Transport Committee
Oral evidence: Scrutiny of the draft Heathrow Expansion National Policy Statement, HC 482
Tuesday 8 September 2026
Ordered by the House of Commons to be published on 8 September 2026.
Transport Committee members present: Ruth Cadbury (Chair); Steff Aquarone; Dr Scott Arthur; Jacob Collier; Daniel Francis; Olly Glover; Alex Mayer.
Environmental Audit Committee member present: Barry Gardiner.
Questions 140–186
Witnesses
II: Professor Charlotte Clark, Professor of Environmental Epidemiology, City St George’s, University of London, Professor Anna Hansell, Professor of Environmental Epidemiology, University of Leicester, and Professor Alastair Lewis, Professor of Atmospheric Chemistry, University of York.
Written evidence from witnesses:
Witnesses: Professor Charlotte Clark, Professor Anna Hansell and Professor Alastair Lewis.
Q140 Chair: Welcome to our second panel this afternoon. Could I ask our witnesses to introduce themselves?
Professor Clark: Hi. I am Professor Charlotte Clark. I am professor of environmental epidemiology at City St George’s, University of London.
Professor Hansell: Hello, I am Professor Anna Hansell. I am a professor of environmental epidemiology at the University of Leicester. I am also director of the Health Protection Research Unit in Chemical Threats and Hazards, which includes noise and air pollution, and chair of the Committee on the Medical Effects of Air Pollutants.
Professor Lewis: Hi, I am Alastair Lewis, professor of atmospheric chemistry at the University of York and the National Centre for Atmospheric Science. I chair DEFRA’s air quality expert group and the Department for Transport’s Science Advisory Council.
Q141 Chair: Welcome. In this session, we are going to cover air quality and noise. Is the air quality test as expressed in the draft HENPS sufficient to protect public health in the event of Heathrow expansion?
Professor Lewis: I will give you a short answer, which is that it is pretty deficient. It is probably the weakest of the tests, because it is the only test that allows the current position to get substantially worse. As formulated, it would allow air quality to degrade up to the limit prescribed in law. It also only covers air pollutants that are included in the 2010 air quality regulations. Given that we are planning for the future, that means it does miss out some other pollutants as well.
Professor Hansell: The difficulty we have is around ultra-fine particles in particular. We have concerns about those, but the evidence base is not so strong as to be able to give definitive answers on the exposure/response relationship on health. But that evidence base is increasing over time. The evidence base is good on short-term effects, and less good on long-term effects, but we may find ourselves in a situation that we are overtaken by the evidence if we don’t look at it now. It was considered in the World Health Organisation air quality guidelines update in 2021, and they have issued a good practice statement rather than including it in the guidelines at present.
Chair: I should have said at the start that we expect several votes at 6 pm. We will have to finish then, so I make the same point that I made to the previous panel about answers being brief, but we are happy to receive supplementary information in writing afterwards.
Q142 Jacob Collier: Is a pass/fail test appropriate to assess air pollution? If not, what would be a more appropriate way?
Professor Lewis: It is a good question. Air quality benefits from having a limit value for annual mean exposure. It is a positive thing. There isn’t one for noise. It does mean that everything tends to then focus on, “Have you passed or failed the legal test?” It is often misinterpreted as being “healthy” or “not healthy”. The reality is that the limit value is the maximum allowable harm, essentially, that Government have permitted from air pollution. Simply passing the test or failing the test does not mean that no harm is accruing.
It is a very useful measure at the macro level for the country—it is called an apex standard. It is unhelpful when you are looking at individual new sources because it creates the impression that you should pollute up to the limit, as if no harm will keep adding as you add more pollution, and that is not the case. Here, what we are talking about is a test that would essentially allow more pollution to be added, right up until filling the pot to the brim of pollution. Actually, air quality around Heathrow has improved quite a bit over the past few years, so that would essentially allow us to go into reverse and to worsen air pollution up to those limits.
Professor Hansell: I strongly support those comments. One of our issues currently is that our regulatory limits are higher than the WHO health-based air quality guidelines. We know that there are health effects under those levels. There are ongoing health impacts even when we are at the regulatory limit.
Q143 Jacob Collier: How consistent is the HENPS approach across different pollutants?
Professor Lewis: It is essentially focused on two pollutants: PM2.5, which was mentioned briefly, and nitrogen dioxide. They are both in the air quality regulations. In terms of breaching current limits, nitrogen dioxide is the one that is closest to the limit. In fact, we only have to go back about five years, and lots of areas around Heathrow were actually above the legal limit for NO2; they are now below.
