Extractability and mobility of mercury from agricultural soils surrounding industrial and mining contaminated areas

This study focussed on a comparison of the extractability of mercury in soils with two different contamination sources (a chlor-alkali plant and mining activities) and on the evaluation of the influence of specific soil properties on the behaviour of the contaminant. The method applied here did not target the identification of individual species, but instead provided information concerning the mobility of mercury species in soil. Mercury fractions were classified as mobile, semi-mobile and non-mobile. The fractionation study revealed that in all samples mercury was mainly present in the semi-mobile phase (between 63% and 97%). The highest mercury mobility (2.7 mg kg(-1)) was found in soils from the industrial area. Mining soils exhibited higher percentage of non-mobile mercury, up to 35%, due to their elevated sulfur content. Results of factor analysis indicate that the presence of mercury in the mobile phase could be related to manganese and aluminium soil contents. A positive relation between mercury in the semi-mobile fraction and the aluminium content was also observed. By contrary, organic matter and sulfur contents contributed to mercury retention in the soil matrix reducing the mobility of the metal. Despite known limitations of sequential extraction procedures, the methodology applied in this study for the fractionation of mercury in contaminated soil samples provided relevant information on mercury's relative mobility.

Mercury bioaccumulation in the spotted dogfish (Scyliorhinus canicula) from the Atlantic Ocean

The annual and life-cycle mercury bioaccumulation pattern in selected tissues of the economically relevant Elasmobranchii species Scyliorhinus canicula was studied, and the risks associated with its consumption evaluated. Preferential mercury bioaccumulation occurred in muscle tissue, and followed the order muscle>heart>liver>gills>pancreas. Total mercury in muscle tissue ranged from 0.13mgkg(-1) (wwt) in 1+year old males to 0.8mgkg(-1) (wwt) in 8+ year old mature females, with no significant differences found between genders, and no clear lifespan bioaccumulation pattern observed, except for mature females. Organic mercury in the muscle ranged from 0.05mgkg(-1) (wwt) to 0.52mgkg(-1) (wwt), corresponding to an average of 70% of total mercury content. In mature females, a significant correlation (R=0.99, P=0.01) was found between size and organic mercury fraction, suggesting reproduction as an important factor controlling organic mercury bioaccumulation in the spotted dogfish.

Mercury contamination in the vicinity of a chlor-alkali plant and potential risks to local population

A mercury-cell chlor-alkali plant operated in Estarreja (North-western Portugal) for 50 years causing widespread environmental contamination. Although production by this process ceased in 2002, mercury contamination from the plant remains significant. The main objective of this study was to investigate mercury impact on the nearby environment and potential risks to local population. To assess the level of contamination soil samples were collected from agricultural fields in the vicinity of the plant, extending the study by taking samples of the predominant vegetation suitable for animal and human consumption, water samples, and fish species from a nearby coastal lagoon, to gain a preliminary insight into the potential for contamination of the terrestrial and aquatic food web. To determine population exposure to mercury, hair samples were collected from local residents. Total mercury concentration in the 0-15 cm layer of soil was found to be highly variable, ranging between 0.010 and 91 mg kg(-1), although mercury contamination of soils was found to be restricted to a confined area. Lolium perenne roots contained between 0.0070 and 2.0 mg kg(-1), and there is evidence that root systems uptake mercury from the soil. Levels of mercury in the aerial parts of plants ranged between 0.018 and 0.98 mg kg(-1). It appears that plants with higher mercury concentration in soils and roots also display higher mercury concentration in leaves. Total mercury concentration in water samples ranged between 12 and 846 ng L(-1), all samples presenting concentrations below the maximum level allowable for drinking water defined in the Portuguese law (1.0 microg L(-1)). Mercury levels in fish samples were below the maximum limit defined in the Portuguese law (0.5 mg kg(-1)), ranging from 0.0040 to 0.24 mg kg(-1). Vegetables collected presented maximum mercury concentration of 0.17 mg kg(-1). In general, food is not contaminated and should not be responsible for major human exposure to the metal. Mercury determined in human hair samples (0.090-4.2 mg kg(-1); mean 1.5 mg kg(-1)) can be considered within normal limits, according to WHO guidelines suggesting that it is not affecting the local population. Despite being subject to decades of mercury emissions, nowadays this pollutant is only found in limited small areas and must not constitute a risk for human health, should these areas be restricted and monitored. Considering the present data, it appears that the population from Estarreja is currently not being affected by mercury levels that still remain in the environment.

