The world's most polluted cities, ranked

478 of 2,624 measured cities in 86 countries breathed air above the WHO 24-hour guideline of 15 µg/m³ over the last 30 days. The worst was Miryang, South Korea, at 307.9.

#717 Nakhon Nayok 9.6 µg/m³, more polluted than 72% of 2,624
← Miryang 307.9 µg/m³ 300 µg/m³15 WHO 24-hour guideline
Every ranked city, one column each, worst on the left and cleanest on the right; height is PM2.5 in µg/m³. Point at it to read a city; tap to open it.
  1. 1MiryangGyeongsangnam-do, South Korea 10+
  2. 2HwasunJeollanam-do, South Korea 10+
  3. 3NangenJeollabuk-do, South Korea 10+
  4. 4SeosanChungcheongnam-do, South Korea 10+
  5. 5GaigeturiJeju-do, South Korea 10+
  6. 6Hwaseong-siGyeonggi-do, South Korea 10+
  7. 7Taesal-liChungcheongnam-do, South Korea 10+
  8. 8KosongGangwon-do, South Korea 10+
  9. 9SeogwipoJeju-do, South Korea 10+
  10. 10AnseongGyeonggi-do, South Korea 10+
  11. 11SinhyeonGyeongsangnam-do, South Korea 10+
  12. 12NonsanChungcheongnam-do, South Korea 10+
  13. 13ChangsuJeollabuk-do, South Korea 10+
  14. 14MokpoJeollanam-do, South Korea 10+
  15. 15KimjeJeollabuk-do, South Korea 10+
  16. 16JeongeupJeollabuk-do, South Korea 10+
  17. 17HadongGyeongsangnam-do, South Korea 10+
  18. 18Yangp'yŏngGyeonggi-do, South Korea 10+
  19. 19CheorwonGangwon-do, South Korea 10+
  20. 20KunwiGyeongsangbuk-do, South Korea 10+
  21. 21GeojeGyeongsangnam-do, South Korea 10+
  22. 22ChinjuGyeongsangnam-do, South Korea 10+
  23. 23YesanChungcheongnam-do, South Korea 10+
  24. 24PubalGyeonggi-do, South Korea 10+
  25. 25BuanJeollabuk-do, South Korea 10+
  26. 26YeojuGyeonggi-do, South Korea 10+
  27. 27YŏnmuChungcheongnam-do, South Korea 10+
  28. 28NamsaJeollabuk-do, South Korea 10+
  29. 29YangsanGyeongsangnam-do, South Korea 10+
  30. 30BuyeoChungcheongnam-do, South Korea 10+
  31. 30HwawŏnDaegu, South Korea 10+
  32. 32GunsanJeollabuk-do, South Korea 10+
  33. 33TangjinChungcheongnam-do, South Korea 10+
  34. 34GangneungGangwon-do, South Korea 10
  35. 35Cheongju-siNorth Chungcheong, South Korea 10
  36. 36YeonggwangJeollanam-do, South Korea 10
  37. 37YecheonGyeongsangbuk-do, South Korea 10
  38. 38JungpyongNorth Chungcheong, South Korea 10
  39. 39Ganghwa-gunIncheon, South Korea 10
  40. 40KoesanNorth Chungcheong, South Korea 10
  41. 41GoseongGyeongsangnam-do, South Korea 10
  42. 42YeongdongNorth Chungcheong, South Korea 10
  43. 42YangjuGyeonggi-do, South Korea 10
  44. 42BoryeongChungcheongnam-do, South Korea 10
  45. 45JangheungJeollanam-do, South Korea 10
  46. 46Jeju CityJeju-do, South Korea 10
  47. 47Koch'angJeollabuk-do, South Korea 10
  48. 48Icheon-siGyeonggi-do, South Korea 10
  49. 49MuanJeollanam-do, South Korea 9
  50. 50HongseongChungcheongnam-do, South Korea 9
All 2,624 cities
Low risk1–3
Moderate risk4–6
High risk7–10
Very high risk10+

Canada's AQHI+ for PM2.5 (1 point per 10 µg/m³), which is defined on hourly values. Show values as: µg/m³ · US AQI · India AQI · China AQI · European AQI · UK DAQI · Canada AQHI+. About the scales

