TOXICOLOGICAL PROFILE FOR CHROMIUM - Davidborowski.com

CHROMIUM 1862. HEALTH EFFECTSthe cement industry (Engebrigsten 1952), in railroad systems and diesel locomotive repair shops whereantirust diesel-engine coolants and radiator fluids contained sodium chromate (Kaplan and Zeligman1962; Winston and Walsh 1951), in tanneries (Fregert 1975), and in the welding, plating, wood and paperindustries (Burrows 1983). Other sources of chromium that have resulted in chromium sensitivity includedichromate-containing detergents and bleach (Wahba and Cohen 1979), glues, machine oils, foundrysand, match heads, boiler linings, and magnetic tapes (Burrows 1983).Several studies have estimated the exposure level necessary to elicit a 10% response in chromiumsensitizedindividuals. Nethercott et al. (1994) examined 54 individuals known to be sensitive tochromium-induced allergic contact dermatitis. For chromium(VI), about 10% elicited a response at0.09 µg chromium(VI)/cm 2 , whereas similar studies with chromium(III) were essentially negative. Sternet al. (1993) examined the data from seven studies conducted mostly in the 1960s on chromium(VI) patchtests and developed an aggregate dose-response curve using the Probit model. Although there wereconsiderable differences in methodologies and in the chromium(VI) compounds used (potassiumchromate, potassium dichromate, chromic acid, and lead acetate) with some administered in basic watersolutions, the aggregate data described a regular and consistent dose-response relationship which had astrong linear correlation (r=0.85). From this line, a 10% response of allergic dermatitis would occur inthe sensitized population at 10 ppm chromium(VI) and 5% at 7.6 ppm chromium(VI). Similarly,Paustenbach et al. (1992) used computer data fitting techniques to estimate the 10% threshold level. Thedata from eight historical chromium sensitization threshold studies involving patch testing with potassiumdichromate were used to estimate a weighted mean 10% threshold of 54 ppm chromium(VI) (150 ppmpotassium dichromate). As noted by Paustenbach et al. (1992), there are a number of methodicallimitations to the older patch test studies, including failure to disclose information on the diagnosticcriteria used to determine allergy, duration of application, and analytical method used to verify chromiumconcentration and valence. Thus, the 54 ppm threshold level may be somewhat conservative. Scott andProctor (1997) re-analyzed the data from three older chromium sensitization threshold elicitation studieswith information on the surface area of the patches and the more recent study by Nethercott et al. (1994).The 10% minium elicitation threshold ranged from 0.55 to 12.5 µg/cm 2 for the historical studies, ascompared to 0.09 µg/cm 2 for the Nethercott et al. (1994) study. Scott and Proctor (1997) note that thedifference between the 10% elicitation thresholds may be due to the use of 0.5% potassium dichromatediagnostic patches in the historical studies compared to 0.25% potassium dichromate in the more recentstudy. Using the lower concentration probably eliminated individuals who were less sensitive and thosewho had an irritant rather than allergic response to the higher concentration.