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Ian McCrae Award 2021

With COP26 fast approaching, a growing number of commercial organisations have committed to a long-term net zero target for GHG emissions. Achieving this target could be commensurate with reducing emissions of air pollutants and improving air quality. What inventive air quality strategies/plans could commercial organisations implement that would simultaneously improve air quality and contribute to net zero goals?

COP26 comprises four main goals. Goal 4 relates to commercial organisations, aiming to accelerate action to tackle the climate crisis through collaboration between governments, businesses, and civil society”. Meeting Goal 4 will help achieve Goal 1 of “keeping global temperature rise within 1.5°C” (as per Article 2 Section 1a of the Paris Agreement). In line with Goal 4, many commercial organisations are committing to climate action; for instance, 115 companies have signed up to the Climate Pledge, which aims to achieve Paris Agreement goals 10 years early.

There are two main methods to achieve net zero: emissions reduction and emissions removal. Emissions reduction includes measures such as transitioning to green energy. Emissions removal includes measures such as reforestation. Such measures contribute to companies’ net zero goals, but don’t necessarily improve air quality; for instance, reforestation would occur in rural areas where air is cleaner than in urban areas, which have a greater need for better air quality. To significantly improve air quality whilst also achieving net zero, commercial organisations must focus on heavily polluted urban areas.

Many commercial organisations are already employing common emission reduction strategies which improve air quality in urban areas and work towards net zero, such as electrifying fleets. However, companies should aim to lock in the additional reduction methods that were inadvertently experienced during the Covid-19 pandemic. Ambient air quality benefitted during the “stay at home” phase of the pandemic; reported “air pollution halved during the first day of the UK coronavirus lockdown”. Where feasible, companies could work entirely from home; in May 2020, Twitter took a similar approach, announcing some of its employees could permanently work from home. This would remove significant amounts of vehicles from the road, reduce queueing traffic, and potentially allow reduced bus schedules.

Although reduction methods are generally cheaper and more feasible, more inventive, and perhaps more radical, removal methods may also be necessary to significantly improve air quality, achieve net zero, and accelerate towards Paris Agreement goals. Reducing emissions is beneficial but does not remove existing atmospheric emissions. Removal measures would also allow companies to become carbon negative.

Urban greening is a common emissions removal measure and follows the 25 Year Environment Plan strategy of “planting one million trees in urban areas”. However, to get the “right tree in the right place” and maximise sequestration, studies should establish the most effective greenery for each area by focussing on regional, climatic, and species variance in carbon uptake. Effective planning and efficient use of space are also key to successful urban greening.

Direct air capture (DAC) is a larger-scale emissions removal measure; the International Energy Agency reports that there is a 1 MtCO2/year capture plant in advanced development in the USA. DAC is technologically similar to carbon capture and storage but focusses on removing existing pollutants in the atmosphere rather than capturing pollutants at source. DAC plants are generally very large scale, but smaller scale plants could be installed in areas of urban environments where pollutant concentrations are highest, perhaps on rooftops or even façades. Companies should invest in this technology now to advance the technological progress and increase the rollout rate.

Using pollution absorbing paints, both inside and outside, is a simple emissions removal method. Unlike urban greening and DAC, these paints absorb CO2 and other pollutants, further benefitting air quality. Using light-coloured paint on buildings has the added benefit of increasing albedo.

Implementing the above measures in urban areas is an effective way to significantly improve air quality and achieve net zero goals. There is no “silver bullet”; a combination of measures must be implemented. To lock in their commitment, companies should introduce strict policies and deadlines for successfully implementing measures and should dedicate more of their budget to facilitate this.

Finally, net zero should be considered a steppingstone on the journey, not the final answer. Beyond net zero, companies should aim for carbon negativity and absolute zero.

