Vivian & Eng Hen: Other Countries Publish 24-Hourly PSI Readings. Sure Or Not?

Did you hear what Vivian just said?

Take a look at the video at the link below. Listen to what our dear Vivian has to say at 2:35:

http://www.razor.tv/site/servlet/segment/main/news/91928.html (sorry, I couldn’t embed the video)

These were his exact words:

We are probably the only country that’s publishing 3-hourly rolling average PSI. If you look at PSIs in almost any other jurisdictions, it will be on a 24-hour average and the updating is not going to be at an hourly interval and published almost instantly as what we have now.

Does Vivian think that we are idiots?

You want to know what the truth is? Just take a look at the images below and you will SEE for yourself what the truth is.

This is Hong Kong:

photo 1 (26)

Hong Kong: Air Pollution Index (API)

This is Montreal, Canada:

photo 2 (25)

Canada: Air Quality Health Index

This is London, United Kingdom:

photo 3 (22)

United Kingdom: PM10 (particulate matter)

This is America/Canada – click on the link to see the real-time loop.

photo 4 (20)

America/Canada: Air Quality Index (AQI)

Do any of these look like 24-hour averages to you?

Do they not get published instantly?

What is Vivian talking about when he said that Singapore is “in almost any other jurisdictions, (the PSI reading) will be on a 24-hour average”?

Ok, so even if it’s a technicality and we should look at the PSI – which other country uses the PSI? Singapore and?

You see can at the two links below the other air quality indexes used by the other countries:

http://airnow.gov/index.cfm?action=airnow.international

http://taqm.epa.gov.tw/taqm/en/b0901-2.aspx

The only other country that uses the PSI index is Taiwan and even then, it also provides real-time data:

http://taqm.epa.gov.tw/taqm/en/PsiMap.aspx

What “other jurisdictions” is Vivian talking about? Timbuktu? Even when just compared to Taiwan, what Vivian had said is a fallacy!

And if you look at air quality indexes as a whole, you can see that many of the countries provide hourly readings which are published at “hourly interval(s) and published almost instantly”.

Vivian, who are you trying to smoke? You think that with the haze, you can really haze our brains, is it? Is that it?

Apparently, Vivian isn’t the only funny person to say this. According to Channel NewsAsia, “Defence Minister and Chairman of the Haze Inter-Ministerial Committee Ng Eng Hen on Friday urged the public to refer to the 24-hour Pollutant Standards Index (PSI) reading rather than the three-hour reading.”

It also reported that, “He added that most studies on the exposure to pollutants are based on 24-hour measurements. That is why the government’s guidelines are also based on those measurements.”

Just last night, Acting Manpower Minister Tan Chuan-Jin also chimed in and said on his Facebook page that, ” We understand that the 3-hourly PSI readings can spike and cause much anxiety, but they fluctuate greatly during the day. It is the total exposure that the 24-hr readings provide that will matter most.” FYI, readings are supposed to spike! – this is much better an indication for the people as to what they should do, rather than a 24-hour reading which doesn’t give them clear instructions. Hello???

Is Vivian, Eng Hen and Chuan-Jin trying to pull a fast one? What other “jurisdictions”? What other “studies”? The indexes I have shown clearly publish hourly readings!

If I use the same logic and apply it to the weather – now in some countries, the temperature fluctuates severely throughout just one day – if I should be looking at the 24-hour temperature, I should be wearing a thick sweater for the whole day even if the weather becomes sweltering hot at some parts of the day or I should be wearing only singlets and shorts for the whole day even if it becomes freezing cold at night? Is that it?

That’s rubbish. Obviously, the weather doesn’t operate on human timelines – the weather fluctuates according to, well, mother nature! I hardly imagine the weather, or the haze for that matter, fluctuates based on our clock! It’s completely erroneous to expect us to monitor the haze on an 24-hour average basis!

The basic idea should be that we should wear our masks when we go outdoors, and when the haze hits a high level – on as immediate a basis as we can notice! It simply doesn’t make logical sense to decide whether to put on a mask based on the 24-hourly average.

Why The Government Wanted To Pull The Wool Over Our Eyes

By now, many of us would understand why Vivian and Eng Hen had made such illogical statements. In the past where there was only the state-controlled media controlling what is reported, Singaporeans would have blindly bought into what these highly-paid ministers had said. But not now – not when we have the Internet to help us locate the real answers.

