Healthy Buildings 2021 conference report by Kate de Selincourt

At the 2021 ASBP Healthy Buildings Conference, Covid-19 in the built environment was, unsurprisingly, a prevailing theme. Delegates heard about the many environmental factors that increase our risk from Covid. But nearly all of them are factors that already harm our health, and will continue to do so if they are not tackled.

The built environment and in particular, air quality, has a huge impact health of our lungs, hearts and brains: exactly those systems that are attacked by Covid.

As speaker after speaker noted, Covid has highlighted just how inadequate many of our buildings are – the workplaces and public spaces where people gather, and the unhealthy homes in which many of us , and particularly the most disadvantaged, live.

Ventilation and the virus

One of the main reasons buildings have a powerful effect on the risk of Covid 19 is the simple fact that the virus is airborne, as Professor Cath Noakes, Professor of Environmental Engineering for Buildings at University of Leeds explained.

When the virus is suspended in the air, it will spread through a space. Neither hand washing nor social distancing protect against airborne virus: if you want to be safe, infected  air has to be replaced quickly with air that is Covid-free. Unfortunately ventilation is not something that we do well – in the UK, and indeed, internationally.

“Covid work opened my eyes a lot to the situation with building ventilation,” said Professor Noakes. “The crisis has shown us that actually we know very little about the ventilation in most buildings –  how it was designed, and how it performs.”

Her concern was echoed by Jeffery Smith, Air Quality Consultant with the World Health Organisation who said the Covid pandemic has “shone a light on our built environment”.

Covid is far from the only airborne infection transmitted in under-ventilated and crowded spaces – another, notoriously, is tuberculosis, and Professor Noakes explained that much information on airborne transmission of infection has come from research into TB, which remains a major killer worldwide.

The scientific community has not had so long to study the routes by which Covid transmits. No potential route has yet beeen ruled out; but aerosol spread is pretty much ruled in.

“The evidence base is not nice and neat at this stage, but pieced together,” said Professor Noakes. “However there are instance, in particular, ‘super-spreading’ events, where it is not really possible to envisage any other means by which so many people could become infected at the same time, in different parts of a space, unless it was via the shared air.”

Speakers explained that we exhale droplets in a range of sizes when we breathe and  talk, more when we cough, laugh or sing. As Jeff Smith put it “the viruses are not riding naked, they are in these droplets.”

Larger aerosols and droplets can be inhaled when people are close to each other; large “ballistic” droplets may even fly out of someone’s mouth and hit the hands, eyes or mouth of someone nearby, or land on shared surfaces. But most will quickly fall to the ground.

Very small aerosols by contrast can spread all around a room and remain airborne for some time – possibly hours – during which time they can be inhaled by someone anywhere in that space.

The risk from airborne infection is underlined by some of the factors that have been shown to be associated with transmission, said Professor Noakes. Being indoors rather than outdoors, and poor ventilation, are known risks: “There are fewer new cases in well ventilated spaces: transmission is associated with spaces with ventilation rates of 1-3l/s/person. Length of time of exposure also increases risk.” (Proximity and crowds are also associated with more infections.)

Lab studies show the virus survives better if conditions are relatively cool, dry and dark – the virus generally survives better indoors where tends to be a bit darker, and there is no UV light.

“In a room with an infectious individual, or just after they were there, is the likeliest situation for airborne transmission by far,” Professor Noakes said.

What can we do to reduce the risk

The smaller the percentage of ‘pre-breathed’ air in a room where there’s someone infected with Covid, the lower the concentration of Covid aerosol there will be. Carbon dioxide concentration is a fairly straightforward proxy for how well people’s exhaled breath is being removed and replaced.

While it is not possible to give hard-and-fast recommendations on levels to aim for, Professor Noakes did offer some rough guidance:

“I’d love to say there’s a number that safe but there isn’t. But if the CO2 level in a shared space is over around 1500 ppm, you should do something as soon as possible to increase ventilation.”

“If the level is below 800 ppm, you are doing well; if somewhere in between, do what you can to get it down to a lower level. And if you get the odd spike don’t panic, it’s the long duration high levels that matter more.”

