The Safe Drinking Water Act (SDWA) as amended in 1986 requires the U.S. Environmental Protection Agency (USEPA) to regulate sulfate. USEPA proposed a maximum contaminant level (MCL) July 25, 1990, for sulfate at 400 mg/L or 500 mg/L in the Phase V proposal. The agency decided to reconsider the regulatory approach for sulfate when Phase V was promulgated July 17, 1992. Includes 6 references, tables.