Sulfur is a chemical element that is a crystalline solid at room temperature and has a characteristic bright yellow color. It is the fifth most abundant element by mass on Earth and the tenth most abundant element in the universe. On Earth it usually occurs in compounds with oxygen and other elements as sulfide and sulfate minerals. It is obtained mainly as a byproduct of oil production.
Sulfur is an essential element for all life and is the eighth most abundant element in the human body by weight. It has been used in medicines since ancient times and today is found in numerous types of pharmaceuticals. It is one of the most extensively produced inorganic industrial chemicals, and its largest commercial application is the production of sulfuric acid, which is used in numerous chemical processes. Among the many other types of products that utilize sulfur are fertilizers, plastics, explosives, fungicides and pesticides.
Sulfur compounds are a major source of pollution. Most notably, the burning of coal and petroleum for electric power generation and in transportation vehicles produces sulfur dioxide, which reacts with atmospheric water and oxygen to produce sulfuric acid and sulfurous acid. These acids are components of acid rain, which can reduce the pH of soil and water bodies, can harm the health of humans and other organisms, and can damage painted and stone surfaces, including on buildings and statues.