Environmental pollution is contamination of air, water and land from man-made waste. Pollution leads to depletion of the ozone layer, global warming and climate change. Air pollution is the release of chemicals and particles into the atmosphere. Water pollution includes surface runoff, leakage into groundwater, liquid spills, wastewater discharge and littering. If toxins are spilled on the ground or if an underground storage tank leaks, soil can become contaminated. Well known contaminants include herbicides and pesticides. Toxic waste is waste material, often in chemical form, which pollutes the natural environment and contaminates groundwater.