Nitro compounds environmental sources

The larger concern about nitro-aromatic compounds is that environmental exposure to these molecules can cause cancer in humans and in other living organisms. Nitro-aromatic compounds are acutely toxic, mutagenic, and carcinogenic in laboratory mammals and in vitro test systems [6, 8]. Despite the potential negative impact of nitro-aromatic compounds on human health, they continue to be emitted into ambient air from municipal incinerators [9], motor vehicles (particularly from diesel exhausts) [10, 11], industrial power plants [12], and other sources. Evidence... 

Absence of nitro derivatives was also observed upon irradiation of nitro-phenols and nitrate. Also in this case, the electron-withdrawing character of the nitro group can account for the inhibition of nitration [109]. The difficulty to nitrate nitrophenols to dinitrophenols is widely recognised [125] and also constitutes a problem in environmental chemistry, since field data seem, in contrast, to indicate that the nitration of 2-nitrophenol to 2,4-dinitrophenol in the atmospheric aqueous phase (e.g. cloud water) is an important process [126]. In fact, aqueous-phase nitration might be a relevant sink for 2-nitrophenol and possibly the main source of the dinitro compound, which is a powerful phytotoxic agent [127,128]. In the presence of nitrate under irradiation the main transformation intermediates of nitrophenols are the hydroxyl derivatives, while other compounds may derive from the direct photolysis of the substrates (catechol and 2-nitrosophenol from 2-nitrophenol hydroquinone, benzoquinone, hydroxybenzoquinone and 4-nitrosophenol from 4-nitrophenol) [109]. 

---