How air pollution became one the UK's deadliest problems – The Telegraph

The A205 ducks and dives as it crosses Hither Green in south London, squeezing three lanes of relentless traffic under a low railway bridge before arcing away through interwar parades of small shops and mock-Tudor semis. On an average day, according to the most recent available data, 21,670 motor vehicles pass along this stretch of the South Circular Road, generally in stop-start slow motion. 

Ella Adoo-Kissi-Debrah grew up 30 yards from the railway bridge, in the home her mother Rosamund had lived in for more than a decade. In 2010, just before Ella turned seven, Rosamund took her to the GP to assess ‘a peculiar cough’. Within two months she was in intensive care, one of about 30 hospital admissions that would follow over the next two years. The eventual diagnosis was hypersecretory asthma – a rare and dangerous variant that periodically floods the lungs with mucus. This condition almost always affects children, who usually grow out of it. But Ella never had the chance. On 15 February 2013, three weeks after her ninth birthday, Ella suffered a severe asthma attack and passed away. An inquest the following year ascribed her death to acute respiratory failure.

Ella’s grieving mother only considered the influence of airborne pollution later, when a neighbour shared their research into local air-quality measurements. ‘In the evening when she had her last asthma attack,’ Rosamund Adoo-Kissi-Debrah told a reporter from Energy Live News, ‘Lewisham had one of the worst air pollution episodes ever.’ This revelation would catalyse a tireless campaign, which in December 2020 finally won her a second inquest into her daughter’s death. 

Professor Sir Stephen Holgate, an authority on air quality, told the Southwark court that Ella was ‘a canary in the coal mine’ on account of her exceptionally sensitive airways. ‘When I had the opportunity to look at her lungs on the microscope,’ he later said, ‘I saw that the lining was largely stripped off [prolonged asthma can erode this lining] and therefore the chemicals in the air would interact with the nerves and the tissues directly.’

Coroner Philip Barlow delivered an historic verdict. ‘Air pollution was a significant contributory factor to both the induction and exacerbation of [Ella’s] asthma,’ he concluded. ‘During the course of her illness between 2010 and 2013 she was exposed to levels of nitrogen dioxide and particulate matter in excess of World Health Organization guidelines. The principal source of her exposure was traffic emissions.’

It was the first time a UK court – in fact, it’s thought, any court in the world – had listed air pollution as a cause of death. 

The expert consensus suggests it is unlikely to be the last. The UK’s Committee on the Medical Effects of Air Pollutants (COMEAP) estimates that 29,000 to 43,000 Britons over 30 die every year as a consequence of air pollution, part of a global annual toll of premature deaths that the World Health Organization (WHO) puts at a staggering seven million. Long-term exposure to airborne pollutants has been reliably linked to an elevated incidence of cancer, asthma, strokes, heart disease and diabetes. 

COMEAP has stated that it is likely exposure to air pollution can contribute to cognitive decline and dementia. A 2019 study found that London schoolchildren in the highest quartile of airborne pollution exposure were three to four times more likely to be diagnosed with depression by the age of 18 than those with the lowest exposure. This grim burden of death and disease also carries a steep economic penalty. The Royal College of Physicians estimates that the price of UK air pollution – aggregating related healthcare costs, lost days at work and so on – runs to more than £20 billion per year. 

Pick up a paper or click through a news site and you’re never far from a weird but worrisome air-pollution factoid. ‘Living near a busy road in Oxford may stunt lung growth in children by 14.1 per cent.’ ‘Air pollution in Northampton is equivalent to indirectly smoking 189 cigarettes a year.’ If all these nebulous figures and estimates seem to be getting scarier by the day, that’s in part because we’re constantly finessing our long-term statistical analyses and grasp of medical causality. At the time, the 1952 Great Smog was thought to have killed 4,000 Londoners; today, many argue the toll was three times higher. There’s also much more data being harvested, and with ever finer precision, accumulating evidence that has multiplied connections between air quality and public health. As COMEAP chair Professor Anna Hansell notes, ‘Recent large and well-conducted studies show that air pollution adds to health risks even at low concentrations.’ 

Yet standing under the bridge at Hither Green as buses and vans inch past at gloomy close quarters, it’s hard to take those alarming stats at face value. This is certainly no place to linger: there’s a lot of heat and noise, and an underfoot rumble whenever a train rattles overhead. But beyond a slight whiff of sulphur, there’s little sensory evidence of the pollution that incited the coroner’s damning verdict in Ella Adoo-Kissi-Debrah’s case. No acrid haze, no choking fumes. There are two dominant demons in traffic-emitted air pollution, and since Ella’s tragic death 10 years ago, the one you can smell – and on occasion see, as a beige tinge over an urban horizon – is, in London at least, being taken out of the game.

