Mercury toxicity in children

Event-Based Atmospheric Precipitation Uncovers Significant Even and Odd Hg Isotope Anomalies Associated with the Circumpolar Vortex

The determination of the mass-independent fractionation of even Hg isotopes (even-MIF, Δ²⁰⁰Hg) in atmospheric samples adds another intriguing feature to the Hg isotope system. Despite our lack of sufficient experimental verification and the momentary absence of a valid mechanism to explain its occurrence, even-MIF could be instrumental in understanding the cycle and deposition of atmospheric Hg. In contrast to slightly positive Δ²⁰⁰Hg values (<0.30‰) frequently observed in most atmospheric samples, large Δ²⁰⁰Hg values (up to 1.24‰) determined in precipitation from Peterborough (Ontario, Canada) stand out and could provide valuable information for the origin of the even-MIF mystery. We now report a systematic analysis of high-resolution rainfall and snowfall samples collected in winter during cold weather at Peterborough, Canada. Dissolved and particulate Hg both displayed large variations of odd-MIF (from -0.93‰ to 2.02‰ for Δ¹⁹⁹Hg), which may result from long-range transportation, as the negative odd-MIF in particulate Hg is likely a result of long-distance transport of arctic atmospheric Hg(II). Dissolved Hg revealed significant even-MIF values (from 0.25‰ to 1.19‰ for Δ²⁰⁰Hg) and a negative relationship between Δ²⁰⁰Hg and Δ²⁰⁴Hg, which provide further evidence for the previously proposed conceptual model of Δ²⁰⁰Hg. Disconnected odd-MIF and even-MIF trends were detected in sequentially collected precipitation samples, which further suggests different sources or mechanisms for Δ¹⁹⁹Hg and Δ²⁰⁰Hg. Particularly, the high Δ²⁰⁰Hg values highlight the transport of stratospheric Hg through a polar vortex to the sampling region, stimulating further systematic investigation. The new Δ²⁰⁰Hg data for particulate Hg add to existing information on atmospheric Hg(II) worldwide, suggesting a global distribution of Hg characterized by even-MIF in the atmosphere, and further constrain the model of atmospheric Hg deposition.

A Molten-Salt Pyrolysis Synthesis Strategy toward Sulfur-Functionalized Carbon for Elemental Mercury Removal from Coal-Combustion Flue Gas

The emission of mercury from coal combustion has caused consequential hazards to the ecosystem. The key challenge to abating the mercury emission is to explore highly efficient adsorbents. Herein, sulfur-functionalized carbon (S-C) was synthesized by using a molten-salt pyrolysis strategy and employed for the removal of elemental mercury from coal-combustion flue gas. An ideal pore structure, which was favorable for the internal diffusion of the Hg0 molecule in carbon, was obtained by using a SiO2 hard template and adjusting the HF etching time. The as-prepared S-C with an HF etching time of 10 h possessed a saturation Hg0 adsorption capacity of 89.90 mg·g−1, far exceeding that of the commercial sulfur-loaded activated carbons (S/C). The S-C can be applied at a wide temperature range of 25–125 °C, far exceeding that of commercial S/C. The influence of flue gas components, such as SO2, NO, and H2O, on the Hg0 adsorption performance of S-C was insignificant, indicating a good applicability in real-world applications. The mechanism of the Hg0 removal by S-C was proposed, i.e., the reduced components, including sulfur thiophene, sulfoxide, and C-S, displayed a high affinity toward Hg0, which could guarantee the stable immobilization of Hg0 as HgS in the adsorbent. Thus, the molten-salt pyrolysis strategy has a broad prospect in the application of one-pot carbonization and functionalization sulfur-containing organic precursors as efficient adsorbents for Hg0.

Removal of flue gas mercury by porous carbons derived from one-pot carbonization and activation of wood sawdust in a molten salt medium

Porous carbons derived from one-pot carbonization and activation of wood sawdust in a molten salt (LiCl-KCl) medium were employed for Hg⁰ removal. The carbons derived from molten salt carbonization (MSC) displayed much superior Hg⁰ removal performance comparing with the carbons derived from N₂ pyrolysis method (NC). The best molar ratio of LiCl-KCl was 59:41, the optimal molten salt temperature was 700 °C, and the best mass ratio of wood sawdust to molten salt was 1:10. The MSC displayed good applicability at 50-125 °C. The saturation Hg⁰ adsorption capacity of MSC was about 7828.39 μg·g^-1, far exceeding those for carbonaceous adsorbents reported in literatures. A Hg⁰ removal mechanism over MSC was proposed, i.e., the hierarchical porous structure accelerated mass transfer of Hg⁰, and the CO groups served as electron acceptors from Hg⁰ atoms to form organic matter bonded mercury (Hg-OM). The molten salt could be easily separated from the mixture of MSC for recycling multiple times. Thus, molten salt carbonization method appears to be promising in one-pot carbonization and activation of biomass as efficient adsorbents for gaseous Hg⁰.

