Mean Concentration Research Articles

Assessment of Activity Concentrations and Soil-to-Plant Transfer Factors of Natural Radioactivity in Rice Plant Components grown in Kano State, Nigeria

Transfer Factor (TF) depicts the percentage or fraction of natural radioactivity in the soil that is absorbed by different parts of a plant which are eventually transferred, directly or indirectly, to man during ingestion. Activity concentrations of primordial radionuclides were determined in farm soil and rice plant components (root, stem, leaf and seed) in six Local Government Areas (Bagwai, Bunkure, Dambatta, Garko, Kura and Wudil) renowned for production of rice in Kano State, Nigeria, using gamma-ray spectrometry method with sodium iodide scintillation detector. The mean activity concentrations of 40K, 238U and 232Th were: 509.51, 27.75, and 12.26 Bq.kg-1 correspondently in soil; 227.40, 14.24, and 5.19 Bq.kg-1 correspondingly in seed; 935.53, 32.73, and 7.29 Bq.kg-1 accordingly in leaf; 803.65, 16.72, and 6.76 Bq.kg-1 respectively in stem; and, 408.91, 30.03, and 10.31 Bq.kg-1 correspondingly in root. The mean concentrations of 40K reported in soil were greater than the world average of 400 Bq.kg-1, while those of 238U and 232Th were less than the world mean values of 35 Bq.kg-1 and 30 Bq.kg-1 respectively. The estimated mean of TFs of 40K, 238U and 232Th were: 0.52, 0.61, and 0.43 respectively in the seed; 1.95, 1.45, and 0.69 respectively in leaf; 1.72, 0.75, and 0.64 correspondingly in the stem; and, 0.85, 1.27, and 0.76 accordingly in the root. Except for a few plant samples where BDL were recorded for 238U and 232Th, all values of TFs were greater than the recommended values of 4.9 x 10-3 and 2.1 x10-4 given for 238U and 232Th...

What caused large ozone variabilities in three megacity clusters in eastern China during 2015–2020?

Abstract. Due to a robust emission control policy, significant reductions in major air pollutants, such as PM2.5, SO2, NO2, and CO, were observed in China between 2015 and 2020. On the other hand, during the same period, there was a notable increase in ozone (O3) concentrations, making it a prominent air pollutant in eastern China. The annual mean concentration of maximum daily 8 h average (MDA8) O3 exhibited alarming linear increases of 2.4, 1.1, and 2.0 ppb yr−1 (ppb is for parts per billion) in three megacity clusters: Beijing–Tianjin–Hebei (BTH), the Yangtze River Delta (YRD), and the Pearl River Delta (PRD), respectively. Meanwhile, there was a significant 3-fold increase in the number of O3-exceeding days, defined as MDA8 O3 > 75 ppb. Our analysis indicated that the upward increases in the annual mean concentration of MDA8 were primarily driven by the rise in consecutive O3-exceeding days. There were expansions of high O3 in urban centers to rural areas accompanied by a saturation effect so that MDA8 O3 concentrations at the high-O3 stations in 2015 remained nearly constant at 100 ppb. Last, we found a close association between O3 episodes with 4 or more consecutive O3-exceeding days and the position and strength of tropical cyclones (TCs) in the northwest Pacific and the West Pacific subtropical high (WPSH). The TC and WPSH contributed to meteorological conditions characterized by clear skies, subsiding air motion, high vertical stability in the lower troposphere, increased solar radiation, and a positive temperature anomaly at the surface. These favorable meteorological conditions greatly facilitated the formation of O3. Thus, we propose that the worsening O3 increases observed in the BTH, YRD, and PRD regions from 2015 to 2020 can be mostly attributed to enhanced photochemical O3 production resulting from an increased occurrence of meteorological conditions with high solar radiation and positive temperature anomalies under the influence of the WPSH and TCs.