Nitrogen dioxide (NO2) is a brown gas released when fossil fuels are burned. Its dangers, most notably as a risk to respiratory health, are well documented: a global study estimated that in 2000, 19.8 per cent of childhood asthma cases in urban areas were attributable to NO2 exposure. Almost all the NO2 emitted by city traffic comes from diesel vehicles. Yet over recent decades, advances in fuel, engine and emission-control technologies – many of them, notwithstanding the odd bit of chicanery by German car manufacturers, imposed or catalysed by anti-pollution legislation – have steadily reduced levels of diesel-related NO2. 

In 1990, road transport accounted for almost 1.25 million tonnes of emissions of NOx – the combined total of NO2 and the less dangerous gas NO – in the UK. By 2020, this had dropped to less than 0.25 million tonnes.

In London, the trend has accelerated dramatically since 2019 as a result of the Ultra Low Emission Zone – the world’s first – which effectively banished older, dirtier diesel vehicles from the city centre. In 2021, the ULEZ was extended up to (but not to include) the North and South Circular Roads, as multiple signs around the railway bridge attest. 

The ULEZ scheme hasn’t been short of critics, most prominently owners of older diesels who found themselves compelled to pay a £12.50 daily charge or shell out for newer cars and vans. A second expansion, covering all boroughs in Greater London, received the go-ahead in a High Court ruling on 28 July.

Objections to the expansion are thought to have played a decisive role in the recent Uxbridge by-election. But the  effect of the ULEZ on NO2 levels in the capital has been clear and profound. Air-quality monitoring stations at Hither Green Lane and Catford, close to Ella’s home, show local NO2 concentrations have fallen by more than 50 per cent since 2012, with half that drop occurring since the area was encompassed within the ULEZ. 

Chief medical officer Professor Sir Chris Whitty has estimated that NO2 concentrations alongside roads in central and inner London are respectively 44 per cent and 20 per cent lower than they would have been without the ULEZ and its expansion. So in the capital at least, with the battle against airborne NO2 traffic emissions all but won, the experts are shifting focus. 

‘Now that vehicles are so much cleaner,’ says Professor Alastair Lewis, atmospheric chemist and chair of the Defra Air Quality Expert Group, ‘more than half of the NO2 in central London air comes from burning fuels for heating. Mostly this is natural gas. So buildings are a major source that need addressing, either with electrification of heating, or cleaner boilers.’ 

When it presents as an obvious, noxious single compound, invariably one emitted while burning hydrocarbons, airborne pollution can be targeted and tackled. Sulphur dioxide, a principal component of those deadly yellow London smogs, has been effectively ousted from the UK urban environment – initially by the 1956 Clean Air Act, and then the shift away from coal. Airborne levels of lead in London have fallen by almost 99 per cent since it began being phased out as a fuel additive. NO2 is now heading the same way. But that ‘particulate matter’ referenced by the coroner as another major contributor to Ella’s death is a very different adversary – stealthier, tough to pin down, insidious. ‘With fine particulates, you don’t get the severe reductions in visibility that people sometimes associate with pollution,’ says Lewis. ‘And there isn’t really any smell either.’

Particulate matter is everything in the air that isn’t gas, a micro cocktail mixed up from things like smoke, dust, pollen and liquid droplets. In the urban environment, dominant constituents include sulphate, nitrates, ammonium compounds and ‘black carbon’, from man-made combustion. PM2.5 encompasses particles under 2.5 microns – about three per cent of the diameter of a human hair. At this size they can penetrate your lungs and bloodstream, playing a significant role in a roster of respiratory and cardiovascular illness, cancer and neurodegenerative disease. As with every pollutant, children and the elderly are most vulnerable.

Every new study and report seems to elevate the malignant potency of PM2.5: a correlation with infertility, another with low birth weight. Tim Dexter, clean air lead at the charity Asthma + Lung UK, says that though NO2 exposure can present a more severe short-term threat as a respiratory-disease antagonist, ‘PM2.5 is the air pollutant most harmful to human health’. ‘Altogether, it’s the fifth biggest cause of death in the world,’ writes Jay Owens in her new book, Dust: The Modern World in a Trillion Particles. ‘If London’s air was compliant with World Health Organization standards for PM2.5,’ she notes, ‘we’d all gain on average an extra 2.5 months of life. Some would gain much more.’ One report estimated that in 2017, exposure to PM2.5 was linked to 3,799 fatalities in London – one in 16 of the capital’s total death toll in people aged 25 and older. In Newham, one of the most polluted boroughs, the estimate for 2020 was one in 13 deaths. 

