Timaru has worst air pollution in Australasia (?)
Stories like this have been appearing in the press around the world recently:
http://www.stuff.co.nz/timaru-herald/news/80075184/timarus-air-pollution-the-worst-in-oceania-figures-reveal
This has been triggered by the release of a global air quality database by the World Health Organisation (WHO). The data they have used (in the case of Timaru) actually comes from Environment Canterbury (ECan) and specifically the continuous monitoring site they operate in the town. It's just the same as the ECan site in the centre of our CONA pilot study town of Rangiora.
Press in other countries have basically done the same thing - looked through the database to find the worst or most surprising results in their local area and done some international comparison.
I'm sure many readers abroad have come across the NZ figures and gone "Timaru? Never heard of it!" Well they have now.
But is this 'notoriety' justified? I've already responded to several enquiries asking me if the figures are true, biased, distorted or downright lies.
Several have commented that ECan have "cheated". There is a feeling amongst some that ECan want the figures to be bad so that they can justify their air plan. It has been pointed out that ECan's monitor is deliberately placed in the most polluted spot in town to ensure high concentrations are recorded which do not reflect actual conditions in most of the town.
Well, they are dead right - that is exactly what ECan have done. It's exactly what they've don in every monitored town in Canterbury. They've done that because that is what the regulations require them to do. Them and every regional council in the country. The official guidance to councils is to conduct air quality monitoring in a location at which peak concentrations are to be expected. The rationale is that if air quality standards are met at these peak locations, then they are met everywhere in the town. This approach reduces the cost of monitoring as (in principle) only a single site is required.
So, ECan are not "cheating" at all - they are following quite sensible guidance.
There are, however, a few unfortunate limitations to this approach.
Firstly, it requires you to know in advance where concentrations are going to be highest. Now in the case of Timaru (and several other towns) ECan have done some 'screening monitoring' of other locations (this and other data is covered in ECan's report here) and so have some reasonable evidence that they've picked the right place. This is sometimes supported by dispersion modelling, and by expert knowledge - an understanding of the physical principles of dispersion compared with a good feel for where the worst emissions are happening.
But in many places this work or understanding is lacking, or could be out of date. Dispersion modelling conducted a few years ago (not yet published) suggested that peak concentrations in Rangiora might not occur in the centre of town (where the ECan monitor is) but towards the eastern edge of town because of the effect of "drainage flows" - the weak westerly winds that roll across the Canterbury Plains from the Alps to the sea on many winter evenings. Our CONA 2015 pilot study was not long enough to confirm this, but data from our ODIN sensors suggested it could be true. During winter 2016 we plan to deploy more ODINs across Rangiora and by the end of 2016 we hope to have a clearer idea of how air quality varies across the town.
As for Timaru - it does indeed report the highest annual average concentrations of particulate matter recorded in the country. We'd love to bring CONA down to Timaru as soon as we've verified that the technology works, to clarify not just how air quality actually varies across the town, how representative or 'biased' the ECan site is, and most importantly WHY its air quality is stubbornly poor.
Which brings me finally, to the other limitation of monitoring peak sites. And that is that most other countries don't do it. Australia, for instance, does the complete opposite - requiring that air quality is monitored in 'typical' locations, with peak sites being explicitly avoided. This makes international comparisons somewhat problematic. Our PM10 and PM2.5 values are automatically higher than they would be if we followed the approach of other countries. There is not much Joe Public can do about this.
Except that, in the near future, CONA will start to reveal what those 'typical levels' of air quality in NZ towns are.
http://www.stuff.co.nz/timaru-herald/news/80075184/timarus-air-pollution-the-worst-in-oceania-figures-reveal
This has been triggered by the release of a global air quality database by the World Health Organisation (WHO). The data they have used (in the case of Timaru) actually comes from Environment Canterbury (ECan) and specifically the continuous monitoring site they operate in the town. It's just the same as the ECan site in the centre of our CONA pilot study town of Rangiora.
Press in other countries have basically done the same thing - looked through the database to find the worst or most surprising results in their local area and done some international comparison.
I'm sure many readers abroad have come across the NZ figures and gone "Timaru? Never heard of it!" Well they have now.
But is this 'notoriety' justified? I've already responded to several enquiries asking me if the figures are true, biased, distorted or downright lies.
Several have commented that ECan have "cheated". There is a feeling amongst some that ECan want the figures to be bad so that they can justify their air plan. It has been pointed out that ECan's monitor is deliberately placed in the most polluted spot in town to ensure high concentrations are recorded which do not reflect actual conditions in most of the town.
Well, they are dead right - that is exactly what ECan have done. It's exactly what they've don in every monitored town in Canterbury. They've done that because that is what the regulations require them to do. Them and every regional council in the country. The official guidance to councils is to conduct air quality monitoring in a location at which peak concentrations are to be expected. The rationale is that if air quality standards are met at these peak locations, then they are met everywhere in the town. This approach reduces the cost of monitoring as (in principle) only a single site is required.
So, ECan are not "cheating" at all - they are following quite sensible guidance.
There are, however, a few unfortunate limitations to this approach.
Firstly, it requires you to know in advance where concentrations are going to be highest. Now in the case of Timaru (and several other towns) ECan have done some 'screening monitoring' of other locations (this and other data is covered in ECan's report here) and so have some reasonable evidence that they've picked the right place. This is sometimes supported by dispersion modelling, and by expert knowledge - an understanding of the physical principles of dispersion compared with a good feel for where the worst emissions are happening.
But in many places this work or understanding is lacking, or could be out of date. Dispersion modelling conducted a few years ago (not yet published) suggested that peak concentrations in Rangiora might not occur in the centre of town (where the ECan monitor is) but towards the eastern edge of town because of the effect of "drainage flows" - the weak westerly winds that roll across the Canterbury Plains from the Alps to the sea on many winter evenings. Our CONA 2015 pilot study was not long enough to confirm this, but data from our ODIN sensors suggested it could be true. During winter 2016 we plan to deploy more ODINs across Rangiora and by the end of 2016 we hope to have a clearer idea of how air quality varies across the town.
As for Timaru - it does indeed report the highest annual average concentrations of particulate matter recorded in the country. We'd love to bring CONA down to Timaru as soon as we've verified that the technology works, to clarify not just how air quality actually varies across the town, how representative or 'biased' the ECan site is, and most importantly WHY its air quality is stubbornly poor.
Which brings me finally, to the other limitation of monitoring peak sites. And that is that most other countries don't do it. Australia, for instance, does the complete opposite - requiring that air quality is monitored in 'typical' locations, with peak sites being explicitly avoided. This makes international comparisons somewhat problematic. Our PM10 and PM2.5 values are automatically higher than they would be if we followed the approach of other countries. There is not much Joe Public can do about this.
Except that, in the near future, CONA will start to reveal what those 'typical levels' of air quality in NZ towns are.
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