Chromium, Nickel and Welding

Overview

The IARC Working Group convened in Lyon (5-13 June 1989) reviewed the human, animal, and mechanistic evidence for chromium compounds, nickel compounds, and welding fume exposures, and issued the foundational carcinogenicity classifications that subsequent food-safety, occupational-health, and drinking-water authorities continue to cite. The volume establishes chromium (Cr)[VI] compounds (as encountered in chromate production, chromate pigment production, and chromium plating) and nickel compounds (sulfate and sulfide/oxide combinations encountered in refining) as Group 1 human carcinogens; metallic chromium and Cr[III] are Group 3; metallic nickel is Group 2B; welding fumes are Group 2B. The monograph also catalogues background concentrations of chromium and nickel in food, drinking water, air, and human biological samples, plus the analytical methods then in use across all those matrices.

Key numbers

Carcinogenicity classifications (Sections 4.5, pp. 213-214, 410-411, 530-531)

Chromium compounds:

• Cr[VI] compounds as encountered in chromate production, chromate pigment production, and chromium plating — sufficient evidence in humans — Group 1.
• Metallic chromium and chromium[III] compounds — inadequate evidence in humans, inadequate evidence in animals — Group 3.
• Sufficient evidence in animals: calcium chromate, zinc chromates, strontium chromate, lead chromates.
• Limited evidence in animals: chromium trioxide, sodium dichromate.
• Inadequate evidence in animals: metallic chromium, barium chromate, chromium[III] compounds.

Nickel compounds:

• Nickel compounds as a group — sufficient evidence in humans (nickel sulfate, and combinations of nickel sulfides and oxides encountered in the nickel refining industry) — Group 1.
• Metallic nickel — inadequate evidence in humans, limited evidence in animals — Group 2B.
• Sufficient evidence in animals: metallic nickel, nickel monoxides, nickel hydroxides, crystalline nickel sulfides.
• Limited evidence in animals: nickel alloys, nickelocene, nickel carbonyl, nickel salts (other than sulfate), nickel arsenides, nickel antimonide, nickel selenides, nickel telluride.
• Inadequate evidence in animals: nickel trioxide, amorphous nickel sulfide, nickel titanate.

Welding fumes: inadequate evidence in humans for stainless-steel welding fumes specifically, but overall sufficient epidemiological evidence across welding occupations for lung cancer — Group 2B.

Chromium in food (Section 2.3(f), p. 101)

• Vegetables: 20-50 µg/kg.
• Fruits: 20 µg/kg.
• Grains and cereals (excluding fats): 40 µg/kg.
• Range across foodstuffs (Hartford 1979): 20-590 µg/kg.
• Daily Cr intake from food (Hartford 1979): 10-400 µg/day; mean ~80 µg/day.
• Daily Cr intake (Bunker et al. 1984): 24.5 µg/day measured in 22 healthy subjects.
• Mean daily Cr intakes from food / water / air (Fishbein 1976): 280 / 4 / 0.28 µg respectively.
• Foodstuff Cr concentrations spanned 20-590 µg/kg across surveyed categories (Hartford 1979).

Chromium in drinking water (Section 2.3(d), pp. 99-100; Section 2.3(i) Regulatory status, p. 104)

• WHO European Standards (1970): Cr[VI] in drinking water 0.05 mg/L.
• Japanese drinking-water standard (1978): Cr[VI] 0.05 mg/L.
• EU surface-water-for-drinking Directive (1975): total Cr 0.05 mg/L.
• US EPA MCL: total Cr 0.05 mg/L.
• US tap-water survey (1974-75): 0.4-8 µg/L, median 1.8 µg/L.
• Rhine drinking water (1975): 0.29 µg/L.