The capital and its environs are the fiercest battleground in the fight for clean air, and for reasons that for once have nothing to do with regional favouritism. As Lewis explains, it’s simply down to demographics, geography and climate. ‘The south-east has a huge density of people living and moving about, and this leads to emissions. It’s less wet and windy than the north-west of the UK, the sort of weather that’s good for air quality since it blows and washes it away. And it’s also closest to Europe, so most affected by transboundary emissions.’ In other words, pollution from the continent that blows over the Channel. On a Defra map showing background PM2.5 levels across the UK, the south-eastern quarter of England is a blot of yellow and red, depicting medium and high concentrations. Give or take a few yellow speckles in major conurbations, the rest of the country is a soothing, lower-level blue. 

But that map is based on current UK PM2.5 limits. The legal maximum annual average here is 20 millionths of a gram, or micrograms, per cubic metre of air, with a ‘target figure’ of 10 by 2040. The WHO guideline limit for annual average exposure to PM2.5 is five micrograms per cubic metre of air – reduced from 10 in 2021. The newer number is exceeded by no less than 97 per cent of all the neighbourhoods in England and Wales – and doubled in a third of local authorities.

In a report, before the change, the coroner at Ella’s inquest declared that ‘the evidence at the inquest was that there is no safe level for particulate matter and that the WHO guidelines should be seen as minimum requirements’. 

Lewis makes a plea for realism: ‘You could feasibly reach five micrograms per cubic metre in cities in the north and west, through better vehicles, cleaning heating systems, and the end of fossil-fuel electricity generation. But in the south-east corner of the UK, due to natural sources of pollution and pollution flowing in from mainland Europe, even without any people living there the ambient concentration would be around five. I’d say 10 is a feasible target in the medium term.’

Hitting this level by 2040, as per the target, would exert a profoundly positive effect on the UK’s physical and economic health: a Government cost/benefit analysis expressed in terms of ‘net present social value’ estimates a 500 per cent return on the necessary air-cleaning costs. Yet there’s a long way to go. After a steep drop from 1990, linked to cleaner diesels and industrial combustion techniques, total UK PM2.5 emissions have remained stubbornly static since 2010. The principal culprit may come as a surprise.

‘Wood-fired stoves have become the single biggest source of small particle air pollution in the UK,’ writes Owens, ‘fully three times worse than road traffic.’ Noting that Defra has reported a 42 per cent increase in domestic wood burning since 2000, Asthma + Lung UK’s Tim Dexter agrees that the practice is now ‘the biggest contributor to PM2.5’. He points out that 46 per cent of those who burn wood at home are in the top social-class category, suggesting ‘the primary reason to burn wood is not because of its economic or heating benefits, but predominantly for aesthetic reasons: to make the house seem more homely or because of the atmosphere created by a fire’. Lewis castigates wood-burning stoves ‘for undoing a lot of good work that has been achieved in other areas, like cleaner vehicles’.

Since 2022, new stoves must comply with much more stringent emission standards, but Lewis also wants to see a ban on open fires and the burning of wet wood, as well as suggesting a temporary total ban on using solid fuel during high-air-pollution days in winter.

‘We need people to view the use of a solid-fuel fire in towns and cities as a special event,’ he says, ‘not a regular day to day source of heat.’ Everyone loves a blazing hearth, but in terms of helping to rid our air of its most damaging pollutant, for the experts this is low-hanging fruit. 

If one thing is clear in this swirling murk, it’s that air-pollution control is an endless process. Every time one danger is killed off or neutered, another comes along – either a new threat to health, or an old one whose potency is only fully appreciated when the boundaries of scientific and environmental study are pushed out to encompass it. We are learning that some of the most insidious PM2.5s are formed when ammonia from agriculture drifts into cities, an emission source that has barely been addressed but which Lewis says ‘we really have to reduce’. 