PM2.5 is a really important air pollutant, but aircraft engines do not generate very much PM2.5; they generate the tiny fine particles that Anna mentioned, so they do not add much mass to PM2.5—they are a subset of PM2.5. The tests mention monitoring of those ultra-fine particles, but then there is a whole set of other pollutants, which might emerge in future from the use of SAF, like formaldehyde and so on, so it is a very narrow legal interpretation of the bare minimum, I would say. Essentially, it is written as, “You cannot break the law.”
However, because we have seen such progress in air pollution in London in general and around Heathrow, it is worth unpacking why those pollutants have got better. They have largely got better because the public and businesses have invested in cleaner vehicles. So, as written, the test says, “Those investments that the public and businesses have made in cleaner vehicles can be reversed by growth in pollution at the airport.” I do not think that that is made clear in the planning statement. It is actually not consistent with the broader national planning policy statement on how pollution is treated, but we might cover that later.
Chair: Scott, you wanted to come in on the WHO.
Q144 Dr Arthur: Apologies, I do not know what the air quality is like outside this building or at Heathrow, but—
Chair: It is bad.
Dr Arthur: My understanding is that we are some way as a country from meeting the WHO targets in our towns and cities. That is why the targets are not in law in the UK just now, but it seems likely that, at some point over the next decade, a Government might put them into law and start to work us towards them, probably over the decades to come. What I think you are saying, however, is that in and around Heathrow, if we go ahead as planned, it will never meet those targets, which could be future legally binding targets in the UK; it will never meet them in the decades that we are looking at in this model. Sorry if I put words in your mouth.
Professor Lewis: I am going to sound like I am picking the words apart like a lawyer, but there is quite a big difference between a guideline and a target. Guidelines are values at which the evidence for harm becomes clear, so those numbers are actually quite low—there is very good evidence about low concentrations where harm accrues—and a target is a pragmatic value that a Government have to pick. It may not necessarily be possible to align the guideline with the target, but you are right that we are likely to see further pressure to reduce the maximum limit for PM2.5, although I do not think that that is the biggest issue, because it seems likely that, in future, some target will emerge on ultra-fine particles. We have already seen in the EU that the limits it sets for nitrogen dioxide have moved from 40 micrograms to 20 micrograms. If you perceive that we might at some point align with those, there will be some quite large jumps in the targets as well. As written, I believe that the draft plan requires only no breaches of the current targets; I do not think it is written in a way to say, “or any future target”—
Q145 Dr Arthur: Those targets were set when? Those targets are quite old, aren’t they?
Professor Lewis: It depends which one: the nitrogen dioxide one has been in place for quite a long time—I think 20 years—
Barry Gardiner: Since 2010.
Professor Lewis: Okay, getting on for 20 years. The PM2.5 target was revised as part of the Environment Act 2021, so that is more up to date. We do not have anything yet on UFP, although as Anna mentioned, there are now guidelines on at least starting to monitor UFP, which is the precursor, potentially, to setting a target. It is quite a fast-moving field. We have to project, on the timescales of this potential development, that almost certainly the targets that are being worked towards will be lower.
Q146 Barry Gardiner: Professor Lewis, are you aware of the National Highways air quality mapping service, which did a review of the M4 between Boston Manor Road and Heston services in 2025? It showed that the NO2 concentration at that point was 39 micrograms per cubic metre. The 2010 limit or target—not—is 40. Given the amount of work that needs to be done by heavy goods vehicles to create a third runway, is it possible to meet the test in the draft HENPS that says that “the Secretary of State must be satisfied that—with appropriate mitigation, surface access strategies and operational measures—the scheme would not cause air quality impacts that result in any new breaches of legal obligations on air quality or make existing breaches materially worse”? That refers to the 2010 limit of 40 micrograms per cubic metre. That is a long question, but I hope you see that there is a very short distance between where we are already and what would breach the guidance.
Professor Lewis: There are slightly special rules for how concentrations along motorways are treated, because people do not typically live there. I am pretty positive that we will continue to see reductions in concentrations of NO2 around Heathrow, largely down to the improvements in the road transport fleet, because we are electrifying both passenger cars and goods vehicles. We are on a trajectory that is going to see NO2 concentrations improve. I suspect that, with nothing happening, we will begin to see those concentrations reduce.
There are some actions within the H8 price controls, potentially around proposals to do things like put heat pumps into some of the terminal buildings. Those will all go in the right direction.
Q147 Barry Gardiner: I asked you specifically about the construction traffic and the impact it would have.