Ian McCrae Award 2020

The outbreak of COVID-19 led to unprecedented changes in living and working patterns of our society. As a result, many people and places now experience different exposure to air pollution. What new policies, tools and strategies should be introduced to produce long-term benefits to the indoor and outdoor environments in terms of air quality

COVID-19 has led to significant changes to our living and working patterns following the nationwide lockdown in March; it forced many of us to stay at, and work from, home.

With much of the population staying indoors and not using road vehicles, ambient air quality benefitted; reported that “air pollution halved during the first day of the UK coronavirus lockdown”. However, the subsequently lower NO2 concentrations have led to potentially harmful higher O3 concentrations.

Although there have been benefits to outdoor pollution, people spending more time indoors has adverse indoor air quality implications. reported that air pollution indoors is over 3 times worse than outdoors. With people now spending more time indoors, indoor air quality is now more important.

COVID-19 has evidently impacted indoor and outdoor air quality. Strategies should be implemented to help maintain the positives, while mitigating the negatives. The strategies suggested here include cheaper and simpler options and more expensive and difficult-to-implement options.

Significant amounts of traffic removed from roads during lockdown was due to working from home. Companies encouraging their employees to remain working from home reduces pollution by reducing road traffic and emissions attributed to office energy demand. In May, Twitter announced that some of its employees could permanently work from home, having said that “the experience of working from home for the past several months has shown that it can work at scale”. It is unlikely that all employees will work from home permanently, but by giving employees the option more of them may choose to do so. This scheme would help maintain the reduced road traffic.

More radical changes could be taken to help maintain the reduced road traffic. In June, the Mayor of London increased the London congestion charge, with one aim to reduce traffic levels. There has been opposition, and it probably impacts the lower-income population more, but such a scheme would likely produce a long-term benefit to air quality by discouraging personal road vehicles in highly congested and polluted areas.

With the emphasis of air quality being on outdoor pollution, air quality professionals and citizens alike must be aware of indoor pollution and its impacts, particularly with people currently spending more time at home indoors. One option could be an incentivised scheme where households have an indoor air quality monitors, much like a smart meter scheme. Imagine an app-enabled smart monitor advising occupants and even supplying data to local and national databases. Pollutants such as PM2.5 and VOCs would be continually measured and displayed. Indicators would highlight exceedances of each pollutant, explain the health benefits of good indoor air quality, and how to improve it.

With many indoor pollution sources, such as cooking, varnishes, and paints, purging these pollutants is key to improving indoor air quality. Irrespective of my proposed indoor air quality monitor scheme, households should know how and why to allow good ventilation. The app-enabled monitor would suggest ventilation advice tailored to different types of households. Different households would require different strategies; older houses would likely rely on natural ventilation, whereas newer houses may have mechanical ventilation. This scheme could also be rolled out to other building types such as leisure and commercial properties. The Guardian reported that “many Germans habitually open their windows twice a day, even in winter, which is often a requirement included as a legally binding clause in rental agreements”, and many people can relate to the benefits of “getting some fresh air in”. This approach could be recommended in the monitoring app and could be adopted in UK rental agreements. Security concerns, among others, may not encourage this in certain areas. Adequate ventilation may also help purge COVID-19 from indoor environments.

COVID-19 has led to positive and negative changes to air quality. Top-down government-led schemes coupled with public awareness campaigns and flexible working may be the most effective solutions for maintaining better outdoor air quality and improving indoor air quality.


A research letter published in Environmental Research Letters, and subsequently reported on by Air Quality News, links COVID-19 mortality to exposure to “hazardous air pollutants (HAPs)” in the USA. This article is already able to list several references that appear to report similar findings in other countries including Italy, India, and the Netherlands.

