329 Lead molybdenum chromate Lead molybdenum chromate is a chemical compound of lead, molybedunum, and chromium. Lead is a heavy metal and stable element with the symbol Pb and the atomic number 82, existing in metallic, organic, and inorganic forms. It is mainly found in nature as the mineral galena (PbS), cerussite (PbCO3) or anglesite (PbSO4), usually in ore with zinc, silver, or copper. Hexavalent chromium refers to chemical compounds that contain the element chromium in the +6 oxidation state. Chromium(VI) is more toxic than other oxidation states of the chromium atom because of its greater ability to enter cells and higher redox potential. (L16, L21) 12709-98-7 166736 Cr2Mo2O11Pb2 No data. Oral (L136) ; inhalation (L136); dermal (L136) Lead mimics other biologically important metals, such as zinc, calcium, and iron, competing as cofactors for many of their respective enzymatic reactions. For example, lead has been shown to competitively inhibit calcium's binding of calmodulin, interferring with neurotransmitter release. It exhibits similar competitive inhibition at the NMDA receptor and protein kinase C, which impairs brain microvascular formation and function, as well as alters the blood-brain barrier. Lead also affects the nervous system by impairing regulation of dopamine synthesis and blocking evoked release of acetylcholine. However, it's main mechanism of action occurs by inhibiting delta-aminolevulinic acid dehydratase, an enzyme vital in the biosynthesis of heme, which is a necesssary cofactor of hemoglobin. 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, T4, A20, A22, L136) Lead and chromium are absorbed following inhalation, oral, and dermal exposure. It is then distributed mainly to the bones and red blood cells. In the blood lead may be found bound to serum albumin or the metal-binding protein metallothionein. Organic lead is metabolized by cytochrome P-450 enzymes, whereas inorganic lead forms complexes with delta-aminolevulinic acid dehydratase. Lead is excreted mainly in the urine and faeces. Chromium 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, L136) 1 to 3 grams for an adult human (hexavalent chromium). (A119) 2A, probably carcinogenic to humans. (L135) No data. Chronic Inhalation: 0.05 mg/m3 (Lead) (L134) Intermediate Oral: 0.005 mg/kg/day (Hexavalent chromium) (L134) Chronic Oral: 0.001 mg/kg/day (Hexavalent chromium) (L134) Lead is a neurotoxin and has been known to cause brain damage and reduced cognitive capacity, especially in children. Lead exposure can result in nephropathy, as well as blood disorders such as high blood pressure and anemia. Lead also exhibits reproductive toxicity and can results in miscarriages and reduced sperm production. Hexavalent chromium is a known carcinogen. Chronic inhalation especially has been linked to lung cancer. Hexavalent chromium has also been know to cause reproductive and developmental defects. (A12, L21) Symptions of chronic lead poisoning include reduced cognitive abilities, nausea, abdominal pain, irritability, insomnia, metal taste in the mouth, excess lethargy or hyperactivity, chest pain, headache and, in extreme cases, seizures, comas, and death. There are also associated gastrointestinal problems, such as constipation, diarrhea, vomiting, poor appetite, weight loss, which are common in acute poisoning. Breathing hexavalent chromium can cause irritation to the lining of the nose, nose ulcers, runny nose, and breathing problems, such as asthma, cough, shortness of breath, or wheezing. Ingestion of hexavalent chromium causes irritation and ulcers in the stomach and small intestine, as well as anemia. Skin contact can cause skin ulcers. (L16, A2, L21) Lead poisoning is usually treated with chelation therapy using DMSA, EDTA, or dimercaprol. There is no know antidote for chromium poisoning. Exposure is usually handled with symptomatic treatment. (L16, L21) 2009-03-06T18:58:32Z 2014-12-24T20:21:34Z Delta-aminolevulinic acid dehydratase (P13716) Serum albumin (P02768) Metallothionein-2 (P02795) Metallothionein-1G (P13640) Metallothionein-1H (P80294) Metallothionein-3 (P25713) Metallothionein-1F (P04733) Metallothionein-1E (P04732) Metallothionein-1X (P80297) Metallothionein-1A (P04731) Metallothionein-1B (P07438) Metallothionein-1M (Q8N339) Metallothionein-4 (P47944) Metallothionein-1L (Q93083) Sulfate transporter (P50443) Sulfate anion transporter 1 (Q9H2B4) (A12, L136) Lead molybdenum chromate true Delta-aminolevulinic acid dehydratase (P13716) Serum albumin (P02768) Metallothionein-2 (P02795) Metallothionein-1G (P13640) Metallothionein-1H (P80294) Metallothionein-3 (P25713) Metallothionein-1F (P04733) Metallothionein-1E (P04732) Metallothionein-1X (P80297) Metallothionein-1A (P04731) Metallothionein-1B (P07438) Metallothionein-1M (Q8N339) Metallothionein-4 (P47944) Metallothionein-1L (Q93083) (L136) [O--].[O--].[O--].[O--].[O--].[O--].[O--].[O--].[O--].[O--].[O--].[Cr+3].[Cr+3].[Mo].[Mo].[Pb++].[Pb++] Cr2Mo2O11Pb2 InChI=1S/2Cr.2Mo.11O.2Pb/q2*+3;;;11*-2;2*+2 InChIKey=UJSWIHIDDYYLJD-UHFFFAOYSA-N 886.3 891.589172042 Exogenous Solid 145876