Professor Lewis: My guess would be that it will not have a substantial impact, largely because modern construction equipment, like modern HGVs, is pretty clean. If it follows the same pattern as large construction projects like the Thames crossing and so on, it tends to be part of the DCO that you have to use the most up-to-date emissions standards. I am more relaxed on that because large developments tend to have to use the most modern equipment anyway, which is typically pretty clean. That is embedded in a system where transport is largely electrified.
Barry Gardiner: In terms of a recommendation, would you wish to see in the revised HENPS a condition that developers only use the electrified HGVs?
Chair: Given that we do not have enough grid power around Heathrow, I think that is a step too far. We could do with some more electrification on their side as well. It is a useful point, Barry, but I want to move on.
Q148 Steff Aquarone: You have talked about targets and thresholds, but what about limits? What happens if a business or a project like this is found to have broken air quality limits in the course of time?
Professor Lewis: This is where it becomes quite Byzantine and complicated. If you are asking who is going to carry the can—
Steff Aquarone: What are effective enforcement mechanisms?
Professor Lewis: If we go forward 30 years and a third runway has been built, air quality standards are being exceeded and a lot of pollution is being generated, the person who you will be asking the questions of and who will be carrying the can will be the relevant DEFRA Minister. In the UK, ambient air quality around Heathrow is DEFRA’s responsibility. That Minister would probably tell you that they had a plan with Hillingdon council to try to improve air quality, and someone from the council would say, “We’ve got virtually no levers of control.” Something like an airport is dealt with very differently to if you were building a factory, where the Environment Agency would permit to the nearest gram how much pollution could come out of your chimney. On these sorts of things, we set some broad trajectories and say, “Well, we hope that the emissions won’t be too high,” but if they fail, largely the responsibility falls back on DEFRA to manage the problem.
Q149 Steff Aquarone: Is that adequately addressed in the HENPS? We seem to be discovering quite a few areas where it does not go into enormous detail.
Professor Lewis: Like the evidence you had on the carbon emissions, one of the objectives is that it has to fall within the UK’s emissions budget for things like NOx and PM2.5. Again, that is a national budget. We are saying, “Well, if this sector’s going to emit more somewhere else in the economy, somebody else is going to have to make a cut.” I do not think it is unreasonable to say, for a large development, “This is your budget for emissions; go away and manage them.” That is exactly what we would do to a gas-fired power station or a carbon capture and storage plant, but we treat these rather differently: we sort of socialise the emissions and say, “Well, we’re all in it together, and between us all we’ll manage the emissions.” That is not how it works in the industrial sector, where you would be given a hard target, and where DEFRA or the Environment Agency would come along, check your annual emissions and so on and hold you to account if you had breached your permit.
Q150 Chair: I want to pick up on what happens in other countries. Are there enforcement mechanisms elsewhere in the world that have proven to be effective on air quality?
Professor Lewis: It is very different in the US compared with, say, Europe. Our system looks, perhaps unsurprisingly, a lot like the European system. The targets are set at a national level, and largely they are a Government responsibility to meet. If you go to the US, there are some national targets and some state-level targets, and the states are much more interventionist in their ability to close down and intervene on air pollution emissions.
Q151 Chair: Have they closed airports?
Professor Lewis: Airports, no, because they would consider them to be fairly fundamental, but they are more interventionist on airport emissions, I would say. There is a lot more activity and concern around airport emissions in the US, because they tend to be pretty close to cities, than perhaps there is in the UK. I don’t think I could give you an example of another country that did something directly on airport emissions.
Q152 Barry Gardiner: Professor Hansell, you mentioned UFPs—these ultra-fine particles. Could you give us a bit more detail about the health impacts of UFPs, how they have been linked with aviation and therefore what the potential significance might be of UFP pollution to residents in the west London area? Should the HENPS be treating this as an issue to incorporate in what it is saying?
Professor Hansell: The history of looking at UFPs has been difficult because there has not been the monitoring, and that has made it difficult to do the modelling to look at the exposures and then to link that to the health effects. There has been quite a lot of attention in the air pollution community in recent years to trying to improve that situation. It has been relatively straightforward to expose people, on a short-term basis, to these and to measure things. You can measure changes in heart rate variability, and you can look at potential impacts on the respiratory system and at the relationship with, say, heart attacks. The reason you might want to do that is that these things are so small that they get not only into the bottom of the lungs but into the bloodstream.
