From: "Saved by Windows Internet Explorer 7" Subject: Known Carcinogen: Chromium and Certain Chromium Compounds Date: Mon, 28 Apr 2008 16:21:17 -0700 MIME-Version: 1.0 Content-Type: text/html; charset="Windows-1252" Content-Transfer-Encoding: quoted-printable Content-Location: X-MimeOLE: Produced By Microsoft MimeOLE V6.0.6000.16545 Known Carcinogen: Chromium and Certain = Chromium Compounds



There is inadequate evidence for the = carcinogenicity of=20 chromium (7440-47-3) and most trivalent chromium compounds in = experimental=20 animals. There is sufficient evidence for the following hexavalent = chromium=20 compounds in experimental animals: calcium chromate (13765-19-0), = chromium=20 trioxide (1333-82-0), lead chromate (7758-97-6), strontium chromate = (7789-06-2),=20 and zinc chromate (13530-65-9) (IARC V.2, 1973; IARC V.23, 1980; IARC = S.4, 1982;=20 IARC S.7, 1987). Calcium chromate produced bronchial carcinomas after=20 implantation of an intrabronchial pellet in rats and injection-site = sarcomas=20 after intramuscular implantation in rats and mice and after intrapleural = injection in rats. Bronchial carcinomas were produced in rats after=20 intrabronchial implantation of strontium chromate and zinc chromate.=20 Injection-site sarcomas were produced in rats and mice after = intramuscular,=20 intrapleural, and subcutaneous injections of chromite ore, strontium = chromate,=20 chromium trioxide, lead chromate, and zinc chromate, but few or no = sarcomas were=20 induced by barium chromate (10294-40-3), sodium chromate (7775-11-3), = sodium=20 dichromate (10588-01-9), or chromic acetate (1066-30-4).=20

An IARC Working Group concluded that there were no adequate data = available to=20 evaluate the carcinogenicity of chromium and trivalent chromium = compounds in=20 humans; however, they also concluded that there was sufficient evidence = for the=20 carcinogenicity of hexavalent chromium compounds in humans (IARC S.7, = 1987). An=20 increased incidence of lung cancer has been observed among workers in = both the=20 bichromate-producing industry and chromate-pigment manufacturing. There = is=20 evidence of a similar risk among chromium platers and chromium-alloy = workers.=20 The incidences of cancers at other sites may also be increased in such=20 populations. However, a clear distinction between the relative = carcinogenicity=20 of chromium compounds of different oxidation states or solubilities has = been=20 difficult to achieve. Recent studies of chromate-pigment makers and = users,=20 chrome platers, welders and chrome-alloy foundry workers have shed some = light on=20 this problem. For chromate-pigment makers and users, respiratory cancer = excesses=20 have usually been found. Chromium pigments are usually hexavalent and = commonly=20 include zinc, lead, or strontium chromate. Chrome platers have also been = found=20 to have excess lung cancer. Stainless steel welding involves the = greatest=20 exposure to hexavalent chromium, as well as to nickel, and one study of=20 chromium-nickel alloy foundry workers showed a statistically significant = excess=20 of lung cancers. (For a discussion on the carcinogenicity of metals, see = the=20 Introduction, p. viii).=20


Chromium is an odorless, steel-to-semi-grey, lustrous = metal=20 available as crystals or powder (99.97% purity). It is insoluble in hot = and cold=20 water, nitric acid, and aqua regia, but reacts with dilute sulfuric acid = and=20 hydrochloric acid. Calcium chromate occurs in the form of yellow = monoclinic=20 prisms. It is soluble in cold and hot water and reacts with acids and = ethanol.=20 Chromium trioxide is odorless, dark-purplish-to-red-rhombus crystals = that are=20 deliquescent. It is soluble in alcohol, ethanol, sulfuric acid, and = nitric acid.=20 When heated to decomposition, chromium trioxide emits smoke and = irritating=20 fumes. Lead chromate occurs as yellow or orange monoclinic crystals that = are=20 insoluble in water, acetic acid, and ammonia but are soluble in acid and = alkali.=20 Lead chromate, when heated to decomposition, emits toxic fumes of lead. = Basic=20 lead chromate is a red amorphous or crystalline powder. It is insoluble = in hot=20 and cold water, reacts with most acid and alkali but not with acetic = acid or=20 ammonia, and emits very toxic fumes of lead when heated to = decomposition.=20 Strontium chromate occurs as monoclinic yellow crystals. It is soluble = in cold=20 and hot water and reacts with hydrochloric acid, nitric acid, acetic = acid, and=20 ammonium salts. Zinc chromate occurs as lemon yellow prisms. It is = insoluble in=20 cold water and acetone, dissolves in hot water, and is soluble in acid = and=20 liquid ammonia.=20


