Pollution in whatever form has negative impacts on the environment and the plants that reside in it. Pollution has many sources, from direct discharge of waste oil into waterways to air pollution from automobile exhaust. Some effects are short term and easily mitigated. Other effects are long term, with pollutants persisting in the environment or accumulating in plant tissues. Photosynthesis is an essential process within the ecosystem. Using sunlight, carbon dioxide and water, plants manufacture food and energy in a chemical process which occurs in plant leaves.