“People have been aware of air pollution for centuries”

Anna Hansell is Professor of environmental epidemiology and director of the Centre for Environmental Health and Sustainability at the University of Leicester, which was set up three years ago. The centre has established a new health protection research unit in environmental exposures in health, and is working with Public Health England (PHE) and the Health and Safety Executive.

Hansell has been a member of the Committee on the Medical Effects of Air Pollutants (COMEAP) for the past 12 months and has just been appointed its chair. Prior to that she spent nine years on the Committee on Toxicity of Chemicals in Food, Consumer Products and the Environment.

As told to Katie Coyne

Congratulations on being appointed COMEAP chair. What does the committee do?
What's quite important to realise about COMEAP is that it's a technical advisory committee. So it's not a campaigning body, it's not setting policy, it's providing scientific advice to the government. A lot of the work that's done is not us saying 'we ought to study this'. It's the government saying ‘we need some advice on the science so that we can think about the policies that we implement’.

[On air pollution] COMEAP's role is to produce the right exposure-response coefficient – so air pollution concentrations and hospital emissions, or air pollution concentrations and mortality – and we'd recommend [the government] use those in cost benefit calculations. Additionally, we'll say 'and here are some of the issues related to those’. One of the problems we're dealing with is in normal life you're not just exposed to particulates, you have NO2, you have ozone, you have various other pollutants you're exposed to at the same time. And it may be not correct to just add everything up.

Has the pandemic made people generally more aware of air pollution?
Yes but it was happening anyway. I think it's fair to say people have been aware of air pollution for centuries. We had dreadful air pollution in the Middle Ages from dirty coal. There were campaigns in the 19th century about air pollution, and then we had the London smogs, and the great London smog in 1952, which really focused people's minds and we had the Clean Air Act after that.

Air pollution levels in general have fallen over that time, and we thought for a while things had improved because we couldn't see it. Then our studies got better and we realised air pollution is still having effects even at much lower levels. What’s really concerning is that you can't say below a certain level there's no effect of air pollution, because you can actually detect effects down to extremely low levels. And there are currently studies, large European studies and studies in Canada, that have been looking at much lower levels of air pollution and still detecting associations with health outcomes.

Has the pandemic increased an awareness of the importance of environment on health?
People are becoming much more aware of how what we do to the environment can come back and affect us on an individual level. That is a really big change. And that's a positive change because people want to live in a good environment. One of the unexpected benefits [of lockdown] was reductions in air pollution and people getting out and walking about a lot more and appreciating the environment. That awareness is really important.

There is also more awareness of what you're exposed to indoors. We've got a much better idea of what people are exposed to outdoors than we do indoors, because everybody's home varies. There's a lot more research now going on into this area, and that's going to be important going forward.

You have been personally working on how air pollution interacts with COVID-19. Can you tell us a bit more?
It's actually been quite difficult to do this because we knew very little about the disease when it first started. Knowing something about this disease is quite important to understand how air pollution might affect it. But it's quite clear that chronic conditions were associated with worse outcomes if you were infected with COVID. And we already knew from the literature that those types of chronic conditions are associated with air pollution. So there's a plausible hypothesis that air pollution in the long term can increase your risk of chronic conditions that put you at high risk of complications from COVID.

It’s been harder to show that directly for various reasons, one of which is that COVID outcomes are also worse – there are associations with ethnicity and deprivation. And those deprived areas with higher proportions of ethnic minorities tend to be areas that have higher air pollution. Disentangling all those factors is quite difficult.

And it's been even harder to do that type of research during a pandemic when everything's got a bit disrupted. It’s a work in progress and it's important because COVID is going to be around for a long time.

You’ve also been working on noise pollution. Can you tell us more?
I've been looking at looking at noise pollution for over 10 years now. And I think it's been increasing in awareness. There are thousands and thousands of air pollution studies, and a few hundred on the noise side. One of the first studies that I did was looking at aircraft noise around Heathrow and finding associations with hospital admissions and deaths from heart disease and stroke. That was what we call an ecological study – an area level study – so it's not conclusive proof, but it provided you with something that was quite important to investigate further.

What's been really helpful in terms of raising awareness is the World Health Organisation has been looking at it as well. They published noise guidelines for the European region in 2018 and systematically reviewed all of the evidence looking at noise and health and found that for some things like ischemic heart disease, the evidence was of reasonable quality of an association.

It's not a large association, but it's there. Almost everybody's exposed to some form of transport noise, so a small increase in risk can translate into reasonably large numbers. PHE is currently trying to look at this in the burden of disease. My centre did work for them looking at more recent evidence than for the WHO reviews, to inform their exposure-response coefficients and build a tool that could be used to calculate the burden of disease. That's an ongoing piece of work PHE are leading on, but my team has had some input.

Is the calculator just for noise, or other pollutants as well?
This is just for noise. But we think it could incorporate other things as well such as air quality. It's a bit abstract talking about increases in risk, and it’s important to quantify. People sometimes think 'it's risky to go outside' and that's the last thing we want people to be to be taking as the message. There’s quite a lot of studies that show that when doing exercise the benefits to your body much outweigh the adverse effects of air pollution exposure or noise exposure.

One of the things about looking at noise and also looking at air pollution is you become very aware of co-benefits – and that comes in very much with climate change as well. Changing the way in which we move about our cities could have benefits to reduce air pollution, to reduce noise exposure and help reduce carbon emissions. That's the sort of sweet spot that we'd like to see us moving to in a society. That’s a policy issue. COMEAP provides the evidence for changes in policy relating to air pollution, but as chair I can also flag that there are benefits from potentially other exposures that could be quantified and fed into cost benefit calculations.

Air pollution doesn't exist in a little bubble on its own, it's linked with various other types of exposures. It's quite clear that there are co-benefits that you can get from changes in air quality.

Do you think environmental health as a discipline helps you see the bigger picture?
That bigger picture is really important. I think the committee is good at looking at that because there's people from all sorts of disciplines. We very much think in a multidisciplinary way at the centre too. I think it’s good to lean to speak other scientific languages, which is important. It’s easy to slip into jargon, and it’s good to get an understanding of what people mean by certain terms.