| Clue | Source | Date |
|---|---|---|
| Concern for an asthmatic | Universal | 27 Feb 2025 |
| Measure of environmental pollutants affected by wind, temperature and humans | USA Today | 02 Jul 2024 |
| What fuel economy standards might address | New York Times | 10 Sep 2021 |
| U.S. environmental measurement that's been getting worse since 2016 | The New Yorker | 30 Mar 2020 |
| EPA measurement | ||
| *Asthmatic's concern | ||
| Pollution rating |