About PM10 and API, and WHO guidelines
4 days into the traffic restrictions, today is even worse than yesterday, with an API of 113 for 24 July- this is equivalent to a PM10 value of about 175 micrograms/m3. Let’s go back to the World Health Organisation (WHO) Air Quality Guidelines of 2005 (AQG) to understand this number. For PM10 they suggest on page 10:
- annual mean: 20 micrograms/m3
- 24-hour mean: 50 micrograms/m3
The 24-hour average from 23 July noon to 24 July noon in Beijing was 175 micrograms/m3, that is 250% higher than the WHO guideline. The Chinese authorities are saying that level 2 (API up to 100 = PM10 of 150 micrograms/m3) is safe for athletic competition (’blue sky day’). The WHO guideline for short exposure is a PM10 of 50 micrograms/m3, which corresponds to an API of 50. We have only had 2 days like that in July until now: 6 and 15 July.
On page 13 of the WHO document it says what short exposure to an API of 100 does to you:
Therefore, a PM10 concentration of 150 μg/m3 would be expected to translate into roughly a 5% increase in daily mortality, an impact that would be of significant concern, and one for which immediate mitigation actions would be recommended.
The annual average API in Beijing is around 100 = PM10 of 150 micrograms/m3, which is 650% higher than the WHO guideline for long-term exposure. The WHO’s first ‘interim target’ for long-time exposure starts at 70 micrograms/m3 (API of 60) so no further comment on this.
Also check out this recent comment by Dr. George D. Thurston, Professor at the NYU School of Medicine:
…All in all, anything above Chinese API=50 is very unhealthy. Even if it is at API=50, that is still more than double New York City usual levels, so that is not acceptable either. They really need to get the API down to 25 or below to call the air acceptable for Olympic competition. It seems only strong (clean) winds from the North can provide lowered concentrations, and this just doesn’t happen often enough in Beijing.
The Beijing Environmental Protection Bureau is providing daily reports of SO2, PM10, NO2 levels on a special section of their website, even in English, screenshot below. It seems these numbers are already converted to the API scale, so that makes it quite confusing; actual values in micrograms/m3 are higher for the 3 pollutants, as described here.
Also interesting to see how the interpretations of the API levels has shifted a bit (upper left box on the above screenshot, compared to the same 2007 document):
1 = API 0-50 = excellent (old) => good (new)
2 = API 51-100 = good => moderate
3A = API 101-150 = slightly polluted => unhealthy for sensitive groups
3B = API 151-200 = light polluted => unhealthy
4A = API 201-250 = moderate polluted => very unhealthy
4B = API 251-300 = moderate-heavy polluted => hazardous
Especially the re-classification of ‘light polluted’ to ‘unhealthy’ is remarkable; the new classification is in fact very similar to the US-EPA.
August 4th, 2008 at 5:16 pm
Hi Tom,
Regarding your last point about the translations changing, it seems that the use of the US EPA system didn’t last long. Now they are simply using Roman numerals I-V with no additional description. I recently blogged about it here:
http://live-from-beijing.blogspot.com/2008/08/air-quality-translation-inconsistencies.html. How often do you take screenshots? There was a third set of translations in between, maybe early next week, but I don’t have it saved…
Vance
August 6th, 2008 at 8:45 am
I think Americans need to realize that right now, Beijing’s air quality is about the same as many major cities in the US. The quote from Dr. George D. Thurston mentions that even at AP:50, that is about double the levels of NYC. Well, thanks to its location on the ocean, NYC’s air is actually pretty clean. As someone mentioned already, an API:50 conforms to WHO standards for short exposure. The weekly average for Beijing is currently 54, so they are pretty close. On the other hand, Los Angeles is not.
On Saturday, Los Angeles city center showed “unhealthy for sensitive groups” with an AQI: 101-150. San Bernadino showed “unhealthy” with an AQI:151-200. Santa Clarita was “very unhealthy” with an AQI:201-250. In Beijing on the same day the API was 34. Yesterday Beijing was 83, the weekly average is 54, and the monthly average is 73. As you can see, the air quality in Beijing is better than the LA area.