Understanding phosphorus fractions and influential factors on urban road deposited sediments

Phosphorus (P) is a primary pollutant that builds-up on urban road surfaces. Understanding the fraction and load characteristics of P, as well as their relationship with urban factors, is helpful for assessing the ecological risk of urban receiving water bodies. This study presents the characteristics of build-up loads of P fractions in road-deposited sediments (RDS) in Guangzhou, China, analyzes their correlation with three urban factors (road, traffic, and land-use area), and then estimates the exceedance probability of P in stormwater runoff over the past 10 years. The results showed that detrital apatite phosphorus (De-P) performed the highest build-up load on urban road surfaces, followed by apatite phosphorus (Ca-P), iron-bound phosphorus (Fe-P), exchangeable phosphorus (Ex-P), aluminum-bound phosphorus (Al-P), organophosphorus (POP), dissolved inorganic phosphorus (DIP), occluded phosphorus (Oc-P), and dissolved organic phosphorus (DOP). Depression depth, road materials, and land-use fractions affected the P fractions. The P in the RDS may have originated from three distinct sources: road background, domestic waste, and untreated wastewater discharge. In the most recent 10 years, the event mean concentrations of total P in the RDS have had a 30 % probability of exceeding 0.4 mg L−1, which indicates a serious threat of P to receiving water bodies. The outcomes of this study are expected to provide valuable guidance for elucidating the principal categories of urban non-point source P pollution and enhancing the ecological health of urban water environments.

Investigating the Seroconversion Patterns of Specific Antibodies Against Various Antigens of SARS-CoV-2 in Hospitalized COVID-19 Patients and Vaccinated Individuals

Background: Inducing a humoral response to SARS-CoV-2 may partially control virus dissemination. However, there is a lack of consistency in the reported kinetics of IgM and IgG responses to SARS-CoV-2. Additionally, the humoral response to SARS-CoV-2 may differ from that elicited by vaccination. Therefore, we were motivated to evaluate the kinetics of antibodies against SARS-CoV-2 in both infected and vaccinated individuals. Objectives: This study aimed to investigate the seroconversion patterns of specific antibodies against various antigens of SARS-CoV-2 in hospitalized COVID-19 patients and vaccinated individuals, focusing specifically on comparing the humoral responses elicited by infection and vaccination. Methods: Serial blood and swab samples were collected from 134 COVID-19 patients at six time points following admission. Real-time RT-PCR specific for SARS-CoV-2, as well as anti-SARS-CoV-2 IgM and IgG, were tested using ELISA. Additionally, 141 serum samples were obtained from vaccinated individuals. Anti-SARS-CoV-2 spike and RBD IgGs, along with neutralizing antibodies (NAs), were assessed using ELISA in both the vaccinated group and 96 COVID-19 patients. Results: Anti-SARS-CoV-2 IgM was found positive in 23.3% of patients at 0 - 7 days after symptom onset, with seropositivity increasing to 71.7% at 15 - 21 days. Subsequently, IgM positivity gradually decreased to 62.7% at > 28 days post-symptom onset. Meanwhile, anti-SARS-CoV-2 IgG was positive in 28.3% of patients at 0 -7 days, rising to 83.7% at 22 - 28 days after symptom onset, and remained constant thereafter. Anti-spike and RBD IgGs, along with NAs, were detected in 89.7%, 87.4%, and 87.9% of vaccinated individuals, respectively, and in 37.5%, 32.3%, and 32.3% of COVID-19 patients, respectively. There was a significant correlation between anti-spike IgG and anti-RBD IgG levels and NAs in both COVID-19-infected and vaccinated individuals. The mean concentrations of anti-spike and RBD IgGs were higher in vaccinated individuals with a history of COVID-19 infection compared to those without prior infection. Conclusions: The antibody profile for IgM and IgG against SARS-CoV-2 suggests that as time passes after the onset of disease symptoms, the seropositivity in COVID-19 patients increases. Furthermore, antibodies against SARS-CoV-2 are produced more efficiently through COVID-19 vaccination than natural infection.

