IARC Classifies Some Nitrobenzenes, Other Industrial Chemicals

Published November 7, 2018

A working group of experts affiliated with the International Agency for Research on Cancer has classified ortho-phenylenediamine and its dihydrochloride salt, 2-chloronitrobenzene, 4-chloronitrobenzene, 1,4-dichloro-2-nitrobenzene, 2,4-dichloro-1-nitrobenzene, 2-amino-4-chlorophenol, para-nitroanisole, and N,N-dimethylacetamide as “possibly carcinogenic to humans.” These substances were given the designation “Group 2B” in IARC’s classification system for carcinogens based on “sufficient evidence of carcinogenicity in experimental animals” and no data or “inadequate evidence” in humans. IARC previously evaluated 2-chloronitrobenzene and 4-chloronitrobenzene in 1995. The other chemicals were evaluated by IARC for the first time.

IARC expects that occupational exposure to these chemicals occurs during their production and use via inhalation, skin contact, or inadvertent ingestion. The agency’s evaluation describes typical uses of these industrial chemicals:

Ortho-phenylenediamine. Used in the production of agrochemicals and pharmaceuticals, and in dyes and pigments used for coloring hair.

Ortho-phenylenediamine dihydrochloride. Used in the manufacture of dyes, coatings, and photographic chemicals.

2-Chloronitrobenzene. Used to make colorants and various other chemicals. Other downstream uses include lumber preservatives, corrosion inhibitors, pigments, and agricultural chemicals.

4-Chloronitrobenzene. Used in the production of agricultural chemicals, pharmaceuticals, paints, pigments, colorants, plastics, and paper, and in the treatment of textiles and leather. According to IARC, urinary metabolites of 4-chloronitrobenzene have been detected in factory workers. The agency notes that both 2-chloronitrobenzene and 4-chloronitrobenzene have been measured in workplace air in chemical factories.

1,4-Dichloro-2-nitrobenzene and 2,4-dichloro-1-nitrobenzene. Intermediates in the manufacture of diazo pigments, agrochemicals, ultraviolet absorbents, and pharmaceuticals.

2-Amino-4-chlorophenol. Used in the manufacture of dyes used in textiles and other consumer products, and in the manufacture of pharmaceuticals.

Para-nitroanisole. Used in the manufacture of synthetic dyes used for cosmetics and other consumer products.

N,N-Dimethylacetamide. Used in the manufacture of textile fibers, agrochemicals, pharmaceuticals, coatings and films, and as a solvent for resins. IARC found that N,N-dimethylacetamide and its metabolites have been measured in workplace air and in urine of workers employed in synthetic-fiber production facilities.

News of the working group’s determination is available from The Lancet Oncology (free registration required). Full assessments will be published in volume 123 of the IARC Monographs.