There can however be obstacles to  good levels of air exchange. There may be little or no mechanical ventilation; windows may not open far (or at all), be poorly sited, or open onto a polluted or noisy environment. And in winter, a high ventilation rate may make the occupants cold.

“In an ideal world, buildings such as schools with inadequate ventilation would fit a new ventilation system, but that’s not quick. In the immediate term, if adequate ventilation is not yet possible, air cleaning is probably the most effective way to increase safety,” Professor Noakes advised.

The baseline technology is HEPA filtration. “It is a proven technology, readily available, and as a bonus also helps remove particulate pollution.”

Jeff Smith addressed another building issue that impacts Covid infection risk: low humidity. This, ironically can be the result of high ventilation rates in a heated space in winter. Not often a concern in homes in the UK, low humidity can nonetheless be an issue in schools and offices, where moisture-producing activities like showering and laundry don’t take place, but where high occupancy can mean high air exchange rates are needed.

Unhelpfully, he explained, exhaled viruses such as coronavirus are better able to remain active at low humidity. “Their coating of respiratory fluid is an important factor moderating the danger as it helps to degrade the virus more quickly. If the virus’s initial coating of respiratory fluid evaporates, the virus lasts longer.”

And a smaller droplet will also remain airborne for longer, as it is it less likely to be pulled by gravity to the floor.

Filtration can also remove virus, without further lowering the  humidity of a heated space. Jeffery Smith shared WHO/International Labour Organisation joint guidance on workplace Covid safety that he has helped to develop. It includes increased ventilation, and  keeping indoor relative humidity above 50%.

Better Covid safety – better building safety

Short term measures can ‘engineer’ spaces to help people to use them safely, for example by reducing and staggering occupancy times, installing  screens and establishing one-way systems,  wearing masks, and overriding ventilation systems. However, said Professor Noakes, these are  only ‘sticking plaster’ solutions that will not be sustainable  long term.

The risk from airborne infection,  and poor indoor environmental quality more generally, needs addressing on a permanent basis, speakers stressed.

Professor  Noakes told the conference that a high proportion of the most common causes of death worldwide are associated with some sort of respiratory condition, and almost all the leading causes of death are linked to the built environment in some way.

“Respiratory  conditions are anyway an enormous health challenge worldwide. And the sobering fact is that with 2.4 million deaths globally from the pandemic so far, Covid19 will easily enter the top 10 causes of death for 2020.

“Ventilation is linked to user behaviour, but there is no widespread public understanding of how it works,” said Professor Noakes. “A lot of people realise that they have not thought much about ventilation,  and they ought to.”

“This is not just about Covid; there are potentially much bigger problems out there. The impacts go way beyond Covid, and  affect us throughout our lifetime.”

Geraint Davies MP, Labour MP for Swansea West, chairs the All-Party Parliamentary Group [APPG] on Air Pollution and is a long-time campaigner for clean air. He agreed it was vital to take the lessons of Covid forward into improving public health.

“This appalling episode has led to some things very belatedly being learned. It has brought attention to the nature of some workplaces, and we should keep these messages in mind for the future.”

What do we know about what ‘clean air’ means?

Permanent  improvements to ventilation and indoor air quality are clearly needed. Jeff Smith told the conference that the Well Building Standard already had a recommendation to keep CO2 levels below 800 ppm, because of the many health benefits of good ventilation.

“High levels of fresh air ventilation reduce the risk of re-breathing and becoming sick with any type of airborne illness. On top of that, higher ventilation rates are linked to better cognitive performance; some studies have shown 14-15%  higher scores on standardised tests. The benefit is increased productivity at work, and improved learning at school or college.”

Ben Channon, Director of healthy buildings consultancy Ekkist Advisory added that CO2 levels were associated with increased sick building syndrome. He warned that high levels of CO2 can impair our responses in a way similar to alcohol, and very high levels may  impact our organs and even our bones.

All speakers were concerned about particulate pollution, both outdoors and in. Jeff Smith warned that in areas with heavy pollution, outdoor air quality has to be taken into account in building design, and natural ventilation might not be possible. “In wildfire areas, and where there is high local pollution, you’ve got to consider mechanical ventilation and filtration,” he said.

