Batgung

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.