Intervening on air pollution

How is air pollution from transport affecting our health, and what can be done about it?
28 May 2019

Interview with 

Chris Griffiths, QMUL; Anneliese Allen-Norris, EDF




Air pollution is having a significant impact on human health. So how is it impacting us, and what can be done about it? Katie Haylor spoke with primary care expert Chris Griffiths from Queen Mary University of London, and Anneliese Allen-Norris from Environmental Defense Fund Europe...

Chris - Well pollution is a complex mixture of gases and particles. When people talk about air pollution at the moment they're generally thinking about traffic related pollution, although it's broader than that. The particles from for example burning wood and coal and so forth, others from diesel engines and internal combustion engines, gaseous pollution, a mixture of gases, nitrogen oxides, nitrogen dioxide, sulfur dioxide, ozone, carbon monoxide and so forth. These vary in concentration in the atmosphere depending on climate, wind, sources of pollution, and so forth.

Katie - So what is the evidence that links poor air quality to adverse health outcomes?

Chris - Largely comes from epidemiological studies so large observational studies. But it goes back a long way. Now the evidence is very strong across the life course, the Royal College of Physicians published a major report a couple of years ago showing that before a child is born, right the way through to old age, pollution is adversely affecting health. Whether it's the development of the child in the womb, development of conditions like asthma during early years, stunting of lung growth, stunting of brain development, to in older life incidence of heart attacks, strokes, dementia and of early death.

Katie - As Chris explains, it's not just the lungs that are affected by air pollution.

Chris - Pollutants which are inhaled, are absorbed and are able to travel around the body and have distant effects. So soot particles get lodged in cells from the immune system in the lining of the lungs and the greater the concentration of particles, the greater the adverse effects on the lung. But these particulates, particularly tiny particles, travel further so they've been detected in the bloodstream, brain and most recently in the placenta. The way in which they're adversely affecting health is not well understood, but it's likely to be a combination of deranging the immune system, causing long term inflammatory effects within the tissues, which will deliver the observed effect.

Katie - Now the exact mechanisms involved here aren't well understood and there are potential confounding factors which need teasing out, but scientists are concerned that air pollution could have life long and developmental impacts. So who is most at risk?

Chris - One of the important things is that poor air quality tends to be visited on disadvantaged populations more than advantaged populations. So the health effects tend to be unequally distributed across the population, so disadvantaged people tend to live in more congested, densely packed areas often closer to polluting roads and environments and so forth. So an important element of this whole drive to address air quality is to try to redress the health inequalities.

Katie - Now that we have some understanding of what air pollution is doing to our health, how much of this can be laid at the door of roads?

Anneliese - In London which is primarily where we're doing a lot of our scientific work with our Breathe London project, we know that the last lot of data, from 2016, the verified data, shows that around 50 percent of the nitrogen dioxide emissions come from transport, so mainly passenger transport  - that is diesel cars primarily. So we know that it's a significant issue.

Katie - That's Anneliese Allen-Norris from the Environmental Defense Fund, an international charity who bring scientists, economists and lawyers together to tackle environmental issues.

Anneliese - Trying to divide this column of pollution, that's a difficult thing to do. But it's one of the things that the work that we're doing with our Breathe London project is trying to address. The technology and the science is very complicated and it's also affected by weather. But there's very sophisticated modelling there that enables us to really tease out what these different sources of pollution are, if we know that we can put in place regulations that tackle those individual sources.

Katie - The Breathe London project that Anneliese mentioned there is a 12 month project involving partners from a variety of different organizations which aims to bolster the air quality monitoring infrastructure in London. The aim is to get a much better idea of air pollution exposure at a hyper-local level which can then better inform policymakers about the effectiveness of interventions designed to tackle air pollution.

Anneliese - London actually has a quite large network of reference grade monitors across the city, it's got around 100 in its main network which is one of the largest of most cities. However there's a lot of people in London and there's a lot of vulnerable populations in London, and there's not necessarily that hyper-local, empirical data in each of those locations. A lot of the gaps are often filled by modelling and obviously the more actual data that we can get, particularly in sensitive locations, schools for example around hospitals, that's really important. And that's kind of where we come in.

