Petroleum spills and other sources of hydrocarbons contamination represent risks for society. Regardless of whether oil is stranded on a shoreline, spilled from a pipeline, or leaked from underground storage tanks, the same physical and chemical properties characterize exposure level of contaminants. Many microorganisms have evolved the ability to feed on naturally occurring petroleum hydrocarbons, which they use as sources of carbon and energy to make new microbial cells. Bacterial population indigenous to marine ecosystems can attack most of the tens and thousands of chemical compounds that make up crude oil. Different bacterial species rather than any single species act together to break hydrocarbons into carbon dioxide, water, and inactive residues. Even toxic oil residues, including highly toxic hydrocarbon polycyclic aromatic hydrocarbons (PAH), can be detoxified. Microorganisms do not accumulate hydrocarbons as they consume and degrade them, so they are not conduit for transferring hydrocarbons into the food web. In fact, microorganisms grown on hydrocarbons can be a potential source of protein for animals and human food. In this study, the purpose is to show factors affecting persistence and environmental risk.