Rice is a potential dietary source of not only arsenic but also other toxic elements like lead and chromium

Rice is a staple food and a good source of nutrition for half of the earth’s population including Middle Eastern countries. However, rice may accumulate hazardous levels of toxic elements. In KSA, rice is imported from many countries; some of which suffer from arsenic contamination in their groundwater and soil. Despite the large daily consumption of rice in KSA, no investigations on the contamination of rice sold there are published so far. Additionally, reports on the contamination of rice with other toxic elements are rare in the literature. To investigate this issue, a total of 84 rice samples were collected from local markets in Almadinah Almunawarah, KSA (n = 70) and Brisbane, Australia (n = 12) and analyzed for arsenic and other elements by ICP-MS. The mean concentrations (mg kg−1) for the KSA samples with concentrations >LOQ were 0.136 for As (range 0.026–0.464, n = 70); Cd: 0.017 (0.003–0.046, n = 64); Pb: 0.029 (0.003–0.218, n = 40); Ni: 0.064 (0.042–0.086, n = 5); Mg: 157 (51.8–777, n = 70); Mn: 4.28 (0.960–10.9, n = 70); Fe: 7.07 (1.9–55.1, n = 70); Zn: 6.19 (1.15–13.5, n = 70); Cu 1.28 (0.508–2.41, n = 70); Se 0.202 (0.007–0.574, n = 70); Cr: 0.057 (0.010–0.184, n = 19); and Co: 0.012 (0.001–0.116, n = 56). Several samples were found to contain at least one element in excess of the Chinese MCL (0.2 mg kg−1for Cd, Cr, Pb, and iAs each). A large variation in element concentration was observed for samples of different origins. In comparison, the American rice accumulated the highest arsenic concentration (mean 0.257 mg kg−1) followed by the Thai rice (mean 0.200 mg kg−1), the Pakistani rice (mean 0.147 mg kg−1), the Indian rice (mean 0.103 mg kg−1), and finally the Egyptian rice (mean 0.097 mg kg−1). Additionally, 3 individual samples from Surinam, Australia, and France contained arsenic concentrations (mg kg−1) of 0.290, 0.188, and 0.183. The findings of this investigation indicate that some of the rice varieties sold in KSA contain hazardous levels of arsenic and other toxic elements. For a better public health protection, concerned authorities are highly recommended to regularly monitor the concentrations of not only arsenic, but also other toxic elements (e.g. Cr, Cd, Pb) in rice grains.This research was funded by the Deanship of Scientific Research Taibah University (Project No. 432-107). The National Research Centre for Environmental Toxicology (EnTox) is a joint venture of the University of Queensland and Queensland Health.Scopu

3-Aminopyridine Salicylidene: A Sensitive and Selective Chemosensor for the Detection of Cu(II), Al(III), and Fe(III) with Application to Real Samples

Interest in developing selective and sensitive metal sensors for environmental, biological, and industrial applications is mounting. The goal of this work was to develop a sensitive and selective sensor for certain metal ions in solution. The goal was achieved via (i) preparing the sensor ((E)-2-((pyridine-3-ylimino)methyl)phenol) (3APS) using microwave radiation in a short time and high yield and (ii) performing spectrophotometric titrations for 3APS with several metal ions. 3APS, a Schiff base, was prepared in 5 min and in a high yield (95%) using microwave-assisted synthesis. The compound was characterized by FTIR, XRD, NMR, and elemental analysis. Spectrophotometric titration of 3APS was performed with Al(III), Ba(II), Cd(II), Co(II), Cu(II), Fe(III), Mn(II), Ni(II), and Zn(II). 3APS showed good abilities to detect Al(III) and Fe(III) ions fluorescently and Cu(II) ion colorimetrically. The L/M stoichiometric ratio was 2:1 for Cu(II) and 1:1 for Al(III) and Fe(III). Low detection limits (μg/L) of 324, 20, and 45 were achieved for Cu(II), Al(III), and Fe(III), respectively. The detection of aluminum was also demonstrated in antiperspirant deodorants, test strips, and applications in secret writing. 3APS showed high fluorescent selectivity for Al(III) and Fe(III) and colorimetric selectivity towards Cu(II) with detection limits lower than corresponding safe drinking water guidelines.This work was made possible by NPRP grant # 7-495-1-094 from the Qatar National Research Fund (a member of Qatar Foundation). The findings achieved herein are solely the responsibility of the authors. The authors also acknowledge the support of Qatar University through grant # QUCG-CAS-20/21-1

Density functional theory study on the catalytic dehydrogenation of methane on MoO3 (010) surface

Methane conversion offers hydrocarbon building blocks of high market value, which are easier to transport than natural gas. Under non-oxidative conditions, the process can also produce clean hydrogen fuel. In this study, we explored the catalytic dehydrogenation of methane on molybdenum oxide (MoO3) surface. Periodic density functional theory calculations were performed to study the adsorption of CH4 on two different supercells of the MoO3 (010) surface. It was found that CH4 adsorption was more favorable on a smooth surface constructed of Mo and O network, rather than a surface made with dangling O atoms as thought before. A reaction mechanism for hydrogen formation was then proposed. The first energy barrier for the H-abstraction step was calculated to be 66.4 kJ/mol, which is lower than previously reported values obtained for simple MoxOy clusters. The reactions were discussed using the two-state reactivity approach, where different electronic states can play a role in the H-abstraction step. The mechanism also showed the formation of methyl radicals and ethylene, in addition to molecular hydrogen.This research is funded by Qatar University’s grant number QUCG-CAS-21221

