Timeline of Lead (Pb) National Ambient Air Quality Standards (NAAQS)
| Final Rule/Decision | Primary/Secondary | Indicator1 | Averaging Time | Level2 | Form |
|---|---|---|---|---|---|
| 1978 43 FR 46246 Oct 5, 1978 |
Primary and Secondary | Pb-TSP | Calendar Quarter | 1.5 µg/m3 | Not to be exceeded |
| 1991 | Agency released multimedia "Strategy for Reducing Lead Exposures" | ||||
| 2008 73 FR 66964 Nov 12, 2008 |
Primary and Secondary | Pb-TSP | 3-month period | 0.15 µg/m3 | Not to be exceeded |
| 2016 81 FR 71906 Oct 18, 2016 |
Primary and secondary standards retained, without revision. | ||||
1. Pb-TSP = Lead in total suspended particles
2. Units of measure are micrograms per cubic meter of air (µg/m3).