PCBs have low water solubility, so they adhere tightly to soil and cannot be easily accessed by bacteria. Especially, if the contaminations site has been exposed to PCBs for long period, PCBs can be integrated into soil or sediment matrices, then further decrease their bioavailability. Some surfactants can help solubilize but cannot increase the rate of PCBs degrading. However, if PCBs are linked to surfactants tightly too, then this process cannot promote the absorption of PCBs and even lower it. Also, many surfactants have been proven to be toxic to cells and the high cost of surfactants is another issues.