New tetradentate Schiff base Cu(II) complexes: synthesis, physicochemical, chromotropism, fluorescence, thermal, and selective catalytic oxidation

Three neutral Cu(II)/ƞ4-NNNO Schiff base complexes (1-3) were prepared from the (E)-4-nitro-2-(((2-(piperazin-1-yl)ethyl)imino)methyl)phenol, tetradentate Schiff base (SB) ligand, and the corresponding copper(II) salts. The new SB and its complexes were fully characterized by CHN-EA, standard spectroscopic, thermal, and fluorescence analyses. The formation of the complexes was monitored by EDX, FT-IR, and UV-Vis. The chromotropism studies of the complexes reflected remarkable findings, in which bathochromic solvato- and thermochromism shifts were detected. The turn-off-on halochromism phenomena were observed in the acidic and basic medium. On the other hand, the fluorescence of the free SB ligand was turned off via complexation to the Cu(II) center. In the presence of H2O2 as green oxidant and under mild oxidation catalytic condition, the three complexes successfully catalyzed the formation benzaldehyde from benzyl alcohol

A global health problem caused by arsenic from natural sources

Arsenic is a carcinogen to both humans and animals. Arsenicals have been associated with cancers of the skin, lung, and bladder. Clinical manifestations of chronic arsenic poisoning include non-cancer end point of hyper- and hypo-pigmentation, keratosis, hypertension, cardiovascular diseases and diabetes. Epidemiological evidence indicates that arsenic concentration exceeding 50 mug l(-1) in the drinking water is not public health protective. The current WHO recommended guideline value for arsenic in drinking water is 10 mug l(-1), whereas many developing countries are still having a value of 50 mug 1(-1). It has been estimated that tens of millions of people are. at risk exposing to excessive levels of arsenic from both contaminated water and arsenic-bearing coal from natural sources. The global health implication and possible intervention strategies were also discussed in this review article. (C) 2003 Elsevier Ltd. All rights reserved

Nitrate contamination in wells water: A case study of Al-Rehan Village in Syrian Arab Republic

Most villages in the Syrian Arab Republic with populations less than 5000 inhabitantslack adequate wastewater disposal systems. These villages depend on individual household cesspits to discharge domestic wastewater. This has resulted in contamination of groundwater resources where groundwater is utilized for dringing purposes without treatment. Farmers in these villages use chemical and organic (manure) fertilizers in large quantities which has also led to further contamination of groundwater, in particular,with nitrates. To assess the groundwater nitrate contamination in some villages in Syria, a village called Al-Rihan has been selected for this study. This village has a population of 8000 and is located in the Douma area of the Damascus countryside. Nitrate concentrations in 15 water wells from this village have been monitored for five (5) months (March-July, 2002). The measured nitrate concentrations (as NO3-) are as follows: range 40-122 mg/L, mean 55 mg/L and standard deviation 15 mg/L (N 75). More than 95% of the studied wells were found to contain a nitrate concentration greater than the permissible level. The major sources of nitrate contamination in the monitored water wells have been identified as: individual household cesspits, use of treated municipal wastewater for irrigation and unregulated use of fertilizers

The accumulation and toxicity of methylated arsenicals in endothelial cells: important roles of thiol compounds

Excess intake of arsenic is known to cause vascular diseases as well as skin lesions and cancer in humans. Recent reports suggest that trivalent methylated arsenicals, which are intermediate metabolites in the methylation process of inorganic arsenic, are responsible for the toxicity and carcinogenicity of environmental arsenic. We investigated acute toxicity and accumulation of monomethylarsonic acid (MMAV), dimethylarsinic acid (DMAV), trimethylarsine oxide (TMAO), and monomethylarsonous acid diglutathione (MMAIII (GS)2) in rat heart microvessel endothelial (RHMVE) cells. MMAV (LC50 = 36.6 mM) and DMAV (LC50 = 2.54 mM) were less toxic than inorganic arsenicals (cf. LC50 values for inorganic arsenite (iAsIII), and inorganic arsenate (iAsV) was reported to be 36 and 220 μM, respectively, in RHMVE cells. TMAO was essentially not toxic. However, MMAIII (GS)2 was highly toxic (LC50 = 4.1 μM). The order of cellular arsenic accumulation of those four organic arsenic compounds was MMAIII (GS)2 >> MMAV > DMAV > TMAO. MMAIII (GS)2 was efficiently taken up by the cells and cellular arsenic content increased with the concentration of MMAIII (GS)2 in culture medium. N-acetyl-Image -cysteine (NAC) reduced cellular arsenic content in DMAV-exposed cells and also decreased the cytotoxicity of DMAV, whereas it changed neither cellular arsenic content nor the viability in MMAV-exposed cells. mRNA levels of heme oxygenase-1 (HO-1) were decreased by NAC in DMAV-exposed, but MMAV-exposed cells. Buthionine sulfoximine (BSO), a cellular glutathione (GSH) depleting agent, enhanced the cytotoxicity of MMAV. However, BSO reduced, rather than enhanced, the cytotoxicity of DMAV. These results suggest that intracellular GSH modulated the toxic effects of arsenic in opposite ways for MMAV and DMAV. Even though intracellular GSH decreased the cytotoxicity of MMAV, extracellularly added GSH enhanced the cytotoxicity of MMAV. The use of high-performance liquid chromatography (HPLC)-inductively coupled plasma mass spectrometric analyses suggested that a small amount of MMAV was converted to MMAIII (GS)2 in the presence of GSH. These results suggest that MMAIII (GS)2 is highly toxic compared to other arsenic compounds because of faster accumulation of this species by cells, in addition to having the toxic nature of methylated trivalent organic arsenics