Chromium is absorbed from oral, inhalation, or dermal exposure and distributes to nearly all tissues, with the highest concentrations found in kidney and liver. Bone is also a major storage site and may contribute to long-term retention. Hexavalent chromium's similarity to sulfate and chromate allow it to be transported into cells via sulfate transport mechanisms. Inside the cell, hexavalent chromium is reduced first to pentavalent chromium, then to trivalent chromium by many substances including ascorbate, glutathione, and nicotinamide adenine dinucleotide. Chromium is almost entirely excreted with the urine. (A12, L16)
IDENTIFICATION AND USE: Strontium chromate is a yellow powder. It is used as a corrosion inhibitor in pigments; in electrochemical processes to control sulfate concn of solns; as a colorant in polyvinyl chloride resins; and in pyrotechnics. HUMAN EXPOSURE AND TOXICITY: If ingested, violent gastroenteritis, severe circulatory collapse and toxic nephritis may ensue. None of the results showed statistically significant differences that would suggest an excess risk for malignant neoplasms, particularly lung cancer, among workers engaged in the manufacture of chromate pigment in Japan. ANIMAL STUDIES: In groups of 22-34 rats that received intramuscular implantations of various chromium cmpd, the following incidences of implantation-site tumors (type unspecified) were observed after 27 months: strontium chromate, 15/33 (20 alive at one yr); none of 35 control rats given implants of sheep fat alone developed local tumors (30 alive at 1 year). In experiments lasting 27 mo rats gave the following number of tumors at site of intrapleural injection of strontium chromate, 17/28 (nine alive at one yr); none of 34 control rats showed tumors. In other experiment, 15 male, bred, 12-week-old rats were used. A pellet of strontium chromate were inserted into the bronchus of the rats. The rats were sacrificed 9 months after the pellet was inserted. Of the 15 rats, 1 rat had a lesion of squamous cell carcinoma, 7 rats had carcinoma in situ or dysplasia, 8 rats had squamous metaplasia, and 5 rats had goblet cell hyperplasia. Twenty-one chromium containing materials were examined for carcinogenic activity in a two year study using an intrabronchial pellet implantation system whereby pellets loaded with test material were surgically implanted into the lower left bronchus of rats. Two of these were groups receiving different samples of strontium chromate which gave 43/99 and 62/99 tumors. Strontium chromate (0-0.8 ug/plate) was mutagenic in Salmonella typhimurium TA100 in the presence or absence of a metabolic activation system and at 0.1 ug/mL sister chromatid exchanges were observed in cultured Chinese hamster fibroblasts.
Hexavalent chromium's carcinogenic effects are caused by its metabolites, pentavalent and trivalent chromium. The DNA damage may be caused by hydroxyl radicals produced during reoxidation of pentavalent chromium by hydrogen peroxide molecules present in the cell. Trivalent chromium may also form complexes with peptides, proteins, and DNA, resulting in DNA-protein crosslinks, DNA strand breaks, DNA-DNA interstrand crosslinks, chromium-DNA adducts, chromosomal aberrations and alterations in cellular signaling pathways. It has been shown to induce carcinogenesis by overstimulating cellular regulatory pathways and increasing peroxide levels by activating certain mitogen-activated protein kinases. It can also cause transcriptional repression by cross-linking histone deacetylase 1-DNA methyltransferase 1 complexes to CYP1A1 promoter chromatin, inhibiting histone modification. Chromium may increase its own toxicity by modifying metal regulatory transcription factor 1, causing the inhibition of zinc-induced metallothionein transcription. (A12, L16, A34, A35, A36)