In 1987 and 1989, estimated consumption of chromium ferro- = alloys,=20 metals, and other chromium-containing materials by end use was as = follows:=20 stainless and heat-resisting steel, 79%; full- alloy steel, 8%; = super-alloys,=20 3%; and other alloys, 10% (USDOI, 1988, 1990). The steel industry is the = major=20 consumer of chromium. Chromium is used as an alloying and plating = element on=20 metal and plastic substrates for corrosion resistance in chromium- = containing=20 and stainless steels and in protective coatings for automotive and = equipment=20 accessories. It is also used in nuclear and high-temperature research.=20 Similarly, barium chromate and calcium chromate find use in = high-temperature=20 applications, e.g., barium chromate in safety matches and pyrotechnics = and both=20 are used in high-temperature batteries. In 1985, 39% of the chromium = trioxide=20 produced was used for metal plating and treatment, 44% was used in wood=20 treatment and preservatives, and 11% was exported (Chem. Profile, 1985). = Chromium trioxide is used in chromium plating and in the manufacture of=20 chromated copper arsenate (NCI DCE, 1985c). Chromium acetate, sodium = chromate,=20 and potassium chromate are used in the textile industry. Basic trivalent = chromic=20 sulfate is used in the tanning industry (Leather Industries of America, = Inc.,=20 personal communication). Chromium compounds are also used as pigments = (IARC=20 V.23, 1980). Lead chromate is chrome yellow and a component of chrome = orange and=20 green; chromium trioxide is green cinnabar; and zinc chromate is zinc = yellow=20 (Kirk-Othmer V.6, 1979). Chromium phosphate, strontium chromate, calcium = chromate, chromium acetate, and potassium chromate and dichromate are = also used=20 in pigments. Other uses for chromium and its compounds include organic = chemical=20 synthesis, photomechanical processing, and industrial water treatment. = In=20 medicine, chromium compounds are used in astringents and antiseptics = (Sax,=20 1987).=20


Two U.S. firms produced primary chromium chemicals, = three=20 firms produced chromium-ferro alloys, and four refractory firms produced = chromite-containing refractories (USDOI, 1990). Chromite has not been = mined in=20 the United States since 1961. Domestic deposits are small or of low = grade. The=20 Bureau of Mines has estimated that in 1989 248.6 million lb of chromium = were=20 produced in the United States and 946 million lb were imported and 35.2 = million=20 lb were exported (USDOI, 1990). In 1988, 261.8 million lb were produced=20 domestically, 990 million lb were imported, and 30.8 million lb were = exported.=20 In 1987, it was estimated that 213.4 million lb of chromium were = produced, 708.4=20 million lb were imported, and 19.8 million lb were exported. Of the = 184.8=20 million lb of chromium produced and 767.8 million lb of chromium = imported in=20 1986, 77 million lb were exported. In 1985, the United States produced = 187=20 million lb, imported 640.2 million lb, and exported 83.6 million lb of = chromium.=20 Production of chromium in 1984 was 176 million lb and exports were 72 = million=20 lb. Imports of chromium rebounded in 1984 after a 55% decrease from 1981 = to=20 1983. The amount imported in 1984 was 694 million lb while in 1983, 462 = million=20 lb were imported. In 1983, 154 million lb of chromium were produced of = which 26=20 million lb were exported. Of the 96 million lb of chromium produced in = 1982, 20=20 million lb were exported (USDOI, 1988; USDOI, 1987). In 1982, 478 = million lb of=20 chromium were imported, which was over 50% less than the 1.0 billion lb = imported=20 in 1981. Exports of chromium in 1981 were 104 million lb while in 1980, = 80=20 million lb were exported. The amount of chromium imported in 1980 was = 922=20 million lb (USDOI, 1987; USDOI, 1985). The 1979 TSCA Inventory = identified a=20 total of 11 producers producing 91 million lb of chromium and 12 = importers=20 importing 6.2 million lb of chromium in 1977 (TSCA, 1979).=20

