Batgung - pollution

Poor air quality – what's the cause?

mrb — Thu, 17 Sep 2009 01:00:00 +0000

Here's a graph from the government that gave me a shock. It shows that the pollution we generate in Hong Kong fell significantly between 1990 (on the left) and 2007 [1]:

How can that be, when we all know that air quality has got much worse?

Compare it with the Batgung Smog Index[2] for the same years:

In the early 1990s, as we produced more pollutants the amount of smoggy weather (the red line) also increased. But in the mid 1990's there was an important change: we cut our emissions of pollutants, yet the amount of smog just kept on rising.

So since the mid-1990s, we've lost control of the smog. It now depends on levels of pollutants that are produced outside Hong Kong, ie in southern China.

But we still see claims that local emissions are the source of our air-quality problems:

HK Magazine, June 12, 2009
At the beginning of this month, levels recorded at all 11 general monitoring stations were above World Health Organisation (WHO) guidelines. This despite the low-wind [sic] speeds recorded by the Observatory, which Greenpeace campaigner Prentice Woo Wai-Muk said revealed that it was surely being produced locally.
Albert Cheng in his SCMP column, 15^th Aug 2009
Hongkongers have for many years blamed the city's poor air quality on the polluting factories on the other side of the border. Indeed, many of these factories have suspended operation since the economic downturn began last year. But, despite this, our air quality remains atrocious, which has unequivocally proved that the pollution is local.

I think we're disagreeing because we're really talking about two different things. Let's clear that up first, by turning to the government for their description of the problem [3]:

The two greatest challenges are local street-level pollution and regional smog. Diesel vehicles, particularly trucks, buses and light buses, are the main source of street-level pollution. Smog is caused by a combination of pollutants mainly from motor vehicles, industry and power plants in Hong Kong and the Pearl River Delta.

Instead of talking about 'Hong Kong's poor air quality', let's be clear we're really talking about two different issues:

Local street-level pollution
Regional smog

If we can agree on that, we can move past the argument about whether our air-quality problems are caused by local, or regional pollution: Street-level pollution is a result of local, diesel vehicles, while the smog is mainly caused by pollution from outside Hong Kong.

Then on to the important question, which of those two should we fix first?

References:

These are the government's estimates of Sulphur Dioxide (SO2) produced in Hong Kong over the years 1990-2007. The graphs for other pollutants vary slightly in shape, but all end at much lower values in 2007 than in 1990. See them all here.
This line shows the Batgung Smog Index, derived from the Observatory's 'number of hours of reduced visibility' figures. Full details.
GovHK: Air Quality in Hong Kong

Bay windows: Begone!

mrb — Thu, 30 Apr 2009 01:00:00 +0000

A couple of things have come to bug me about Hong Kong apartments. First, they're built to catch as many rays of sunshine as possible. Second, the quoted floor-areas bear little relation to how much usable space you'll actually get.

Ten bonus points if you can guess the common cause of both bugs.

'Bay windows' you answer? Full marks, take the rest of the day off!

First, the bay window's role in making confusing floor-area measurements...

If you've bought or rented a flat in Hong Kong, you've quickly realised (if this is news to you, sorry!) that the quoted floor area is useless until you know the 'efficiency'. So if estate agent tells you 'this flat is 800 sq ft, with a 75% efficiency', what they mean is you're looking at a 600 sq ft flat.

Since the gross area is the figure that is quoted publicly (estate agent windows, developers' websites, etc), it makes comparing different buildings a hassle. You can't really compare them until you've got the efficiency from the agent, and done the quick calculation to find the net, usable space.

In the above example, the 'missing' 200 sq ft is made up of your share of public areas, and the area of any bay windows in your apartment. Bay windows are common in older UK houses, but there the bay area runs from floor to ceiling, meaning you really get extra floor space. Here in Hong Kong a bay window starts a couple of feet from the floor, and ends a couple of feet below the ceiling. So you get a big window ledge, but certainly no more floor space.

Now I have in mind that bay windows are so common because the developers (the people that build the high-rise apartments in the first place) get some benefit from them. Can anyone point me at any documentation that confirms this? Since everyone that buys or rents a flat is only interested in net values, I don't understand why we all have to put up with gross areas.