However, particulate pollution was also frequently created indoors, Ben Channon warned: “Cooking, log-burning, burning candles – all these create particulate pollution that finds its way into our lungs and into our bloodstream. Particulate matter sources can also generate pollutants such as carbon monoxide and nitrogen dioxide.”

These pollutants can cause both short-term irritation and cardiovascular problems, and long-term harm, including premature death from heart and lung diseases, and cancer. As Geraint Davies remarked: “There’s nothing less romantic than a candlelit dinner for two with closed windows, unless you want to kill each other!”

Volatile organic compounds were another common indoor pollutant that Ben Channon’s consultancy took particular care over; they are often related to the specification of furnishings and finishes. It was important that manufacturers had transparent composition lists, so for example, specifiers can find out which glues had been used in furniture, he said.

“Sources of VOCs include sealants, paints, insulations and some furniture that contains a lot of wood glue. Vinyl floorings can be a big culprit. These sources can release volatile organic compounds for weeks, months – even years.”

Short term impacts of VOCs included problems such as headaches and memory impairments. Long term they can cause significant issues including respiratory conditions like asthma, even damage to your kidneys, liver or central nervous system, Ben Channon explained.

“You can get a nice new sofa which for long period of time will be giving off pretty nasty chemicals into your home, which you and your family are then breathing in.”

He agreed with Jeff Smith that humidity below 30% is problematic (with or without a Covid pandemic). He also reminded the audience of the need to limit high humidity, to avoid damp, condensation and allergies. “VOC release may also increase with higher humidity,” he warned.

One concern with soft furnishings and some other materials in the home, is the flame retardants they contain, as Geraint Davies explained:

“The average house in Britain now contains maybe 45 kg of fire retardants. These chemicals get into the air you breathe, and your skin.”

Echoing the findings reported by Professor Anna Stec at previous ASBP conferences, Mr Davies added: “In  fires, people die from the smoke but flame retardants make the smoke a lot more toxic. This was a major contributor to the tragic Grenfell deaths.”

Noise is also a health hazard

One problem with increasing ventilation rates to reduce coronavirus in the air, is that in  many places this means bringing in polluted air from outside, as speakers observed. But there are other pollutants too that make ventilation difficult, and  the most important after the products of combustion, is noise.

Jack Harvie-Clarke of Apex acoustics told the conference that the WHO assessed that noise led to the loss of millions of healthy life years in Europe each year.

“Noise causes stress, it disrupts sleep and increases the risk of cardiovascular disease.”

Noise might not always be taken seriously as a health risk, because it is such a personal thing, Mr Harvie-Clark explained. However, it had not only a direct impact via the annoyance and stress provoked, but it also results in people failing to be able to ventilate their spaces comfortably – putting them at risk of both poor indoor air quality (and Covid), and also overheating.

“We looked at 160 planning applications that had had both a noise and an overheating assessment. 85% of the assessments were completed with the assumption that the windows would be open, and got their tick for acceptable protection from overheating. But in the noise assessments for the same projects, nearly all assumed windows would be *closed*  – meaning that the noise levels appeared acceptable and those assessments also passed.

“This was why we decided to work with the Association of Noise Consultants to produce some guidance on acoustics, ventilation and overheating.” (see ‘AVO Guide’ here)

Another way that noise can lead to under-ventilation is the poor ventilation  design and installation that is endemic in this country:

“If ventilation is noisy, people turn it off – and almost never turn it on again.”

Awareness and empowerment

The Covid pandemic has brought a fresh interest in monitoring indoor air – and a fresh interest from building users in knowing, for example, the CO2 levels in spaces they are using.

Jeff Smith believes that displaying air quality readings on a “building dashboard” should become standard practice. He believes this can drive improvements in air quality.

A dashboard display showing good air quality gives building users – customers, leaseholders, and employees – confidence in the premises. Combined the reduced absenteeism from improved occupant health, this will build staff retention, and retention of leaseholders. “Data gets shared and impacts customer behaviours,” Smith said.

