A 47-year-old woman, after being exposed to nitrobenzene for 17 months, was admitted to hospital because of headache, nausea, cyanosis, and general weakness. Laboratory study revealed, in addition to methaemoglobinaemia, the presence of p-aminophenol as well as p-nitrophenol in the urine. Both compounds gradually disappeared from the urine during the two weeks after she was removed from the tox...