anchor: The concentration of the metals Al, As, Cr, Co, Cu, Fe, Pb, Ni, and Zn, expressed as total metal, should not exceed 1 mg/L each, and Cd, Hg, and Ag, expressed as total metal, should not exceed 100 ng/L each.
positive: Different metals have different levels that are allowed within the water.
negative: There are no maximum levels for metals in the water.