The impact of an oil spill on marine life is related to the size of the spill, the type of oil, and sensitivity of the ecosystem. Oil spills kill fish, mammals, birds, and their offspring; destroy plant life; and reduce the food supply for organisms that survive. Spills also disrupt the structure and function of marine communities and ecosystems. The riskiest toxins are a class of organic compounds known as polycyclic aromatic hydrocarbons, or PAHs. Growing evidence suggests that PAHs and other toxic compounds can have adverse effects on marine species even at very low concentrations. This means chronic releases from runoff and recreational boating may inflict more damage than previously thought, and that the effects of large spills may last as long as residual oil persists in the area.