Risk factors for Helicobacter pylori infection in children: is education a main determinant?

To investigate potential risk factors associated with Helicobacter pylori (Hp) infection, we performed a case-control study in 167 consecutively selected hospitalized children in Salvador, Brazil. Hp infection was identified by the presence of IgG against Hp in serum samples. Data were gathered using a structured questionnaire, 38.3% children were found to be seropositive and classified as cases, and 61.7% were seronegative controls. After multivariate analysis, independent variables associated with Hp infection included: the educational attainment of the child's provider > or = 11 years (OR 0.1, 95% CI 0.01-0.9), poor garbage disposal service (OR 2.2, 95% CI 1.0-4.9), thumb sucking (OR 4.6, 95% CI 1.1-19.8), brushing teeth more than once a day (OR 5.6, 95% CI 1.8-17.7), having a pet dog (OR 2.5, 95% CI 1.0-6.1), and a history of chronic urticaria (OR 4.0, 95% CI 1.5-10.8). The risk factors identified are consistent with some, but not all, previous studies supporting either oral-oral or faecal-oral transmission of Hp. Our data suggested that a higher educational attainment might play an important role in preventing Hp infection.

Assessing the in vitro toxicity of airborne (nano)particles to the human respiratory system: from basic to advanced models

Several studies have been conducted to address the potential adverse health risks attributed to exposure to nanoscale materials. While in vivo studies are fundamental for identifying the relationship between dose and occurrence of adverse effects, in vitro model systems provide important information regarding the mechanism(s) of action at the molecular level. With a special focus on exposure to inhaled (nano)particulate material toxicity assessment, this review provides an overview of the available human respiratory models and exposure systems for in vitro testing, advantages, limitations, and existing investigations using models of different complexity. A brief overview of the human respiratory system, pathway and fate of inhaled (nano)particles is also presented.

Unravelling the Potential Cytotoxic Effects of Metal Oxide Nanoparticles and Metal(Loid) Mixtures on A549 Human Cell Line

Humans are typically exposed to environmental contaminants' mixtures that result in different toxicity than exposure to the individual counterparts. Yet, the toxicology of chemical mixtures has been overlooked. This work aims at assessing and comparing viability and cell cycle of A549 cells after exposure to single and binary mixtures of: titanium dioxide nanoparticles (TiO2NP) 0.75-75 mg/L; cerium oxide nanoparticles (CeO2NP) 0.0.75-10 μg/L; arsenic (As) 0.75-2.5 mg/L; and mercury (Hg) 5-100 mg/L. Viability was assessed through water-soluble tetrazolium (WST-1) and thiazolyl blue tetrazolium bromide (MTT) (24 h exposure) and clonogenic (seven-day exposure) assays. Cell cycle alterations were explored by flow cytometry. Viability was affected in a dose- and time-dependent manner. Prolonged exposure caused inhibition of cell proliferation even at low concentrations. Cell-cycle progression was affected by TiO2NP 75 mg/L, and As 0.75 and 2.5 μg/L, increasing the cell proportion at G0/G1 phase. Combined exposure of TiO2NP or CeO2NP mitigated As adverse effects, increasing the cell surviving factor, but cell cycle alterations were still observed. Only CeO2NP co-exposure reduced Hg toxicity, translated in a decrease of cells in Sub-G1. Toxicity was diminished for both NPs co-exposure compared to its toxicity alone, but a marked toxicity for the highest concentrations was observed for longer exposures. These findings prove that joint toxicity of contaminants must not be disregarded.

