ENVIRONMENTAL ASPECTS OF PAH BIODEGRADATION

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous pollutants, som e of which are on the US Environmental Protection Agency priority poll utant list. Consequently, timely clean-up of contaminated sites is imp ortant. The lower-mol-wt PAHs are amenable to bioremediation; however, higher-mol-wt PAHs seem to be recalcitrant to microbial degradation, The rates of biodegradation of PAHs are highly variable and are depend ent not only on PAH structure, but also on the physicochemical paramet ers of the site as well as the number and types of microorganisms pres ent. PAHs sorb to organic matter in soils and sediments, and the rate of their desorption strongly influences the rate at which microorganis ms can degrade the pollutants. Much of the current PAH research focuse s on techniques to enhance the bioavailability and, therefore, the deg radation rates of PAHs at polluted sites. Degradation products of PAHs are, however, not necessarily less toxic than the parent compounds. T herefore, toxicity assays need to be incorporated into the procedures used to monitor the effectiveness of PAH bioremediation. In addition, this article highlights areas of PAH research that require further inv estigation.