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

(Group 3)
(Group 2B)

For definition of Groups, see Preamble Evaluation.

Supplement 7: (1987) (p.192)

CAS No.: 95-50-1
Chem. Abstr. Name: Benzene, 1,2-dichloro-

CAS No.: 106-46-7
Chem. Abstr. name: Benzene, 1,4-dichloro-

A. Evidence for carcinogenicity to humans (inadequate for ortho- and para-dichlorobenzene)

One report of a series of five cases has suggested an association between leukaemia and exposure to dichlorobenzenes [ref: 1].

B. Evidence for carcinogenicity to animals (inadequate for ortho-dichlorobenzene; sufficient for para-dichlorobenzene)

ortho-Dichlorobenzene was tested in mice and rats by gastric intubation; no evidence of carcinogenicity was observed [ref: 2]. A study by inhalation in several species was considered inadequate [ref: 1].

para-Dichlorobenzene was tested in mice and rats by gastric intubation; it caused renal tubular-cell adenocarcinomas in male rats and hepatocellular carcinomas in male and female mice [ref: 3]. It was also tested in mice and rats by inhalation; no increase in the incidence of tumours was noted, but the duration of exposure was limited [ref: 4].

C. Other relevant data

No data were available on the genetic and related effects of ortho- or para-dichlorobenzene in humans. ortho-Dichlorobenzene was not mutagenic to fungi or bacteria. para-Dichlorobenzene was mutagenic to fungi but not to bacteria [ref: 5].

Overall evaluation

para-Dichlorobenzene is possibly carcinogenic to humans (Group 2B).

ortho-Dichlorobenzene is not classifiable as to its carcinogenicity to humans (Group 3).

For definition of the italicized terms, see Preamble Evaluation.

Subsequent evaluation: Vol. 73 (1999)

Also see previous evaluations: Vol. 7 (1974); Vol. 29 (1982)


1. IARC Monographs, 29, 213-238, 1982

2. National Toxicology Programme (1985) Toxicology and Carcinogenesis Studies of 1,2-Dichlorobenzene (o-Dichlorobenzene) (CAS No. 95-50-1) in F344/N Rats and B6C3F1 Mice (Gavage Studies) (NTP TR 255; NIH Publ. No. 86-2511), Research Triangle Park, NC

3. National Toxicology Program (1987) Toxicology and Carcinogenesis Studies of 1,4-Dichlorobenzene (CAS No. 106-46-7) in F344/N Rats and B6C3F1 Mice (Gavage Studies) (NTP TR No. 319; NIH Publ. No. 86-2575), Research Triangle Park, NC

4. Loeser, E. & Litchfield, M.H. (1983) Review of recent toxicology studies on p-dichlorobenzene. Food chem. Toxicol., 21, 825-832

5. IARC Monographs, Suppl. 6, 222-225, 1987

Synonyms for ortho-Dichlorobenzene

Synonyms for para-Dichlorobenzene
Last updated: 30 September 1999

    See Also:
       Toxicological Abbreviations