SmogRank / History / April 21, 2023

Most polluted cities on April 21, 2023

1,458 cities ranked by their average PM2.5 over the day; the worst was Piedras Negras, Mexico, at 353.0 µg/m³. Each city's own local calendar day.

Bad-air episodes during April 21, 2023. All episodes.

← Piedras Negras 353.0 µg/m³ 300 µg/m³15 WHO 24-hour guideline
Every city ranked for April 21, 2023, 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. 1Piedras NegrasCoahuila, Mexico
    500+23.5×
  2. 2Mae SaiChiang Rai, Thailand
    1806.4×
  3. 3Ban HouakhouaBokeo, Laos
    1776.2×
  4. 4NanNan, Thailand
    1776.1×
  5. 5LampangLampang, Thailand
    1756.0×
  6. 6Chiang RaiChiang Rai, Thailand
    1725.7×
  7. 7UttaraditUttaradit, Thailand
    1675.2×
  8. 8PhayaoPhayao, Thailand
    1665.1×
  9. 9PhichitPhichit, Thailand
    1665.1×
  10. 10Bang Khun ThianBangkok, Thailand
    1655.0×
  11. 11Chiang MaiChiang Mai, Thailand
    1655.0×
  12. 12PhraePhrae, Thailand
    1644.9×
  13. 13Kamphaeng PhetKamphaeng Phet, Thailand
    1624.8×
  14. 14Sing BuriSing Buri, Thailand
    1614.6×
  15. 15PhetchabunPhetchabun, Thailand
    1614.6×
  16. 16Kathmandulow-cost sensorsBagmati Province, Nepal
    1614.6×
  17. 17Suphan BuriSuphan Buri, Thailand
    1604.6×
  18. 18Lop BuriLopburi, Thailand
    1604.6×
  19. 19LamphunLamphun, Thailand
    1604.5×
  20. 20HanoiHanoi, Vietnam
    1604.5×
  21. 21Dhakalow-cost sensorsDhaka Division, Bangladesh
    1594.5×
  22. 22Chai NatChai Nat, Thailand
    1584.4×
  23. 23TlaquepaqueJalisco, Mexico
    1584.4×
  24. 24Nakhon SawanNakhon Sawan, Thailand
    1574.3×
  25. 25BloemfonteinFree State, South Africa
    1564.2×
  26. 26KalasinKalasin, Thailand
    1564.1×
  27. 27Bang NaBangkok, Thailand
    1554.0×
  28. 28Udon ThaniUdon Thani, Thailand
    1544.0×
  29. 29ChaiyaphumChaiyaphum, Thailand
    1533.9×
  30. 30HyderabadTelangana, India
    1533.9×
  31. 31SukhothaiSukhothai, Thailand
    1533.9×
  32. 32Mae SotTak, Thailand
    1533.9×
  33. 33LoeiLoei, Thailand
    1523.8×
  34. 34Phra Nakhon Si AyutthayaPhra Nakhon Si Ayutthaya, Thailand
    1523.8×
  35. 35Nong KhaemBangkok, Thailand
    1523.8×
  36. 36Ubon RatchathaniUbon Ratchathani, Thailand
    1513.7×
  37. 37TakTak, Thailand
    1493.7×
  38. 38Khlong Sam WaBangkok, Thailand
    1483.6×
  39. 39DelhiDelhi, India
    1483.6×
  40. 40Ban Samae DamBangkok, Thailand
    1473.6×
  41. 41Samut PrakanSamut Prakan, Thailand
    1453.6×
  42. 42Khon KaenKhon Kaen, Thailand
    1453.5×
  43. 43Nong Bua LamphuNong Bua Lamphu, Thailand
    1443.5×
  44. 44Roi EtRoi Et, Thailand
    1433.5×
  45. 44Khan Na YaoBangkok, Thailand
    1433.5×
  46. 46RatchaburiRatchaburi, Thailand
    1433.5×
  47. 47BrakpanGauteng, South Africa
    1433.5×
  48. 48BangkokBangkok, Thailand