Who led, day by day

Hwasun2 days #12026-09-02: 424.0 µg/m³2026-09-03: 13.4 µg/m³2026-09-04: 8.0 µg/m³2026-09-05: 422.0 µg/m³, #52026-09-06: 1,260.0 µg/m³, #12026-09-07: 12.2 µg/m³2026-09-08: 11.8 µg/m³2026-09-09: 9.9 µg/m³2026-09-10: 839.0 µg/m³, #42026-09-11: 426.0 µg/m³2026-09-12: 843.0 µg/m³, #22026-09-13: 844.0 µg/m³, #12026-09-14: 845.0 µg/m³, #82026-09-15: 433.0 µg/m³2026-09-16: 15.4 µg/m³2026-09-17: 423.0 µg/m³2026-09-18: 424.0 µg/m³2026-09-19: 425.0 µg/m³, #32026-09-20: 425.0 µg/m³, #32026-09-21: 428.0 µg/m³2026-09-22: 12.6 µg/m³2026-09-23: 12.1 µg/m³2026-09-24: 10.4 µg/m³2026-09-25: 17.3 µg/m³2026-09-26: 5.8 µg/m³2026-09-27: 8.1 µg/m³2026-09-28: 10.8 µg/m³2026-09-29: 10.9 µg/m³2026-09-30: 10.0 µg/m³2026-10-01: 8.3 µg/m³Miryang2 days #12026-09-02: 1,260.0 µg/m³, #32026-09-03: 15.8 µg/m³2026-09-04: 7.3 µg/m³2026-09-05: 5.4 µg/m³2026-09-06: 10.3 µg/m³2026-09-07: 12.5 µg/m³2026-09-08: 7.1 µg/m³2026-09-09: 840.0 µg/m³, #72026-09-10: 423.0 µg/m³2026-09-11: 839.0 µg/m³2026-09-12: 425.0 µg/m³, #52026-09-15: 14.4 µg/m³2026-09-16: 842.0 µg/m³2026-09-17: 5.8 µg/m³2026-09-18: 1,260.0 µg/m³, #12026-09-19: 842.0 µg/m³, #22026-09-20: 842.0 µg/m³, #12026-09-21: 844.0 µg/m³, #72026-09-22: 10.6 µg/m³2026-09-23: 8.0 µg/m³2026-09-24: 15.3 µg/m³2026-09-25: 19.6 µg/m³2026-09-26: 10.2 µg/m³2026-09-27: 11.0 µg/m³2026-09-28: 15.9 µg/m³2026-09-29: 14.0 µg/m³2026-09-30: 9.8 µg/m³2026-10-01: 11.4 µg/m³Gurugram2 days #12026-09-02: 48.7 µg/m³2026-09-03: 46.3 µg/m³2026-09-04: 30.4 µg/m³2026-09-05: 28.9 µg/m³2026-09-06: 33.2 µg/m³2026-09-07: 45.1 µg/m³2026-09-08: 28.8 µg/m³2026-09-09: 52.3 µg/m³2026-09-10: 82.9 µg/m³2026-09-11: 66.4 µg/m³2026-09-12: 33.5 µg/m³2026-09-13: 24.3 µg/m³2026-09-14: 38.2 µg/m³2026-09-15: 44.2 µg/m³2026-09-16: 31.0 µg/m³2026-09-17: 33.4 µg/m³2026-09-18: 34.3 µg/m³2026-09-19: 111.0 µg/m³, #102026-09-20: 122.9 µg/m³, #92026-09-21: 160.5 µg/m³2026-09-22: 165.1 µg/m³, #42026-09-23: 170.0 µg/m³, #12026-09-24: 112.2 µg/m³, #22026-09-25: 47.2 µg/m³2026-09-26: 57.0 µg/m³2026-09-27: 60.9 µg/m³2026-09-28: 104.0 µg/m³, #12026-09-29: 20.5 µg/m³Kinshasa2 days #12026-09-02: 70.1 µg/m³2026-09-03: 43.2 µg/m³2026-09-04: 73.1 µg/m³2026-09-05: 51.9 µg/m³2026-09-06: 78.5 µg/m³2026-09-07: 111.2 µg/m³2026-09-08: 138.0 µg/m³2026-09-09: 58.3 µg/m³2026-09-10: 70.7 µg/m³2026-09-11: 83.0 µg/m³2026-09-12: 70.9 