The other problem with bay windows is that they stick out of the building to catch every ray of sunshine. If you look at old buildings, some sort of veranda was common, shading the windows and helping to keep the interior cool. Ok, verandas aren't likely on the 40th floor, but keeping the window flat to the wall will be cooler than having a bay window. And a simple ledge above a flat window to provide shade will keep it cooler still. Cooler flats mean less aircon, and lower energy consumption.

If any architects are reading this, I'm sure it is nothing new or exciting. But can you explain why we don't do it?

Can't we start using net values when quoting floor areas? Especially if that takes away the incentive for developers to stick bay windows on new apartment buildings, and so save energy for all.

Hong Kong air pollution: better than it looks?

mrb — Thu, 26 Jun 2008 01:00:00 +0000

A few weeks back I asked if our air pollution is getting better or worse, then answered myself: worse over the last 18 years, but possibly getting better slowly in the last one or two years.

Then I went looking for some more numbers to back this up, but found that ... well, see if you find them as surprising as I did.

Visibility

That's the measure I used in the last post - 'hours of reduced visibility'. Here are the totals for recent years:

	Hours of reduced visibility over the year	Change since 1990	Change since 2000
1990	274	100
1995	459	168
2000	623	227	100
2005	1502	548	241
2007	1298	474	208

That matches my own perception, that the air has got considerably smoggier since the 1990s. Then a common assumption is that reduced visibility means lower air quality, so how can we check that?

Pollution concentrations

If you walk around Central, what's in the air that you breathe, and how has it changed?

The EPD have one of their roadside measuring stations in Central [1], and publish its records of pollution levels every hour [2]. I recognised 'Sulphur Dioxide' (SO2) as something unpleasant from school chemistry lessons, so how has that changed over the years. [3] (They only have records back to year 2000 for this station)

	Avg. hourly concentration of SO2 over year, ug/m3	Change since 1990	Change since 2000
1990		-
1995		-
2000	28.1	-	100
2005	24.2	-	86
2007	22.0	-	78

That wasn't what I expected to see: if you look back at the first table, there's over twice as much smoggy weather in 2007 compared to 2000. But if you look at what you're actually breathing, levels of one of the main pollutants has dropped over that same time!

Maybe I chose the best pollutant by luck? The station also records values for Carbon Monoxide (CO), Nitrogen Dioxide (NO2), Nitric Oxide (NO), and Respirable Suspended Particulates (RSP). How have they changed at this station over the same time?

	CO, change since 2000	NO2, change since 2000	NO, change since 2000	O3, change since 2000	RSP, change since 2000	SO2, change since 2000
2000	100	100	100	-	100	100
2005	107	101	98	-	104	86
2007	84	107	96	-	103	78

So it's not just the SO2. Across several pollutants the levels we actually breathe at street level have stayed fairly constant, or even fallen slightly.

Up on the roof

Maybe this only happens at street level? What if we look at the readings from the 'Central & Western' station [4]? This is one of the general measuring stations (the EPD calls them 'roadside' or 'general'). It is on a rooftop 18 metres off the ground, and is away from a main road. It doesn't measure Carbon Monoxide, but it does measure Ozone (O3). A bonus is that we can see measurements back to 1990 for this station.

	CO, change since 2000	NO2, change since 2000	NO, change since 2000	O3, change since 2000	RSP, change since 2000	SO2, change since 2000
2000	-	100	100	100	100	100
2005	-	111	105	106	107	122
2007	-	100	92	114	106	132

So here the changes are in the bad direction, with concentrations increasing. But still nothing like the doubling we saw with the smog levels. What if we look at the Central & Western figures back to 1990?

	CO, change since 1990	NO2, change since 1990	NO, change since 1990	O3, change since 1990	RSP, change since 1990	SO2, change since 1990
1990	-	100	100	100	-	100
1995	-	108	113	125	114	108
2000	-	106	106	180	96	91
2005	-	117	111	190	103	111
2007	-	106	98	205	102	120

Remember that over that time the weather got around 4 times smoggier? But if you live on a side street in Western Hong Kong, in say an old 6-storey building, then apart from Ozone, pollution levels in the air you breathe today aren't that much different from the air in 1990.

What am I missing?

Again, that's not what I expected, so am I missing something obvious?

And why do we feel the air quality has got so much worse over the last 10-20 years, when levels of most pollutants have only changed by a few percent?

