrometry; Sodium Iodide [NaI(Tl)] scintillation detector. Among the estimated mean 238U, 232Th, and 226Ra activity concentrations of the studied beryl-bearing rocks, Homret Mukpid (79, 87.15, 60.26 Bq kg−1) and Homret Akarem (111.6, 51.17, 85.1 Bq kg−1) contain the highest values. This may be attributed to their highly fractionated granitic rocks that host uranium and thorium reservoir minerals such as zircon, allanite, and monazite. The estimated data of multi-radiological parameters such as absorbed gamma dose, outdoor and indoor annual effective dose, radium equivalent activity, internal and external indices, index of excess cancer, and effective dose to human organs reflecting no significant impacts from the emitted natural gamma radiation.

Health risk assessment of toxic metal(loids) (As, Cd, Pb, Cr, and Co) via consumption of medicinal herbs marketed in Malawi

This study aimed to assess the potential health risks associated with consuming three commonly consumed medicinal herbs in Malawi: Azadirachta indica, Mondia whitei, and Moringa oleifera. The concentrations of five metal(loids) (As, Cd, Pb, Cr, and Co) were determined using inductively coupled plasma mass spectrometry, while their safety was assessed by comparing the measured values with the legislated maximum contaminant levels (MCL)and reported metal(loids) concentrations in other countries. The results indicated significant variations of metal(loids) concentrations amongst the studied medicinal herbs, with Azadirachta indica containing the highest mean As (0.078 ± 0.010 mg kg−1) and Cd (0.049 ± 0.05 mg kg−1) concentrations and Mondia whitei and Moringa oleifera contained the highest mean Co (1.01 ± 0.05 mg kg−1) and Cr (1.42 ± 1.18 mg kg−1) concentrations, respectively. However, the mean concentrations of As, Cd, Pb, Cr, and Co fell below the MCL set by World Health Organization (WHO), Alimentarius Commissions, and European Commission. The estimated daily intake (EDI) for each metal(loid) was less than 1, indicating that the studied medicinal herbs do not pose serious health risks to non-regular consumers. The study also emphasizes the importance of assessing the potential risks associated with consuming medicinal herbs contaminated with heavy metals or metalloids, as it can seriously threaten human health.

Hydrolyzed polyacrylonitrile UF-membrane for surface and TAP water treatment: Influence on DBPs formation and removal

The integration of pre-treatment methods with low pressure-driven ultrafiltration (UF) has been found effective for reducing the formation of disinfection by-products (DBPs) in drinking water. In this study, a low dose peroxone (H2O2/O3) assisted alkaline hydrolyzed polyacrylonitrile (HPAN) UF-membrane system was explored, to determine its performance efficiency against two dissolved organic matter (DOM) sources and TAP water, specifically focusing the formation and removal of regulated DBPs. Increased hydrophilicity, enhanced incorporation of carboxyl groups, and decreased surface porosity were observed for the PAN membrane as a function of increased hydrolysis time. Filtration experiments involving humic acid (HA) and samples of real DOM sources displayed a high flux recovery (>90%) with the HPAN membrane. The initial flux for the optimized HPAN was found to be twice than that of the NF-3 membrane, irrespective of the DOM source. However, a relatively comparable removal efficiency was observed for both HPAN and NF-3 membranes in terms of organic matter and DBPs formation potential. Additionally, the H2O2/O3-HPAN system significantly reduced the aromatic and fluorescent content of the DOM by upto 70–80%, as represented by the DOC, UV254 and parallel factor analysis (PARAFAC) components. The fluorescence ratio C1/C2 showed a relatively greater reduction for soil-derived organic matter (SOM) as compared to the Olympic Lake (OL) water. Post-chlorination was found highly effective for the degradation of the humic-like DOM component (C1) than that of the fulvic and protein-like components. Moreover, the integration of H2O2/O3 with HPAN was able to remove 80% of the THMs and HAAs formation for both OL and SOM samples, together with a comparable reduction in DBP cytotoxicity. Interestingly, the HPAN membrane by reducing the TAP water DBPs upto 50%, fulfills the criteria of USEPA maximum contaminant level for drinking water.

Radon Assessment in Water Samples in a University Community in Osogbo Osun State

Introduction: Radon is a radioactive gas and one of the leading causes of cancer at high concentrations globally. Inhalation or ingestion of radon-contaminated water through drinking, cooking, or bathing has reportedly increased human health risks. Measuring radon levels in water helps assess the potential health risks associated with ingestion and inhalation. Aims: In this study, the assessment of radon activity in water in some selected places within a university community in Osogbo, Osun State, Nigeria, was carried out. Materials and Methods: Fifteen (15) water (groundwater and borehole water) samples were collected, and the radon concentration was measured using a DURRIDGE RAD7 H2O accessory radon detector. Results: The results of the radon activity ranged from 6.3 ± 1.7 Bq/L to 60.8 ± 5.6 Bq/L with a mean of 21.33 ± 2.95 Bq/L. Nine (9) out of the fifteen (15) water samples measured were observed to be higher than EPA’s maximum contaminant level of 11.1 Bq/L, while the other six (6) water samples were within the range. The annual effective dose values lie within 3 -10 mSv/yr., reported by the International Commission on Radiological Protection. Conclusion: Water within the university community in Oshogbo, Osun State, is recommended for regular radon monitoring due to the high radon concentration above the Nigerian Standard for Drinking Water Quality. To Keywords: radon, Osogbo, water, RAD7 H2O

Impact of lowering the US maximum contaminant level on arsenic exposure: Differences by race, region, and water arsenic in NHANES 2003–2014

Our objective was to evaluate regional and sociodemographic inequalities in water arsenic exposure reductions associated with the US Environmental Protection Agency's Final Arsenic Rule, which lowered the arsenic maximum contaminant level to 10 μg/L in public water systems. We analyzed 8544 participants from the 2003-14 National Health and Nutrition Examination Survey (NHANES) reliant on community water systems (CWSs). We estimated arsenic exposure from water by recalibrating urinary dimethylarsinate (rDMA) to remove smoking and dietary contributions. We evaluated mean differences and corresponding percent reductions of urinary rDMA comparing subsequent survey cycles to 2003-04 (baseline), stratified by region, race/ethnicity, educational attainment, and tertile of CWS arsenic assigned at the county level. The overall difference (percent reduction) in urine rDMA was 0.32 μg/L (9%) among participants with the highest tertile of CWS arsenic, comparing 2013-14 to 2003-04. Declines in urinary rDMA were largest in regions with the highest water arsenic: the South [0.57 μg/L (16%)] and West [0.46 μg/L, (14%)]. Declines in urinary rDMA levels were significant and largest among Mexican American [0.99 μg/L (26%)] and Non-Hispanic White [0.25 μg/L (10%)] participants. Reductions in rDMA following the Final Arsenic Rule were highest among participants with the highest CWS arsenic concentrations, supporting legislation can benefit those who need it the most, although additional efforts are still needed to address remaining inequalities in CWS arsenic exposure.