The thing that has been quite hard to demonstrate, because of the exposure issues, is consistent evidence linking these with mortality. While the evidence on the short-term effects has been much more consistent, it has been less consistent on the mortality, longer-term exposure and hospital admissions. Within the air pollution community, we hope to address that within the next five to 10 years of studies. There has been a lot of work at European level to try to model these things and link them to very large databases.
Somehow the statement needs to capture what might emerge from that and to be able to look at emerging evidence. That relates to not only air pollution but noise, because noise and health is another field where the evidence base is changing very quickly, and I do not think the statement or the Government have really caught up with where we are in terms of the health impacts.
Professor Lewis: You mentioned west London. Ultra-fine particles live in the atmosphere for quite a long time and they impact central London too. So while the nitrogen dioxide is probably a local air issue around the airport, there has been some evidence, on quite a few occasions, that the ultra-fine particles measured in central London—through the monitoring that is done on Marylebone Road—actually originated from Heathrow airport. So these are not very localised effects; some of these effects will affect the whole of London.
Professor Hansell: The particles can move 10 to 20 km, and more, depending on the wind direction.
Q153 Chair: But they can be sourced back to aircraft, not other sources?
Professor Hansell: Yes. Because of the size distribution, you can do source apportionment.
Chair: Right. Let’s now move on to noise with Daniel.
Q154 Daniel Francis: The draft HENPS requires the applicant to demonstrate that significant adverse impacts on health and quality of life are avoided, and that overall aircraft noise is limited against the 2024 baseline. Is the noise test sufficiently clear and robust to guide decision making on a DCO application?
Professor Clark: I think that, as set out, it isn’t; I think there are some details that are missing. For example, to avoid effects, you usually set a SOAEL—a significant observed adverse effect level. That usually means that residents would get their homes insulated—if the new scheme means you are above the SOAEL, you would be offered insulation.
The current draft policy sets out insulation based only on daytime noise exposure; it only uses one aspect. Heathrow have recently relaunched their home insulation scheme. I sit on the prioritisation panel for that scheme, and I am aware that to qualify for the current scheme that has just been launched, it is if you are in the daytime contour or the night-time contour, or if you are at risk of one awakening. I think they even take into account flights between 6 and 7 in the morning. So you would be offered insulation at a far more inclusive contour than is currently set out in the policy.
I was quite surprised that the policy does not even consider night-time exposure, given how much community complaint and health impacts come from the effects on sleep. That was quite a surprise for me. I will let Anna come in now and then come back.
Professor Hansell: One of my concerns is that there is a big emphasis on annoyance and sleep, and there is now a very good body of evidence about that, which includes experimental evidence from getting people to sleep in a sleep chamber, playing them noise overnight and then looking at their inflammation markers and cardiovascular parameters the next morning. So, there is that type of evidence that aircraft noise has physical effects on the body.
There is strong evidence on cardiovascular disease; there is also evidence on type 2 diabetes, links to later-onset diabetes and links with blood pressure. My own group has been looking at this and publishing papers. We have looked at MRI scans of the heart, which have shown that people exposed to higher noise levels have thicker, stiffer hearts. That is around the Heathrow area, which has levels high enough at least to double your risk of having a major cardiac event.
There is emerging evidence, and I am really concerned that we are not incorporating that clearly enough into the health impact assessment, and that there is not a mechanism to try to onboard the new studies, not just from the UK but from across Europe, on noise and health. We need to make sure that health impact assessments look at the whole body of evidence and decide what is the key evidence, while thinking about sensitivity analyses so that you have the whole range of what the physical health impacts might be.
Professor Clark: I completely agree that there are other health outcomes. The draft is not very clear about the use of transport appraisal guidance. It is mentioned for air quality and carbon, but I did not see it mentioned for noise, and that is where these other health outcomes would be considered.
It is worth being aware that the health evidence is woefully out of date in the current TAG for noise. We are using 20-year-old evidence for sleep and things like that, and it does not have all these new health outcomes in there. Consideration should definitely be given to updating what appears in TAG and providing a clearer statement in the draft policy on the use of TAG for noise. It is implicit in there, but it does not seem to get the same attention as the others.
There is LOAEL and SOAEL. The LOAEL is where we think adverse effects begin, and the SOAEL—the significant level—is very important for the assessment, and it is what is used for infrastructure projects. Personally, I think that, if we set them for annoyance and sleep, we should be protecting for all the other health outcomes in general, such as the cardiovascular ones. But the draft is using the old annoyance and sleep relationships, and the Government have funded the ANAS and ANNE studies on annoyance and sleep—I am the principal investigator for the ANNE study on sleep. These relationships should be used, and they are in the sensitivity analyses for noise, so an assessment is done using those new relationships, but they need to be brought into the policy. There is no real reason why the Government-funded studies are not being used and we are using data from many years ago to set those levels.