Having a public readout is a  powerful way to improve safety and health in buildings, very directly. For example, monitors can alert staff and building users immediately when CO2 levels are too high.

A dashboard also provides early warnings of building system faults. “A real-time readout of air quality can detect problems like maintenance errors immediately. And sensing pollutant levels indoors, and comparing them with outdoors, will tell us  if our actions are working or not,” Jeff Smith added.

And if we work collectively, we can achieve even more:  “When you deploy sensors, join a network and share your data. If you are recording outdoor pollution, your data will inform citizen science and city managers.

“We can learn from our monitoring data how to build back better in an intelligent way.”

Politics & the need for statutory action

As well as highlighting the need for better understanding and control of the environment in individual buildings, the Covid pandemic has highlighted the need for political action to set better standards  – both for the indoor and outdoor environments – in order to save lives.

As Jeff Smith put it: “So many of the factors that affect human health: the energy use, materials and processes in our buildings – are choices, choices made for us by city and national governments. Science has the solutions, but  the impact currently of those choices,  is that millions and millions of deaths around the world are being caused by the environment people live in.”

The terrible impact of failing to make good choices was brought vividly home by Rosamund Kissi-Debrah, mother of Ella Kissi-Debrah. Ella’s death in 2013, at the age of nine, was recently confirmed by the coroner to have been a result of air pollution near her south London home. This second inquest overturned the previous, 2014, verdict, following a long campaign for a fresh hearing. This time, the coroner ruled that the illegally high levels of pollution had exacerbated Ella’s asthma, and precipitated her fatal attack.

After Ella’s death, Rosamund Kissi-Debrah, with Ella’s doctors, established Ella Roberta Family Foundation, which campaigns for clean air in London, and for better diagnosis and treatment of asthma and other respiratory illnesses. “Yesterday I joined the Healthy London Partnership with respiratory consultants  whose aim is to ensure no children die from asthma,” Ms Kissi-Debrah said.

“In London, 8-12 children die from asthma each year. This is a terrible figure, and we are concerned it is going to go up.”

These tragic deaths are only one face of the dreadful harm wrought on so many lives by the disease. “Although Ella’s extremely  severe form of asthma is very rare, asthma itself is extremely common. There are 250 thousand children London with asthma, and it is the most common reason for children in this country to miss school.”

Ms Kissi-Debrah  recalled the rapid deterioration in the health of her daughter. “ When Ella was born she wasn’t sickly child – she was hardly at the GP at all. No coughs, nothing like that .”

“The asthma appeared to us when she was almost 7, but we think a lot had been going on in her body before then. Her illness was so frightening – she began having hypoxic seizures.” Within the space of just a couple of years, and before the diagnostic process was complete, Ella had the attack that killed her.

An inquest was called, but at that first inquest, the coroner ruled only that Ella had died from respiratory failure. “Her doctors didn’t really feel that did justice to her condition,” Ms Kissi-Debrah said. “Someone suggested to me that I should look into the air pollution levels near my house, especially before she passed away.”

Respiratory specialist Professor Stephen  Holgate (who has spoken at previous ASBP conferences) reviewed Ella’s medical records. He found a “striking association” between Ella’s emergency hospital admissions and recorded spikes in nitrogen dioxide (NO2) and PM10s, the most noxious air pollutants, concluding there was a “real prospect that without unlawful levels of air pollution, Ella would not have died”.

Rosamund Kissi-Debrah’s campaign with Ella Roberta Family Foundation for a second inquest was finally successful last year, and Professor Holgate presented his evidence to the coroner.

Proving a link between pollution and  an individual death was not easy, Ms Kissi-Debrah explained. Even though, as she discovered that the overall link at population level are well-established, proving an individual case is a different matter. But the evidence here was convincing.

“This time, the same coroner ruled that air pollution had been to blame. It’s the only time it’s been on a death certificate.”

 “Professor Holgate has told me he firmly believes the damage was going on long before her problems appeared, and by the time she began to suffer symptoms, the die had been cast.  So many children and vulnerable people are affected by air pollution.

