Very small amounts of carbon disulfide occur in coal tar and in crude petroleum. Carbon disulfide is a natural product of anaerobic biodegradation and is released to the atmosphere from oceans and landmasses as well as geothermal sources. The ocean appears to be a major source of carbon disulfide. Coastal and marshland areas of high biological activity are also major sources. Carbon disulfide reacts with the hydroxyl radical () in the atmosphere, with the effective rate constant depending on O2 concentration and pressure. Based on the literature rate constant the estimated lifetime of carbon disulfide due to its reaction with the hydroxyl radical is about 12 days. Carbon disulfide is released naturally into the atmosphere through various sources, including the metabolic processes of plants, the decaying of animal feces, from volcanoes, and also as a byproduct of oil and gas processing.