(for those interested, the letter is entitled Hazardous air pollutant exposure as a contributing factor to COVID-19 mortality in the United States, by Petroni et al (2020) and is open access)

Research by the Office of National Statistics (ONS) also found that long-term exposure to PM2.5 could increase the risk of contracting and dying from COVID-19 by 7%, when not controlling for ethnicity – while the study goes on to say that this may be an overestimation, it raises important questions about the socioeconomic positioning of BAME people in the UK (the same study goes on to say “A recent study of 400 COVID-19 patients admitted to a Birmingham hospital said that BAME patients were “more likely to be admitted from regions of highest air pollution, housing quality and household overcrowding deprivation”; I think we’ll save this conversation for another time soon).

Some changes have been made which may have a positive effect on outdoor air quality – the temporary increase in price of London’s congestion charge should have a positive outcome when considering how it effectively decreased congestion within central London when it was introduced, and with following price increases. While this price increase was not necessarily implemented to benefit the environment, it could be assumed that there will be benefits thanks to observations of previous occasions. However, with the havoc COVID-19 has wrought on people’s economic stability, this move has been met with significant blowback.

We could also capitalise on the natural change in people’s behaviour brought by COVID-19 – while lockdown was at its peak, bicycles were like gold dust; sold out everywhere, mile long queues at Halfords, the works. Walking and cycling became the main methods of avoiding public transport, which poses an obvious risk in contracting the virus due to relatively cramped conditions and exposure to more people.

These improvements in outdoor air quality will have a knock-on impact on indoor air quality. Indoor air quality has been identified as a pathway for COVID-19 infection. Air Quality News reported on a petition started by scientists which called on the World Health Organisation (WHO) to take action to prevent the risk of infection within public buildings. These scientists identified indoor air with a relative humidity lower than 40% as having a negative impact on the respiratory immune system, as well as enabling droplets containing COVID-19 to persist in the air for longer and travel further.

Organisations such as the US EPA have already begun disseminating advice on how to improve indoor air quality, focussing on improving ventilation. The German Government have also added room ventilation as part of their arsenal to tackle COVID-19 (the AHA – Abstand halten, Hygiene und Alltagsmaske, soon to become the AHACL – the “C” stands for the Corona-Warn-App, and “L” for Lüften or airing a room). All methods to combat the spread of COVID 19 indoors I have seen so far focus on ventilation, which is largely dependent on the quality of outdoor air (and perhaps the spec of your ventilation filters).

After examining the information I’ve found, I’ve concluded that:

  • We should be going full speed ahead with outdoor air quality improvement measures – this will make the most positive impact on the greatest number of lives, irrespective of COVID-19. The idea that COVID-19 infection rates and outcomes could be minimised by air quality improvements should provide greater incentive to speed up the progress on doing so.
  • Improvements to indoor air quality will follow improvements to outdoor regardless of whether the buildings you routinely inhabit have mechanical ventilation. At this point we can look towards building a framework ant national and/or local level to improve air quality within buildings. This may involve grants and/or packages for retrofitting old buildings (kind of like what the government is currently doing for roof insulation), by providing filters, replacing windows, installing air quality monitors etc. We could couple this with providing information about indoor air quality improvement strategies (a la US EPA) so that people can make informed decisions on how to best improve the environments within buildings they routinely inhabit etc.
  • Our current cycles of lockdown and release are not sustainable – the people most at risk from poor air quality are likely also most at risk of COVID-19, due to other vulnerabilities they may have or socioeconomic position. These people will be more heavily impacted in trying to maintain our “business as usual” scenarios.

With the advent of the shiny new coronavirus vaccines, there is the potential that we could return to the “business as usual model” in time. Saving lives is paramount – we now have a time limit to move ahead with air quality improvement measures and instil good habits, before the general populace (myself included) become lax about the situation and let is sink to the back of our minds that air quality improvement measures will also save thousands of lives.  Truly, more than ever, the time to act is now.

This week’s thoughts on “Lockdown” are added to last week’s and are shown below

The arrival of COVID-19 has changed the world we live in. People have been forced to adapt their lives to protect themselves, their colleagues and loved ones. The change in behaviour brought by the rise of COVID-19 has had some curious effects on air quality.