    1413.4×
  49. 49Bueng KumBangkok, Thailand
    1403.4×
  50. 50CholulaPuebla, Mexico
    1393.4×
  51. 51Nakhon PathomNakhon Pathom, Thailand
    1393.4×
  52. 52MukdahanMukdahan, Thailand
    1373.4×
  53. 52Lak SiBangkok, Thailand
    1373.4×
  54. 54SaraburiSaraburi, Thailand
    1373.3×
  55. 55YangonYangon, Myanmar
    1353.3×
  56. 56Ban ChangRayong, Thailand
    1353.3×
  57. 57RabinalBaja Verapaz, Guatemala
    1343.3×
  58. 58Guatemala CityGuatemala, Guatemala
    1343.3×
  59. 59Nakhon RatchasimaNakhon Ratchasima, Thailand
    1343.3×
  60. 59Saphan SungBangkok, Thailand
    1343.3×
  61. 61Nong ChokBangkok, Thailand
    1333.2×
  62. 62Lat KrabangBangkok, Thailand
    1333.2×
  63. 63Phra PradaengSamut Prakan, Thailand
    1323.2×
  64. 63Bang KapiBangkok, Thailand
    1323.2×
  65. 65Mueang NonthaburiNonthaburi, Thailand
    1313.2×
  66. 66Sai MaiBangkok, Thailand
    1313.2×
  67. 67ChanthaburiChanthaburi, Thailand
    1303.2×
  68. 68Samut SakhonSamut Sakhon, Thailand
    1303.1×
  69. 69Tha BoNong Khai, Thailand
    1303.1×
  70. 70Khlong LuangPathum Thani, Thailand
    1293.1×
  71. 71Laem ChabangChon Buri, Thailand
    1273.1×
  72. 72Ban Khlong PrawetBangkok, Thailand
    1263.0×
  73. 73Ga-RankuwaNorth West, South Africa
    1253.0×
  74. 74Sakon NakhonSakon Nakhon, Thailand
    1243.0×
  75. 75BamakoBamako, Mali
    1243.0×
  76. 76Hua HinPrachuap Khiri Khan, Thailand
    1233.0×
  77. 77RayongRayong, Thailand
    1212.9×
  78. 78Ciudad Benito JuárezNuevo León, Mexico
    1202.9×
  79. 79AshgabatAshgabat, Turkmenistan
    1192.9×
  80. 80GuadalajaraJalisco, Mexico
    1192.9×
  81. 81Ban Talat BuengChon Buri, Thailand
    1192.9×
  82. 82Si Sa KetSi Sa Ket, Thailand
    1162.8×
  83. 82Buri RamBuriram, Thailand
    1162.8×
  84. 84ThembisaGauteng, South Africa
    1162.8×
  85. 85PakxanBolikhamsai, Laos
    1142.7×
  86. 86JohannesburgGauteng, South Africa
    1122.7×
  87. 87AranyaprathetSa Kaeo, Thailand
    1112.6×
  88. 88KanchanaburiKanchanaburi, Thailand
    1112.6×
  89. 89Jastrzębie ZdrójSilesia, Poland
    1082.6×
  90. 90Puerto VarasLos Lagos Region, Chile
    1072.5×
  91. 91TratTrat, Thailand
    1062.5×
  92. 92CuranilahueBiobio, Chile
    1032.4×
  93. 93Şabāḩ as SālimMubārak al Kabīr, Kuwait
    1022.4×
  94. 94PristinaPristina, Kosovo
    1022.4×
  95. 95Hacienda Santa FeJalisco, Mexico
    1022.4×
  96. 96CelayaGuanajuato, Mexico
    1022.4×
  97. 97MonterreyNuevo León, Mexico
    1002.4×
  98. 98ShenyangLiaoning, China
    982.3×
  99. 99Novi PazarCentral Serbia, Serbia
    982.3×
  100. 100BaghdadBaghdad, Iraq
    962.2×
  101. 101RacibórzSilesia, Poland
    952.2×
  102. 102SalorTashkent Region, Uzbekistan
    952.2×
  103. 103Czechowice-DziedziceSilesia, Poland
