Methoxyaniline, 2-; o-Anisidine

Abstract

o-Anisidine is used in the manufacture of dyes, pigments, and pharmaceuticals. The National Institute for Occupational Safety and Health (NIOSH) considers o-anisidine to be a potential occupational carcinogen (at the exposure level: 50 mg m−3). o-Anisidine is a very toxic agent that causes blood, enzyme, and nerve damage with cyanosis and the danger of suffocation. It is produced from 2-methoxynitrobenzene by reduction with iron or by hydrogenation in the presence of precious-metal catalysts (platinum or palladium on activated carbon; solvent: toluene). It can also be prepared by reduction of o-nitroanisole with tin or iron and hydrochloric acid. Acute (short-term) exposure to o-anisidine results in skin irritation in humans. Exposure to o-anisidine at the workplace by inhalation for 6 months caused headaches, vertigo, and effects on the blood. Animal studies have reported effects on the blood from chronic (long-term) dermal exposure to o-anisidine. o-Anisidine has been found in cigarette smoke and as an environmental pollutant in wastewater from oil refineries and chemical plants. Concentration of o-anisidine in average smoke and other cigarettes has been reported to be up to 5.12 ng per cigarette. Individuals in the population could be exposed to o-anisidine in the environment, because it was detected in urine, and as a hemoglobin adduct in humans. Monitoring data indicate that the general population may be exposed to o-anisidine via inhalation of cigarette smoke. Animal studies have reported tumors of the urinary bladder from oral exposure to o-anisidine. EPA has not classified o-anisidine for carcinogenicity, but the International Agency for Research on Cancer (IARC) has classified o-anisidine as a Group 2B, possible human carcinogen. No information is available on the reproductive, developmental, or carcinogenic effects of o-anisidine in humans. The LD50 for Wistar rats was found to be 1890 mg kg−1 bw.