(1) Standard for lead. The three-month rolling average concentration of lead and its compounds in the ambient air must not exceed 0.15 μg/m3.

(2) Measurement method. The levels of lead in the ambient air must be measured by:

(a) A FRM based on 40 C.F.R. Part 50, Appendix G and designated according to 40 C.F.R. Part 53; or

(b) A FEM designated according to 40 C.F.R. Part 53.

(3) Interpretation method. The interpretation method found in 40 C.F.R. Part 50, Appendix R must be used.