Effects of Zinc Oxide Nanoparticle Exposure on Human Glial Cells and Zebrafish Embryos

Zinc oxide nanoparticles (ZnO NPs) are among the most widely used nanomaterials. They have multiple applications in cosmetics, textiles, paints, electronics and, recently, also in biomedicine. This extensive use of ZnO NPs notably increases the probability that both humans and wildlife are subjected to undesirable effects. Despite being among the most studied NPs from a toxicological point of view, much remains unknown about their ecotoxicological effects or how they may affect specific cell types, such as cells of the central nervous system. The main objective of this work was to investigate the effects of ZnO NPs on human glial cells and zebrafish embryo development and to explore the role of the released Zn2+ ions in these effects. The effects on cell viability on human A172 glial cells were assessed with an MTT assay and morphological analysis. The potential acute and developmental toxicity was assessed employing zebrafish (Danio rerio) embryos. To determine the role of Zn2+ ions in the in vitro and in vivo observed effects, we measured their release from ZnO NPs with flame atomic absorption spectrometry. Then, cells and zebrafish embryos were treated with a water-soluble salt (zinc sulfate) at concentrations that equal the number of Zn2+ ions released by the tested concentrations of ZnO NPs. Exposure to ZnO NPs induced morphological alterations and a significant decrease in cell viability depending on the concentration and duration of treatment, even after removing the overestimation due to NP interference. Although there were no signs of acute toxicity in zebrafish embryos, a decrease in hatching was detected after exposure to the highest ZnO NP concentrations tested. The ability of ZnO NPs to release Zn2+ ions into the medium in a concentration-dependent manner was confirmed. Zn2+ ions did not seem entirely responsible for the effects observed in the glial cells, but they were likely responsible for the decrease in zebrafish hatching rate. The results obtained in this work contribute to the knowledge of the toxicological potential of ZnO NPs.

In Vitro Hepatotoxic and Neurotoxic Effects of Titanium and Cerium Dioxide Nanoparticles, Arsenic and Mercury Co-Exposure

Considering the increasing emergence of new contaminants, such as nanomaterials, mixing with legacy contaminants, including metal(loid)s, it becomes imperative to understand the toxic profile resulting from these interactions. This work aimed at assessing and comparing the individual and combined hepatotoxic and neurotoxic potential of titanium dioxide nanoparticles (TiO₂NPs 0.75–75 mg/L), cerium oxide nanoparticles (CeO₂NPs 0.075–10 μg/L), arsenic (As 0.01–2.5 mg/L), and mercury (Hg 0.5–100 mg/L) on human hepatoma (HepG2) and neuroblastoma (SH-SY5Y) cells. Viability was assessed through WST-1 (24 h) and clonogenic (7 days) assays and it was affected in a dose-, time- and cell-dependent manner. Higher concentrations caused greater toxicity, while prolonged exposure caused inhibition of cell proliferation, even at low concentrations, for both cell lines. Cell cycle progression, explored by flow cytometry 24 h post-exposure, revealed that TiO₂NPs, As and Hg but not CeO₂NPs, changed the profiles of SH-SY5Y and HepG2 cells in a dose-dependent manner, and that the cell cycle was, overall, more affected by exposure to mixtures. Exposure to binary mixtures revealed either potentiation or antagonistic effects depending on the composition, cell type and time of exposure. These findings prove that joint toxicity of contaminants cannot be disregarded and must be further explored.