Urban green space area mitigates the accumulation of heavy metals in urban soils

Despite that the heavy metals in urban soils pose a threat to public health, the critical factors that influence their concentrations in urban soils are not well understood. In this study, we conducted a survey of surface soil samples from urban green spaces in Shanghai, to analyze the concentrations of the key heavy metals. The results showed that Zn was the most abundant metal with an average concentration of 122.99 mg kg−1, followed by Pb (32.72 mg kg−1) and Cd (0.23 mg kg−1). All concentrations were found to be below the risk screening values defined by the National Environmental Quality Standards for soils of development land in China (GB36600-2018), indicating no current risk in Shanghai. However, there was a clear accumulation of heavy metals, as the mean concentrations were significantly higher than the background values. Furthermore, we explored the relationships between key heavy metals with population density, GDP and green space area. Both Spearman correlation and Random Forest analysis indicated that per capita green space area (pGSA) and population density were the most crucial factors influencing the status of heavy metals in urban soils, unlike edaphic factors e.g. SOM content in farmland soils. Specifically, there was a significantly positive linear correlation between heavy metal concentrations and population density, with correlation coefficients ranging from 0.3 to 0.4. However, the correlation with pGSA was found to be non-linear. The nonlinear regression analysis revealed threshold values between heavy metals concentrations and pGSA (e.g Zn 22.22 m2, Pb 24.92 m2, and Cd 25.92 m2), with a sharp reduction in heavy metal concentrations below the threshold and a slow reduction above the threshold. It suggests that an increase in per capita green space area can mitigate the accumulation of heavy metals caused by growing population density, but the effect is limited after the threshold. Our findings not only provide insights into the distribution patterns of heavy metals in the urban soils at the local scale, but also contribute to the urban greening at the global scale and offer guidance for city planning in the face of increasing population densities over the coming decades.

Molecular characterization of human bocavirus in municipal wastewaters using amplicon target sequencing

Human bocavirus (HBoV) is an emerging health concern worldwide, associated with range of clinical manifestations, including gastroenteritis and respiratory infections. Therefore, it is crucial to comprehend and minimize their prevalence in different systems. In this study, we conducted regular sampling throughout the year in two different sizes and work processes of wastewater treatment plants (WWTPs) in Tianjin, China. Our objective was to investigate the occurrence, prevalence, and endurance of HBoV in wastewater, while also evaluating the efficacy of amplicon target sequencing in directly detecting HBoV in wastewater. At two WWTPs, HBoV2 (45.51 %—45.67 %) and HBoV3 (38.30 %—40.25 %) were the most common genotypes identified, and the mean concentration range of HBoV was 2.54—7.40 log10 equivalent copies/l as determined by multiplex real-time quantitative PCR assay. A positive rate of HBoV was found in 96.6 % (29/30) samples of A-WWTP, and 96.6 % (26/27) samples of B-WWTP. The phylogenetic analysis indicated that the nucleotide similarity between the HBoV DNA sequences to the reference HBoV sequences published globally ranged from 90.14 %—100 %. A significant variation in the read abundance of HBoV2 and HBoV3 in two wastewater treatment plants (p < 0.05) was detected, specifically in the Winter and Summer seasons. The findings revealed a strong correlation between the genotypes detected in wastewater and the clinical data across various regions in China. In addition, it is worth mentioning that HBoV4 was exclusively detected in wastewater and not found in the clinical samples from patients. This study highlights the high prevalence of human bocavirus in municipal wastewater. This finding illustrates that amplicon target sequencing can amplify a wide variety of viruses, enabling the identification of newly discovered viruses.

Evaluating the ecological consequences of heavy metal contamination in soil induced by spent engine oil and palm oil mill effluents for sustainable development

&lt;p&gt;This study assessed the ecological consequences of heavy metal contamination in soil induced by spent engine oil (SEO) and palm oil mill effluents (POME) in Ebonyi State, Nigeria. Concentrations of zinc, nickel, mercury, manganese, lead, iron, copper, chromium, and cadmium were analyzed across contaminated and uncontaminated sites. The research, conducted at Ebonyi State University’s Presco Campus, employed rigorous sampling and analytical methods. Results revealed that soil contaminated with spent engine oil effluent exhibited elevated mean concentrations of zinc, nickel, manganese, lead, iron, copper, chromium, and cadmium compared to the palm oil mill effluent and control sites. Conversely, mercury concentrations were higher in soil contaminated with palm oil mill effluent. Comparative analyses highlighted unique dynamics, such as lead concentrations being highest at the control site, challenging general trends observed for other metals. Importantly, none of the mean concentrations exceeded the WHO acceptable limits at the time of the study, indicating compliance with internationally recognized safety thresholds. The findings underscore the need for tailored environmental management strategies, considering specific contaminants associated with each effluent type. Continuous monitoring is crucial to ensure sustained adherence to safety standards and prevent potential future exceedances. This study contributes a valuable understanding of the nuanced ecological impact of industrial effluents on soil quality in Nigeria, emphasizing the importance of sustainable practices for environmental protection.&lt;/p&gt;