    932.1×
  104. 103RengoO'Higgins Region, Chile
    932.1×
  105. 105YalaYala, Thailand
    922.1×
  106. 105PueblaPuebla, Mexico
    922.1×
  107. 107PirotCentral Serbia, Serbia
    922.1×
  108. 108TolucaMéxico, Mexico
    912.1×
  109. 109Peshawarlow-cost sensorsKhyber Pakhtunkhwa, Pakistan
    912.0×
  110. 110ValjevoCentral Serbia, Serbia
    912.0×
  111. 111Surat ThaniSurat Thani, Thailand
    902.0×
  112. 112Jelenia GóraLower Silesia, Poland
    902.0×
  113. 113PhuketPhuket, Thailand
    902.0×
  114. 114Puerto MonttLos Lagos Region, Chile
    902.0×
  115. 115Addis AbabaAddis Ababa, Ethiopia
    892.0×
  116. 116TocopillaAntofagasta, Chile
    892.0×
  117. 117Hat YaiSongkhla, Thailand
    892.0×
  118. 117VeracruzVeracruz, Mexico
    892.0×
  119. 119ZemunCentral Serbia, Serbia
    881.9×
  120. 120Kampalalow-cost sensorsCentral Region, Uganda
    881.9×
  121. 121Santa CatarinaNuevo León, Mexico
    871.9×
  122. 122San Mateo AtencoMéxico, Mexico
    871.9×
  123. 123KhartoumKhartoum, Sudan
    871.9×
  124. 124XonacatlánMéxico, Mexico
    861.9×
  125. 124RancaguaO'Higgins Region, Chile
    861.9×
  126. 126LazarevacCentral Serbia, Serbia
    861.9×
  127. 126NacimientoBiobio, Chile
    861.9×
  128. 128TijuanaBaja California, Mexico
    851.8×
  129. 129AntofagastaAntofagasta, Chile
    841.8×
  130. 130BakuBaki, Azerbaijan
    841.8×
  131. 131VisbyGotland, Sweden
    841.8×
  132. 132TrangTrang, Thailand
    841.8×
  133. 132NarathiwatNarathiwat, Thailand
    841.8×
  134. 134KłodzkoLower Silesia, Poland
    841.8×
  135. 135KigaliKigali, Rwanda
    831.8×
  136. 136HavířovMoravian-Silesian Region, Czechia
    831.8×
  137. 137La SerenaCoquimbo Region, Chile
    821.7×
  138. 138ThabazimbiLimpopo, South Africa
    821.7×
  139. 138BohumínMoravian-Silesian Region, Czechia
    821.7×
  140. 140ObrenovacCentral Serbia, Serbia
    821.7×
  141. 140NišCentral Serbia, Serbia
    821.7×
  142. 142OsornoLos Lagos Region, Chile
    821.7×
  143. 143San Francisco TlalcilalcalpanMéxico, Mexico
    821.7×
  144. 144BelgradeCentral Serbia, Serbia
    811.7×
  145. 144SatunSatun, Thailand
    811.7×
  146. 146GarcíaNuevo León, Mexico
    811.7×
  147. 146ComptonCalifornia, United States
    811.7×
  148. 148OstravaMoravian-Silesian Region, Czechia
    811.7×
  149. 149KragujevacCentral Serbia, Serbia
    801.6×
  150. 150San Andrés TuxtlaVeracruz, Mexico
    801.6×
  151. 151Frýdek-MístekMoravian-Silesian Region, Czechia
    791.6×
  152. 152JeddahMecca Region, Saudi Arabia
    791.6×
  153. 153MorrisvilleNorth Carolina, United States
    791.6×
  154. 154SantiagoSantiago Metropolitan, Chile
    791.6×
  155. 154SaltilloCoahuila, Mexico
    791.6×
  156. 156CoronelBiobio, Chile
    781.6×