WEIGHT OF EVIDENCE CHARACTERIZATION: Under the current guidelines (1986), Cr(VI) is classified as Group A - known human carcinogen by the inhalation route of exposure. Carcinogenicity by the oral route of exposure cannot be determined and is classified as Group D. Under the proposed guidelines (1996), Cr(VI) would be characterized as a known human carcinogen by the inhalation route of exposure on the following basis. Hexavalent chromium is known to be carcinogenic in humans by the inhalation route of exposure. Results of occupational epidemiological studies of chromium-exposed workers are consistent across investigators and study populations. Dose-response relationships have been established for chromium exposure and lung cancer. Chromium-exposed workers are exposed to both Cr(III) and Cr(VI) compounds. Because only Cr(VI) has been found to be carcinogenic in animal studies, however, it was concluded that only Cr(VI) should be classified as a human carcinogen. Animal data are consistent with the human carcinogenicity data on hexavalent chromium. Hexavalent chromium compounds are carcinogenic in animal bioassays, producing the following tumor types: intramuscular injection site tumors in rats and mice, intrapleural implant site tumors for various Cr(VI) compounds in rats, intrabronchial implantation site tumors for various Cr(VI) compounds in rats and subcutaneous injection site sarcomas in rats. In vitro data are suggestive of a potential mode of action for hexavalent chromium carcinogenesis. Hexavalent chromium carcinogenesis may result from the formation of mutagenic oxidatitive DNA lesions following intracellular reduction to the trivalent form. Cr(VI) readily passes through cell membranes and is rapidly reduced intracellularly to generate reactive Cr(V) and Cr(IV) intermediates and reactive oxygen species. A number of potentially mutagenic DNA lesions are formed during the reduction of Cr(VI). Hexavalent chromium is mutagenic in bacterial assays, yeasts and V79 cells, and Cr(VI) compounds decrease the fidelity of DNA synthesis in vitro and produce unscheduled DNA synthesis as a consequence of DNA damage. Chromate has been shown to transform both primary cells and cell lines. HUMAN CARCINOGENICITY DATA: Occupational exposure to chromium compounds has been studied in the chromate production, chromeplating and chrome pigment, ferrochromium production, gold mining, leather tanning and chrome alloy production industries. Workers in the chromate industry are exposed to both trivalent and hexavalent compounds of chromium. Epidemiological studies of chromate production plants in Japan, Great Britain, West Germany, and the United States have revealed a correlation between occupational exposure to chromium and lung cancer, but the specific form of chromium responsible for the induction of cancer was not identified ... Studies of chrome pigment workers have consistently demonstrated an association between occupational chromium exposure (primarily Cr(VI)) and lung cancer. Several studies of the chromeplating industry have demonstrated a positive relationship between cancer and exposure to chromium compounds. ANIMAL CARCINOGENICITY DATA: Animal data are consistent with the findings of human epidemiological studies of hexavalent chromium ... /Chromium (VI)/
Evaluation: There is sufficient evidence in humans for the carcinogenicity of chromium(VI) compounds. Chromium(VI) compounds cause cancer of the lung. Also positive associations have been observed between exposure to Chromium(IV) compounds and cancer of the nose and nasal sinuses. There is sufficient evidence in experimental animals for the carcinogenicity of chromium(VI) compounds. Chromium(VI) compounds are carcinogenic to humans (Group 1). /Chromium(VI) compounds/
Chromium–doped MoS2 “inorganic fullerene” nanoparticles prepared by topotactic reaction from oxosalt precursor
作者：Camella Oumahi、Pavel Afanasiev
DOI：10.1016/j.jallcom.2018.07.312
日期：2018.11
Abstract Hollow sulfides nanoparticles of MoS2, Cr2S3 and Mo0.9Cr0.1S2 (“inorganic fullerenes”) were prepared from SrMo(Cr)O4 precursors by means of a topotactic solid-gas reaction with H2S/CCl4 mixture. The obtained hollow sulfide nanoparticles have narrow size distributions and high specific surface areas. In the Mo-Cr doped sulfide material, chromium is homogeneously distributed substituting molybdenum
The synthesis of strontium-doped lanthanum chromite, La1−xSrxCrO3 (x=0.1 and 0.3), used as an interconnect material for solid oxide fuel cells (SOFC), was investigated using two unconventional synthesis methods: (1) organic precursors’ method based on the thermal conversion of complex combination resulted in the oxidation reaction of 1,2-ethanediol by La3+, Sr2+ and Cr3+ nitrates; (2) combustion synthesis based on the exothermic redox reaction of La3+, Sr2+ and Cr3+ nitrates with urea and glycine as fuels. We also used a mixture of urea and glycine as fuel. The samples were characterized by means of thermal analysis and X-ray diffraction.