Streamwise dispersion of soluble matter in solvent flowing through a tube

For the dispersion of soluble matter in solvent flowing through a tube as investigated originally by G.I. Taylor, a streamwise dispersion theory is developed from a Lagrangian perspective for the whole process with multi-scale effects. By means of a convected coordinate system to decouple convection from diffusion, a diffusion-type governing equation is presented to reflect superposable diffusion processes with a multi-scale time-dependent anisotropic diffusivity tensor. A short-time benchmark, complementing the existing Taylor–Aris solution, is obtained to reveal novel statistical and physical features of mean concentration for an initial phase with isotropic molecular diffusion. For long times, effective streamwise diffusion prevails asymptotically corresponding to the overall enhanced diffusion in Taylor's classical theory. By inverse integral expansions of local concentration moments, a general streamwise dispersion model is devised to match the short- and long-time asymptotic solutions. Analytical solutions are provided for most typical cases of point and area sources in a Poiseuille tube flow, predicting persistent long tails and skewed platforms. The theoretical findings are substantiated through Monte Carlo simulations, from the initial release to the Taylor dispersion regime. Asymmetries of concentration distribution in a circular tube are certified as originated from (a) initial non-uniformity, (b) unidirectional flow convection, and (c) non-penetration boundary effect. Peculiar peaks in the concentration cloud, enhanced streamwise dispersivity and asymmetric collective phenomena of concentration distributions are illustrated heuristically and characterised to depict the non-equilibrium dispersion. The streamwise perspective could advance our understanding of macro-transport processes of both passive solutes and active suspensions.

Characterizing suspended particle dispersion in wetland flows: Impact of settling velocity and vegetation factor

Predicting the dispersion process of suspended particles with settling velocity in wetland flows holds significant implications for various ecological and environmental applications. This study analytically investigates the dispersion process of fine settling particles in wetland flows due to an instantaneous release source through the asymptotic expansion method. The effect of high-order terms is incorporated. The impact of vegetation factor and settling velocity on characteristic coefficients (including mass retained in the flow, advection velocity, longitudinal dispersion coefficient, skewness, and kurtosis), vertical mean, and two-dimensional concentration distribution are analyzed. Analytical solution is validated by numerical result through random displacement method. Results demonstrate that the vegetation factor does not influence the vertical mass distribution, and a larger settling velocity results in a higher concentration of mass in the bed wall layer. The longitudinal dispersion coefficient does not exhibit a monotonic relationship with the settling velocity. The position of mass centroid of the vertical mean concentration is biased more to the upstream with the larger settling velocity. At larger times, the vertical mean concentration approximates a normal distribution, with skewness and kurtosis nearing zero. Under the influence of settling velocity, the bed wall layer exhibits a high concentration zone in the two-dimensional concentration distribution. These results can help the understanding of sediment dynamics, nutrient cycling, pollutant transport associated with the wetland flows.

Vitamin D Deficiency in Advanced Laryngeal Cancer and its Association with Pharyngocutaneous Fistula Following Total Laryngectomy.

Nutritional factors in developing some malignancies have been investigated recently. In this study, we evaluated the role of vitamin D in advanced laryngeal cancer and its association with the development of pharyngocutaneous fistula (PCF) following total laryngectomy. A cross-sectional, case-control study was conducted. Fifty-five patients with advanced laryngeal cancer referred for total laryngectomy were included. We also considered 55 healthy individuals after matching age and sex as a control group. Serum levels of 25(OH)D3 were measured using a commercially available enzyme-linked immunosorbent assay (ELISA) kit. The association of serum 25(OH)D3 with PCF following total laryngectomy was also determined. Vitamin D was significantly lower in patients with advanced laryngeal cancer than in the control group (p < 0.001). Moreover, our results showed that a mean serum concentration of 25(OH)D3 in patients with PCF was significantly lower than in patients without PCF (p < 0.001). Vitamin D deficiency is highly prevalent in advanced laryngeal cancer, most pronounced in those who develop a PFC following total laryngectomy.