µg/m³2026-09-14: 86.5 µg/m³2026-09-15: 102.1 µg/m³2026-09-16: 51.1 µg/m³2026-09-17: 56.0 µg/m³2026-09-18: 72.4 µg/m³2026-09-19: 71.9 µg/m³2026-09-20: 73.4 µg/m³2026-09-21: 71.2 µg/m³2026-09-23: 113.0 µg/m³, #32026-09-24: 151.0 µg/m³, #12026-09-25: 114.0 µg/m³, #12026-09-26: 65.6 µg/m³2026-09-27: 50.1 µg/m³2026-09-28: 58.2 µg/m³2026-09-30: 75.5 µg/m³, #42026-10-01: 49.9 µg/m³, #10Gujranwala2 days #12026-09-02: 48.3 µg/m³2026-09-03: 50.9 µg/m³2026-09-04: 45.9 µg/m³2026-09-05: 63.5 µg/m³2026-09-06: 51.0 µg/m³2026-09-07: 69.1 µg/m³2026-09-08: 80.0 µg/m³2026-09-09: 65.9 µg/m³2026-09-10: 49.4 µg/m³2026-09-11: 58.0 µg/m³2026-09-12: 59.6 µg/m³2026-09-13: 77.4 µg/m³, #72026-09-14: 46.7 µg/m³2026-09-15: 45.1 µg/m³2026-09-16: 55.2 µg/m³2026-09-17: 34.1 µg/m³2026-09-18: 46.2 µg/m³2026-09-19: 89.2 µg/m³2026-09-20: 87.6 µg/m³2026-09-21: 130.0 µg/m³2026-09-22: 108.5 µg/m³, #62026-09-23: 104.0 µg/m³, #42026-09-24: 96.4 µg/m³, #52026-09-25: 83.0 µg/m³, #62026-09-26: 67.8 µg/m³, #102026-09-27: 105.5 µg/m³, #12026-09-28: 53.9 µg/m³2026-09-29: 52.5 µg/m³2026-09-30: 81.0 µg/m³, #32026-10-01: 104.0 µg/m³, #1Yesan1 day #12026-09-02: 1,270.0 µg/m³, #12026-09-03: 21.0 µg/m³2026-09-04: 7.9 µg/m³2026-09-05: 7.7 µg/m³2026-09-06: 6.2 µg/m³2026-09-07: 8.9 µg/m³2026-09-08: 16.4 µg/m³2026-09-09: 840.0 µg/m³, #62026-09-10: 7.9 µg/m³2026-09-11: 11.0 µg/m³2026-09-12: 22.2 µg/m³2026-09-13: 26.0 µg/m³2026-09-14: 21.9 µg/m³2026-09-15: 11.3 µg/m³2026-09-16: 13.3 µg/m³2026-09-17: 7.6 µg/m³2026-09-18: 840.0 µg/m³, #62026-09-19: 9.9 µg/m³2026-09-20: 14.0 µg/m³2026-09-21: 17.9 µg/m³2026-09-22: 17.3 µg/m³2026-09-23: 19.3 µg/m³2026-09-24: 19.6 µg/m³2026-09-25: 20.5 µg/m³2026-09-26: 10.7 µg/m³2026-09-27: 13.3 µg/m³2026-09-28: 17.0 µg/m³2026-09-29: 18.6 µg/m³2026-09-30: 17.2 µg/m³2026-10-01: 5.8 µg/m³Gaigeturi1 day #12026-09-02: 1,260.0 µg/m³, #52026-09-03: 1,260.0 µg/m³, #12026-09-04: 632.0 µg/m³, #62026-09-05: 5.5 µg/m³2026-09-06: 8.5 µg/m³2026-09-07: 12.3 µg/m³2026-09-08: 9.8 µg/m³2026-09-09: 425.3 µg/m³2026-09-10: 5.7 µg/m³2026-09-11: 215.0 µg/m³2026-09-12: 7.8 µg/m³2026-09-13: 6.6 µg/m³2026-09-14: 1,260.0 µg/m³, #22026-09-15: 8.6 µg/m³2026-09-16: 9.5 µg/m³2026-09-17: 628.3 µg/m³2026-09-18: 5.7 µg/m³2026-09-19: 8.2 µg/m³2026-09-20: 6.8 µg/m³2026-09-21: 11.7 µg/m³2026-09-22: 8.4 µg/m³2026-09-23: 6.3 µg/m³2026-09-24: 9.3 µg/m³2026-09-25: 