15A NCAC 02D .0408 LEAD The ambient air quality standard for lead and its compounds, measured as elemental lead by a reference method based on Appendix G of 40 CFR Part 50 or by an equivalent method established under 40 CFR Part 53, is 0.15 micrograms per cubic meter. The standard is met when the maximum arithmetic three month mean concentration for a three year period, as determined in accordance with Appendix R of 40 CFR Part 50, is less than or equal to 0.15 micrograms per cubic meter. History Note: Authority G.S. 143-215.3(a)(1); 143-215.107(a)(3); Eff. June 1, 1980; Amended Eff. January 1, 2010; July 1, 1984.