Lead exposure from honey: meta-analysis and risk assessment for the Arab region

The Codex Alimentarius Commission has adopted a maximum level for lead in honey (0.1 mg/kg). Despite representing a population of more than half a billion, exposure and risk assessments for lead specific to the Arab region are lacking. The aim of this work was to collect analytical data for lead in honey available in Arab countries and to assess the risk caused by exposure to lead from these samples for local consumers. A regional mean lead concentration in honey, obtained through a meta-analysis of 57 studies, was used in deterministic risk assessments for adults (nephrotoxicity and cardiovascular effects) and young children (developmental neurotoxicity). A regional pooled mean concentration of 0.12 mg/kg [95%CI: 0.07–0.21] (0.13 mg/kg, if non-detects are considered at their highest possible value) was obtained. Margins of exposure of 363 [71–17182] and 865 [168–40909] were calculated for adults, and of 48 [9–2273] for children, indicating potential concern for the latter population subset. These values were produced using GEMS consumption data, and considering the same intake for both children and adults, potentially overestimating the risk for children. Nevertheless, food competent authorities should consider measures to reduce lead concentration in honey available for sale in the region to prevent trade constraints and to better protect vulnerable populations.

Abstract WP255: Association Between Asymptomatic Intracranial Large Artery Stenosis and Neurofilament Light Chain: The Northern Manhattan Study

Introduction: The Neurofilament light chain (NfL) is a neuronal cytoplasmic protein and a reliable biomarker for assessing axonal damage in neurological diseases and traumatic brain injury. Asymptomatic intracranial large artery stenosis (ILAS) has been associated with higher risk of stroke and dementia. Although widely studied in the last few years, the role of NfL concentrations in ILAS is not well understood. Methods: We leveraged data from stroke-free participants in the population-based cohort Northern Manhattan Study (NOMAS) for a pilot study. Arterial stenosis was measured on magnetic resonance angiography in 11 intracranial large arteries and graded as 0 = no stenosis, 1 ≤ 50%, 2 = 50-69%, 3 ≥ 70% stenosis and 4 = flow gap. An asymptomatic Intracranial Large Artery Stenosis (ILAS) score was then developed to reflect the global stenotic burden, with a range of 0 to 44. We also dichotomized the ILAS score into any stenosis &gt; 50% versus none to reflect a more clinically relevant definition of ILAS. NfL concentrations were measured in plasma using Quanterix Simoa™ platform. We conducted generalized linear models adjusting for demographic and vascular risk factors and Wald Chi-Square test to analyze the association between NfL and ILAS score. Results: We included 79 stroke-free NOMAS participants (66% women, 77% Hispanic/Latino, and 75% with hypertension). The mean concentration of NFL was 0.19±0.10 pg/mL with a mean intra-assay coefficient of variation equal to 8.2%. In a model adjusted for age, sex, race/ethnicity, hypertension, diabetes, dyslipidemia and smoking, a higher ILAS score was associated with increased levels of NfL (B=0.01 ± 0.004, p=0.007). In an adjusted model, any stenosis &gt;50% was also associated with increased levels of NfL (B=0.11 ± 0.03, p&lt;0.001). Conclusions: The increased levels of plasma NfL associated with asymptomatic ILAS suggest neuronal injury that may implicate development of neurodegeneration. Confirming these results in a larger sample and longitudinal evaluation of NfL may advance the understanding of the mechanisms by which ILAS may increase the risk of dementia.

Transient dispersion of a reactive solute in an oscillatory Couette flow through an anisotropic porous medium

This research discusses the significance of reactive solute dispersion relevant to ecological, biological, and geological contexts. It examines solute movement under oscillatory Couette flow through anisotropic porous media between parallel plates under the effect of heterogeneous boundary reactions. The flow is driven by the combined effect of upper plate oscillation in its plane and time-dependent pressure gradient. The lower plate is assumed rough, which introduces slip velocity. A semi-analytical approach, with the method of moments and finite difference scheme, is utilized to explore the transient dispersion in steady and oscillatory flows with or without a non-zero mean. Using the Hermite polynomial, the mean concentration for purely oscillatory and combined flow is obtained, highlighting notable variations based on flow factors. The results suggest that increment in anisotropic angle ϕ reduces dispersion and enhances mean concentration for permeability ratio K &amp;lt; 1, but this reverses for K &amp;gt; 1. Three dispersion phases emerge: diffusive, anomalous, and Taylor's regimes. Gaussian cloud distribution occurs at small and large times, with intermediate stages displaying anomalous dispersion and asymmetric longitudinal distribution. Effects of boundary absorption stabilize over time. The research focuses on the practical significance of different permeabilities of porous media, emphasizing applications of anisotropic porous media in fields such as chemical engineering and industrial processes.