9.7 µg/m³2026-09-26: 5.5 µg/m³2026-09-27: 3.7 µg/m³2026-09-28: 6.7 µg/m³2026-09-29: 5.6 µg/m³2026-09-30: 7.3 µg/m³2026-10-01: 6.4 µg/m³Yecheon1 day #12026-09-02: 421.0 µg/m³2026-09-03: 6.3 µg/m³2026-09-04: 1,260.0 µg/m³, #12026-09-05: 5.0 µg/m³2026-09-06: 7.6 µg/m³2026-09-07: 10.0 µg/m³2026-09-08: 10.3 µg/m³2026-09-09: 5.7 µg/m³2026-09-10: 5.8 µg/m³2026-09-11: 7.4 µg/m³2026-09-12: 9.0 µg/m³2026-09-13: 11.3 µg/m³2026-09-15: 14.5 µg/m³2026-09-16: 843.0 µg/m³2026-09-17: 5.9 µg/m³2026-09-18: 8.4 µg/m³2026-09-19: 8.1 µg/m³2026-09-20: 7.9 µg/m³2026-09-21: 12.0 µg/m³2026-09-22: 9.8 µg/m³2026-09-23: 8.3 µg/m³2026-09-24: 15.3 µg/m³2026-09-25: 17.8 µg/m³2026-09-26: 9.2 µg/m³2026-09-27: 8.5 µg/m³2026-09-28: 12.2 µg/m³2026-09-29: 10.0 µg/m³2026-09-30: 10.9 µg/m³2026-10-01: 8.4 µg/m³Cheorwon1 day #12026-09-02: 427.0 µg/m³2026-09-03: 13.0 µg/m³2026-09-04: 10.4 µg/m³2026-09-05: 1,260.0 µg/m³, #12026-09-06: 5.6 µg/m³2026-09-07: 1,050.5 µg/m³, #32026-09-08: 12.5 µg/m³2026-09-09: 217.2 µg/m³2026-09-10: 8.4 µg/m³2026-09-11: 11.2 µg/m³2026-09-12: 16.8 µg/m³2026-09-13: 17.5 µg/m³2026-09-14: 19.3 µg/m³2026-09-15: 13.5 µg/m³2026-09-16: 12.4 µg/m³2026-09-17: 11.4 µg/m³2026-09-18: 218.6 µg/m³2026-09-19: 12.4 µg/m³2026-09-20: 13.7 µg/m³2026-09-21: 224.2 µg/m³2026-09-22: 20.0 µg/m³2026-09-23: 18.5 µg/m³2026-09-24: 19.9 µg/m³2026-09-25: 12.5 µg/m³2026-09-26: 7.7 µg/m³2026-09-27: 15.8 µg/m³2026-09-28: 16.9 µg/m³2026-09-29: 12.5 µg/m³2026-09-30: 15.5 µg/m³2026-10-01: 9.5 µg/m³T’aebaek1 day #12026-09-02: 419.0 µg/m³2026-09-03: 3.7 µg/m³2026-09-04: 3.3 µg/m³2026-09-05: 2.3 µg/m³2026-09-06: 4.1 µg/m³2026-09-07: 1,260.0 µg/m³, #12026-09-08: 4.4 µg/m³2026-09-09: 3.1 µg/m³2026-09-10: 2.7 µg/m³2026-09-11: 3.0 µg/m³2026-09-12: 3.5 µg/m³2026-09-13: 8.5 µg/m³2026-09-14: 11.1 µg/m³2026-09-15: 9.0 µg/m³2026-09-16: 7.3 µg/m³2026-09-17: 3.1 µg/m³2026-09-18: 3.5 µg/m³2026-09-19: 5.0 µg/m³2026-09-20: 6.3 µg/m³2026-09-21: 6.9 µg/m³2026-09-22: 5.4 µg/m³2026-09-23: 4.6 µg/m³2026-09-24: 10.0 µg/m³2026-09-25: 9.3 µg/m³2026-09-26: 4.4 µg/m³2026-09-27: 4.4 µg/m³2026-09-28: 8.6 µg/m³2026-09-29: 4.8 µg/m³2026-09-30: 7.6 µg/m³2026-10-01: 9.0 µg/m³Sep 2Oct 1
Every city that was the world's most polluted on at least one of the last 30 days. Filled square: #1 that day; ring: in the top 10; dot: measured but lower. Each city's own local day.