In 1986, 3.9 million lb of zinc chromate, reported as zinc yellow, = and 39.2=20 million lb of lead chromate, reported as chrome yellow and orange, were=20 produced. In 1985, 4.42 million lb of zinc yellow, and 41.4 million lb = of chrome=20 yellow and orange were produced (USDOC Inorganic, 1987). In 1985, the = following=20 chemicals were imported: 9.8 million lb of chromic acid, 403,447 lb of = chrome=20 green (lead chromate), 6.4 million lb of chrome yellow, 3.0 million lb = of=20 chromium oxide green, 862,465 lb of strontium chromate, and 3.5 million = lb of=20 zinc yellow (USDOC Imports, 1986). In 1985, 731,941 lb of chromic acid = were=20 exported (USDOC Exports, 1986). In 1984, the production of chrome yellow = and=20 orange was 46.8 million lb, and of lead chromate, as chrome green, was = 16.5=20 million lb (USDOC Inorganic, 1987). In 1984, the United States imported = 105,569=20 lb of chrome green, 5.1 million lb of chrome yellow, 393,529 lb of = strontium=20 chromate, 2.4 million lb of zinc yellow, and 4.9 million lb of chromic = acid=20 (USDOC Imports, 1985). In 1983, production of chrome yellow and orange = was 43.1=20 million lb and production of chrome green was 10.4 million lb. In 1982, = 40.8=20 million lb of chrome yellow and orange and 8.6 million lb of chrome = green were=20 produced (USDOC Inorganic, 1987; Chem. Prod., 1983a). The 1979 TSCA = Inventory=20 reported that in 1977, 10 companies produced 74,000 lb of calcium = chromate and 2=20 companies imported 6,000 lb; 10 companies produced 11.6 million lb of = lead=20 chromate and there were 3 importers; 6 companies produced 555,000 lb of=20 strontium chromate and 9 firms imported 124,500 lb. Also reported in the = TSCA=20 Inventory was that 199,000 lb of zinc chromate and 6 companies imported = 7.2=20 million lb. The CBI Aggregate was less than 1 million lb barium chromate = and=20 between 1 million and 100 million lb for zinc chromate (TSCA, 1979).=20


The primary routes of potential human exposure to = chromium and=20 certain chromium compounds are inhalation, ingestion, and dermal = contact.=20 Chromium (in the form of unidentified chromium compounds) is widely = distributed=20 in air, water, soil, and food. In trace amounts, its trivalent form may = be an=20 essential ingredient in the diet. The entire population is possibly = exposed to=20 some of these compounds, but the levels of exposure vary. Hexavalent = chromium=20 (chromium (VI)) compounds are of greater health concern than trivalent = chromium=20 compounds (chromium (III)), but hexavalent compounds are readily reduced = to=20 trivalent forms in the presence of organic matter.=20

NIOSH has found that certain forms of chromium (VI) are = noncarcinogenic; they=20 are the monochromates and dichromates of hydrogen, lithium, sodium, = potassium,=20 rubidium, cesium, and ammonium, and chromium (VI) oxide (chromic acid = anhydride)=20 (NIOSHb, 1979b). The National Occupational Hazard Survey, conducted by = NIOSH=20 from 1972 to 1974, estimated that 2.5 million workers were possibly = exposed to=20 chromium and its compounds in the workplace (NIOSH, 1976). NIOSH = estimated that=20 175,000 workers were potentially exposed to chromium (VI), which is = produced=20 principally from chromite ore (NIOSHb, 1979b). The National Occupational = Exposure Survey (NOES) (1981-1983) estimated that a total of 115,788 = workers,=20 including 3,101 women, were potentially exposed to chromium; 6,339 total = workers=20 were potentially exposed to chromite ore (NIOSH, 1984). The NOES also = estimated=20 that a total of 196,725 workers, including 31,444 women, were = potentially=20 exposed to hexavalent chromium (VI) compounds (barium chromate, calcium=20 chromate, chromium trioxide, lead chromate, strontium chromate, and zinc = chromate). Occupational airbone chromium concentrations have declined=20 significantly during the past decades because of improved emission = controls.=20 Occupational exposure occurs mainly from stainless steel production and = welding,=20 chromate production, chrome plating, ferrochrome alloys, chrome pigment, = and=20 tanning industries. Occupational exposure is due to the soluble and = insoluble=20 fractions of chromium (III) and chromium (VI), depending upon the = industry. The=20 typical concentration ranges of chromium (VI) in these industries are: = stainless=20 steel welding, 50-400 =B5g/m3; chromate production, 100-500 =B5g/m3; = chrome plating,=20 5-25 =B5g/m3; ferrochrome alloys, 10-140 =B5g/m3; and chrome pigment, = 60-600 =B5g/m3.=20 In the tanning industry, exposure is almost exclusively to soluble = chromium=20 (III), typically in the range of 10-50 =B5g/m3 (ATSDR, 1989h). ACGIH has = designated the following threshold limit values (TLVs) as 8-hr = time-weighted=20 averages (TWAs) for chromium compounds, as chromium: 0.5 mg/m3 for = chromium (VI)=20 compounds, and 0.05 mg/m3 for lead chromate, water soluble chromium (VI) = compounds, and certain water insoluble chromium (VI) compounds (ACGIH, = 1986).=20

