In years past automotive brake pads were made with Asbestos. This material, Asbestos, worked very well. The Asbestos material made little no no noise at all and had no wear affect on the brake rotors. Brake pads made today are not made with Asbestos. The EPA or Governmental regulations no longer allow it. "Asbestos is made up of microscopic bundles of fibers that may become airborne when asbestos- containing materials are damaged or disturbed." ( source: http://www.epa.gov/asbestos/ ) EPA maintains a listing of the laws and regulations applicable to asbestos. There are still some brake pads out there that contain Asbestos but it is a smaller amount as compared to the pads of the past.
Brake pads made today are not as giving as the Asbestos brake pads were. The pads of today cause noise when used on old style rotors and so the rotor manufacturers make the rotors out of a different material. This reduces noise, but at a cost. The rotors also wear along with the pads. This means you are looking at replacing the rotors virtually every time you do a brake job as the rotors generally are worn past safety specifications provided by the manufacturer.