(Note: The following four paragraphs have been omitted, as Mr Harinderpal S Grewal had clarified that he had derived his statistics from invalid assumptions. He would be revising the statistics over the next few days, and I would post them here accordingly. (Sunday 23 June 5.30pm). Please see his clarification at this link below:

https://www.facebook.com/harin.s.grewal/posts/10151556928193763)

Mr Harinderpal S Grewal did up some amazing comparison charts between the hourly and 3-hourly average PSI readings.

If you look at the chart directly below, the government had initially published 3-hourly average readings because initially (between 6am to 12pm), the 3-hourly average readings (red line) were lower than the hourly readings (blue line) and it could help give the illusion that the PSI reading is actually lower than it really is.

Photo credit: Harinderpal S Grewal’s Facebook Page

However, as Thursday went by, the hourly readings began to fluctuate – it fluctuated to a point where the hourly readings dipped to such lows (8pm and 11pm), where the government was even thinking about whether to focus on reporting on hourly readings, because they would have looked “nicer”.

But on Friday (in the chart directly below), as the both the hourly and 3-hourly average readings grew to hazardously levels, the government wanted to find other ways to present the PSI readings to depress the readings further – what else but a 24-hour average, which they hope would flatten the PSI curve.

Photo credit: Harinderpal S Grewal’s Facebook Page

Why they could so seriously underestimate Singaporeans’ intelligence, I don’t understand how. The haze might have gotten into their heads but it has only opened our eyes further to the government’s blasé attitude in managing the haze.

Seriously, who is Vivian and Eng Hen trying to kid? The 60% who voted for them – or would it be the 50%, which would have become by now.

Who should we believe? Who can we believe? Can we believe the government when what it says is utter nonsense?

This reminds me of when the Chinese government didn’t want to report on the actual SARS cases in 2003 and caused the SARS epidemic to eventually blow out of proportion, because of their lack of honesty.

We Need To Protect The Freedom Of Our Internet

This also reminds me of what Yaccob had said earlier this month about the newly-implemented “licensing framework” by the Media Development Authority (MDA) when he said that, “Singapore is not the only country tweaking the laws governing traditional and online media.” Yaacob had also said that, “New Zealand and Britain are also reviewing their regulatory approaches and frameworks for new and old media (where) he noted that New Zealand’s Law Commission recently called for an independent watchdog to oversee broadcast, print and online news. It will have the power to censure and ask for material to be removed from a website as well as for a published apology.”

But again, these were erroneous arguments presented by Yaacob. The truth was clearly illustrated by Kirsten Han who said that, “The MDA’s licensing scheme shows that nothing was learnt from the UK’s example. It has completely missed the point of the Leveson Report, which specifically stated that the government should have no power over what is published in the media;” and Choo Zheng Xi, who said that, “The New Zealand Law Commission consulted widely and solicited views and opinions from members of industry, the legal fraternity, bloggers, commercial news agencies, and the public at large before formulating their recommendations,” whereas there was no public consultation done on the MDA’s Licensing Framework.

Do you remember how Yaacob had wanted us to “read the right thing”? Would you have known all these if you had read what they wanted you to read – what they had put out in their own newspapers and TV channels?

You wouldn’t have known what hit you!

I don’t trust what this government wants to say anymore – I will read everything with a very discerning eye, and I suggest that you do the same, as many have done so. The haze episode has revealed many Singaporeans who have taken things into their own hands to find out the truths about the haze on their own.

If the haze episode has shown anything, it is that we cannot allow the government to control our Internet. This is the only source of information that we have left where we can investigate on matters on our own and put the truth out.

If we had allowed our Internet to be controlled by the government, that’s it, Singaporeans. We would be cheated, lied and told half-truths and we would be made to believe “the right thing”. This is very, very dangerous. We need to protect the freedom of our Internet and we need to protect our right to read, know and make informed decisions.

And if we need to take away anything from this haze episode, it’s to remember that the people are a lot stronger than the government. Our people – Singaporeans – have shown that we are better able to come together and help one another, while we have to wait for the government to do anything at all to manage the situation.

This government has shown a lack of leadership and strength in this episode, and this shouldn’t even be considered a major crisis! If they are not even able to show the ability to manage the haze, then I shudder to imagine how they would be able to effectively manage other major crises.

Remember these names: Vivian, Eng Hen and Yaccob.

*****

Afterword:

Some commenters have questioned the methodology behind the hourly statistics brought up in the comparison readings of the other countries highlighted in this article and claim that they these readings are actually 24-hourly averages.

My search on the websites shown in this article say otherwise.

Please see below what I had managed to find on these websites:

Hong Kong’s API:

“The API information is based on raw data taken directly from EPD’s Air Quality Monitoring Network.”

http://www.epd-asg.gov.hk/english/24api/24api.html

Canada AQHI:

I wasn”t able to locate information on the index calculation.