Salivary Leucocytes as In Vitro Model to Evaluate Nanoparticle-Induced DNA Damage

Metal oxide nanoparticles (NPs) have a wide variety of applications in many consumer products and biomedical practices. As a result, human exposure to these nanomaterials is highly frequent, becoming an issue of concern to public health. Recently, human salivary leucocytes have been proposed as an adequate non-invasive alternative to peripheral blood leucocytes to evaluate genotoxicity in vitro. The present study focused on proving the suitability of salivary leucocytes as a biomatrix in the comet assay for in vitro nanogenotoxicity studies, by testing some of the metal oxide NPs most frequently present in consumer products, namely, titanium dioxide (TiO2), zinc oxide (ZnO), and cerium dioxide (CeO2) NPs. Primary and oxidative DNA damage were evaluated by alkaline and hOGG1-modified comet assay, respectively. Any possible interference of the NPs with the methodological procedure or the hOGG1 activity was addressed before performing genotoxicity evaluation. Results obtained showed an increase of both primary and oxidative damage after NPs treatments. These data support the use of salivary leucocytes as a proper and sensitive biological sample for in vitro nanogenotoxicity studies, and contribute to increase the knowledge on the impact of metal oxide NPs on human health, reinforcing the need for a specific regulation of the nanomaterials use.

Major, minor, trace and rare earth elements in sediments of the Bijagós archipelago, Guinea-Bissau

Sixty sediment samples from four sites in the Bijagós archipelago were characterized for fine fraction, loss on ignition, major, minor and trace elemental composition (Al, Fe, Ca, Mg, Ti, P, Zr, Mn, Cr, Sr, Ba, B, V, Li, Zn, Ni, Pb, As, Co, U, Cu, Cs and Cd), and the elements of the La-Lu series. Element concentrations were largely explained by the Al content and the proportion of fine fraction content, with the exception of Ca and Sr. Sediments showed enhanced Ti, U, Cr, As and Cd concentrations with respect to estimated upper crust values, most likely mirroring a regional signature. Rare earth elements were in deficit relatively to the North American Shale Composite (NASC), mainly in coarser material. No pronounced Ce-anomaly was observed, while Eu-anomalies were positive in most analyzed sediments.

Pattern and pathways for mercury lifespan bioaccumulation in Carcinus maenas

Carcinus maenas is an important and exploited natural resource in temperate estuaries, being consumed by local populations and also used as fish bait. Through bioaccumulation and bioamplification processes occurring in polluted estuarine ecosystems, this species may directly or indirectly represent a major pathway for Human contamination. No information is available on the overall lifespan bioaccumulation pattern of mercury for this species, which would be an invaluable tool for assessing the risks associated with C. maenas harvest in contaminated areas. Taking that in mind, the main objectives of this work were to clarify the lifespan bioaccumulation pattern of mercury for this species. A consistent lifespan accumulation pattern was found for this species, both for total and organic mercury, and coherent differences were found between genders, suggesting different physiological responses to contamination. From our results two scenarios emerge: (a) for low mercury contamination areas where the diet is the major pathway for metal uptake, with higher levels in muscle and hepatopancreas (twice as high as in gills) and higher organic mercury fractions (as high as 80-90% in muscle), crabs bioaccumulate with age and (b) on high contaminated areas, environmental exposure is predominant, with higher levels found in gills (reaching 0.8 mg kg(-1)), lower organic fractions and no mercury increment with age. Detoxification strategies, dietary differences and species mobility may account for these two accumulation patterns.

Field transplantation of the bivalve Scrobicularia plana along a mercury gradient in Ria de Aveiro (Portugal): uptake and depuration kinetics

The bioaccumulation and depuration capabilities of mercury by the edible bivalve Scrobicularia plana was studied in a coastal lagoon (Ria de Aveiro, Portugal) through a transplantation experiment. Little information on this topic is available in the literature, especially concerning different tissues' responses to contaminant exposure, but the present study is one of the few works that can surpass this knowledge gap. Organisms from a reference area were transplanted to two different contaminated areas in the Ria de Aveiro. In both areas, the bivalves (i.e., entire organism, digestive gland and the rest of the organism) presented a similar saturation model of mercury accumulation, the digestive gland being the tissue that reached the highest concentrations after 25 days of exposure to the contaminant. During this short uptake period, the transplanted organisms reached 20-30% of the concentrations observed in resident contaminated organisms. After the exposure period, the organisms were transplanted to a clean area for more than 25 days of depuration. At the end of the transplantation period, organisms lost approximately 50% of their mercury body burden (60%: the entire organism and digestive gland; 35%: gills and 40%: the rest of the organism) and the ones from the least contaminated site almost reached the concentrations recorded in the reference area. So, the results suggest that S. plana is a promising biomonitoring species, since it accumulates the contaminant in a considerable extent quite rapidly and at the same time it has a low metal retention capacity (low biological half-life) when exposed to clean sediments.

