Revised PM2.5 AQI breakpoints

Posted on September 9th 2013
Share: aqicn.org/faq/2013-09-09/revised-pm25-aqi-breakpoints

For some historical reason, the AQI convertion formula used for some of the cities on the World Air Quality Index project were not using the updated 2012 EPA PM2.5 standard. (This is only relevant for cities in Asia, like Japan and Taiwan. Other continents (America, Europe and Australia) have always been using the 2012 standard.

The main change is this updated EPA standard, published on December 14th 2012, compared to the previous one (published in 1999), is to reduce (limit) the PM2.5 AQI level 50 from 15µg/m3 to 12µg/m3, and this in order to enforce more strict air quality standards.

Since September 9th 2013, all the countries are now using the same PM2.5 AQI conversion scale, which is reflected in this table:

AQI CategoryIndex ValuesPrevious Breakpoints
(µg/m3, 24-hour average)
Revised Breakpoints
(µg/m3, 24-hour average)
Good0 - 500.0 - 15.00.0 – 12.0
Moderate51 - 100>15.0 - 4012.1 – 35.4
Unhealthy for Sensitive Groups101 – 150>40 – 6535.5 – 55.4
Unhealthy151 – 200> 65 – 15055.5 – 150.4
Very Unhealthy201 – 300> 150 – 250150.5 – 250.4
Hazardous301 – 400> 250 – 350250.5 – 350.4
Hazardous401 – 500> 350 – 500350.5 – 500


On a PM2.5 particule mass scale from 0µg/m3 to 100µg/m3, here is a visual comparison for the old and new standard AQI grades:

Particule
mass
10 µg/m320 µg/m330 µg/m340 µg/m350 µg/m360 µg/m370 µg/m380 µg/m390
         
Old AQI
Standard:
0..5050..100100..150150.....
         
New AQI
Standard:
0..5050..100100..150150.....


The Ozone calculation has also been updated to taken into account the 8-hours standard: The Ozone AQI is the calculated as the maximum of the 1-hour and 8 hours AQI, where the 1 hour AQI is only valid above 100 and the 8 hours AQI below 300. The 8 hour averaging is based on the calculation described in the procedure for calculating state 8-hour ozone concentrations.

AQI CategoryIndex Values8-hours breakpoints
(ppm)
1-hour breakpoints
(ppm)
Good0 - 500 - 60-
Moderate51 - 10060 - 75-
Unhealthy for Sensitive Groups101 – 15075 – 95125 - 165
Unhealthy151 – 20095 – 115165 - 205
Very Unhealthy201 – 300115 – 375205 - 405
Hazardous301 – 500-405 - 505



Click here to see all the FAQ entries
  • Nitrogen Dioxyde (NO2) in our atmosphere
  • Ozone AQI Scale update
  • Kriging Interpolation




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    대기 품질 및 환경 오염 측정에 관하여 :

    대기 품질 지수 단계에 대하여

    AQI지수구분구간의미
    0 - 50좋음대기오염 관련 질환자군에서도 영향이 유발되지 않을 수준
    51 -100보통환자군에게 만성 노출시 경미한 영향이 유발될 수 있는 수준
    101-150민감군영향환자군 및 민감군에게 유해한 영향이 유발될 수 있는 수준
    151-200나쁨환자군 및 민감군(어린이, 노약자 등)에게 유해한 영향 유발, 일반인도 건강상 불쾌감을 경험할 수 있는 수준
    201-300매우나쁨환자군 및 민감군에게 급성 노출시 심각한 영향 유발, 일반인도 약한 영향이 유발될 수 있는 수준
    300+위험환자군 및 민감군에게 응급 조치가 발생되거나, 일반인에게 유해한 영향이 유발될 수 있는 수준
    (Reference: see airkorea.or.kr)

    대기 품질과 오염에 대해 더 많은 것을 알아보려면 위키피디아의 공기품질 문서(영어)을 보거나 공기 품질과 건강에 대한 AirNow 가이드(영어)를 참조해보세요.

    베이징 의사 Richard Saint Cyr MD의 건강 관련 팁을 보려면 www.myhealthbeijing.com 에 블로그를 확인하세요.


    Usage Notice: All the Air Quality data are unvalidated at the time of publication, and due to quality assurance these data may be amended, without notice, at any time. The World Air Quality Index project has exercised all reasonable skill and care in compiling the contents of this information and under no circumstances will the World Air Quality Index project team or its agents be liable in contract, tort or otherwise for any loss, injury or damage arising directly or indirectly from the supply of this data.



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    Temperature unit:
    Celcius