Trivalent chromium compounds, toxicity

Reproductive Toxicity. No data are available that impHcate either hexavalent or trivalent chromium compounds as reproductive toxins, unless exposure is by way of injection. The observed teratogenic effects of sodium dichromate(VI), chromic acid, and chromium (HI) chloride, adininistered by injection, as measured by dose-response relationships are close to the amount that would be lethal to the embryo, a common trait of many compounds (111). Reported teratogenic studies on hamsters (117,118), the mouse (119—121), and rabbits (122) have shown increased incidence of cleft palate, no effect, and testicular degeneration, respectively. Although the exposures for these experiments were provided by injections, in the final study (122) oral, inhalation, and dermal routes were also tried, and no testicular degeneration was found by these paths. 

Among warm-blooded organisms, hexavalent chromium was fatal to dogs in 3 months at 100 mg/kg in their food and killed most mammalian experimental animals at injected doses of 1 to 5 mg Cr/kg body weight, but it had no measurable effect on chickens at dietary levels of 100 mg/kg over a 32-day period. Trivalent chromium compounds were generally less toxic than hexavalent chromium compounds, but significant differences may occur in uptake of anionic and cationic CL3 species, and this difference may affect survival. 

Chromium and certain chromium compounds are classified as substances known to be carcinogenic. ERA classifies chromium as a de minimis carcinogen, meaning that the minimum amount of the chemical set by the U.S. Occupational Safety and Health Administration (OSHA) is considered to be carcinogenic. Chromium compounds vary greatly in their toxic and carcinogenic effects. Trivalent chromium compounds are considerably less toxic than the hexavalent compounds and are neither irritating nor corrosive. 

Trivalent chromium compounds (chromium chloride, chromium nicotinate, and chromium picohnate) are used by patients to enhance weight loss, to increase lean body mass, or to improve glycemic control. Drug histories should include attention to the use of over-the-counter nutritional supplements often regarded as harmless by the pubhc and lay media. The recommended daily allowance of chromium picolinate is 50-200 micrograms, but information about its toxicity is limited. 

The primary routes of entry for animal exposure to chromium compounds are inhalation, ingestion, and, for hexavalent compounds, skin penetration. This last route is more important in industrial exposures. Most hexavalent chromium compounds are readily absorbed, are more soluble than trivalent chromium in the pH range 5 to 7, and react with cell membranes. Although hexavalent compounds are more toxic than those of Cr(III), an overexposure to compounds of either oxidation state may lead to inflammation and irritation of the eyes, skin, and the mucous membranes associated with the respiratory and gastrointestinal tracts. Skin ulcers and perforations of nasal septa have been observed in some industrial workers after prolonged exposure to certain hexavalent chromium compounds (108—110), ie, to chromic acid mist or sodium and potassium dichromate. 

Metal Finishing and Corrosion Control. The exceptional corrosion protection provided by electroplated chromium and the protective film created by applying chromium surface conversion techniques to many active metals, has made chromium compounds valuable to the metal finishing industry. Cr(VI) compounds have dominated the formulas employed for electroplating (qv) and surface conversion, but the use of Cr(III) compounds is growing in both areas because of the health and safety problems associated with hexavalent chromium and the low toxicity of trivalent chromium (see... 

Chromium can exist as either trivalent or hexavalent compounds in raw wastewater streams. The chromium that passes through the POTW is discharged to ambient surface water. Chromium is toxic to aquatic organisms at levels observed in POTW effluents15 ... 

Replacement of hexavalent chromium with trivalent chromium offers important environmental advantages. Trivalent chromium is considerably less toxic than hexavalent. Trivalent systems use chromium concentrations that are typically two orders of magnitude less than in hexavalent systems. Thus, far less chromium enters the waste stream. Trivalent systems also generate few toxic air emissions, while hexavalent systems involve a reaction that produces hydrogen bubbles which entrain chromium compounds and carry them out of the baths. Trivalent chromium is readily precipitated from wastewater, while hexavalent chromium solutions must go through an additional step in a treatment system in which the chromium is reduced to its trivalent form before precipitation. It has been shown that trivalent chromium systems can successfully replace hexavalent ones for decorative chrome applications. Trivalent chromium systems are not suitable for hard chrome applications. More information regarding trivalent chromium plating can be obtained from Roy (1984), Robison (1978), Chementator (1982), and Smart (1983). 

Over time, increased quantities of chromium compounds have been used by man and introduced into the environment (Gauglhofer and Bianchi 1991). The danger of environmental contamination depends on the solubility and oxidation state of chromium [International Programme on Chemical Safety (I PCS) 1988], Chromium(III) compounds are generally poorly soluble and show little or no toxicity. Chromium in its hexavalent form is 100 to 1000 times more toxic than the most common trivalent compounds (Katz 1991 Katz and Salem 1993). Hexavalent chromium compounds can reduce plant growth and cause skin and respiratory irritation and ulceration and eventually lung cancer. Hexavalent chromium is recognized... 

After oral ingestion of hexavalent compounds, ascorbic acid has been suggested to assist the conversion of hexavalent to less toxic trivalent compounds. While no definitive studies exist, the treatment is benign and may be helpful. In animal studies the effective dose was 2-4 g of ascorbic acid orally per g of hexavalent chromium compound ingested. 

A trivalent chromium fumarato-coordination compound, Volan 82, has been claimed to be an effective adhesion promoter for polyethylene coatings on aluminum. The toxicity of chromium compounds must place a question mark against their continued use as adhesion promoters. 

The pigments regulated for use and disposal that are most affected are antimony, arsenic, cadmium, hexavalent and trivalent chromium, lead, and nickel compounds. Lead, arsenic and cadmium-containing pigments are nearly obsolete now as plastics packaging materials. In the heavy metal family, solubility in bodily fluids is the key to toxicity. 

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