Is it just that the pollutant that has seen the biggest jump in levels (Ozone) also happens to be one we can see, and so cannot be ignored?

A few more questions spring to mind - let me know if you have any answers, otherwise I'll look at them over the next few weeks:

How much of the reduced visibility / increased smog problem is directly linked to rising Ozone levels?
Then is reducing the ozone level the main activity to concentrate on if we want to lower the Batgung Smog Index, and bring the blue skies back?
Ozone isn't produced directly, instead it is a result of UV radiation acting on NO and CO or Volatile Organic Compounds (VOCs) [5]. Why is the Ozone level rising when the NO level remains steady?

MrB

References:

Central roadside monitoring station
Records of monitoring stations
Calculation of avg hourly concentration for a year:
- Download figures for chosen year (see [2]).
- Add up total of all hourly figures for the year.
- Count how many hours are marked 'N.A.' (not available).
- Work out how many hours are in the year, remembering to take leap years into account.
- Average = Total / (hours in year - number of N.A. hours)
Central and Western general monitoring station
Tropospheric Ozone

Can we have our blue skies back? Please?

mrb — Mon, 02 Jun 2008 07:28:10 +0000

You don't need a chemistry degree or expensive monitoring equipment to tell when the pollution is bad. When the view from the window shows the harbour shrouded in a smoggy haze, you know that whatever is in the air can't be good for us.

But how do you tell if it is getting better or worse?

If you've lived here long enough to look back five years or more, you'll definitely know things have got worse since then. But it's harder to tell if pollution levels are still rising, or we are starting to see signs of improvement.

Enter the Batgung Smog Index, the BSI. It's based on the simple approach described above – looking out of the window. We've taken the 'hours of reduced visibility' records published by the Hong Kong Observatory, and done some simple maths to give an easy to understand number. You can get the full description of the calculations here, but simply put, the more hours of smoggy weather there are, the higher the index goes.

The index is set so that the level for October 1989 is 100. No great scientific reason for choosing that date, it just happens to be the month I first arrived in Hong Kong. We're nearly 20 years on from then, so what do you think the current level of the index is?

The latest figures from the observatory set the April 2008 BSI at 436. That means we all have to put up with over four times as much smoggy weather each year as we did in the late 1980's.

Here's the chart of the index from the early 1970's until April 2008.

The level rises and falls in the 1970's and 80's, but from the 1990's it starts climbing rapidly. From 100 in Oct 1989 it crosses 200 in Oct 1997, 300 in Dec 2003, 400 in Jan 2005, and peaks at 499 in Oct 2006.

Encouragingly the level has fallen since then, but it isn't clear yet if it's the start of a long-term improvement, or a temporary reversal like we saw around 1995 and 2001. We'll have to watch the index to find out - we'll update it as the observatory releases new figures.

Any guesses how long we'll have to wait before the index hits 100 again, and we get our blue skies back?

MrB

How we calculate the BSI (Batgung Smog Index)

mrb — Mon, 02 Jun 2008 07:00:19 +0000

The idea behind the Batgung Smog Index (BSI) is to give a simple measure of whether air pollution in Hong Kong is getting better or worse over time.

It's based on the observation that when the air is smoggy, visibility is low and pollution levels are high.

Fortunately for us, the Hong Kong Observatory publishes monthly records of 'Number of hours of Reduced Visibility observed at the Hong Kong Observatory since 1968' [1]. They define 'reduced visibility' as 'visibility below 8 kilometres when there is no fog, mist, or precipitation'. So if visibility is reduced because there's a heavy rainstorm for example, that isn't counted in these figures.

If it's not fog, mist or rain causing reduced visibility, we can assume it is caused by smoggy air. So now we have a measure of how many hours the air is smoggy each year. Here's a graph covering the period Dec 1968 – April 2008. For each month, it shows the total number of hours of low visibility for the year-to-date.

The figure is relatively steady in the 1970's and 80's, but from the start of the 1990's it starts its climb upwards.

The lowest value was for the period Aug 1973 - Jul 1974, with just 140 hours of poor visibility (dirty air) recorded. The worst period so far was Feb 2004 – Jan 2005, when 1,702 hours of poor visibility were recorded!

Most recently, in the period May 2007 – Apr 2008 there were 1,448 hours of dirty air recorded. Better than the worse, but still a long way away from the best.