  157. 156Silao de la VictoriaGuanajuato, Mexico
    781.6×
  158. 156HueytownAlabama, United States
    781.6×
  159. 159Český TěšínMoravian-Silesian Region, Czechia
    781.6×
  160. 160TarnówLesser Poland, Poland
    781.6×
  161. 160TrnavaTrnava Region, Slovakia
    781.6×
  162. 162Nakhon Si ThammaratNakhon Si Thammarat, Thailand
    781.6×
  163. 162Bielsko-BialaSilesia, Poland
    781.6×
  164. 164CoquimboCoquimbo Region, Chile
    771.6×
  165. 165ValdiviaLos Ríos Region, Chile
    771.5×
  166. 166BorkenNorth Rhine-Westphalia, Germany
    771.5×
  167. 166AricaArica y Parinacota Region, Chile
    771.5×
  168. 168PančevoVojvodina, Serbia
    771.5×
  169. 169SremčicaCentral Serbia, Serbia
    771.5×
  170. 169DieppeNormandy, France
    771.5×
  171. 171Valašské MeziříčíZlín, Czechia
    761.5×
  172. 171ŁaskŁódź Voivodeship, Poland
    761.5×
  173. 173San CarlosÑuble, Chile
    761.5×
  174. 174ČačakCentral Serbia, Serbia
    761.5×
  175. 174WrocławLower Silesia, Poland
    761.5×
  176. 174CoatzacoalcosVeracruz, Mexico
    761.5×
  177. 177ĆuprijaCentral Serbia, Serbia
    761.5×
  178. 177KrakówLesser Poland, Poland
    761.5×
  179. 179DěčínÚstí nad Labem Region, Czechia
    751.5×
  180. 180VanderbijlparkGauteng, South Africa
    751.5×
  181. 180Novi SadVojvodina, Serbia
    751.5×
  182. 182GuangzhouGuangdong, China
    751.5×
  183. 182BelmopanCayo District, Belize
    751.5×
  184. 184HualpénBiobio, Chile
    741.4×
  185. 184CuricóMaule Region, Chile
    741.4×
  186. 186KościanGreater Poland, Poland
    741.4×
  187. 187Puente AltoSantiago Metropolitan, Chile
    741.4×
  188. 187CopiapóAtacama, Chile
    741.4×
  189. 187EdinburgTexas, United States
    741.4×
  190. 190ŠabacCentral Serbia, Serbia
    741.4×
  191. 190ChillánÑuble, Chile
    741.4×
  192. 192SmederevoCentral Serbia, Serbia
    731.4×
  193. 192Ciudad NezahualcoyotlMéxico, Mexico
    731.4×
  194. 194DattelnNorth Rhine-Westphalia, Germany
    731.4×
  195. 195KrefeldNorth Rhine-Westphalia, Germany
    731.4×
  196. 196MonsWallonia, Belgium
    721.4×
  197. 196BerounCentral Bohemia, Czechia
    721.4×
  198. 198LublinLublin, Poland
    721.4×
  199. 198Tepeji del Río de OcampoHidalgo, Mexico
    721.4×
  200. 198LotaBiobio, Chile
    721.4×

Top 200 of 1,458 shown.

Good0–50
Moderate51–100
Sensitive groups101–150
Unhealthy151–200
Very unhealthy201–300
Hazardous301+

The US EPA's Air Quality Index for PM2.5 (2024 breakpoints). Show values as: µg/m³ · US AQI · India AQI · China AQI · European AQI · UK DAQI · Canada AQHI+. About the scales

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SmogRank, most polluted cities, PM2.5, April 21, 2023, smogrank.com/history/2023-04-21 (accessed 2 Oct 2026).

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