Q155 Dr Arthur: Thank you. That is really interesting. To be clear, you say Government-funded studies. Are they funded by DFT or just through research council money?
Professor Clark: There are two studies you will hear talked about. The ANNE study, which I lead, is funded by the Department for Transport.
Q156 Dr Arthur: So they should know about it.
Professor Clark: Yes, they do know about it. It is mentioned in the policy, but the LOAEL value that is cited is based on the survey of noise attitudes from 2014. The ANAS study is undertaken by the Civil Aviation Authority, so it is funded by the CAA/DFT. They are both Government-funded studies designed to look at annoyance and sleep disturbance, and to update the relationships we can use for these assessments. There is a disconnect in the current draft—
Q157 Chair: I think they were both released and circulated after the draft NPS—I certainly got a copy then. You will tell me what they stand for, but they show individuals’ subjective judgment of the annoyance from noise, and they have been done over several decades, so you can see patterns of feelings of noise annoyance changing over time.
Professor Clark: Yes. ANAS is the aviation noise attitudes survey, and ANNE is aviation night noise effects. They are big population surveys involving social survey companies. Over time, we have looked at people with lower and lower exposure so that we can try to home in on where the effects begin. A few years ago, we would have just looked at people with exposure of 50 dB and above.
In my sleep study, for example, we went right down to 35 dB at night, which is quite quiet—people with just a couple of planes—and right up to people with a lot of planes. The CAA study does the same, but it does not go quite so low. People are reporting more annoyance at those lower levels than they ever did before, so it looks like they are more annoyed and their sleep is more disturbed by aircraft noise than in previous surveys.
Q158 Dr Arthur: Forgive me—I am trying to remember what I was taught at university. The difference between 35 dB and 50 dB is not just a third. The latter is way more than 10 times louder, isn’t it?
Professor Clark: Yes. Decibels are not easy for people to understand, but it is a big difference. A fairly rural environment with a bit of background noise would be around 35 dB.
Q159 Chair: Can you remind me what the main noise insulation scheme that already operates at Heathrow comes in at? Is it 51 dB?
Professor Clark: I looked this up—I think it is currently at 60 dB, but it is a composite, not one metric. I think it is around 60 dB for 16 hours, which is the day, and 55 dB at night, but I will check that.
Q160 Chair: That is quite loud. The draft HENPS states that 97,000 extra people will get significant noise annoyance by 2030. Are they proposing a similar or equivalent scheme for the third runway?
Professor Clark: I do not know. I would assume that the airport will use the scheme it has, which is more inclusive than the scheme set out in the draft policy. Perhaps the question about the plans for the scheme is something to ask the airport.
Q161 Chair: But that is not set out in the HENPS?
Professor Clark: No.
Q162 Chair: How does the existing Heathrow scheme compare with what has been requested for the scheme for the second runway at Gatwick, for which the DCO specified the noise levels?
Professor Clark: I think Gatwick gets full acoustic insulation at 60 dB on a 16-hour daytime metric. The big difference is that it offered £3,000 for acoustic insulation down to 54 dB, as that was one of the planning conditions. Heathrow is different and does not go as low as the Gatwick decision.
Chair: Okay, thank you. I apologise for jumping around. Our questions on noise and on health and wellbeing are mixed together, for obvious reasons.
Q163 Jacob Collier: We know that annoyance and sleep disturbance are some of the most prevalent effects of aircraft noise. Do you think the draft HENPS sets an adequate framework for addressing those public health impacts?
Professor Clark: Yes, with the proviso that you set your LOAEL values lower than the draft does. You need to use the new ANAS and ANNE studies to inform where you set your LOAEL. Another intricacy is that the 51 dB LOAEL in the draft reflects the last survey, in which 7% of people were highly annoyed. With the change in ANAS, it is 10%, so that is a slight difficulty you would have to iron out.
There are a few things. Changing the LOAEL is important, but the focus on households needs to change as well. What is typically done is households are counted, but that does not tell you anything about the health impacts because you have no idea where those houses are. The tests should look more at—this relates to Anna’s point—what the health impacts are for all the different outcomes. You can then have a fairer test. You need to lower your LOAEL so that you have more people in your assessment, and you actually need to look at the effects on health, not just count the houses.
Q164 Jacob Collier: What is 51 dB equivalent to in layman’s terms, and how does it compare with the noise level from Heathrow at the moment?
