Organic Pollutant Particles in the Atmosphere

Organic particulate matter consists of a variety of different kinds of materials. Much of this matter is produced as secondary material that results from photochemical processes operating on volatile and semivolatile organic compounds emitted into the atmosphere. Such is the case with the organic particles with an approximate empirical formula of CH2O, characteristic of photochemical smog (see Section 7.8). The compounds emitted into the atmosphere are predominantly hydrocarbon in 

Polycyclic aromatic hydrocarbons (PAH) in atmospheric particles have received a great deal of attention because of the known carcinogenic effects of some of these compounds. The most prominent of these compounds is benzo(a)pyrene and other examples are benz(a)anthracene, chrysene, benzo(e)pyrene, benz(e)acephenanthrylene, benzo(j)fluoranthene, and indenol. Some representative structures of PAH compounds are given as follows  

Elevated levels of PAH compounds of up to about 20 pg/m are found in the atmosphere. Elevated levels of PAHs are most likely to be encountered in polluted urban atmospheres and in the vicinity of natural fires such as forest and prairie fires. Coal furnace stack gas may contain over 1000 pg/m of PAH compounds and cigarette smoke contains almost 100 pg/m. Diesel engines can be prolific emitters of carbonaceous particulate matter including PAHs, and much of the effort to control particulate air pollution is now concentrated on this source. 

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