Original sentence: Bioremediation: use of biological agents to remove oil.Containment Boom (except for gasoline where confinement can cause dangerous levels of fume buildup ).Detergent:  This is never advised  as it makes the oil settle to the bottom and is not a clean up method.It is difficult to clean up oils denser than water as they settle to the bottom;  PCBs are an example of such a pollutant.Sometimes it is better to do nothing and let the oil evaporate or break down on its own than make matters worse by attempting to clean up
Edited sentence: Also it is very difficult to clean up oils denser than water as they settle to the bottom.Bioremediation: The bioremediation of oil spills is a very innovative approach, the advantage clearly being the sustainable impact to the environment.Burning: It can be done only when it is not windy, the oil has not dispersed and there is a calm sea.Containment Boom (except for Gasoline where confinement can cause dangerous levels of fume buildup).Detergent:  This is never advised.It just makes the oil settle to the bottom and is not a clean up method.PCBs are an example of such a pollutant.Skimming: It can't be done if there is a rough sea.Sometimes  it is better to do nothing and let the oil evaporate or break down on its own than make matters worse by attempting to clean up