The RoHS is the Restriction on the use of Hazardous Substances in Electrical and Electronic Equipment.
This is an official directive by the European Union. The RoHS bans any electrial or electronic equipment which contains more than the stipulated levels of lead, cadmium, mercury, hexavalent chromium, polybrominated biphenyl (PBB) and PBDE (Polybrominated diphenyl ether) flame retardants.
http://www.rohsguide.com