Detection of hazardous mercury ion using [5]helicene-based fluorescence probe with "TurnON" sensing response for practical applications

A new fluorescence probe based on [5]helicene derivative (MT) was designed and synthesized. The chemical structure of the probe was fully characterized by NMR, mass spectrometry and X-ray crystallography. MT which is the combination of thioamide[5]helicene with Schiff base-thiophene moiety, exhibited a high selectivity to detect Hg²⁺ through irreversible desulfurization reaction with "TurnON" fluorescence response and large Stokes shift of 110 nm in aqueous methanol solution. The detection limit of MT was 1.2 ppb (6.0 × 10^-3 µM), which is lower than the limit of Hg²⁺ level in drinking water, as specified by WHO (6.0 ppb) and U.S. EPA (2.0 ppb). The Hg²⁺ detection range of the probe was 0.07-1.6 µM with good linearity. Under UV irradiation, MT possessed the capability to detect Hg²⁺ in diverse context of real samples, including drinking and sea waters, vegetable tissue and brain tumor cell. In addition, MT could be used as a paper test strip for monitoring and screening of Hg²⁺ contamination in environment.

Surface-Engineered Sponge Decorated with Copper Selenide for Highly Efficient Gas-Phase Mercury Immobilization

The paramount challenge in design and synthesis of materials for vapor-phase elemental mercury (Hg⁰) immobilization is to achieve a balance between performance and economy for practical applications. Herein, a newly designed electroless plating coupled with an in situ selenization method was developed to construct a copper selenide (Cu₂Se)-functionalized commercial polyurethane sponge (PUS) as an efficient Hg⁰ trap. Intrinsic features such as easy availability of the raw material, facile preparation, and excellent performance guarantee the Cu₂Se/PUS to be applicable in industrial uses. The Cu₂Se/PUS exhibits a maximum adsorption capacity (Q_m,Cu2Se/PUS) of 25.90 mg·g^-1, while this value is 758.80 mg·g^-1 when normalized to the Cu₂Se coating amount. This value of Q_m,Cu2Se is equal to 79.7% of its corresponding theoretical value (Q_t,Cu2Se), far exceeding the availability of Cu₂Se anchored on other supports. Meanwhile, the Cu₂Se/PUS exhibited a quick response for Hg⁰, with an extremely high uptake rate of 1275.84 μg·g^-1·min^-1. Even under harsh conditions, the Cu₂Se/PUS still immobilizes Hg⁰ effectively, which is crucial for real-world applications. This work not only provides a promising trap for permanent Hg⁰ sequestration from industrial sources but also illustrates a versatile platform for the economic fabrication and practical application of advanced functional sponges in diverse environmental remediation.

Photocatalytic removal of elemental mercury via Ce-doped TiO2 catalyst coupling with a novel optical fiber monolith reactor

Reduction of mercury emission from coal combustion is a serious task for public health and environmental societies. Herein, Ce-doped TiO₂ (Ce/TiO₂) catalyst coupling with a novel optical fiber monolith reactor was applied to efficiently remove elemental mercury (Hg⁰) from coal-fired flue gas. Under the optimal operation condition (i.e., 1.5 mW/cm² UV light, 90 °C), above 95% of Hg⁰ removal efficiency was attained over the optical fiber monolith reactor coating with 3.40 g/m² Ce/TiO₂ catalyst. The effects of flue gas compositions on Hg⁰ removal performance were clarified systematically. Gaseous O₂ replenished the surface oxygen, hence maintaining the production of free radicals and promoting the removal of Hg⁰. SO₂, HCl, and NO inhibited Hg⁰ removal in the absence of O₂ due to the competitive adsorption and consumption of free radicals. However, SO₂ and HCl significantly enhanced Hg⁰ removal with the participation of O₂, while NO exhibited obviously inhibitory effect even with the assistance of O₂. H₂O also decreased the Hg⁰ oxidation capacity owing to the competitive adsorption and reduction of HgO. The optical fiber monolith reactor exhibited much superior Hg⁰ removal capacity than the powder reactor. Utilization of Ce/TiO₂ catalyst coupling with an optical fiber monolith reactor provides a cost-effective method for removing Hg⁰ from coal-fired flue gas.