London’s CAQI (Common Air Quality Index):

“An hourly index: which describes the air quality today, based on hourly values and updated every hours.”

http://www.airqualitynow.eu/about_indices_definition.php

America/Canada AQI:

I wasn”t able to locate information on the index calculation.

From the information sources that I had located, the index readings are obtained from hourly real-time raw data.

*****

I had also just been informed that the National Environmental Agency had refuted this article on their Facebook page. You can see their reply at this link or below:

There is a claim on the page – https://thehearttruths.com/2013/06/22/vivian-eng-hen-other-countries-publish-24-hourly-psi-readings-sure-or-not/ – that Minister Vivian Balakrishnan’s statement, that other countries also use 24-hour averages for their air quality indices, is false. 
 
This is an erroneous claim. The following are links to sites which show that the respective air quality indices of the US, UK and Hong Kong are also updated hourly based on 24-hour rolling averages: 

Page 8 of the US Environment Protection Agency technical document at this link, which shows that the AQI is based on 24-hour average PM10 and PM2.5 concentrations:

http://www.epa.gov/airnow/aqi-technical-assistance-document-sep2012.pdf

The UK Air Quality Index is based on a running 24-h mean PM10:

http://uk-air.defra.gov.uk/air-pollution/daqi?view=more-info&pollutant=pm10#pollutant

Details of the Hong Kong Air Pollution Index can be found at the following links. The hourly updates for PM10 (RSP) are based on 24-hour averages:

http://www.epd-asg.gov.hk/english/backgd/calcu.html

*****

I will leave it to discerning readers to make their own conclusions.

At this point, my concern is that the government should act swiftly to mitigate the effects of the haze. Statements which are contrary to the management of our health should be refrained from, and immediate actions taken to alleviate the impact of the haze.

This, I believe, would be more effective than tweaking or re-presenting the PSI readings, which at the height of the haze, will only cause unnecessary worry and due concern among the people. At this time of uncertainty, consistency in representing is important.

The government needs to act on their leadership.

171 comments

  1. Gazali

    Reblogged this on Gazali Unplugged and commented:
    The haze must have affected them. Other countries do publish 24-hour air quality readings.
    That is one reason that the internet mustn’t be censored. Back in the 60s, it was easy because the government controls the press. They can easily ban books, publications, songs easily.
    Now it’s next to impossible. I can easily copy it to my thumbdrive and none the wiser.
    And as usual the Singapore government still thinks that Singaporeans are children.

  2. BK

    Check this http://en.wikipedia.org/wiki/Air_quality_index and u’ll see hong kong, china, UK, US display hourly “24h-averaged” AQI or PM10 or PM2.5. Hope you could clarify your sources on the full detail (ie how the readings were derived) of the readings? Otherwise, this is a dangerous article that divides the knowledgeable and less knowledgeable people.

    • jesper

      I suggest u remove ur post to avoid misleading us. Other countries like Taiwan provide raw data on hourly basis and teach us how to estimate PSI. Singapore uses three hour averages so that we dont know the actual situation of the haze.

    • Ace

      NEA uses a straw man argument to refute this article. What VB said was that Singapore is the only country that provides a 3 hour average and other countries provide 24 hour average. Roy’s point is that there are other countries that provide even hourly reading which is more accurate. The 24 hour average reading is not central to the dispute.

      However, NEA showed that other countries provide 24 hours average reading and then go on and claim that Singapore is doing the same and then says that Roy’s article is misleading. This is another classic case of the use of fallacy (straw man argument) by the MIW to confuse people.
      http://www.nizkor.org/features/fallacies/straw-man.html

  3. EG

    To last comment, We might have other countries that calculate on the average but I would think that its still important that we know actual hour reading as it helps in the sense that I am breathing.. EVERY FEW seconds. It will be best if singapore can be the first honest country to do that! And with these useful information, I can know if Its sensible to do certain activities or not. IF like what these PMs say, healthy people only need to wear a mask if its over 300psi. with 3 hour average, I wont be able to know if at the moment, its 299 or 300…. anyway, we still need to wear it even if its only 101 where PM2.5 will still be present… just not as heavy… 🙂

  4. duh

    I don’t understand how people can still defend this article when the bare truth is that it is wrong. Have we missed the point? Look at the main title. What is it attacking? Is attacking the authenticity of govt claims that overseas readings are based on 24hr averages. The author’s “evidence”? Image captures of the charts showing hourly readings. If he had used a screen capture on the nea psi chart, it would show hourly too! Does that mean the nea chart is hourly? No. But neither are any of the cited countries he used. A simple search on the official sites of his “evidence” show that he is either misinformed or lying. Yet, the damage has already been done to all those who fail to read this article critically and objectively. And one day this myth will become a truth for others, “truth” that will be used to shape the political landscape of the country I hold so dear. Indeed I look forward in pessimism.

