Environmental chemistry of polynuclear aromatic hydrocarbons

Recently developed and highly diagnostic analytical methods have produced new insights into the significance of polynuclear aromatic hydrocarbons (PNA's) in the environment. Proper use of these methods not only can distinguish between the limited number of PNA's that are carcinogenic, but also reveal that PNA's are widely distributed at low concentrations in soils, sediments and coastal waters throughout the world. The clear-cut analytical evidence is that these widespread PNA's are derived from combustion processes occurring over long duration. The relative concentration of parent compounds and their alkyl substituted derivatives of the widely-occurring PNA's is different from that of the PNA's found in crude petroleum, in that the latter contain more molecular substituents. The new diagnostic methods of analysis clearly distinguish petroleum PNA's from those derived from combustion even at low concentrations. It has been found, for example, that PNA's measured at ppB levels in some marine animal tissues are those derived from common combustion sources, not from petroleum. Laboratory tests have demonstrated that marine animals will take up PNA's in their gut and tissues, but that these PNA's are then metabolized or purged when the animals are placed in clean water. Many living organisms have complex and effective enzyme systemsmore » which oxidize aromatic compounds, including PNA's, through a series of reactions to non-toxic end products.« less