Other possibilities include permanganates, chromates, and some oxides. Chromates and molybdates produce the same reaction. Hexavalent chromium compounds (including chromium trioxide, chromic acids, chromates, chlorochromates) are toxic and carcinogenic. It is a vaguely described chemical, despite many well-defined chromates and dichromates being known. Chemical pre-treatments involve the use of phosphates or chromates in submersion or spray application. The most common mixed chromates include hexavalent iridescent, trivalent or black trivalent chromate. Because of environmental and health regulations on chromates, alternative coating methods are under development. Chromium salts (chromates) are also the cause of allergic reactions in some people.