Professor Clark: It is difficult because that number can come from having a few noisy events or lots of slightly quieter events. That is one of the difficulties with noise metrics.
It is considered the lower end of moderate exposure, if that is not too confusing. For example, you have some people exposed to over 60 dB, which is the higher end of the exposures we have in this country. Moderate exposure is 50 dB to 60 dB, but the 40s are increasingly seen to have health effects, too. It is difficult.
One of the things you can do to try to help is look at the noise maps around airports. Perhaps pick a spot on the map that you know well and see what the impact is—that really helps. It is difficult, as Ruth knows from experience.
Q165 Chair: It is about going somewhere one knows and making a guess, which is not too difficult, as to what it would be like for the equivalent position underneath the approach path of the new runway. At the moment, those areas are relatively quiet because of the way noise contours go off very steeply. Does HENPS recognise the cognitive, learning and educational impact of aircraft noise? Does it mention that?
Professor Clark: It counts the schools. The noise-sensitive receptors include schools. You could have it more explicitly in there that you would use the RANCH relationship. That is also used by the European Environment Agency in its burden of disease. Schools are clearly in the mix, but it could be stated more clearly.
Cognitive effects on children are not in transport appraisal guidance either. Transport appraisal guidance has sleep, annoyance, heart attacks, strokes and vascular dementia. Is there another one?
Professor Hansell: No, but they ought to include all-cause mortality.
Professor Clark: Yes, they ought to include mortality. The TAG is very out of date.
Q166 Chair: Given that there is a lot of evidence of the impact on cognitive learning, should it be included in the TAG?
Professor Clark: Yes, very much so.
Q167 Dr Arthur: I know that you are not educationists, but presumably—
Chair: Well, they are—they are all professors.
Jacob Collier: Says the former lecturer.
Dr Arthur: Sorry. The cognitive impact will not just happen in schools, will it? Your kids learn when they are in the park or at home. If they are not sleeping properly, that impacts on their ability to learn at school.
Professor Clark: Absolutely. Many years ago, we did a study around Heathrow, Amsterdam and Madrid. That is still the evidence we use today. It showed reading deficits for children who went to school near airports. We could also look at their home exposure.
Q168 Dr Arthur: So in London, you have done kids who live near airports and not so near?
Chair: It is a very well-known study.
Professor Clark: We were able to look at home exposure as well. Both showed an effect on cognitive outcome.
Q169 Chair: Anna, is there anything you wanted to come in on about some of these health and wellbeing consequences, and on whether or not the NPS addresses them sufficiently?
Professor Hansell: Yes, I wanted to come in on the LOAEL because I am very concerned about having a LOAEL of 51 dB. We have talked about annoyance and sleep deprivation, as they have important effects on physical health outcomes. The reason we are interested in them is because annoyance increases cortisol levels, which will impact blood pressure and glucose handling. We know that sleep disturbance is very well associated with general health. We also know that noise has a physiological impact through the fight-or-flight mechanism. There are different mechanisms that noise is acting on, but annoyance and sleep are part of the pathway to physical health.
The relationships with cardiovascular disease have been looked at in a lot of detail in a very nice set of studies from Switzerland, where they have had exposure data down to 30 dB, which we have not had in the UK. That is why you do not have evidence from our UK groups showing anything below 50 or 45 dB, because that is where the cut-off is for the data available from the CAA. However, those studies from Switzerland show very clearly that there are health effects down to very low levels. There is not a cut-off or a lower observable effect level for cardiovascular disease and myocardial infarction, where the evidence is strongest.
I want to pick up on the issue of what 50 dB feels or sounds like. It is difficult because our metrics are averages, but people hear events—they hear planes going over. We have done some work where we had to get the noise levels around Heathrow modelled for different times of the day. If you look at the night-time period between 11 pm and 7 am, the noisiest time of the entire 24-hour day is actually between 6 and 7 in the morning, when the big planes come in. It is quieter in the middle of the night.
We were able to use that more discrete data to look at the relationship with heart attack admissions the following day. We found that the associations we could see were related to the previous evening and night-time noise. It is quite useful to look at that in terms of better metrics than we currently have standardly available. We tried to look at the number of noisy events. We looked at N60. I think it is too high and, if I had my time again, I would look at the relationship with N50s and N55s, because those discrete events are probably driving at least some of the health effects.
Switzerland has done some work looking at that difference from baseline. If it is very quiet, you are likely to have more of a startle reaction to a noise that is above baseline, even if it is not that loud. There are associations with health that can be seen from using those types of metrics.
