Pyrene is a four-ringed polycyclic aromatic hydrocarbon (PAH). Although not a carcinogen, pyrene is a byproduct of the manufactured gas process and other incomplete combustion processes. Pyrene is present at thousands of sites throughout the United States and pyrene has been shown to be involved in the bacterial cometabolism of the potent carcinogen benzo[a]pyrene ([http://www.ncbi.nlm.nih.gov/pubmed/10698765|Boonchan et al., 2000]), whose metabolism is shown elsewhere on this site. The biodegradation of benzo[a]pyrene is known to proceed through substituted pyrene intermediates (e.g., [http://www.ncbi.nlm.nih.gov/pubmed/8572690|Schneider et al., 1996]). Pyrene can be biodegraded by bacteria and fungi through initial dioxygenase (bacteria) and monooxygenase (bacteria and fungi) reactions.