“My frustration through this process has been finding out how many people knew about this, and still not do what they should do. I found the lack of action quite shocking. And there are even some policies in place that have made it worse. I don’t understand why that’s come about.

“Since 2010, I don’t think the government have met any of their targets, ever.” In a sad irony, Rosamund Kissi-Debrah added, “we had a period during lockdown where no child died from asthma, “ but we are now back where we were in 2017.”

The Ella Roberta Family Foundation supports the APPG’s proposed amendment to the Environment Bill, to make the WHO standards for air pollution legally binding on the government. The Bill is due to come back to Parliament when the new session begins in May. “The Environment bill is a really crucial opportunity, I can’t stress it enough,” Ms Kissi-Debrah said.

The Foundation is also waiting for the recommendations from the coroner, following his fresh verdict. Unfortunately, said Ms Kissi-Debrah, his report has been delayed: “Why has it taken so long? It’s because of Covid: thousands of people that have died, very sadly, and must all be registered.”

“We hope that when coroner comes back with his recommendations than my team can draft Ella’s Law. For me, it will be about the prevention of future deaths.”

Ms Kissi-Debrah added that we need even stronger air pollution guidance than the 2005 WHO figures proposed in the amendments to the environment bill.

“I hope we can bring in the new targets from WHO. The ones we are talking about including in the Environment Bill are from 2005, and WHO has realised they are not strict enough. Even more people are dying from air pollution, 8.8 million per year worldwide.

Geraint Davies warned there was now a powerful additional incentive to reduce air pollution.“There is a clear link between Covid and air pollution. Studies have found increases of between 8 and 15% in death rates in more polluted areas.”

“Given this relationship between poor air quality and Covid deaths,  and given so many people are dying anyway due to air pollution,  we need to legislate for enforceable and legally binding targets.”

Rosamund Kissi-Debrah echoed his concern: “If Covid is here to stay, air pollution is going to make things worse. It’s another reason to clean up the air. If we want Covid to die down, we need to clean up the air.”

Mr Davies pointed out that indoor air quality was even more overlooked by government than outdoors: “Air pollution has only been regulated out of doors, which is a bit farcical when we spend so much time indoors.”

“With that in mind,  I have put forward another amendment to the Environment Bill, putting a duty on all government departments to deliver good air quality, including indoors, and to report annually on what actions they have taken, and what has been achieved.” Unfortunately, he added, “Defra has a problem, and is resisting what we have put forward.” He called on attendees to write to their MPs to support the amendments – a suggested draft letter is available here.

Underlying it all is justice

Dirty air is just one of the environmental risk factors that is spread very unequally around the country, and around the world.

Covid has brought this painfully to light in the UK . Professor Noakes shared a data from Public Health England showing that people who were the most disadvantaged (for reasons including geographical location, income, housing and education) were at almost double the risk of contracting Covid. “Social inequalities mean the impacts of the epidemic have not been even at all”

These inequalities included increase exposure to air pollution, but also to poor housing, and reduce people’s scope to  avoid social contact, to work from home, to travel in a private care, or to afford to self-isolate, she said.

Put people at the centre

The speakers all made it clear that building back better must mean both greener and healthier. “As we approach COP26, how to do climate change and air pollution meet?” Geraint Davis asked. Ben Channon was dismayed at how much immediate harm and death was caused by fossil fuel burning, even before you considered the climate impact. “Not enough people are talking about this” he said.

Professor Noakes summed it up: “We need to design out the inequalities in our built environment, and to tackle not only new buildings but existing buildings too, with health as the metric.”

“To do that we need an interdisciplinary approach: as engineers and architects we need to work together with behavioural science and health sciences. This needs to be embedded right through, from how we educate children, to how we train those who work in the sector. Health must be added into our definitions of sustainability.

“We need to go to human-centred design, where health is the first outcome. We need a change in our built environment thinking.”

Article written by Kate de Selincourt, March 2021.

Further information

Find out more about Healthy Buildings Conference 2021 and view speaker presentations at You can watch a recording of the conference below.

If you have any queries or are interested in taking part in future conferences, please contact Simon Corbey –

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