Anesthesia for Stüve-Wiedemann syndrome: a rare adult patient case report

Stüve-Wiedemann syndrome (SWS) is a rare genetic disorder characterized by skeletal dysplasia and severe dysautonomia, evidencing a difficult airway approach and likely increased malignant hyperthermia susceptibility. Developmental dysmorphism classically worsens with age, therefore translating in a poor prognosis. In this article, we describe a case of a 27-year-old woman diagnosed with SWS proposed for abscess drainage under dissociative anesthesia. This patient has outlived the life expectancy described for SWS, acknowledging the importance of reporting this rare adult clinical case in what SWS anesthetic management is concerned.

Mobility versus retention of mercury in bare and salt marsh sediments of a recovering coastal lagoon (Ria de Aveiro, Portugal)

During decades, mercury (Hg) was discharged into the Aveiro Lagoon. Twenty-five years after the cessation of discharges, sediment cores were collected at two areas to assess the evolution of the mercury contamination status. Vertical Hg profiles differed considerably between bare and vegetated sediments. Bare sediments contained significantly less Hg (<8 mg kg^-1) than historical data of 1995 (up to 40 mg kg^-1), probably resulting from erosion. Salt marsh sediments were marked by a Hg sub-surface enrichment, reaching 44 mg kg^-1 in the site closer to the industrial discharge point. High Hg concentrations in 2007, 2011 and 2016 were found at similar sediment layers. These results emphasise the role of halophyte plants in the cycling and retention of Hg in sediments. The persistency of high Hg in the upper marsh layers highlights the complexity in the recovery of historically contaminated marshes and the vulnerability to modifications in hydrology associated with climate changes.

Editorial of Special Issue: The Toxicity of Nanomaterials and Legacy Contaminants: Risks to the Environment and Human Health

Nanotechnology and the incorporation of nanomaterials (NM) into everyday products help to solve problems in society and improve the quality of life, allowing for major advances in the technological, industrial, and medical fields [...].

Toxicity of zinc oxide nanoparticles: Cellular and behavioural effects

Due to their extensive use, the release of zinc oxide nanoparticles (ZnO NP) into the environment is increasing and may lead to unintended risk to both human health and ecosystems. Access of ZnO NP to the brain has been demonstrated, so their potential toxicity on the nervous system is a matter of particular concern. Although evaluation of ZnO NP toxicity has been reported in several previous studies, the specific effects on the nervous system are not completely understood and, particularly, effects on genetic material and on organism behaviour are poorly addressed. We evaluated the potential toxic effects of ZnO NP in vitro and in vivo, and the role of zinc ions (Zn2+) in these effects. In vitro, the ability of ZnO NP to be internalized by A172 glial cells was verified, and the cytotoxic and genotoxic effects of ZnO NP or the released Zn2+ ions were addressed by means of vital dye exclusion and comet assay, respectively. In vivo, behavioural alterations were evaluated in zebrafish embryos using a total locomotion assay. ZnO NP induced decreases in viability of A172 cells after 24 h of exposure and genetic damage after 3 and 24 h. The involvement of the Zn2+ ions released from the NP in genotoxicity was confirmed. ZnO NP exposure also resulted in decreased locomotor activity of zebrafish embryos, with a clear role of released Zn2+ ions in this effect. These findings support the toxic potential of ZnO NP showing, for the first time, genetic effects on glial cells and proving the intervention of Zn2+ ions.