    • Duh Duh

      Hello duh!,
      Go to the 2 following URL before you start shooting yourself in the foot again
      http://www.epd-asg.gov.hk/english/backgd/faq.html#q6
      The API of each monitoring station is determined every hour from the air pollution levels measured in the past 24 hours or in the past hour, whichever is the higher. The 24-hour and the one-hour period are of concern because air pollution health effects for different air pollutants are observable over exposures to either one or both of these periods.

      http://www.epd-asg.gov.hk/english/backgd/calcu.html
      API is calculated by first computing the subindices of scale extending from 0 to 500 for each air pollutant measured at each air quality monitoring station based on the 1-hour, 8-hour and/or 24-hour average concentrations.

      • duh

        Really.. How about reading the REST of the description? Instead of taking things out of context? In fact.. Some of the comments below already save you the trouble with the facts that I don’t know how more extensive it can be.

  5. My Right to Love

    Hi guys,

    Sorry, I was out for the whole day. Sorry for the late reply.

    Many people had asked similar questions, so I thought that I would reply with a general comment here:

    (1) For commenters who question the premise of this article, I would like to ask this – are you suggesting that you would like to be updated with 24-hourly average readings? Let’s not talk about this article. Let’s talk about your basic health – you would want to make decisions about your life and health based on arbitrary over-averaged readings?

    Personally – I am trying to put a hand on the reason why some people would want to challenge the premise of this article. What are the motives for doing so? I think it’s very clear that up-to-date hourly readings would give us more immediate information as to how we should protect our health – whether we should wear masks, etc. This is logical.

    And if there is anyone who believe that they can decide based on 24-hourly averages – fine, but do not drag the health of others with you. At this point, the clearer and more specific the information, the better for us.

    *****

    (2) Am I against PAP? I have said it many times – I am pro-Singapore. There are people whom I respect and admire among the PAP politicians, but as a whole, I am not convinced that this PAP government can bring us in the right direction. There is a glaring lack of leadership and inaction from PAP, in their response to the haze.

    Should we demand that they play gods and blow the winds away? Obviously not. We cannot expect others to do what we cannot. But they took several press conferences before they could decide on any course of action.

    I have always maintained that we need a government made up of diverse representations – so politicians from different political parties. Diverse representation will ensure that the needs of different segments of the population will be met.

    For people who question if we have good enough opposition parties, my question to them is – what do you want to do for your country? If we rely on only 90 people in government to make all the decisions, then we are doing ourselves in.

    We have 3.5 million Singaporeans – all of us can play a role in policy-making, community service and all other matters – things which we are already doing, for some. No matter who becomes the government, we have to continue coming out with solutions for our countries.

    I don’t buy the argument that we do not have strong enough representatives from the different parties. And I believe that we can all work to make this country work.

    So – I am pro-Singapore. And I believe that we need to take steps to work to make our country the one that I want. Some people might disagree with my views, and that’s fine. The beauty of it is that when we have diverse views, it will only add to the conversation, and it will allow us to create more solutions.

    *****

    (3) Which is why I am very concerned that the government has implemented the licensing framework on online news sites. If this site becomes licensed, I won’t have the $50,000 to pay to the government and the government will get to decide when they want me to take my articles down, and I would have to take it down within 24 hours.

    If they get to use this licensing framework according to how they want it, my question is – will you still be able to read this article? Will you still be able to find out what the truth is and what’s really going on?

    Roy

    • jesper

      Very well said! These PAP cronies must have lost the plot or they are trying to smoke people with their personal attacks.

      • Cool

        Oh, so an alternative opinion is simply dismissed as ‘personal attacks’ from ‘PAP cronies’? Well said jesper, you will always win such arguments. For only those who stand with you are independent thinkers, and those who would argue against you are ‘obviously’ cronies of the government.

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  7. Reeflobang

    Let’s not talk about the article when you started it? You have yet address the core issue (your claims using all the charts) and and now side-track to other matters? Please use common sense, we know clearly that the haze is on! Wear masks when you are outside regardless of 24 / 3 / 1 readings. You mean you will put on and off your masks according to the hourly if they are available?