The world's air, last 30 days

2026-09-02: 128 of 2651 cities very high risk (5%)2026-09-02: 5 of 2651 cities high risk (0%)2026-09-02: 88 of 2651 cities moderate risk (3%)2026-09-02: 2430 of 2651 cities low risk (92%)Sep 22026-09-03: 24 of 2651 cities very high risk (1%)2026-09-03: 8 of 2651 cities high risk (0%)2026-09-03: 97 of 2651 cities moderate risk (4%)2026-09-03: 2522 of 2651 cities low risk (95%)2026-09-04: 17 of 2653 cities very high risk (1%)2026-09-04: 13 of 2653 cities high risk (0%)2026-09-04: 85 of 2653 cities moderate risk (3%)2026-09-04: 2538 of 2653 cities low risk (96%)2026-09-05: 14 of 2663 cities very high risk (1%)2026-09-05: 11 of 2663 cities high risk (0%)2026-09-05: 77 of 2663 cities moderate risk (3%)2026-09-05: 2561 of 2663 cities low risk (96%)2026-09-06: 14 of 2455 cities very high risk (1%)2026-09-06: 11 of 2455 cities high risk (0%)2026-09-06: 87 of 2455 cities moderate risk (4%)2026-09-06: 2343 of 2455 cities low risk (95%)2026-09-07: 25 of 2637 cities very high risk (1%)2026-09-07: 14 of 2637 cities high risk (1%)2026-09-07: 96 of 2637 cities moderate risk (4%)2026-09-07: 2502 of 2637 cities low risk (95%)Sep 72026-09-08: 15 of 2604 cities very high risk (1%)2026-09-08: 14 of 2604 cities high risk (1%)2026-09-08: 101 of 2604 cities moderate risk (4%)2026-09-08: 2474 of 2604 cities low risk (95%)2026-09-09: 34 of 2631 cities very high risk (1%)2026-09-09: 17 of 2631 cities high risk (1%)2026-09-09: 106 of 2631 cities moderate risk (4%)2026-09-09: 2474 of 2631 cities low risk (94%)2026-09-10: 23 of 2585 cities very high risk (1%)2026-09-10: 19 of 2585 cities high risk (1%)2026-09-10: 114 of 2585 cities moderate risk (4%)2026-09-10: 2429 of 2585 cities low risk (94%)2026-09-11: 32 of 2411 cities very high risk (1%)2026-09-11: 9 of 2411 cities high risk (0%)2026-09-11: 100 of 2411 cities moderate risk (4%)2026-09-11: 2270 of 2411 cities low risk (94%)2026-09-12: 7 of 2461 cities very high risk (0%)2026-09-12: 9 of 2461 cities high risk (0%)2026-09-12: 96 of 2461 cities moderate risk (4%)2026-09-12: 2349 of 2461 cities low risk (95%)2026-09-13: 6 of 2301 cities very high risk (0%)2026-09-13: 10 of 2301 cities high risk (0%)2026-09-13: 88 of 2301 cities moderate risk (4%)2026-09-13: 2197 of 2301 cities low risk (95%)2026-09-14: 18 of 2459 cities very high risk (1%)2026-09-14: 10 of 2459 cities high risk (0%)2026-09-14: 88 of 2459 cities moderate risk (4%)2026-09-14: 2343 of 2459 cities low risk (95%)Sep 142026-09-15: 25 of 2547 cities very high risk (1%)2026-09-15: 8 of 2547 cities high risk (0%)2026-09-15: 107 of 2547 cities moderate risk (4%)2026-09-15: 2407 of 2547 cities low risk (95%)2026-09-16: 36 of 2618 cities very high risk (1%)2026-09-16: 16 of 2618 cities high risk (1%)2026-09-16: 120 of 2618 cities moderate risk (5%)2026-09-16: 2446 of 2618 cities low risk (93%)2026-09-17: 23 of 2610 cities very high risk (1%)2026-09-17: 10 of 2610 cities high risk (0%)2026-09-17: 118 of 2610 cities moderate risk (5%)2026-09-17: 2459 of 2610 cities low risk (94%)2026-09-18: 23 of 2681 cities very high risk (1%)2026-09-18: 7 of 2681 cities high risk (0%)2026-09-18: 93 of 2681 cities moderate risk (3%)2026-09-18: 2558 of 2681 cities low risk (95%)2026-09-19: 10 of 2685 cities very high risk (0%)2026-09-19: 24 