Chromium in non-occupationally exposed humans (Section 2.3(h), Table 17, p. 104)

• Serum: median 0.19 µg/L (range 0.12-2.1 µg/L).
• Whole blood: <0.5 µg/L.
• Urine: median 0.4 µg/L (range 0.24-1.8 µg/L).
• Liver: 8-72 ng/g wet weight.
• Lung: median 204 ng/g wet weight (range 29-898 ng/g wet weight).

Chromium occupational exposure limits (Table 18)

• NIOSH (1988) recommended limit for carcinogenic Cr[VI] compounds: 0.001 mg/m³ TWA.
• ACGIH (1988) TLV for chromite ore processing / Cr[VI]: 0.05 mg/m³.
• OSHA (1987) PEL for soluble chromic and chromous salts: 0.5 mg/m³; metallic Cr and insoluble salts: 1.0 mg/m³.
• The monograph tabulates national occupational limits for Cr from Austria, Belgium, Brazil, Bulgaria, Chile, China, Czechoslovakia, Denmark, Egypt, Finland, France, German Democratic Republic, Hungary, India, Indonesia, Italy, Japan, Republic of Korea, Mexico, Netherlands, Norway, Sweden, Switzerland, Taiwan, United Kingdom, United States (ACGIH/NIOSH/OSHA), USSR, and Yugoslavia.

Nickel analytical detection limits (Table 21, pp. 315-316; Section 2.4 summary, p. 317)

EAAS with Zeeman background correction reference detection limits (Sunderman et al. 1986a,b; 1988a; Kiilunen et al. 1987; Angerer & Heinrich-Ramm 1988):

• Urine: ~0.45 µg/L.
• Whole blood: ~0.1 µg/L.
• Serum or plasma: ~0.05 µg/L.
• Tissues, foods, faeces: ~10 ng/g (dry weight equivalent).

DPASV with dimethylglyoxime-sensitized mercury electrode (Flora & Nieboer 1980; Pihlar et al. 1981; Ostapczuk et al. 1983):

• 1 ng/L detection limit in biological media.

Nickel carbonyl in air and exhaled breath has been measured by gas chromatography and chemiluminescence (Sunderman et al. 1968; Stedman et al. 1979).

The EAAS procedure of Brown et al. (1981) was accepted as a reference method by the International Union of Pure and Applied Chemists; an extension covering biological matrices, water, and intravenous fluids was accepted as a reference method by IARC (Sunderman 1986b).

Chromium analytical methods (Table 19)

Cross-matrix methods covered include EAAS (electrothermal atomic absorption spectrometry), flame AAS, ICP/AES (inductively coupled plasma atomic emission spectrometry), NAA (neutron activation analysis), X-REA, IDMS (isotope dilution mass spectrometry), visible spectrometry with sym-diphenylcarbazide at 540 nm for Cr[VI] speciation, DPP (differential pulse polarography), and XRF (X-ray fluorescence). Matrices: air, water, foodstuffs, biological samples, welding fumes, cement, paint, and grinding dusts.

Methods (brief)

This is a consensus working-group monograph, not a primary measurement study. The Working Group (constituted by IARC under the rules described on the volume’s preliminary pages) reviewed published peer-reviewed and agency literature on chromium, nickel, and welding through the meeting date of 13 June 1989. Sources reviewed include occupational cohort and case-control epidemiology, animal carcinogenicity bioassays (inhalation, intratracheal, intrapleural, intramuscular, intraperitoneal, subcutaneous, intravenous, intrarenal, intracerebral, and topical routes), short-term genotoxicity studies, exposure surveys (food, drinking water, ambient air, occupational atmospheres, biological samples), and analytical-method reviews. Carcinogenicity classifications were assigned per the IARC Monographs Programme’s standard scheme (Groups 1, 2A, 2B, 3, 4) based on the strength of human and animal evidence and supporting mechanistic data.

The analytical-method tables (Cr Table 19 starting p. 108; nickel (Ni) Table 21 at pp. 315-316) compile sample-preparation, instrumental-procedure, and detection-limit data from the primary literature; the monograph does not perform new analytical work.

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