    You are not anti-PAP / government but pro-Singapore? My foot! If you are truly pro-Singapore, you will be spending time on what “SG Haze Rescue” is doing and not spreading half-truths and lies to satisfy your own personal angst.

    • duh

      Excellent response reeflobang that is clear and logical. Author completely misses the point intentionally or unintentionally. There are ways to go about putting your point across without spreading lies and fears, which is essentially what this guy has done. All the debate on when to put on mask when people automatically swept them ask the shelves? Indeed as voltairre once said, common sense is not that common after all.

    • Maya

      The core issue is why Vivan Bala is spreading half truths telling the whole world Singapore is the only country publishing 3hr PSI and saying that others only publish 24hr PSI ? What is he trying to achieve by making comparisons using such statements? Is he trying to mislead? How would you interpret? Without Roy digging further, would u have known that other countries do provide hourly updated data? So who is misleading who?

      • duh

        Facepalm. Maya. Read the earlier comments. It is irrefutable that his interpretations of the charts are wrong. Go to the foreign websites and verify yourself. Goodness. So who is misleading who?

      • Simon

        I think what she meant is who is the one who started misleading people. Is it Vivian or Roy? As a layman, I would have taken the minister for his words at face value and think that other countries are not doing any better than Singapore. I think this is what Vivian wants us to believe. If not, why does he mention that Singapore is the only country to provide rolling 3hr PSI? Come to think about it, I would be in the dark if Roy did not present his findings to show that other countries provide more info instead of less. The minister should not have made those utterance, considering the fact that he knows something, and didn’t present the full picture to us. It is like playing politics, the way he did it to AHPETC. No, we don’t want ministers who try to fool us. We need honest people. A honest government. You go back and think about what I wrote and whether it makes sense to you or not.

        As for Roy, if not for his article, I wouldn’t have seen the other side of the coin. Let’s call a spade a spade. Be honest with yourself. I hold the minister to a higher standard in this regard. He can do much better.

    • Ben

      Wearing a mask when the PSI exceeds 400 is not sufficient as my eyes will start to tear (personal experience). I am glad that you need not work outdoors or need to bring your kids to/from day-care but we do. Real-time PSI is helpful to decide if we are to move the young/old folks.
      i checked the weather conditions before I leave my office/hotel when I am overseas so why can’t we have a real-time PSI reading in Singapore?

      To add on, the author is expressing his opinion just like what we are doing now. If you do not agree, state so and move on. How would you know that the author is not doing his part for our country and that the he is against the place we called home? The author provided alternate views for us to consider, even though we may not agree to it. Personally, I would prefer a real-time system.

      • duh

        Because singaoore IS the only country giving 3 hour averages! The “hourly” updates given by the countries Roy cited are 24 hourly averages! The minister is laying out the facts, whilst Roy got his facts wrong based on looking at the horizontal axis of the graphs!
        Teacher. Do not create false dichotomies. The guidelines are there and no school is supposed to conduct physical exercises past 200 and outdoor activities minimised past 100. Just like some people claiming that the minister “said” not to wear mask if not below 300, when the recommendation is actually “wear n95 above 300”. It’s time to stop passing on hearsay as facts.

      • Huh?

        No duh, there are hourly updates of PM2.5, PM10, SO2 etc. Maybe they never calculate the PSI on an hourly basis. But data is provided on an hourly basis. NEA should provide these data on an hourly basis to be transparent. Since it alreay has the hourly PSI, if not it couldn’t have been able to calculate the three hour average, then why not just provide and END OF STORY. Be transparent or people will start to doubt your words.

    • teacher

      When school reopens, just imagine the parents’ response when they find out that their children were having PE during the hour when spot PSI was 400. Get Ng Eng Hen and Vivian Balakrishnan to explain to them that the 24-hr average was in the moderate range 50-100.

      • Cool

        So teacher, you are saying that the staff in the school is blind enough to not see the hazy conditions as the PSI approached 400? I think the ministers would have to explain why the teachers had to consult the 24 hr average PSI instead of their eyes, their noses and their common sense.

      • Hazel

        @Cool, like that might as well do away the 24hr PSI and shutdown NEA. No need report since we all can use our eyes and nose right? Common sense right? The whole government can shutdown too. No need government what, we all can take care of ourselves. Why pay them millions. We don’t need them at all.

  8. The Informed.

    Actually, nearly all of the indexes listed above use 24-hour averages.

    Lets start with the Hong Kong API. From this paper ( http://www.epd.gov.hk/epd/english/environmentinhk/air/studyrpts/files/APIreview_report.pdf ), we can see that the API uses 24-hour averaged values for PM in it’s calculation (3.2.2). As a bonus, we also see a reference to another paper, saying “This is due to the lack of scientific evidence with respect to the exposure-response relationship for PM over a one-hour period (Cairncross et al, 2007).”.