Q170 Chair: Can I ask the question in a different way? Is there a fundamental difference in the impact on health and wellbeing between loud, continuous noise from, say, a motorway and the waves of noise that we have from aircraft?
Professor Hansell: We have not had the data to do that easily, and studies are not fully consistent if you look at the averages. Some studies show that aircraft noise has slightly higher exposure-response functions, but not all of them. They are not appreciably different enough for us to say, “Yes, aircraft noise”—not in the same way that we can with annoyance. Annoyance tends to have higher slopes for the exposure-response function for aircraft noise than for other types of noise. However, it has been very useful from the more recent studies to have those more discrete periods of noise to look at.
Q171 Jacob Collier: With the proposed expansion obviously having an impact on increased annoyance and sleep disturbance, how do you think the policy side of that should account for the negative public health impacts that you have spoken about?
Professor Hansell: I am just thinking about the projections here. The projections are that the aircraft get quieter, but the areas affected remain about the same because the increased aircraft movements are balanced out by the quieter planes. There are some assumptions here that you can maintain that reduction in noise.
Also, what you are saying is, “It won’t get a lot worse than it is now, but it won’t get much better,” or “It will only get a very small amount better.” There is a question about whether that is acceptable, because the people who are exposed in the future are not getting the benefits of the general reduction that we are expecting to see in aircraft noise.
Q172 Jacob Collier: Professor Clark, in your work have you seen the mitigations to people’s houses that Heathrow offers impact the health of those affected?
Professor Clark: I have been doing a study for Heathrow where I have evaluated this new noise insulation scheme. There is very little evidence on these interventions. What we have done is measure annoyance and self-reported sleep. We also did wellbeing and quality of life. We go in before the house is insulated and measure those. We then go back after three months and 12 months.
What we have seen are significant reductions in noise annoyance and self-reported sleep disturbance once the homes are insulated. For example, if we think about annoyance, before, it was 68% of the population who were highly annoyed, because they had very loud exposure. That fell to 17% at three months, and it was a similar number at 12 months.
For sleep disturbance, 46% were highly sleep-disturbed before, and that fell to 15% afterwards. As someone who works in public health, I think those are very large health gains from this scheme. I have two things to say about that. This is an expensive scheme. Heathrow is spending up to £34,000. As a public health person, I thought, “Wow, this is massive. Why is that?”, and then I thought, “Well, actually, it is a big investment, so you would expect that.”
Q173 Chair: Is that per house?
Professor Clark: That is per house. They do the whole house.
Q174 Chair: But presumably those are only the houses in the noisiest area. What noise metric—
Professor Clark: They have prioritised up to 20,000 houses, and they are working it out. They have a very good website that I will share with you that sets out the scheme. They are the noisiest areas, absolutely.
I think the draft policy does not mention this type of mitigation enough. It is all predicated on quieter planes that are going to appear, which I have to say that I am very sceptical about, and the offer of respite. Of course, having an extra runway does offer respite to some people, which is positive. That is a mitigation, but it also brings people in who have not got noise now. It needs to link more clearly to the noise insulation, because that is the typical offer to avoid and to comply with the noise policy statement for England. That is the typical offer to people so that you avoid those effects on health and quality of life. Those are the current findings from the pilot project that we have done for Heathrow. That study is ongoing.
Q175 Jacob Collier: When will it report?
Professor Clark: We should be writing a paper on that in the next few months.
Q176 Chair: The existing noise mitigation scheme has been revised, but I think it is based on the conditions of the terminal 5 approval and maybe subsequent legislative changes.
Is it rolling out at the speed it should be? How long is it going to take until all those homes that should be covered under the current standards get the noise insulation that they would expect? I am speaking for my constituents. Will the scheme also go back to homes that were done 20 or more years ago, where the double glazing is now failing and the ventilation bricks are no longer working and so on? Are they also going back to bring those homes up to standard?
Professor Clark: You will have to check when you meet with Heathrow, but my understanding is that it is a completely new scheme.
Q177 Chair: It is, but it affects some of the same communities.
Professor Clark: My understanding is that it does go back to those people, but you would need to check that with the airport.
Chair: We will do that.
Professor Hansell: Can I just add a comment on this from a public health perspective? There is always an issue about whether you concentrate on the people at the high end of exposure or whether you think about the people who are in the middle. Actually, you should not forget about the people in the middle because that is where most of the health events are going to happen.
If you have got very high exposure you are going to have the highest risk. You are going to have lower risk, but you are still going to have moderate risk in the people who are moderately exposed, and because there is more of them, most of the public health burden is going to be there. Your best public health strategy is in reducing the emissions at source. Having these quieter planes will be very key.