Abstract WP275: Longitudinal Biomarker Analysis in Patients With Ischemic Stroke: Exploratory Targeted and Omics Assessments From a Phase 2a Clinical Trial

Introduction: Elezanumab (EZB), a monoclonal antibody specific to repulsive guidance molecule A (RGMa), is under investigation to treat acute ischemic stroke. Biomarker evidence in ischemic stroke and for the RGMa pathway is limited. Methods: This blinded, in-study analysis from a 52-week phase 2a, multicenter, randomized (1:1; EZB:placebo) clinical trial (NCT04309474) included patients aged 30-90 years with an acute ischemic stroke (onset ≤ 24 hours before baseline), and a NIHSS score of 7-21. Blinded analyses did not distinguish between treatment arms. Healthy adult controls were procured outside this trial. Blood samples were taken post-stroke across 52 weeks, or 1 time (baseline) for healthy adults. Plasma concentrations of neurodegenerative markers neurofilament light chain protein (NfL) and glial fibrillary acidic protein (GFAP) were measured (validated Simoa Human Neurology 4-Plex A assay; Quanterix). Protein, mRNA, and miRNA were assessed with omics approaches. Results: This preliminary analysis included 34 patients with stroke (mean [SD] age 67.1 [12.3] years, 58.8% male) and 31 healthy adults (61.8 [8.0] years, 71.0% male). The mean (SD) baseline NIHSS total score was 10.9 (4.3). NfL and GFAP concentrations were elevated on day 1 in patients with stroke vs healthy adults (healthy adults are included for reference only). Mean concentrations of NfL were 48.7 pg/mL vs 13.9 pg/mL, respectively; mean concentrations of GFAP were 746.0 pg/mL vs 137.2 pg/mL, respectively. In patients with stroke, agnostic to treatment, peak NfL and GFAP elevations occurred at day 28 and days 2-4, respectively; NfL and GFAP concentrations were lower at week 52 than day 1. Conclusions: Preliminary blinded analysis of plasma markers of neurodegeneration confirm increased NfL and GFAP levels during acute stroke, which diminish over time with different temporal patterns. Final unblinded results will provide a robust natural time course of specific biomarkers of neurodegeneration including GAP43. Forthcoming analyses evaluate broad panels of proteins, mRNA, and miRNA markers. Identifying relevant post stroke biomarkers with directed and exploratory omics may allow development of validated assays to assess efficacy and support decision making in clinical trials.

Age-dependent acquisition of IgG antibodies to Shigella serotypes-a retrospective analysis of seroprevalence in Kenyan children with implications for infant vaccination.

Shigellosis mainly affects children under 5 years of age living in low- and middle-income countries, who are the target population for vaccination. There are, however, limited data available to define the appropriate timing for vaccine administration in this age group. Information on antibody responses following natural infection, proxy for exposure, could help guide vaccination strategies. We undertook a retrospective analysis of antibodies to five of the most prevalent Shigella serotypes among children aged <5 years in Kenya. Serum samples from a cross-sectional serosurvey in three Kenyan sites (Nairobi, Siaya, and Kilifi) were analyzed by standardized ELISA to measure IgG against Shigella sonnei and Shigella flexneri 1b, 2a, 3a, and 6. We identified factors associated with seropositivity to each Shigella serotype, including seropositivity to other Shigella serotypes. A total of 474 samples, one for each participant, were analyzed: Nairobi (n = 169), Siaya (n = 185), and Kilifi (n = 120). The median age of the participants was 13.4 months (IQR 7.0-35.6), and the male:female ratio was 1:1. Geometric mean concentrations (GMCs) for each serotype increased with age, mostly in the second year of life. The overall seroprevalence of IgG antibodies increased with age except for S. flexneri 6 which was high across all age subgroups. In the second year of life, there was a statistically significant increase of antibody GMCs against all five serotypes (p = 0.01-0.0001) and a significant increase of seroprevalence for S. flexneri 2a (p = 0.006), S. flexneri 3a (p = 0.006), and S. sonnei (p = 0.05) compared with the second part of the first year of life. Among all possible pairwise comparisons of antibody seropositivity, there was a significant association between S. flexneri 1b and 2a (OR = 6.75, 95% CI 3-14, p < 0.001) and between S. flexneri 1b and 3a (OR = 23.85, 95% CI 11-54, p < 0.001). Children living in low- and middle-income settings such as Kenya are exposed to Shigella infection starting from the first year of life and acquire serotype-specific antibodies against multiple serotypes. The data from this study suggest that Shigella vaccination should be targeted to infants, ideally at 6 or at least 9 months of age, to ensure children are protected in the second year of life when exposure significantly increases.