    Next we have AQHI. This measures ozone, nitrogen dioxide and PM2.5 over a 3-hour averages. http://en.wikipedia.org/wiki/Air_Quality_Health_Index

    Then we have Europe example, which does calculations on PM either hourly or on hourly-adjusted daily averages (probably because different countries may publish information at different intervals). http://www.airqualitynow.eu/about_indices_definition.php

    Then for the US’ AQI, Particulate Matter is calculated for a 24-hour period. http://www.epa.gov/ttn/oarpg/t1/memoranda/rg701.pdf

    Even Taiwan provides data based on 24-hour averages for PM. http://taqm.epa.gov.tw/taqm/en/b0201.aspx

    In anyway, PSI is based on PM10 which is not as harmful as PM2.5 so people have been calling for hourly PM2.5 readings as well but….

    a. Hourly PM2.5 monitoring.
    I’m a grad from environmental engineering so I will share what I roughly know. PM 2.5 can only be measured every 24 hrs due to experimental limitations.

    Due to the low mass, sampling time is extended to at least 24 hours for PM 2.5 because of 1 reason, the air flow rate is set low to mimic inhalation by people, if not, you get a very exaggerated reading which is not realistic.

    Now at low flow rate, you need to reach a certain mass collected before measurement can be done,if not, nothing will be measured, which means a 3 hour reading is not possible because there’s just not enough collected yet and/or we just don’t have the equipment or the technology doesn’t even exist to measure such low mass.

    If you want a hourly reading, you could up the flow rate and get an unrealistic reading(only done in research) or you could try to measure at low flow rate and get no reading. This is why 24 hours is required for PM 2.5

    Fair enough, you probably could overcome this by having 24 x (number of air sampling machines) so as to get a staggered reading. The obvious drawback to this is cost. I googled “high volume air sampler price” but can’t find any pricelist. Suffice to say, I think the cost is hardly justifiable considering that this problem will probably blow away in a few weeks time.

    The next thing is that even if you know the hourly PM2.5 readings, so what? Is the NEA advisory going to change hourly? I seriously doubt so. I bet the advisory will still read: At-risk groups to avoid outdoors, everyone else limit physical exertion.

    This situation is analogous to a patient admitted for pneumonia who wants to have hourly full blood counts to see whether his infection is improving. For what?! Even if the numbers change, the management will still be: IV antibiotics until clinically better, or until daily FBC improves. Hence, the only thing that such repeated tests does are: 1. $$$$ 2. add to anxiety 3. create obsession over numerical values

    Also, I would like to add that every test (including the air sampling tests) has a false positive/false negative value. I’m not sure about the sensitivity/specificity of this test, but technically speaking, the more frequently you sample, the more error you are going to encounter. This can be overcome by using more devices to sample, but again, cost is an inescapable issue.

    b. sampling methods
    Today ST published an interesting article on how PSI is calculated. Everyone should go read. I hope NEA can also publish similar articles on how PM2.5 is calculated, the error rates, and the cost of each sample so we know what the price of information is.

  9. My Right to Love

    Hi everyone,

    Some commenters have questioned the methodology behind the hourly statistics brought up in the comparison readings of the other countries highlighted in this article and claim that they these readings are actually 24-hourly averages.

    My search on the websites shown in this article say otherwise.

    Please see below what I had managed to find on these websites:

    Hong Kong’s API:

    “The API information is based on raw data taken directly from EPD’s Air Quality Monitoring Network.”

    http://www.epd-asg.gov.hk/english/24api/24api.html

    Canada AQHI

    I wasn”t able to locate information on the index calculation.

    London’s CAQI (Common Air Quality Index ):

    “An hourly index: which describes the air quality today, based on hourly values and updated every hours.”

    http://www.airqualitynow.eu/about_indices_definition.php

    America/Canada AQI:

    I wasn”t able to locate information on the index calculation.

    From the information sources that I had located, the index readings are obtained from hourly real-time raw data.

    Thank you.

    Roy

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  11. The Informed.

    try again:

    Actually, nearly all of the indexes listed above use 24-hour averages.

    Lets start with the Hong Kong API. From this paper ( http://www.epd.gov.hk/epd/english/environmentinhk/air/studyrpts/files/APIreview_report.pdf ), we can see that the API uses 24-hour averaged values for PM in it’s calculation (3.2.2). As a bonus, we also see a reference to another paper, saying “This is due to the lack of scientific evidence with respect to the exposure-response relationship for PM over a one-hour period (Cairncross et al, 2007).”.