You can see that these figures swing up and down a lot, so it can be difficult to identify what is a short term change, and what is a longer trend. For instance in 2005 the government claimed the fall in the amount of hours of dirty air recorded meant their policies to reduce pollution were working. The local environmental groups pushed back that the reduction was just a result of higher than average rainfall.

So to smooth out some of the short-term changes, for the BSI I've chosen to use a three-year average of the annual values. The red line shows the effect of the smoothing:

The disadvantage is that it will be slower to show changes than the 'raw' line, and will also hide the worst extremes. Still, as a way to measure the long-term trend, it seems a reasonable compromise.

Interestingly, it looks as though the government may have been right, and the pollution levels have started falling. Time will tell if we're on a long-term downward (improving) trend, or it is a temporary reversal like we saw around 1995 and 2001.

Finally, to make the index a more manageable number, I've scaled all the numbers so that the value of the BSI for October 1989 is 100:

Why October 1989? Because that's when I first arrived in Hong Kong, and I'd like my blue skies back! The most recent value for the index is 436 for April 2008, so we've got a long way to go.

MrB

References:
[1] HK Observatory's Number of hours of Reduced Visibility observed at the Hong Kong Observatory since 1968

Where does Hong kong's air pollution come from?

mrb — Thu, 26 Apr 2007 01:00:00 +0000

Last month saw several articles in the media with headlines like:

Hong Kong producing most of its own pollution (AFP)

Local sources blamed for most air pollution woes (HK Standard)

If they are true, were earlier claims about regional pollution affecting us just a smokescreen? We’d certainly need to focus our efforts on reducing local sources of pollution, instead of those over the border. But if they’re wrong, we risk diverting people’s attention from the real source of the problem.

Unfortunately, they’re wrong.

Both articles were covering a report and press release issued by a local think tank, Civic Exchange. Neither document directly says that ‘Hong Kong Produces Most of its own pollution’. But for several reasons they make it easy for readers to reach this misunderstanding.

First the press release, which is probably what most of the media focused on. It starts with the headline:

NEW RESEARCH SHOWS 53% OF THE TIME HONG KONG’S DIRTY AIR CAUSED BY HONG KONG SOURCES OF POLLUTION

HONG KONG CAN DRAMATICALLY IMPROVE LOCAL AIR QUALITY DESPITE REGIONAL POLLUTION, SAY SCIENTISTS AND THINK TANK

53%? So over half of our air pollution comes from local sources?

No – but it’s an easy mistake to make. Yes, for over half (53%) of the days in a year more of our air pollution comes from local sources than from regional sources (ie those in Guangdong). BUT, on the days when most of our pollution comes from the regional sources, overall pollution levels are higher. So, over a whole year, more of the pollution (other studies put it at 60-70%) comes from regional than local sources.

Then how about that second headline? That also suggests a lot more is under our control. But what would be a ‘dramatic improvement’?

I expect it to mean an end to, or at least a significant cut in the number of days when thick smog blankets all of Hong Kong. It’s that combination of high pollution levels, the fact I can see it, and the feeling there’s nowhere to escape that makes me want to pack my bags and leave.

But even eliminating all locally produced pollution would have little effect on those smoggy days, since they’re usually days when ‘regional pollution’ predominates. Also, even on the worst local-pollution days, the high levels tend to be concentrated in just a few areas of Hong Kong. On the worst of the regional-pollution days, it affects all Hong Kong, giving that ‘no escape’ feeling.

If you then go on to read the full report, there’s another pitfall awaiting you.

It classifies polluted days as belonging to one of five different pollution patterns. There are three patterns where regional pollution dominates, and two when most pollution comes from local sources. The study gives charts showing typical pollution levels at different sites around Hong Kong. Here I’ve brought the readings for Mong Kok together:

So you’d probably rate the days with the ‘Local Vehicle / Power Plant’ pattern as having the worst pollution? But if you squint at the numbers you’ll find the readings are drawn to different scales. If we use the same scales for each chart, we get quite a different result:

I’m in two minds about the report. On one hand it seems unfair to criticize it. It makes an important point that pollution levels are under our control most of the year. It also gives good recommendations (I especially like the measures to reduce pollution from shipping) that will help make Hong Kong’s air cleaner.