The general population can be exposed to chromium through the air, = water,=20 soils and food. Chromium has been detected in at least 386/1,777 sites = on the=20 National Priorities List (ATSDR, 1989h). The Toxic Chemical Release = Inventory=20 (EPA) listed 929 industrial facilities that produced, processed, or = otherwise=20 used chromium in 1988 (TRI, 1990). In compliance with the Community=20 Right-to-Know Program, the facilities reported releases of chromium to = the=20 environmental which were estimated to total 9.9 million lb. The = atmospheric=20 chromium concentration in the United States is typically < 0.01 = =B5g/m3 in=20 rural areas and 0.01-0.03 =B5g/m3 in urban areas. In the United States = it was=20 calculated that 64% of the atmospheric chromium emissions, which = originate from=20 coal, contain 1.5-54 ppm chromium (Merian, 1984). It is been reported = that tap=20 water contains 0.4-0.8 =B5g chromium/l (ATSDR, 1989h). The chromium = concentration=20 in rivers and lakes is usually between 1 and 10 =B5g/l (Merian, 1984). = The earth's=20 crust and rocks contain about 100 ppm chromium; soils contain, on the = average,=20 about 400 ppm (Merian, 1984). Typical chromium levels in most fresh = foods are=20 low. Chromium has been detected in vegetables, fruits, grains, and = cereals at=20 concentrations between 20 and 50 =B5g/kg (ATSDR, 1989h). CPSC = investigated the=20 potential hazard to consumers from chromium-containing inks, printed = products,=20 and nonprinted consumer products. Although chromium was present in some = inks=20 used in printed products, the levels found in the final products did not = warrant=20 further investigation.=20


In FY 1982, an evaluation was made of exposure to = chromium=20 from nonprinted consumer products. EPA regulates chromium and its = compounds=20 under the Clean Water Act (CWA), Comprehensive Environmental Response,=20 Compensation, and Liability Act (CERCLA), Resource Conservation and = Recovery Act=20 (RCRA), Superfund Amendments and Reauthorization Act (SARA), and Toxic=20 Substances Control Act (TSCA). CERCLA establishes reportable quantities = (RQs)=20 for chromium and some chromium compounds. RCRA and SARA subject chromium = and its=20 compounds to report/recordkeeping requirements. The EPA has proposed a = maximum=20 contaminant level goal (MCLG) and maximum contaminant level (MCL) of 0.1 = mg/l=20 for total chromium because no evidence suggests the hexavalent chromium = is=20 carcinogenic by ingestion. EPA's Carcinogen Assessment Group includes 10 = chromium compounds on its list of potential carcinogens. FDA regulates = the use=20 of chromium as an indirect food additive and the use of chromium oxide = in drugs=20 and cosmetics. NIOSH recommends an exposure limit of 1 =B5g/m3 for = carcinogenic=20 hexavalent chromium compounds. For noncarcinogenic chromium compounds, = it=20 recommends an exposure limit of 50 =B5g/m3 as a 10-hr time-weighted = average (TWA).=20 OSHA adopted an 8-hr TWA permissible exposure limit (PEL) of 0.5 mg/m3 = for=20 chromium (II) and chromium (III) compounds and l mg/m3 for chromium = metal; for=20 chromic acid and chromate, the ceiling is 0.1 ppm. OSHA regulates = chromium and=20 certain chromium compounds under the Hazard Communication Standard, and=20 hexavalent chromium compounds as chemical hazards in laboratories.=20