Some changes were expected; a reduction of vehicles on the road, as lockdown forced people to stop travelling and stay indoors, resulted in decreased levels of certain types of pollution (carbon dioxide and nitrogen oxides being the most notable). On the face of it, this is good news.

Conversely, some types of pollution have increased in prevalence. The presence of people is an extremely important driver for the quality of air in indoor environments; indoor air quality is bound to deteriorate when people stay indoors for extended periods of time, and that will be unhealthy in the long term. Cooking, breathing, skin shedding, pet dander and a multitude of other activities we perform in our homes can have a quantifiably negative effect on our respiratory and overall health (most notably, mental health). While in some newer or retrofitted buildings, the effects can be somewhat alleviated by mechanical ventilation, many of us have to rely on the age-old (and English countryside and German favourite) solution of “open a window”. In the absence of guidance or other ideas – this is not a fun prospect in the UK during Winter, or hot Summers, or windy Autumns, or rainy Springs, nor really a feasible option if your windows don’t open or you’re located near roads which are (traditionally) noisy and/or congested. (More on ventilation, noise and  air quality another time) That leaves us one other easy option… Go outside again.

So, we have a problem here; we seem to be entering a feedback loop of lockdown and release with no real end in sight until vaccination programmes reach the wider population.

In the advent of the age of COVID-19, we end up walking a tightrope; it looks as though our immediate choices boil down to:

  • go outside, potentially mix with other households and increase your chances of contracting COVID-19.
  • Stay inside and eventually be forced outside by poor indoor air quality (which can increase your chances of contracting COVID-19 if you come into contact with it) or deteriorating mental and physical health. (More on that later).

Overbalance on either side and the consequences are disastrous, from an individual to societal level. This we have, unfortunately, been a witness to already.

Without invoking “hindsight rage” (none of that “we should have locked down earlier” business please – we most probably should have, but we didn’t and here we are now), and using the knowledge that we have now, can we effectively balance these stressors on our health when it comes to COVID-19 and air quality?

. Now that we have identified a cycle, to mount an effective response, we need to first identify which part of the cycle we’re currently in, and then examine if it’s feasible to exit the cycle at the stage. The potential knock-on impacts of any actions taken to exit the cycle would also need substantial consideration.

In the next couple of posts, I’ll share what my thoughts are. I’d love to hear what your thoughts are on this too.




Where are we in the cycle? What would you add or remove from the cycle?



Breaking the cycle using “lockdowns” is heavily dependent on several factors.

A lockdown must be:

  • Implemented early enough
  • Implemented long enough
  • Restrictive enough, to sufficiently prevent the spread of the virus via people mixing.

A successful lockdown has the potential to greatly reduce cases by drastically reducing the opportunities for the virus to infect a new host. This may eventually either:

  • Lead to the eradication of the virus, as it runs its course through the community
  • Provide enough of a buffer between infections to allow us to find another solution

Lockdown has had several impacts on air quality, and what we’ve learnt is that the effects of lockdown on air quality are more complex than we’d originally assumed.

We saw many decreases in certain types of air pollution and increases in other types of air pollution, for example:

  • A reduction of ambient NO2 /NOx in cities (pretty great!)
  • An Increase in ground level concentrations of Ozone in cities (not so great, but irrevocably linked to the above)

We were able to make potential links between air pollution and the worsening of the pandemic (another link to a similar article here too) and conversely, begin understanding how the improvement of air quality may improve outcomes for those infected , or even help prevent infections occurring in the first place.

It’s important to note that a lockdown doesn’t necessarily stop the long-term deterioration of air quality, or the health effects that arise. If anything, it is our best bet at going back to a “business-as-usual” scenario. Similar approaches have worked throughout history to prevent the spread of the Plague, Spanish Flu, Ebola and Smallpox. Even in the current pandemic, New Zealand and Australia displayed how effective a lockdown could be if implemented properly and supported by the appropriate measures e.g. contact tracing. However, there is also the argument that this approach doesn’t necessarily break the cycle in practice once lockdown is relaxed (as we have experienced in the UK several times already). Even New Zealand and Australia had to apply lockdowns locally and nationally multiple times in order to reap the rewards of it.

