Abstract-Polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) are ubiquitous pollutants in the environment. Due to their physical-chemical properties, PAHs and PCBs can be accumulated in organic matrices such as living organisms, soil and sludge. Their toxicity and mutagenicity is a serious concern. In many cases an effective strategy to assess the pollution of water streams is to detect these compounds using biofilms, sediment and sludge as passive samplers.However, the absorption of hydrophobic compounds in biofilms is a reversible mechanism. The molecules of a specific pollutant can be desorbed back into the water column when specific conditions have changed. Furthermore, those molecules could be biodegraded by the microorganisms living inside that biofilm.Thus, the pollutant is not going to remain detectable inside that biofilm sample permanently, but only for a limited time. This is due to the memory effect.The aim of this work is to retrieve the most relevant data on this subject and build from scratch a simplified model. This will help to understand how microbial biofilms can influence the distribution of PAHs and PCBs in water streams.Absorption, desorption and biodegradation are the three main mechanisms considered for the calculations. This information will surely stimulate further research on this topic. Phenanthrene and pyrene were chosen as reference compounds for PAHs and Kaneclor 300, Aroclor 1260 and other tri-and tetra-chlorinated byphenils were chosen as reference for PCBs.