Characterisation of paediatric brain tumours by their MRS metabolite profiles.

1H-magnetic resonance spectroscopy (MRS) has the potential to improve the noninvasive diagnostic accuracy for paediatric brain tumours. However, studies analysing large, comprehensive, multicentre datasets are lacking, hindering translation to widespread clinical practice. Single-voxel MRS (point-resolved single-voxel spectroscopy sequence, 1.5 T: echo time [TE] 23-37 ms/135-144 ms, repetition time [TR] 1500 ms; 3 T: TE 37-41 ms/135-144 ms, TR 2000 ms) was performed from 2003 to 2012 during routine magnetic resonance imaging for a suspected brain tumour on 340 children from five hospitals with 464 spectra being available for analysis and 281 meeting quality control. Mean spectra were generated for 13 tumour types. Mann-Whitney U-tests and Kruskal-Wallis tests were used to compare mean metabolite concentrations. Receiver operator characteristic curves were used to determine the potential for individual metabolites to discriminate between specific tumour types. Principal component analysis followed by linear discriminant analysis was used to construct a classifier to discriminate the three main central nervous system tumour types in paediatrics. Mean concentrations of metabolites were shown to differ significantly between tumour types. Large variability existed across each tumour type, but individual metabolites were able to aid discrimination between some tumour types of importance. Complete metabolite profiles were found to be strongly characteristic of tumour type and, when combined with the machine learning methods, demonstrated a diagnostic accuracy of 93% for distinguishing between the three main tumour groups (medulloblastoma, pilocytic astrocytoma and ependymoma). The accuracy of this approach was similar even when data of marginal quality were included, greatly reducing the proportion of MRS excluded for poor quality. Children's brain tumours are strongly characterised by MRS metabolite profiles readily acquired during routine clinical practice, and this information can be used to support noninvasive diagnosis. This study provides both key evidence and an important resource for the future use of MRS in the diagnosis of children's brain tumours.

Feasibility of increasing calcium content of drinking tap water following quality regulations to improve calcium intake at population level

Background Calcium intake is below recommendations in several parts of the world. Improving calcium intake has benefits not only for bone health but also helps to prevent pregnancy hypertension disorders. Calcium concentration of tap water is usually low The aim of the present study was to determine the maximum amount of calcium that can be added to tap water while complying with drinking water local regulations. Methods Tap water samples were collected from the Province of Buenos Aires (Argentina). Physicochemical properties and saturation index were measured. Different incremental concentrations of calcium chloride were added to the experimental aliquots. Results Baseline water had a mean calcium concentration of 22.00 ± 2.54 mg/L, water hardness of 89.9 ± 6.4 mg/L CaCO3, and a saturation index of -1.50 ± 0.11. After the addition of 0.4554 ± 0.0071 g of salt, water hard-ness reached 355.0 ± 7.1 mg/L CaCO3, a calcium concentration of 140.50 ± 2.12 mg/L, and a saturation index -0.53 ± 0.02. Conclusions This study shows that at laboratory level it is feasible to increase calcium concentration of drinking water by adding calcium chloride while complying with national standards. Calcium concentration of drinking tap water could be evaluated and minimum calcium concentration of tap water regulated so as to improve calcium intake in populations with low calcium intake.

Determination of concentration of selected heavy metals in the organs of Guinea pigs reared at the University of Port Harcourt, Rivers State, Nigeria