Theoretical and Experimental Study of the Crystal Structures, Lattice Vibrations, and Band Structures of Monazite-Type PbCrO<sub>4</sub>, PbSeO<sub>4</sub>, SrCrO<sub>4</sub>, and SrSeO<sub>4</sub>
作者：Daniel Errandonea、Alfonso Muñoz、Placida Rodríguez-Hernández、John E. Proctor、Fernando Sapiña、Marco Bettinelli
DOI：10.1021/acs.inorgchem.5b01135
日期：2015.8.3
The crystalstructures, lattice vibrations, and electronic bandstructures of PbCrO4, PbSeO4, SrCrO4, and SrSeO4 were studied by ab initio calculations, Raman spectroscopy, X-ray diffraction, and optical-absorption measurements. Calculations properly describe the crystalstructures of the four compounds, which are isomorphic to the monazite structure and were confirmed by X-ray diffraction. Information
Quantification of Cr in Lu1-xSrxFe0.5Cr0.5O3 (0 ≤ x ≤ 1) samples containing impurities using X-ray techniques in combination with several data treatment methodologies
作者：Florencia E. Lurgo、Silvina Limandri、Raúl E. Carbonio、Germán Tirao
DOI：10.1016/j.jpcs.2021.110200
日期：2021.10
systematic study of the crystal structure of the main perovskite phase obtained as well as a characterization of impurities was performed by X-ray techniques: powder diffraction (PXRD), high resolution emission spectroscopy (HR-XES), and photoelectron spectrometry (XPS). The PXRD data of Lu1-xSrxFe0.5Cr0.5O3 (0 ≤ x ≤ 1) were refined using Pbnm orthorhombic unit cell for the perovskite structure. Only samples
应用湿化学方法的目的是获得多晶形式的Lu 1-x Sr x Fe 0.5 Cr 0.5 O 3 (0 ≤ x ≤ 1) 钙钛矿。通过 X 射线技术对获得的主要钙钛矿相的晶体结构和杂质进行了系统研究：粉末衍射 (PXRD)、高分辨率发射光谱 (HR-XES) 和光电子能谱 (XPS) . Lu 1-x Sr x Fe 0.5 Cr 0.5 O 3的PXRD数据(0 ≤ x ≤ 1) 使用 Pbnm 正交晶胞对钙钛矿结构进行细化。只有 x = 0 和 x = 0.1 的样品才是纯的；随着Sr量的增加，它作为杂质分离，首先分离为SrCrO 4，然后分离为SrFe 12 O 19。分析样品中 Cr 的平均氧化态是通过 HR-XES通过不同方法（统计参数和多变量方法）量化 Cr-Kβ" 和 Cr-Kβ 2,5区域的光谱变化而获得的。结果与通过 PXRD 和 XPS 获得的。使用最后一种技术，通过光谱分析在
Structural phase transition and suppressed Griffiths-like phase induced by Sr2+-doping in LaCr0.5Mn0.5O3 compound
作者：Romualdo S. Silva、J. Fernando D. Fontes、Nilson S. Ferreira、Rafael S. Gonçalves、Marcelo E.H. Maia da Costa、Petrucio Barrozo
DOI：10.1016/j.jmmm.2021.168851
日期：2022.3
desired phase was reached with a heat treatment above 800 °C. Moreover, the Sr-doping induced a structural phase transition from orthorhombic to rhombohedral, which is attributed to an increase of the ionic radius on the perovskite A-site. The observed deviation of the Curie-Weiss (C-W) law adjusted above the magneticordering temperature of the LaCr0.5Mn0.5O3 sample was attributed to the presence of Griffiths-like
我们研究了热处理和 Sr 掺杂对使用尿素作为燃料的改良燃烧法生产的 LaCr 0.5 Mn 0.5 O 3化合物的结构和磁性能的影响。结果表明，未掺杂的样品可以在低至 300 °C 的温度下进行热处理。然而，添加 10% Sr 使其难以在低温下获得，因此，通过 800 °C 以上的热处理达到所需的相。此外，Sr 掺杂诱导了从正交到菱面体的结构相变，这归因于钙钛矿 A 位上离子半径的增加。居里-魏斯 (CW) 定律的观测偏差在 LaCr 的磁有序温度以上调整0.5 Mn 0.5 O 3样品归因于格里菲斯样相（GP）的存在，格里菲斯温度为 T G = 280 K，然而，这种偏差被 Sr 掺杂所抑制。最后，Sr 掺杂引起 Cr 4+和 Mn 4+价态的增加，使得存在更多的双交换相互作用，这是磁化和磁有序温度增加的原因。