So Breathe London is multiplying the number of sensors in that network in London, combining what's already there with a whole new suite of sensors. We've got an extra 100 new, state of the art static sensors which measure various different pollutants. We've also got Google Street View cars which are jam packed of all of these sensors which are taking street by street measurements every few seconds across the city. We've also linked up with King's College and they have wearable sensors where schoolchildren and teachers are taking those sensors with them in backpacks on the way to school, so that you get a really local exposure measurement. We're making sure that this project is policy-relevant. A lot of our fixed monitors are deployed in schools so we're measuring pollution in areas where the most vulnerable populations spend their time, at the most polluted times of the day. We're also looking at different types of populations, so high and low deprivation areas and also really mixed areas in kind of major town centres and we're seeing differences in street by street level really.

Katie - For about a month now London has had a 24/7 ultra low emission zone within the central area of the city, where there is already a congestion charge. The ULEZ, as it's termed, ads on an additional twelve pound fifty a day for vehicles entering the zone which are not compliant. So older diesel and petrol vehicles. So how this extra charge made a difference to air quality?

Anneliese - It's only been in place for sort of a month or so and during that period of time we've had quite unusual days where the city centre might be cut off anyway. So we've had the Easter period where a lot of people would be on holiday. Also we've had Extinction rebellion and a lot of protests where the streets have been closed and the London Marathon. So we've only got a few days to look at and certainly the data that the mayor's office has provided suggests that there's far fewer vehicles which are the dirtiest vehicles entering the city centre. Now how that translates into meaningful pollution reductions is something that we're hoping to measure and we're keeping a close eye on that and we're hoping to be able to say more in a few months time about that.

Katie - Crucially, Breathe London started collecting data prior to the introduction of the ULEZ, so they should be able to compare pollution levels before and after the policy introduction.

Anneliese - One of the key things is that we are also measuring carbon dioxide which is not what the current London network does. And that enables us to some extent to correct for the uncertainty that we do have around these meteorological effects and the impact of the weather on the pollution that we see. So we can really start to attribute where that pollution is coming from. So we should be able to better inform the mayor and citizens generally about the true impact of the ultra low emission zone and smaller interventions that might be happening around the same sort of time.

Katie - Chris Griffiths, who we heard from earlier, is also working on investigating the impact of the ultra low emission zone.

Chris - We're evaluating this by setting up cohorts of primary school children both in central London and in a neighbouring large town with relatively poor air quality, that's Luton. Actually in both those areas we're expecting improvements in air quality because the general trend will be towards an improvement. It's likely that there'll be a larger improvement in London and so we have two groups of children, one in whom there will probably be larger improvements in air quality if the ultra low emission zone delivers what it's supposed to do. Over the next year we'll be measuring the health of those children so we'll be trying to demonstrate whether improving air quality prevents the stunting of children's lung development. That's a primary aim of the study.

Katie - In the carrot and stick analogy, discouraging drivers from bringing dirtier vehicles into central London is arguably the stick. So are there any policy carrots when it comes to air pollution?

Anneliese - That plays on my mind a lot of the time. One of the things that the new data and more hyper-local data throughout the day can offer is better forecasting. So you can forecast for episodes of very high pollution and that could be used to restrict access even more stringently to certain areas whilst putting in policies, such as reducing the cost of transport for those particular days, so that you're giving people an alternative means of transport so they don't have to get in their car which might not comply with the restrictions. And we do see that happening in other cities such as Barcelona and Paris to an extent.

Being able to offer people an alternative means of transport through either shared transport or better access to bus services is something that's obviously necessary for people who don't have cars that comply. There's also very little being done in terms of incentivizing either citizens or businesses to transition to cleaner cars and vans. It's something that California has been doing for quite a while. The government could be putting in place market incentives that allow the industry to really progress so that the number of options for customers increases and is pushed forward onto the market, rather than continuing to incentivise people to purchase the dirtiest vehicles which is what we're seeing at the moment. And certainly things like an interest free loan which is what the Scottish Government did a couple of years ago, which is just finished now, which enabled people to actually get a new car which is an electric car, interest free with a loan. Those are the sort of policies that should be explored here, but we don't see much progress in terms of those sort of policies at the moment. It's something that's a real point of tension and it's something that the government needs to be addressing because if you're restricting access to the centre of a city, then you need to be able to offer to people means of transitioning to cleaner modes of transport.


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