Sometimes, the control measures themselves spawn unanticipated new problems. Lewis cites the issue of ozone, a molecule best known for its protective role in the stratosphere, but which down at ground level – as yet another byproduct of fossil-fuel combustion – can trigger serious respiratory issues, as well as reducing crop yields by up to 16 per cent. ‘Ozone is a pollutant that is creeping into cities as NO2 reduces,’ he says. ‘In the past it was suppressed because it reacted with NO.’ 

Inspired by the London ULEZ, clean-air traffic zones are now in effect in Bristol, Bradford, Birmingham, Bath, Glasgow, Sheffield and Oxford. Dexter bemoans the fact that Manchester and Liverpool have scrapped or delayed similar schemes, though as Lewis points out, a vehicle-centric low-emission zone is now rather missing the point. The ULEZ worked by eliminating dirty old cars and vans from London’s streets; elsewhere, the passage of time has largely finished that job.

‘The majority of [vehicle-produced] PM2.5 now comes from brake dust and road and tyre wear, not tailpipes,’ he says. ‘So even a battery electric vehicle inside a ULEZ will still be emitting PM2.5.’ Lewis wants to see a broader urban focus: looking beyond just getting traffic away from people, to getting combustion away from people. ‘That sometimes might mean traffic, but it also might mean taking out a commercial gas boiler and putting in a heat pump.’

The final frontier of air pollution is the most familiar and the least explored. ‘We spend 90 per cent of our time indoors, yet all the focus, when it comes to pollution, is on the 10 per cent that we spend outdoors,’ says Nicola Carslaw, a professor of indoor air chemistry at the University of York. ‘But the vast majority of people’s exposure to pollution happens indoors.’ 

The dangers posed by radon, a gas that produces radioactive dust that can accumulate in homes, are well known: it is associated with about 1,100 UK lung cancer deaths every year. (Radon leaks through the bedrock and the foundations of a house, and there are unusual concentrations in the south-west compared with the rest of England.) But once again, it took the tragic death of a child to raise awareness of a much broader pollution issue. 

After two-year-old Awaab Ishak succumbed to a severe respiratory condition in 2020, a coroner directly attributed his death to prolonged exposure to mould in his family’s housing-association flat in Rochdale. But though environmental mould pollution and condensation are thought to be a potential health risk in 450,000 British homes, there’s a whole roster of rival indoor airborne hazards for which no such estimates exist.

Volatile organic compounds, chemicals linked with respiratory issues, cancer and liver damage, are emitted in varying levels from household cleaning products, shower gels, fragrances, glues and even – with savage irony – air fresheners. ‘If you plug in an air freshener that’s constantly releasing VOCs, we know that they can react indoors to form particles,’ says Carslaw. ‘If you told people they are being exposed to particles outdoors from vehicles they would get quite annoyed and probably want to avoid certain roads – but they would then happily plug in an air freshener not realising that they are also generating particles.’ 

Vacuuming stirs up particulate-laden dust; cooking a Sunday roast can raise the indoor PM2.5 concentration to that of a downtown Delhi street. Larissa Lockwood, director of clean air at Global Action Plan, recently oversaw a study that linked cooking with gas with levels of indoor pollution up to 500 times the outside level. ‘These peaks… then hang around the home,’ she told the Government’s Environmental Audit Committee. ‘They take hours to dissipate.’ 

But because no two households are alike – in terms of the pollutants they generate and how they’re dispersed by ventilation – it’s very hard to provide any meaningful risk assessment. Lewis recalls a study into household VOC levels that found ‘a factor of 1,000 difference between two homes right next to each other’. Among the most effective recommended countermeasures is a public-health lesson we all learned during the Covid pandemic: open a window. 

Ella Adoo-Kissi-Debrah’s schoolbag still hangs in the family sitting room, where she left it 10 years ago. ‘Ella used to worry people might forget her and move on,’ her mother has said. Rosamund has channelled her grief into building a legacy that should ensure they won’t.

Last year, the Clean Air (Human Rights) Bill, also known as Ella’s Law, passed in the House of Lords – the culmination of a long crusade that in 2022 earned Rosamund a CBE for services to public health. Yet to pass in the Commons, it would require public bodies to review pollution limits and establish a commission to scrutinise Government action, with the intent of bringing air quality in every UK community up to minimum WHO standards within five years. It would also enshrine the right to breathe clean air. 

To some extent, the Clean Air (Human Rights) Bill is symbolic, proposing certain limits that one air-pollution specialist tells me would be unachievable ‘anywhere on Earth, even Antarctica’. But as an inspiration, the purest expression of a young child’s idealism, this dream of a flawless, fresh-air future seems entirely appropriate.