API and PM10 - health
API - air pollution index
PM10 - particulate matter smaller than 10 micron (fine dust)
The relevant section of the former SEPA website has disappeared, the new MEP site is mostly Chinese, but the document can still be found at this alternative source. Read more in this post about the WHO Air Quality Guidelines. Recently the interpretation of the different API levels seems to have shifted a bit, as mentioned in the same post.
A very helpful explanation of API - PM10 on Vance’s blog.
The Chinese authorities use an Air Pollution Index (API) to report the air quality. To determin this API, they measure 4 chemical substances and the fine dust concentrations (PM10); the highest value of these 5 becomes the API. In China and especially in Beijing PM10 seems always been the highest of the 5, as you can see in the daily MEP data. That means the fine dust is the worst problem, but it does not mean there is no chemical pollution in the background.
The categories MEP uses are quite interesting, let’s put the equivalent PM10 value next to the API scale (PM10 in mg/m3).
1 = API 0-50 = excellent = PM10 0.000-0.050
2 = API 51-100 = good = PM10 0.050-0.150
3A = API 101-150 = slightly polluted = PM10 0.150-0.250
3B = API 151-200 = light polluted = PM10 0.250-0.350
4A = API 201-250 = moderate polluted = PM10 0.350-0.385
4B = API 251-300 = moderate-heavy polluted = PM10 0.385-0.420
and so on..
Although most countries use the term API, they may have different scales to measure it, so an API of 100 can respresent different levels of pollution. In the below graph i have tried to bring the data together, and although there are slight differences, my conclusion is that roughly the API of China, Hong Kong, and the USA’s AQI refer to the same levels of PM10 so we can compare them.
Let’s compare how they interprete these values:
|China interpretation||Hong Kong interpretation||USA interpretation|
|excellent (level 1)||low to medium pollution||good|
|good (level 2)||high pollution||moderate|
|slightly polluted (level 3A)||very high pollution||unhealthy for sensitive groups|
|light polluted (level 3B)||very high pollution||unhealthy|
This looks like a perfect illustration of the ”one country, two systems” policy - what is very high pollution in Hong Kong only gets a label of slightly-light pollution in Beijing..
So it seems fair to state that the accepted red line for API is 100; above 100 we are breathing unhealthy air. As i mention further on, in Juny 2007 we had 15 red days.
Let’s see to how Europe looks at it. According to “Council Directive 1999/30/EC of 22 April 1999 relating to limit values for sulphur dioxide, nitrogen dioxide and oxides of nitrogen, particulate matter and lead in ambient air” (pdf), from the start of 2005 the daily PM10 value should not exceed 50 microgram/m3 (which is 0.050 mg/m3 - SEPA level 1) for more than 35 days per year, and from 2010 not more than 7 days per year. That means the EU draws a red line at a PM10 of 0.050 mg/m3 - in Beijing we are in the red almost every day: so far (21 August 2007) we have had 15 days of level 1 in Beijing, so it is likely we’ll have more than 300 days in the red this year. It seems that urban areas in Europe also have difficulties to stay below the limit value.
MEP clearly has a different view, categorising air with a PM10 up to 3 times as high as the EU limit value as ‘good’ (level 2) and the Beijing Olympic Committee seems to share the view that level 2 is acceptable for athletic competition.
The USA Environmental Protection Agency (EPA) puts the “primary standard” for PM10 at 150 microgram/m3 (level 1 and 2) which corresponds to a API/AQI below 100, with a footnote that this value should not be exceeded more than once per year on average over 3 years. In June 2007 we had 15 out of 30 days with API over 100 in Beijing (that’s where SEPA starts to talk about “slightly polluted” - level 3).
In Hong Kong, the API looks at RSP (Respirable Suspended Particulates) which is the same as PM10. The HK API limit for “high pollution” starts at 51, and “very high” at 101. This corresponds to RSP (PM10) values of 0.055 mg/m3 and 0.180 mg/m3, which are equivalent to a China API of 53 and 115 (thanks to El Pato for the links).
This recent academic research report (USA) quotes the WHO stating in 2005: ‘the evidence is sufficient to infer a causal relationship between particulate air pollution and respiratory deaths in the post-neonatal period’, and confirms that particulate matter air pollution is a risk factor for respiratory-related postneonatal mortality.