1-Nitropyrene is a widely distributed environmental contaminant, but its fate in the environment remains unknown. 1-Nitropyrene in benzene exposed to sunlight was found to degrade rapidly, whereas 1-nitropyrene adsorbed on soot was stable and degraded at a rate of 42% in 40 d. The major degraded compound was identified as 9-hydroxy-1-nitropyrene, using nuclear magnetic resonance and gas chromatography/mass spectrometry. Concentrations of 9-hydroxy-1-nitropyrene were found to be between 15 and 23 pg/m3 in urban airborne samples. The mutagenic potency of 9-hydroxy-1-nitropyrene was much lower than that of 1-nitropyrene. We concluded that 1-nitropyrene in the environment is photodegraded into 9-hydroxy-1-nitropyrene to become a less mutagenic compound.

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