But on the down side it seems very easy to misinterpret, giving readers unrealistic expectations for the benefits of local changes … 53% reductions! The ‘wrong’ interpretation is exactly what has been reported by several local and international media. When actual improvements turn out to be far less dramatic than expected, it leads to confusion at best, or disappointment and cynicism at worst.

It would have been better to focus on the results of the study that are smaller scale, and improvements that can realistically be achieved, eg the effects of pollution from shipping on the areas around the container port, and the measures to reduce them. Not such a news-grabbing headline perhaps, but one where it is true to say the area can ‘dramatically improve local air quality despite regional pollution’.

Getting rid of those smoggy days is still going to need lots of help from our friends across the border.

MrB

Further info: Has misinterpretation really been a problem, or am I imagining problems where none exist? We can take a look at how the report and press release have been reported in the press to see how they have been interpreted, and the type of expectations they set.

I ran a google search for “civic exchange institute for the environment pollution”, and found the following references to these documents in the first 20 results:

Clean Air Initiative: Headline: “[…] local sources are the primary influence on Hong Kong’s air quality and not regional sources.”
AFP (A worldwide press agency, so this article was also shown on several other news sites such as Yahoo News): “Hong Kong producing most of its own pollution: study HONG KONG (AFP) — Most of the pollution blighting Hong Kong is produced in the city itself rather than neighbouring southern China, according to a study released Wednesday which contradicts previous research.”
The HK Standard: Headline “Local sources blamed for most air pollution woes”
Clear The Air: '"Dirty Sky Days" More than half are from Hong Kong sources’
The Economist: “However, a new report […] finds that in 2006 Hong Kong's air pollution was caused more often by local sources (road traffic, coal-fired power stations and ships) than by factories in southern China. Local emissions were the main cause of pollution on 192 days; those from the Pearl River Delta on the mainland on 132 days. The other 41 days had low pollution.
This does not necessarily contradict the government's findings. Pollution from the mainland may well be worse measured by volume, so more pollution probably does come from the mainland (where many factories are owned by Hong Kong firms). But the findings do suggest that Hong Kong can itself do more to improve its air.”

So, a well-balanced article from the Economist, and the Standard’s article is also more balanced than the headline suggests. But the incorrect ‘Hong Kong producing most of its own pollution’ interpretation is more common.

pollution and housing

Thu, 06 Jul 2006 11:49:35 +0000

We're moving to HK for the 2nd time, but this time with 2 small children (3 and 4.5 years). Lived in Midlevels (western) before, now, where to go now that apparently the pollution has become much much worse! Is South side better? Any tips? Will be working in Central and don't want to commute too much. I've read all the pollution indexes and it seems to boil down to central or western with the lowest average score ... If I want the kids to start learning Mandarin will an Int'l school suffice or will it have to be a local school?

Is the pollution in Hong Kong really bad?

batgung — Wed, 01 Sep 2004 10:02:59 +0000

Question: I've heard that Hong Kong is really, really crowded and polluted. Will I be able to stand it?

Mr T replies: You may find the pollution distressing at times, but there are also many parts of HK that are amazingly unaffected.

Air pollution is a problem in Hong Kong - there's no denying this. But in many outlying areas such as Sai Kung and the south side of Hong Kong Island, it isn't as bad as right down amongst the skyscrapers downtown. A lot of the pollution in HK drifts down from southern China when the winds are from the north, and covers the whole city. When the winds are southwesterly, which is the prevailing directing in the summer, it's often far better.

Hong Kong has quite a few beaches, and most are all right for swimming, if not pristine. I've certainly swum in Deep Water Bay and Repulse Bay (on Hong Kong Island) and Clearwater Bay (in the eastern New Territories) numerous times with no ill effects. The water is at its best in the autumn, when the weather here is dry. In the summer, the water tends to be a bit muddy, because there's so much runoff from the heavy rain we get. A more remote beach, Tai Long Wan, is particularly good -- by far the best beach in HK, by my reckoning, and I know Mr B concurs. See his series of hiking photos of a trip to there here. There are also some decent beaches on Lantau Island, and lots of little 'unofficial' beaches you can get to by hiking only.

Hong Kong is also very mountainous. The built-up areas account for only about 10% of the land area, so there are actually places you can get totally lost in the wild. Both Mr B and Mr T like to hike, and we've got lots of information on this on our hiking page.

All in all, the situation is lot better than you might expect from the world's most densely populated city!