    Next we have AQHI. This measures ozone, nitrogen dioxide and PM2.5 over a 3-hour averages. http://en.wikipedia.org/wiki/Air_Quality_Health_Index

    Then we have Europe example, which does calculations on PM either hourly or on hourly-adjusted daily averages (probably because different countries may publish information at different intervals). http://www.airqualitynow.eu/about_indices_definition.php

    Then for the US’ AQI, Particulate Matter is calculated for a 24-hour period. http://www.epa.gov/ttn/oarpg/t1/memoranda/rg701.pdf

    Even Taiwan provides data based on 24-hour averages for PM. http://taqm.epa.gov.tw/taqm/en/b0201.aspx

  12. Pologayboy

    spread the word on how to manage the haze in susceptible patients, hearttruths. dont politicise at every opportunity if you’re really pro-singapore. pui.

  13. Right to Knowledge

    All right, there seem to be many misconceptions flying around here and there, so let’s clear up the haze on this, shall we? I shall refer to Hong Kong for this one. I will appreciate if you read this to the end.

    However, before that, I would like to mention that stating “The API information is based on raw data taken directly from EPD’s Air Quality Monitoring Network” to support your claim that Hong Kong’s API is hourly-based has zero link – I could conduct a survey off the street, draw conclusions from my results, state that they were “based on raw data taken directly” from my survey, and it wouldn’t give any information with regards to its accuracy or applicability (much less the implication that it was based directly on an hourly reading). So work on your reading comprehension, yes?

    Ok, so first off, Singapore’s PSI and Hong Kong’s API, while apparently different to many passive observers, are fundamentally very similar beasts. So, the API. Hong Kong’s API is an index to measure air pollution, and it ranges from 0 to 500. This website (http://www.epd.gov.hk/epd/english/environmentinhk/air/air_quality/backgdf_3.html) states the calculation method of API. Essentially, the API consists of several subindices, such as the measurement of the concentration of suspended particulate matter in the air, or the concentration of sulphur dioxide. This data is, yes, “based on raw data taken directly from EPD’s Air Quality Monitoring Network”. However, take a look here: http://www.epd.gov.hk/epd/english/environmentinhk/air/air_quality/backgdf_3_3.html . The measurements of the subindices are apparently not all based on the past hour, as you thought they were. Only the ozone subindex has a dedicated 1-hour measurement, while others like the sulphur dioxide can use a 24 hour average or a 1 hour average, depending on the severity of the situation. Clearly, the more hazardous the air seems, the shorter the measurement period used so as to provide more up-to-date data. (Strikingly, the RSP (respirable suspended particulate) is based on a 24 hour average.) Then, the highest subindex among all the parameters is published as the API – on an hourly basis. Thus, the readings on the graphs you provided are hourly updates, yes – but not necessarily directly taken from an hourly reading. It could very well be a 24 hour average, or maybe an 8 hour average, depending on the subindex which was used.

    That all sounds very familiar – because Singapore is doing pretty much the exact same thing. NEA provides this to help understand how the PSI is calculated: http://app2.nea.gov.sg/data/cmsresource/20090401682645441976.pdf . Like the API, it also uses subindices which can also be based on 24, 8 or 1 hour averages, depending on the level of harm each pollutant brings. For example, while PM10 is based on a 24 hour average, ozone is based on an 8-hour average of past data. This site provides some additional info: http://www.e101.gov.sg/haze/info.htm . The 3-hour PSI which Dr. Balakrishnan has mentioned is based on a 3-hour average of PM10 – this is because they have correctly identified PM10 as the main pollutant which is harmful to us in this hazy situation, and also because PM10 is the subindex most likely to have the highest concentration anyway. By the way, the API equivalent of PM10 – the RSP, also uses a 24 hour average, as a useful comparison.

    So, what can be concluded from this? Don’t be misled by hourly updates – understand the calculation process and statistical method behind the data collection used for the indices. What may seem like an hourly update for Hong Kong is still based on 24 hour past data. This is what we mean by Hong Kong using a 24 hour average for its data. Also, the PSI is based on the past! It may or may not have any correlation to the present or even the future, so take note of that as well.

    Thank you very much for reading this. Please unhesitatingly point out if I have made any errors in my explanation.

    • duh

      Even after your very extensive spoon fed research evidence, there will still be those who choose to see part of foreign index descriptive and refuse to read the rest. Haiz.. but well written comment anyway. And if the writer was truly pro singapore and interested in “heart truths” then he would do well to update his post with your information. And that would do so much more for his credibility as a source of truth.

