Outside the usual range13 September 2026Environment
Bihar: highest city air quality index over the 7 days to 13 September 2026 was 129, below the 5-year median of 172 for the same week (−25%).
What happened
- 7-day mean to 13 September 2026
- 129
- That day alone: 92
- 5-year median, same week
- 172
- Change
- −43
- Change, per cent
- −25%
Why it matters
Daily figures mostly reflect the weather, so the observatory compares the mean of the last seven days with the same week in up to five earlier years. A breach means this week sits well outside what those years would lead you to expect, and by at least 15%. It is reported when an unusual run begins and for the latest day while it lasts, not every day.
For highest city air quality index, lower is better. This movement is therefore assessed as an improvement.
Historical context
Same week in earlier years: 2025 172, 2024 166, 2023 215, 2022 172, 2021 68. Daily values are compared as 7-day means because a single day mostly reflects weather.
The underlying data
| Period | Value | Release | Where in the document |
|---|---|---|---|
| 13 September 2026 | 92 | CPCB National Air Quality Index bulletin, 13 September 2026 (233 cities) | AQI bulletin p.1–10, Index Value column: highest of 15 city rows placed in Bihar — Saharsa, S.No 195 (p.10), Satisfactory |
| 12 September 2026 | 92 | CPCB National Air Quality Index bulletin, 12 September 2026 (245 cities) | AQI bulletin p.1–11, Index Value column: highest of 17 city rows placed in Bihar — Katihar, S.No 128 (p.7), Satisfactory |
| 11 September 2026 | 112 | CPCB National Air Quality Index bulletin, 11 September 2026 (242 cities) | AQI bulletin p.1–11, Index Value column: highest of 16 city rows placed in Bihar — Chhapra, S.No 63 (p.4), Moderate |
| 10 September 2026 | 158 | CPCB National Air Quality Index bulletin, 10 September 2026 (243 cities) | AQI bulletin p.1–11, Index Value column: highest of 19 city rows placed in Bihar — Sasaram, S.No 206 (p.11), Moderate |
| 9 September 2026 | 182 | CPCB National Air Quality Index bulletin, 9 September 2026 (252 cities) | AQI bulletin p.1–11, Index Value column: highest of 19 city rows placed in Bihar — Sasaram, S.No 213 (p.11), Moderate |
| 8 September 2026 |
Source and method
- Release
- CPCB National Air Quality Index bulletin, 13 September 2026 (233 cities)Archived fileOriginal URLFirst seen 3 Oct 2026
Cite this
According to the India Health Observatory, Bihar: highest city air quality index over the 7 days to 13 September 2026 was 129, below the 5-year median of 172 for the same week (−25%). Source: Central Pollution Control Board, Ministry of Environment, Forest and Climate Change, CPCB National Air Quality Index bulletin, 13 September 2026 (233 cities). https://indiahealthobservatory.com/signals/worst-city-aqi--bihar--2026-09-13--baseline_breach
See also Bihar and 92 AQI in context.