Automobile batteries are made of toxic materials and they're recycled to protect the environment. Exide, a company in Vernon, melts down 25,000 a day and creates lead ingots for sale. But for years, neighbors insist, the plant has emitted both lead and arsenic, with devastating health effects from Boyle heights to Hancock Park. Earlier this year, a judge refused efforts by the State Department of Toxic Substances Control to shut Exide down. Now, the Southern California Air Quality Management District is holding public hearings. The first was on Saturday.