(We should remember the original reason we entered the lockdown in the UK: it was not necessarily to prevent the spread of COVID but rather, to regulate the spread as to not overwhelm the NHS. As far as I can tell no exit strategies were really considered.)

But given the temporary nature of Lockdown, these effects will simply cease to be once we get back to “business-as-usual”. As far as making long term improvements to air quality is concerned, it’s not practical; we’ve already seen a lot of reports and headlines saying something like “air quality is now worse than it was before lockdown”, or “lockdown wasn’t as effective on air quality as first thought”  now that we have a dataset that represents what was happening over lockdown and the periods of time in between.

So, where else can we break the cycle? Given that we’ve already been through two lockdowns (and currently in the middle of another) perhaps now should have been our time to break the cycle. We already know that “the business-as-usual” scenario doesn’t benefit our health or air quality.

We’re now seeing an influx of research linking COVID-19 infection rates and post-infection outcomes to air quality; in my eyes, this would imply that a “two birds, one stone” approach is theoretically feasible.





It was back in March 2020 when the UK government announced the first set of measures to combat the fast-spreading COVID-19 virus. Part of the measures included: advising people to work from home if possible; to only leave the house for necessities; and the closure of schools, with lessons provided online.

Fast forward 11 months and we are still living with restrictions on our movements, albeit with slight variations – nurseries are open, as well as some workplaces, and these must ensure appropriate COVID-19 mitigation measures in place. As the outside temperatures have dropped significantly, and the nights are drawing in quicker, windows to buildings are often shut to control temperatures. This decreases the rate of ventilation within work, study and living spaces.

Poorly ventilated spaces can lead to a decrease in productivity, overheating and poorer indoor air quality, amongst other things. Poor ventilation in shared spaces also increases the risks of airborne transmission of viruses, etc. including COVID-19. The most efficient and straightforward methods of increasing ventilation are to have fully or partially open windows or to increase the rate of air exchange of the building services. Both actions may have knock-on effects in terms of noise ingress into the spaces and poorer air quality (if the building is in an area with poor outdoor air quality).

Opening windows is a great way to increase ventilation and mitigate overheating. This is a wonderful option to have if the building is in a relatively quiet location that does not suffer from poor outdoor air quality. Opening windows to increase ventilation in noisy environments will increase the internal ambient noise levels within the space.  Excessive internal noise levels have also been shown to result in reduced productivity.  Documents such as BS8233:2014 Guidance on sound insulation and noise reduction for buildings (BS8233), Health Technical Memorandum 08-01: Acoustics (HTM08-01), Acoustic design of schools: performance standards Building bulletin 93 (BB93), British Council for Offices (BCO) Guide to specification, Acoustics, Ventilation and Overheating: Residential Design Guide (AVO Guide) and others provide recommended internal ambient noise levels for spaces within buildings. Wherever possible, a noise assessment must be done to understand the impact of noise break in from open windows.

Opening windows may also have adverse effect on the occupants of the spaces if the building is in an area with poor outdoor air quality. An air quality assessment can help determine the impact of air quality. Follow this link to read what our Air Quality team are thinking.

In buildings that are mechanically ventilated, additional ventilation is usually provided by increasing the rate of air exchange within the spaces. To increase air exchange within these buildings, the building services could be adjusted to operate at a higher load. Operating at a higher load often means that the system will generate higher noise levels, as even if attenuators are installed, they are often only specified to control noise during standard operating conditions. As is the case with opening windows, noise within the spaces may exceed the recommended guidelines when building services are operating at higher loads. Wherever necessary, an assessment of building services noise must be done to quantify noise from the system and determine if attenuators with higher insertion loss are required to control noise.