Chromium nitrate is a nitrate of chromium. It is used in the production of alkali metal-free catalysts and in pickling. Chromium is a chemical element which has the symbol Cr and atomic number 24. It is found naturally occuring in rocks, animals, plants, and soil, and is usually mined as chromite ore. Chromium is most toxic in its +6 oxidation state (chromiumNitrite is a toxic compound known to cause methemoglobinemia. (12)) due to its greater ability to enter cells and higher redox potential. Trivalent chromium (chromium(III)) however, is biologically necessary for sugar and lipid metabolism in humans. Nitrite is a toxic compound known to cause methemoglobinemia. (12, 7, 10)
belongs to the class of inorganic compounds known as transition metal nitrates. These are inorganic compounds in which the largest oxoanion is nitrate, and in which the heaviest atom not in an oxoanion is a transition metal.
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. Nitrate's toxicity is a result of it's conversion to nitrite once in the body. Nitrite causes the autocatalytic oxidation of oxyhemoglobin to hydrogen peroxide and methemoglobin. This elevation of methemoglobin levels is a condition known as methemoglobinemia, and is characterized by tissue hypoxia, as methemoglobin cannot bind oxygen. (5, 13, 1, 6, 2, 3, 4)
Metabolism
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. Intake of some amount of nitrates and nitrites is a normal part of the nitrogen cycle in humans. In vivo conversion of nitrates to nitrites can occur in the gastrointestional tract under the right conditions, significantly enhancing nitrates' toxic potency. The major metabolic pathway for nitrate is conversion to nitrite, and then to ammonia. Nitrites, nitrates, and their metabolites are excreted in the urine. (12, 1, 6)
Ingested nitrate or nitrite under conditions that result in endogenous nitrosation is probably carcinogenic to humans (Group 2A). Chromium (III) compounds are not classifiable as to their carcinogenicity to humans (Group 3). (8)
Uses/Sources
Chromium nitrate is used in the production of alkali metal-free catalysts and in pickling. (10)
Minimum Risk Level
Not Available
Health Effects
Chromium in its trivalent state is not very toxic. It may be oxidized to hexavalent chromium, a known carcinogen. Hexavalent chromium has also been shown to affect reproduction and development. Nitrate and nitrite poisoning causes methemoglobinemia. Nitrites may cause pregnancy complications and developmental effects. They may also be carcinogenic. (12, 1)
Symptoms
Chromium in its trivalent state is not very toxic, but it may be oxidized to hexavalent chromium. 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. Nitrate and nitrite poisoning causes methemoglobinemia. Symptoms include cyanosis, cardiac dysrhythmias and circulatory failure, and progressive central nervous system (CNS) effects. CNS effects can range from mild dizziness and lethargy to coma and convulsions. (12, 6)
Treatment
There is no know antidote for chromium poisoning. Exposure is usually handled with symptomatic treatment. Methemoglobinemia can be treated with supplemental oxygen and methylene blue 1% solution administered intravenously slowly over five minutes followed by IV flush with normal saline. Methylene blue restores the iron in hemoglobin to its normal (reduced) oxygen-carrying state. (13, 6)