of 2685 cities high risk (1%)2026-09-19: 105 of 2685 cities moderate risk (4%)2026-09-19: 2546 of 2685 cities low risk (95%)2026-09-20: 11 of 2432 cities very high risk (0%)2026-09-20: 27 of 2432 cities high risk (1%)2026-09-20: 95 of 2432 cities moderate risk (4%)2026-09-20: 2299 of 2432 cities low risk (95%)2026-09-21: 31 of 2553 cities very high risk (1%)2026-09-21: 28 of 2553 cities high risk (1%)2026-09-21: 113 of 2553 cities moderate risk (4%)2026-09-21: 2381 of 2553 cities low risk (93%)Sep 212026-09-22: 7 of 2619 cities very high risk (0%)2026-09-22: 33 of 2619 cities high risk (1%)2026-09-22: 117 of 2619 cities moderate risk (4%)2026-09-22: 2462 of 2619 cities low risk (94%)2026-09-23: 6 of 2685 cities very high risk (0%)2026-09-23: 38 of 2685 cities high risk (1%)2026-09-23: 100 of 2685 cities moderate risk (4%)2026-09-23: 2541 of 2685 cities low risk (95%)2026-09-24: 2 of 2700 cities very high risk (0%)2026-09-24: 33 of 2700 cities high risk (1%)2026-09-24: 105 of 2700 cities moderate risk (4%)2026-09-24: 2560 of 2700 cities low risk (95%)2026-09-25: 1 of 2658 cities very high risk (0%)2026-09-25: 19 of 2658 cities high risk (1%)2026-09-25: 85 of 2658 cities moderate risk (3%)2026-09-25: 2553 of 2658 cities low risk (96%)2026-09-26: 20 of 2665 cities high risk (1%)2026-09-26: 73 of 2665 cities moderate risk (3%)2026-09-26: 2572 of 2665 cities low risk (97%)2026-09-27: 2 of 2564 cities very high risk (0%)2026-09-27: 12 of 2564 cities high risk (0%)2026-09-27: 70 of 2564 cities moderate risk (3%)2026-09-27: 2480 of 2564 cities low risk (97%)2026-09-28: 1 of 2634 cities very high risk (0%)2026-09-28: 10 of 2634 cities high risk (0%)2026-09-28: 106 of 2634 cities moderate risk (4%)2026-09-28: 2517 of 2634 cities low risk (96%)Sep 282026-09-29: 1 of 2679 cities very high risk (0%)2026-09-29: 10 of 2679 cities high risk (0%)2026-09-29: 132 of 2679 cities moderate risk (5%)2026-09-29: 2536 of 2679 cities low risk (95%)2026-09-30: 11 of 2442 cities high risk (0%)2026-09-30: 33 of 2442 cities moderate risk (1%)2026-09-30: 2398 of 2442 cities low risk (98%)2026-10-01: 1 of 1541 cities very high risk (0%)2026-10-01: 3 of 1541 cities high risk (0%)2026-10-01: 32 of 1541 cities moderate risk (2%)2026-10-01: 1505 of 1541 cities low risk (98%)Oct 1
Each day's ranked cities split by band, worst at the top: a taller red and purple share means a worse day for more of the world, not just one city.

Climbing fastest

Movement shows once the board is a day old.

Cleanest air

Cities with reference monitors only.

What's missing

We rank only cities whose monitor data we're allowed to reuse. The government monitoring networks of China and Turkey publish no terms that allow this, so we leave them out: most cities there are missing here, not clean. The few of their cities that appear are measured by community low-cost sensors, tagged as such. Why.

Use this board

SmogRank, most polluted cities, PM2.5, last 30 days to 2 Oct 2026, 05:00 UTC, smogrank.com/?w=30d.

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You're welcome to reuse a single chart, image or figure with this citation and a link. Terms.

Updated 2026-10-02 05:07 UTC. Values are PM2.5 (fine particles), the median of each city's monitors, as the Canada AQHI+ PM2.5 sub-index.