The importance of smoking cessation during pregnancy and its association with perinatal outcomes

 

In utero exposure to tobacco smoke is associated with an increased risk of multiple adverse perinatal outcomes. Smoking cessation during pregnancy has been related to the improvement of these outcomes, but often relies on self-reporting, impairing an accurate assessment of smoking cessation impact on newborńs health. Building on data obtained in the frame of the NEOGENE project, this work aimed to estimate the association between smoking cessation among pregnant women, confirmed by maternal urinary cotinine concentrations, and perinatal outcomes. The study population included 595 pregnant women who sought prenatal care in a public hospital in Porto (Portugal), from April 2017 to July 2018. Data on tobacco consumption and cessation was obtained in a face-to-face interview, during the hospital stay. Perinatal outcomes, namely birth weight (BW), length (BL) and head circumference (HC) were retrieved from the hospital medical records. Maternal self-reported tobacco use was validated by urinary cotinine concentrations, using the solid-phase competitive ELISA technique. Maternal active smoking was associated with a significant decrease in BW, BL and HC of 157.66 g (p &lt; 0.001), 0.78 cm (p = 0.001) and 0.39 cm (p = 0.016). Notably, maternal smoking cessation led to a significant increase in BW of approximately 172 g (p = 0.006), when compared to mothers who have not ceased. Increases in BL and HC did not reach significance. This study upholds that tobacco consumption is still an important public health threat in Portugal and that smoking cessation during pregnancy reverses smoking-associated deficits in perinatal outcomes, emphasizing the crucial need for awareness campaigns to promote smoking cessation during pregnancy.

Acknowledgments: This work was supported by FCT and FAPESP (FAPESP/19914/2014). AIS, JM and CC also acknowledge FCT for individual funding (SFRH/BD/145101/2019, SFRH/BPD/115112/2016 and SFRH/BPD/96196/2013 grants, respectively).

Key messages

Maternal active smoking was significantly associated with lower birth weight, length and head circumference. Maternal smoking cessation reverses the smoking-associated deficits in birth weight.

Urinary cotinine assessment of maternal smoking and environmental tobacco smoke exposure status and its associations with perinatal outcomes: a cross-sectional birth study

Tobacco consumption and environmental tobacco smoke (ETS) exposure remains an important public health concern. Pregnant women require particular attention as active and passive smoking during pregnancy are associated with multiple adverse perinatal outcomes. This study aimed to biochemically validate self-reported smoking and ETS exposure status among pregnant women, to more precisely ascertain its association with adverse perinatal outcomes. Data refers to 595 pregnant women who sought prenatal care in a public hospital in Porto, Portugal. A standard questionnaire on smoking and ETS-related variables was completed. Urinary cotinine (UC) concentrations were assessed by solid-phase competitive ELISA, in maternal urine samples collected on the day of delivery. The results showed that the optimal UC cut-off value to distinguish smokers from non-smokers and within non-smokers those who were exposed to ETS from those non-exposed in the third trimester of pregnancy was 74.1 ng/mL (sensitivity and specificity of 96.7% and 98.0%, respectively) and 1.6 ng/mL (sensitivity of 66.2% and specificity of 75.7%, respectively). The agreement between maternal self-reported and UC-based smoking status was very good (κ=0.919, p<0.001), but much lower for ETS exposure (κ=0.386, p<0.001). Maternal active smoking in the third trimester of pregnancy was associated with a significant decrease in birth weight, length and head circumference of 157.66 g (95% CI: -245.81, -69.52; p<0.001), 0.78 cm (95% CI: -1.22, -0.34; p=0.001) and 0.39 cm (95% CI: -0.70, -0.07; p=0.016), respectively. Maternal ETS exposure in the third trimester of pregnancy was associated with a non-significant increase in birth weight of 38.37 g (95% CI: -28.91, 105.64; p=0.263). Furthermore, maternal smoking cessation was associated with the increase of approximately 172 g in birth weight (95% CI: 50.00, 293.19). As such, there is an urgent need for increased public health awareness campaigns to encourage smoking cessation during pregnancy, in order to improve perinatal outcomes.