August 7th, 2008 at 12:40 am
Larry: I’m not really sure where you are getting your numbers and how you are doing your comparison but your conclusion is completely off base. Granted Los Angeles does have bad air but saying that Beijing’s air quality is better than LAs is well off.
Lets just takes some simple facts. Beijing’s air was 83 based on non-independent sampling. And, of course, nobody trusts (nor should) any government.
Beijing’s air was 83 when
-Construction was stopped
-over 50% of the cars were taken off the roads
-Major factories were shut down
-Major coal fired plants were shut down
Now LAs air was 101-150 (we’ll never mind the fact that the numbers are not comparable) but was measured on a day when
)
-All cars were on the road
-The city was in full swing
-All factories were operating (do they have factories?
-Electricity was being sucked at astronomical rates due to AC use.
so we’re comparing one city that’s dramatically toned down and another that into complete full swing or in short we’re comparing the BEST day in beijing to the WORST day in LA and making the conclusion that Beijing is now better than or equal to U.S cities.
wow.. I’m sorry but I live in Beijing and I can tell you after having lived in most major cities in the U.S (as well as major cities in Europe) that Beijing’s air is absolutely horrible although I am loving these nice clean air days during the Olympics.
Please come back in December and make the same comparison. You know that month when the whole of Beijing is burning coal to heat their houses and destroy their lungs.
I am praying and hoping that Beijing takes the example from the games learns from this experience and makes the air better for their citizens. After all cleaning their air for a few thousand Athletes is great but cleaning their air for tens of millions of people is much better.
August 8th, 2008 at 5:42 am
Gidday Larry,
I am sceptical of the claim that, “Beijing’s air quality is about the same as many major cities in the US.”
Until years of raw monitoring data on various air species are freely available for comparisons, I have no faith in any comparing of API or AQI or any other composite index, particularly when the Chinese authorities to the best of my knowledge release no Ozone data at all.
September 3rd, 2008 at 3:10 am
The monitoring of air quality in Beijing is an international effort that includes the EPA, the US-based Argonne National Laboratory, the University of Tennessee, and the US Department of Energy. There are also plenty of people doing independent air monitoring including every major news agency. The AP and the BBC have both stated that their measurements match the official API figures.
Jacob says that the API used by China and the AQI used by the US are not comparable. That is correct. In 2006, the US stopped including particulare matter between 2.5 and 10 microns in the AQI. The result is that for a given amount of particulate matter, the AQI scores will always be lower. So while Jacob is correct in saying they are not comparable, what he fails to mention is that this gives the US cities a distinct advantage over cities in China.
Jacob says he knows from personal experience that the air in Beijing is worse, but my personal experience was quite different. Unfortunately for Jacob, I have the scientific data on my side. Aside from the Olympics, the averages for Beijing for the entire past year are still better than Los Angeles.
I think many people are ignorant about the effect humidity has on breathing. I have rather serious asthma, and high levels of humidity make breathing very difficult. The humidity in Beijing is very bad, but the high levels of ozone in Los Angeles make it much harder for me to breathe there than in Beijing.
I think Jacob and Warwick Hughes provide a good example of why the US needs to focus more heavily on science education. Many Americans have almost a hatred of science, and most find it too difficult to understand. Rather than learning about science and using objective measurements, Americans would rather trust their subjective intuition and observation. Of course it doesn’t help when the media does its very best to misinform the populace. The media has done an excellent job at “informing” Americans about the high levels of pollution in Beijing. However, they intentionally hide the fact that Los Angeles has even higher levels of pollution. So you see, it’s not really the fault of the average American…they are just mindlessly believing what the media tells them to believe.
September 3rd, 2008 at 3:20 am
Using the average annual API, which is about 100, is a bit deceptive. The air quality in Beijing has been significantly improving each year. Using an average annual API is an attempt to make the air quality in Beijing seem worse than it currently is by including previous years when the air quality was much worse.
The truth is, the air quality in Beijing during the Olympics was better than many cities in the US, and WAY better than Los Angeles. If this wasn’t the case, the media would have been talking about it all the time.
The US media probably had a bunch of pre-written stories about pollution in Beijing that they didn’t get to use because the pollution was not as bad as they had hoped.