Forms: coal, oil, natural gas d. d. tar sands, oil shales. Forms from organic material which escaped complete decomposition after burial. Tidal raising and falling tides; bay of. The presence of chemicals in high enough concentrations to harm organisms, materials and change climate. When 50% of all oil on earth has been extracted and used. Urban air pollution: greenhouse gas emissions, global economic and political instability. Nearly 90 percent of the world"s energy needs are derived from non-renewable fossil fuels. Significant amount from fossil fuel burnings: oxidation to form sulfuric acid. Damage to plants and to lungs of humans and animals. Impact: nose, eye, and throat irritation, corrosion, harms plants. 10% from human-induced incomplete burning of organic compounds. Extremely toxic to humans and animals even at very low concentrations. Types of smog: sulfurous smog = london smog e. g. fog, photochemical smog: related to autos. Products used in dry cleaning, degreasing detergent, graphic arts, adhesive production.