Fate of polycyclic aromatic hydrocarbons (PAHs) in ambient air

Atmospheric degradation of PAHs is mainly governed by the reaction with the OH radicals and the nitrate radicals (during night-time). The main product s identified from the gas phase reaction are oxygenated PAHs and other pola r compounds which result from the oxidative ring opening of the parent mole cule. In addition, nitrated compounds are formed from the reaction of PAHs with NOx. PAHs adsorbed on particles are converted to highly mutagenic nitr ated compounds when irradiated in the presence of nitrogenous (NO2-) air po llutants. Nitration of PAHs is favoured when the compounds are adsorbed ont o active surfaces (particles) rather than in the gas phase.