Vegetation along major traffic roads are predisposed to heavy metals contamination due to wear and tear of vehicular components and emissions from vehicles. The concentration of ten heavy metals (Fe, Mn, Zn, Pb, Cu, Ni, Cr, Co Ag and Cd) in the leaves of four test plants (Panicum maximum Jacq.,Eleusine indica L., Xanthosoma mafafa Schott. and Amaranthus spinosus L.) growing along four busy roads (Aba road, Ikwerre road, East/West road and NTA road) in parts of Obio/Akpor Local Government Area and a control ( in Ozuguru in Ikwerre Ngwo) in Etche Local Government Area, both in Rivers State, Nigeria were investigated in the study area. Along each road, four sampling points were set up at 1 km apart. The test plants were collected randomly and were pooled together to form composite sample. The collected test plants at each sample location were put in different sterile cellophane bags, labelled and served as soilage to the experimental animals. Eighteen guinea pigs were used for this investigation. Three guinea pigs were picked out of the eighteen guinea pigs using randomized block design for a preliminary test. The remaining fifteen guinea pigs were fed with the test plants from the experimental and control sites for six weeks. The concentration of the ten heavy metals were determined using Atomic Absorption Spectrophotometry (ASS). The results revealed that Aba road had the highest mean concentration value of heavy metals in Cu, Zn, Co, Cr and Cd with values (28.75±1.34), (32.46±0.9), (5.14±0.11), (4.79±0.21) and (3.17±0.12) respectively. The highest mean concentration value for Mn and Pb were observed in East/West road with values (7.57±1.48) and (5.39±1.53) respectively, while the highest mean concentration value for Fe was observed in Ikwerre road (192.84±2.64). NTA road had the least values for all heavy metals tested while Ni and Ag were not detected in all livers and kidneys of the experimental animals. The results from this findings show the health implication of roadside grazing of ruminants.

Concentration and Ecological Risk Assessments of Potentially Toxic Elements in Soils around Lapite Dump Site, Akinyele Local Government Area, Ibadan, Nigeria

The contamination and ecological risk posed by Potentially Toxic Elements (PTEs) on soils around Lapite dumpsite and its environs were assessed using different analytical techniques after complete digestion of the soil using mixed acids. Results showed that the mean concentration of chromium (Cr), cadmium (Cd), and lead (Pb) (153.2mg/kg, 13.83mg/kg, 137.2mg/kg and respectively) have higher concentrations than their crustal abundance (CA). The enrichment factor analysis revealed that most of the soils collected have been enriched with Pb showing the most enrichment at the upper and middle slopes while Cd is the most enriched at the downslope. The contamination factor showed that Cr, Pb and Cd are also the elements showing significant contamination with Cr and Pb moderately contaminating soil (1.54 and 1.62 respectively) and Cd showing very high contamination in the soil (17.3). The ecological risk indices revealed that only Cd has high risk of polluting the soils (519) of the study area while the whole area is considered to be at a high risk of various degrees of pollution (534). Considering the health implications of these concerned elements (Cr, Pb and especially Cd) to the body, the habitants of the study area are advised to move away from these dumpsite and also relocate their farmlands to more environmental friendly sites.

Determination of aflatoxin M1 and ochratoxin A in breast milk in rural centers of Yazd, Iran: Exposure assessment and risk characterization.

Breast milk (BM) is considered as the best source of nutrition which could have prevention effects on various diseases in the first years of a child. Along with nutritive compounds, presence of contaminants such as mycotoxins in BM could be transmitted into neonate. The aim of this study was to determine the occurrence, levels, and factors associated with the presence of aflatoxin M1 (AFM1) and ocratoxin a (OTA) in BM samples of nursing mothers in rural centers of Yazd, Iran. The presence and average AFM1 and OTA concentration in 72 BM samples was measured by competitive ELISA. The demographic and diet parameters of nursing mothers were collected by a questionnaire and were analyzed using SPSS 18 software. AFM1 and OTA were detected in 63 (87.5%) and 47 (65.2%) samples with the mean concentration levels of 19.46 ± 13.26ng/L (ranges from 5.1 to 53.9) and 200 ± 160ng/L (ranges from 100 to 2460), respectively. Of these, 32 samples (50.7%) for AFM1 and 23 samples (48.9%) for OTA had values exceeding the limit set by the European Union regulation for infant foods (25ng/L for AFM1 and 500ng/L for OTA). It was also found that the risk of AFM1 and OTA occurrence in BM increased significantly with the consumption of beans, bread, cereals, fruit juice and crackers, and cream, respectively. This study showed that the estimated daily intake for AFM1 and OTA by 1month of age infants was 2.7 and 28.5ng/kg bw/day, respectively, while, as the age of the infant increased, the values were lower and close to 0.9 and 9.9ng/kg bw/day for AFM1 and OTA in 12months of age infants, respectively. The high occurrence and noticeable levels of AFM1 and OTA detected in this study indicated that some infants receive undesirable exposures to AFM1 and OTA with breast milk. Therefore, it is recommended that mothers are advised to avoid certain foods during pregnancy and breastfeeding that are likely sources of mycotoxins.