1.1.1. Nomenclature

• Chem. Abstr. Serv. Reg. No.: 90-04-0
• Chem. Abstr. Name: 2-Methoxybenzenamine
• IUPAC Systematic Name: o-Anisidine
• Synonyms: ortho-Aminoanisole; 2-aminoanisole; ortho-aminomethoxybenzene; 2-aminomethoxybenzene; 1-amino-2-methoxybenzene; 2-methoxy-1-aminobenzene; ortho-methoxyaniline; 2-methoxyaniline; 2-methoxybenzenamine; ortho-methoxyphenylamine; 2-methoxyphenylamine

1.1.2. Structural and molecular formulae and relative molecular mass

1.1.3. Chemical and physical properties of the pure substance

• (a) Description: Yellowish liquid; becomes brownish on exposure to air (Budavari, 1996)
• (b) Boiling-point: 224°C (Lide, 1997)
• (c) Melting-point: 6.2°C (Lide, 1997)
• (d) Density: 1.096 g/cm³ at 20°C (Lide, 1997)
• (e) Solubility: Slightly soluble in water; soluble in ethanol, diethyl ether and acetone (Lide, 1997)
• (f) Stability: Susceptible to oxidation in air (National Toxicology Program, 1991)
• (g) Octanol/water partition coefficient (P): log P, 0.95 (calculated), 1.18 (measured) (Verschueren, 1996).
• (h) Conversion factor: mg/m³ = 5.04 × ppm

1.3.1. Natural occurrence

ortho-Anisidine is not known to occur naturally.

1.3.2. Occupational exposure

According to the 1981–83 National Occupational Exposure Survey (National Institute for Occupational Safety and Health, 1998), approximately 700 workers in the United States were potentially exposed to ortho-anisidine. Occupational exposure to ortho-anisidine may occur during its production and during its use as a chemical intermediate, corrosion inhibitor or antioxidant.

1.3.3. Environmental occurrence

ortho-Anisidine has been identified in wastewater from chemical plants and from oil refineries, and in cigarette smoke (National Library of Medicine, 1998a).

According to the United States Environmental Protection Agency Toxic Chemical Release Inventory for 1987, 1600 kg of ortho-anisidine were released into the air, 280 kg were discharged into water, and 110 kg were released onto the land from manufacturing and processing facilities in the United States. By 1996, 690 kg were released into the air and 13 kg discharged into water (National Library of Medicine, 1998b).

4.1.1. Humans

No data were available to the Working Group.

4.1.2. Experimental systems

Horseradish peroxidase oxidized ortho-anisidine via a nitrogen-centred cation radical to the diimine, quinone imine and an azo dimer in vitro. The metabolism led to covalent binding to calf thymus DNA. Metabolites of ortho-anisidine were consistently more reactive with protein and glutathione than metabolites of para-anisidine (Thompson & Eling, 1991). [The Working Group noted that studies with mammalian enzymes have not been carried out.]

4.2.1. Humans

No data were available to the Working Group.

4.2.2. Experimental systems

The oral LD₅₀ of ortho-anisidine has been reported to be 2000 mg/kg bw in rats, 870 mg/kg bw in rabbits and 1400 mg/kg bw in mice. Its subacute effects include haematological changes, anaemia and nephrotoxicity (Prosolenko, 1975).

ortho-Anisidine induced methaemoglobinaemia in CBA mice and Alpk:APfSD rats after oral administration (Ashby et al., 1991). The authors suggested that their results indicate that ortho-anisidine is distributed and N-oxidized in rodents.

Male and female B6C3F₁ mice were fed diets containing up to 30 000 mg/kg of diet (ppm) ortho-anisidine hydrochloride for seven weeks. A dose-dependent depression in mean body-weight gain of up to 40% was observed. The spleens of mice given doses > 10 000 mg/kg of diet were black and enlarged. Female mice that received doses of 2500 or 5000 mg/kg of diet for up to 103 weeks developed more cystic hyperplasia of the uterus and endometrium than did control animals. Mice of each sex at 30 000 mg/kg of diet had an increased incidence of hyperplasia of the bladder (National Cancer Institute, 1978).

Feeding of diets containing up to 30 000 mg/kg (ppm) ortho-anisidine hydrochloride to Fischer 344 rats for seven weeks led to reductions in weight gain of up to 52% in males and 27% in females. Feeding of diets containing 1000 or 3000 mg/kg resulted in granular spleens in males but not in females; the spleens of rats of each sex given diets containing ortho-anisidine at > 10 000 mg/kg were dark and granular. A dose of 10 000 mg/kg of diet for up to 103 weeks resulted in depressions of body-weight gain of 21% in males and 11% in females. Male and female rats fed diets containing 5000 or 10 000 mg/kg ortho-anisidine hydrochloride developed non-neoplastic lesions of the thyroid gland and kidney more frequently than did control animals (National Cancer Institute, 1978).

4.4.1. Humans

No data were available to the Working Group.

4.4.2. Experimental systems (see Table 1 for references)

Table 1

Genetic and related effects of ortho-anisidine.

ortho-Anisidine did not induce reverse mutation in Escherichia coli or in Salmonella typhimurium strains TA100, TA1535, TA1537, TA1538, TA98 or YG1012. In the presence of exogenous metabolic activation, it induced mutations in strain YG1029, both YG strains having elevated levels of N-acetyltransferase. ortho-Anisidine did not induce sex-linked recessive lethal mutations in Drosophila. It gave rise to gene mutations in mouse lymphoma L5178Y cells in vitro both in the presence and absence of exogenous metabolic activation, while DNA breaks and cross-links were observed only in the presence of an exogenous metabolic system. Sister chromatid exchange and chromosomal aberrations were induced in Chinese hamster ovary cells in vitro, both in the presence and absence of exogenous metabolic activation. In the absence of exogenous metabolic activation, ortho-anisidine induced cell transformation in Syrian hamster embryo cells in vitro. ortho-Anisidine did not bind covalently to DNA in mouse bladder or liver cells in vivo; it did not induce single-strand breaks in liver, thymus, testis, kidney, spleen or bladder DNA of rats treated in vivo, nor did it induce unscheduled DNA synthesis in rat hepatocytes or kidney cells in vivo. In mice treated in vivo, ortho-anisidine gave rise to breaks in bladder and colon DNA but not in DNA of stomach, kidney, liver, lung, brain or bone marrow. ortho-Anisidine induced DNA repair in E. coli in a host-mediated assay in male mice when the animals were treated intraperitoneally but not when they were treated by oral gavage. ortho-Anisidine weakly induced gene mutation in the lacI transgene in mouse bladder but not in liver. It did not induce micronuclei in bone marrow of mice or in bone-marrow or liver cells of rats treated in vivo.

ortho-Anisidine inhibited gap-junctional intercellular communication in mouse hepatocytes in the absence of an exogenous metabolic system in vitro.