English: Sulfur is an element which is known since ancient times. It sometimes naturally occurs in its elemental form and as such often is emitted in volcanic eruptions. Sulfur has a complex chemistry and is essential to life. On the other hand, it has some very toxic and environmentally hazardous compounds. Notable here are hydrogen sulfide, which gives rotten eggs their smell and sulfur dioxide and trioxide, which, when dissolved in water, give sulfurous acid and sulfuric acid. Those are primarily emitted by the usage of fossil fuels like oil and coal.