Chair: Bring on glider passenger aircraft!
Q178 Barry Gardiner: Picking up on your comment, Chair, is there a trade-off? Putting this insulation into those properties has positive health benefits in terms of noise pollution, but it can have negative health benefits in terms of internal air pollution. The Chair made points about filtration and condensation in homes. What assessment has been done on the impact of the proposed scheme on that trade-off?
Professor Clark: The scheme accounts for noise and ventilation. The two are tackled at the same time, to account for that potential downfall. That is a big change in the schemes. That is being rolled out across schools as well, to do the ventilation as well as the noise. That is addressed.
Q179 Alex Mayer: Aeroplanes have got quieter. Are they going to keep getting quieter?
Professor Clark: I have been hearing all my life about these quieter planes. They have got slightly quieter. I think the modelling in the assessment actually suggests 0.1 dB per year. Most people would be able to hear a 3 dB difference; if I played you the two sounds, you would hear that.
I think there is far too much reliance in the policy on planes getting quieter. Once you dig into some of those reports, you see that we need high-risk investment to make it happen and a lot of it is predicated on things that are not in development yet. I do not think you can rely on quieter aircraft. Also, aircraft may get bigger. As capacity gets constrained, there is really only one way that things can go, and they start using bigger planes again. I really do not buy into the belief that planes are going to get radically quieter during this time.
Q180 Alex Mayer: Does the type of fuel used make any difference to the amount of noise? If we used sustainable aviation fuel, as mentioned in the previous panel, would that make any difference overall?
Professor Clark: That is not my area, but my understanding is that it would not be a lot. It could for some.
Professor Lewis: I have never heard anything that said it got quieter. They slightly change the air pollution emissions, so they are potentially a little bit lower on UFP. It is pretty much exactly the same on NOx. As it is combustion and, a bit like NOx production, it is a function of combustion, I would not imagine it changes the noise.
Professor Clark: And the airframe will still make sound.
Q181 Chair: According to the DFT, it is estimated that an additional 92,700 people will see a significant noise annoyance. They will be the people nearer to runway 3, mainly under the approach pass on westerly operation, which is 70% of the time.
Are the mitigations proposed in the draft NPS adequate to take account of their needs, as opposed to changes in the overall aircraft noise, which they think will not get any worse? Is the mitigation proposed adequate and consistent with current best practice as well as the evidence base?
Professor Clark: I think that number will be much larger once you use the new evidence, for one; I believe that number is based on using the old one. You have the slightly quieter planes, if they are slightly quieter. You have the ability to turn the ends of runways on and off, to offer people that respite. It is a lot of houses to insulate. We have not mentioned this, but you also have what we call a change effect.
If you live somewhere that is quieter now, and we start to fly planes over you, your annoyance and your response will be greater than we would estimate because you are used to it being quiet and you probably chose your home for some of those reasons. Your annoyance may be even higher than estimated in this.
For noise, you always offer multiple mitigations—there is no one quick fix for it. Other than respite, you would be mostly relying on the insulation scheme. That is for the Committee to ponder. Are the numbers who need it doable before it starts to operate?
Q182 Chair: Would it be expensive?
Professor Clark: Yes.
Q183 Chair: Has anyone done the calculations?
Professor Clark: Not that I know of, but that does not mean that they are not somewhere.
Q184 Chair: We are going to hear the Division bell any minute. Does anybody want to ask any other questions on noise, air quality or health and wellbeing?
Professor Hansell: Can I make a final point? At some stage, we have to make sure that there is ongoing evaluation. Assuming this all goes ahead, we will have a new runway, but there has to be a commitment to ongoing evaluation of the health impacts, and I do not see that at the moment. There is a health impact assessment now that is based on estimates, but we also want to see what happens when things start to become operational and use that to guide the ramping up of operations in a new runway that gets built.
Professor Clark: Melbourne airport has just got permission for a new runway—a big change—and it has a 20-year expectation for a research study to do exactly that.
Q185 Chair: What will it do if the health impacts are worse than it had forecast? Will it then change and strengthen the mitigation?
Professor Clark: Yes, I think it will have to. It is very much a monitoring health study to assess against what was estimated and spot any issues as they come along.
Q186 Chair: Would the additional mitigation costs be funded by the airport or the public sector?
Professor Clark: I will have a look and get back to you. I will check the specifics on that and let you know.
Chair: Thank you very much indeed for your evidence and the time you have spent preparing. As I said to the previous panel, if there is anything you think we did not cover, please feel free to write to us.