In Situ Decoration of Selenide on Copper Foam for the Efficient Immobilization of Gaseous Elemental Mercury

Mercury emission from industrial activities is a great threat to public health and ecosystems. Developing new strategies and materials to remove mercury still remains a serious task. Herein, selenide-decorated copper foam prepared by a heating-stirring method (Cu-hs) was used as a monolithic mercury adsorption material. The Cu-hs exhibited much better adsorption of elemental mercury (Hg⁰) compared with the selenide-decorated cordierite honeycomb prepared by the same method (Cordierite-hs). Nearly 100% Hg⁰ adsorption efficiency was obtained under a high gaseous hourly space velocity of 6.0 × 10⁴. Excellent Hg⁰ adsorption capacity was obtained in a wide range of reaction temperatures from 40 to 120 °C, suggesting the good adaptability of Cu-hs in different operating conditions. The Cu-hs exhibited high selectivity for Hg⁰ against H₂O and SO₂, which is advantageous for real applications in industrial flue gas. The Hg⁰ adsorption capacity of Cu-hs reached 3743 g/m³, about 14 times higher than the 243 g/m³ of Cordierite-hs. The excellent Hg⁰ adsorption performance of Cu-hs was attributed to the high affinity of the selenium in Cu₂Se for mercury, the homogeneous distribution of Cu₂Se, and the superior fluid characteristics of the Cu foam substrate. The adsorption performance of the spent Cu-hs could be effectively recovered by HCl solution leaching and subsequent reselenization. The utilization of recyclable Cu-hs provides a cost-effective and environmentally friendly method for removing mercury from industrial flue gas.

Quantification of Trace Mercury in Water: Solving the Problem of Adsorption, Sample Preservation, and Cross-Contamination

Adsorption, sample preservation, and cross-contamination are the major impediments to the accurate and sensitive analysis of low-level mercury samples. Common measures to deal with this issue are to use Teflon, quartz, or borosilicate glass bottles for sampling, standard solution and sample preservation with oxidative chemicals, to prepare standard solutions daily and to use dedicated glassware. This paper demonstrates that these measures are neither efficient nor effective. Two common laboratory sample containers (borosilicate volumetric glass flasks and polypropylene tubes) are investigated for the preparation and preservation of water samples and standard solutions of 0.2-1 µg L-1 with 2% HNO3. Mercury adsorption rates of 6-22% are observed within 30 min and after 48 days, the adsorption is greater than 98%. In stark contrast, no adsorption is found during a testing period of 560 days when the solutions are subject to potassium permanganate-persulfate digestion. New glass flasks and polypropylene bottles are free of mercury contamination but reused flasks are a major source of mercury cross-contamination. To minimize adsorption and cross-contamination, standard solutions are treated by potassium permanganate-persulfate or BrCl digestion, and each individual sample and standard solution should be stored and prepared in single-use polypropylene bottle, without transference.

Enhancement of CeO2 modified commercial SCR catalyst for synergistic mercury removal from coal combustion flue gas

CeO₂ modification improves the synergistic Hg⁰ removal performance of commercial SCR catalyst.

Current progress on understanding the impact of mercury on human health

Mercury pollution and its impacts on human health is of global concern. The authors of this paper were members of the Plenary Panel on Human Health in the 12th International Conference on Mercury as a Global Pollutant held in Korea in June 2015. The Panel was asked by the conference organizers to address two questions: what is the current understanding of the impacts of mercury exposure on human health and what information is needed to evaluate the effectiveness of the Minamata Convention in lowering exposure and preventing adverse effects. The authors conducted a critical review of the literature published since January 2012 and discussed the current state-of-knowledge in the following areas: environmental exposure and/or risk assessment; kinetics and biomonitoring; effects on children development; effects on adult general populations; effects on artisanal and small-scale gold miners (ASGM); effects on dental workers; risk of ethylmercury in thimerosal-containing vaccines; interactions with nutrients; genetic determinants and; risk communication and management. Knowledge gaps in each area were identified and recommendations for future research were made. The Panel concluded that more knowledge synthesis efforts are needed to translate the research results into management tools for health professionals and policy makers.

Exposure to mercury and aluminum in early life: developmental vulnerability as a modifying factor in neurologic and immunologic effects

Currently, ethylmercury (EtHg) and adjuvant-Al are the dominating interventional exposures encountered by fetuses, newborns, and infants due to immunization with Thimerosal-containing vaccines (TCVs). Despite their long use as active agents of medicines and fungicides, the safety levels of these substances have never been determined, either for animals or for adult humans—much less for fetuses, newborns, infants, and children. I reviewed the literature for papers reporting on outcomes associated with (a) multiple exposures and metabolism of EtHg and Al during early life; (b) physiological and metabolic characteristics of newborns, neonates, and infants relevant to xenobiotic exposure and effects; (c) neurobehavioral, immunological, and inflammatory reactions to Thimerosal and Al-adjuvants resulting from TCV exposure in infancy. Immunological and neurobehavioral effects of Thimerosal-EtHg and Al-adjuvants are not extraordinary; rather, these effects are easily detected in high and low income countries, with co-exposure to methylmercury (MeHg) or other neurotoxicants. Rigorous and replicable studies (in different animal species) have shown evidence of EtHg and Al toxicities. More research attention has been given to EtHg and findings have showed a solid link with neurotoxic effects in humans; however, the potential synergic effect of both toxic agents has not been properly studied. Therefore, early life exposure to both EtHg and Al deserves due consideration.