  14. Just curious

    What’s all that argument on average 24-hourly used and actual hourly used? A simple check on a official website will do. Right? Refer to the HK’s website. http://www.epd-asg.gov.hk/english/api_you/apical.html
    Reproduced below for your easy reference.

    Cased closed.
    ————–
    How is the API Calculated and Reported?
    We report the real-time general and roadside APIs hourly. These indices are calculated by comparing the measured concentrations of the major air pollutants with their respective health related Air Quality Objectives (AQOs) established under the Air Pollution Control Ordinance. These pollutants are nitrogen dioxide, sulphur dioxide, ozone, carbon monoxide and respirable suspended particulates. An index is calculated for each of the five pollutants and the highest index is reported as the API of that hour.

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  17. Daniel C

    If you are honest and have courage and integrity, you will put the updates at the top of the page, where new information should rightly be found. Faced with the possibility that you did not know enough about the things you posted, you dont want to ignore it yet you also hope people wont get that far down. Move them up.

  18. Pingback: Dumb and Dumber Singaporean Reactions to the Haze « SG Hard Truth
  19. Hazemeister

    This if from an FAQ on API in HK. We clearly see that hourly API is available and reported as the API of the hour if it is higher than the 24-hour average.

    http://www.epd-asg.gov.hk/english/backgd/faq.html#q6

    FAQ: Does the API reflect the air pollution level for a particular hour or a longer period?

    The API of each monitoring station is determined every hour from the air pollution levels measured in the past 24 hours or in the past hour, whichever is the higher. The 24-hour and the one-hour period are of concern because air pollution health effects for different air pollutants are observable over exposures to either one or both of these periods.

  20. Hazemeister

    This if from another FAQ on API in HK. We clearly see that hourly API is available and reported as the API of the hour if it is higher than the 24-hour average.

    http://www.epd-asg.gov.hk/english/backgd/faq.html#q12

    FAQ: Is the API an average of the pollution levels measured at a monitoring station?

    It is not an average. It is the highest API number calculated from the concentrations of the different air pollutants recorded at the monitoring station in the past one-hour or 24-hour whichever is the higher.

  21. Hazemeister

    http://www.e101.gov.sg/haze/cutthruehaze.htm

    This “Cut Thru The Haze” site sets out to disprove a bunch of rumours. I am not sure how successful they accomplish their task but that is not the point. One of the rumours they claim to be false was one of the claims in your article here where they posted a bunch of links to the pollution indices of various countries to try to show that all of them provided 24-hour average data only. However, in the last hour, they seemed to have deleted that particular entry while the rest of the “disproven rumours” are still up on the site. Does it mean they realised they were wrong and you could be right?

    I cannot comment on all the many pollution indices around the world and I can see that many of them are indeed rolling 24-hour averages. But from what I can see, the HK ones definitely offer the option to report the 1-hour data should they become critically high and supercedes the importance and magnitude of the 24-hour averages.

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  23. alibaba

    Anyone ever wonders why PSI got 24 hour average , 3 hrs average , 1 hour average , real time ?

    hint : This is same as stock market ‘s 1year average 3 month average 1 month average, weekly average, daily average 3 hrs average 1 hourly average, 1 minutes average real time .

    Imagine in the 97 or 07 stock market crashed and our finance minster came on TV and tell us more accurate to come back 1 month and look and the 1 month average ‘price’ . I think end off one month buy coffin also no stock liao ! If you can check into his own portfolio he does it real time and had sold off all his holding even before he give that TV speech to you .

  24. Vivpin

    G:”The statement in Heart Truths is FALSE. The US, UK and Hong Kong also update their PSI hourly, using rolling 24-hour averages.
    We are the only country that also publishes the 3-hour PSI every hour.

    Details of the Hong Kong Air Pollution Index can be found at the following links. The hourly updates for PM10 (RSP) are based on 24-hour averages:
    http://www.epd-asg.gov.hk/english/backgd/calcu.html
    http://www.epd-asg.gov.hk/english/backgd/table122.html”

    This part about HK is telling half the truth. The API (not PSI) uses PM10 24-hr average data. Ok. BUT HK also publish hourly concentration numbers. This is even better than NEA’s 3-hr average data.
    http://www.epd-asg.gov.hk/english/24pollu_fsp/24pc_fsp.html
    These are hourly concentrations. And hourly index can be calculated from these hourly concentrations.

    And a 3-hr average can be easily calculated from these HK hourly concentrations.

    The full picture supports the Heart Truths.

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