International Agency for Research on Cancer (IARC) - Summaries & Evaluations


VOL.: 29 (1982) (p. 311)

CAS No.: 2602-46-2
Chem. Abstr. Name: 2,7-Naphthalenedisulfonic acid, 3,3'-[(1,1'-biphenyl)-
4,4'-diylbis(azo)]bis(5-amino-4-hydroxy)-,tetrasodium salt

5. Summary of Data Reported and Evaluation

5.1 Experimental data

Oral administration to rats of one commercial sample of Direct Blue 6 resulted in hepatocellular carcinomas and neoplastic nodules in males and females sacrificed 13 weeks after start of exposure to the highest dose at which animals survived. Lower doses produced only liver-cell changes such as foci of cellular alteration.

Direct Blue 6 is teratogenic in rats only when injected during the first half of pregnancy.

No data were available to assess the mutagenicity of this compound.

5.2 Human data

Occupational exposure to Direct Blue 6 has and probably still does occur during its production and its use for the dyeing of textiles, leather and paper. Benzidine and its metabolic derivatives have been detected in the urine of workers exposed to direct azo dyes.

No data were available to assess the mutagenicity or chromosomal effects of this compound to man.

No study of exposure to Direct Blue 6 was available to the Working Group. An epidemiological study of silk dyers and painters who had multiple exposure to benzidine-based and other dyes indicated that those exposures were strongly associated with the occurrence of bladder cancer. Case reports and other epidemiological studies support the existence of such a relationship.

5.3 Evaluation

There is sufficient evidence that commercial Direct Blue 6 is carcinogenic to rats.

Although the epidemiological data were inadequate to evaluate the carcinogenicity to man of Direct Blue 6 alone, they, together with the presence of benzidine in the urine of exposed workers, provide sufficient evidence that occupational exposure to benzidine-based dyes represents a carcinogenic risk to man.

For definition of the italicized terms, see Preamble Evaluation.

Subsequent evaluation: Suppl. 7 (1987)


Last updated: 9 April 1998

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