« Indoor Air Quality and COVID-19

Gepubliceerd op 25-04-2020

Breathing - NSFW

Richard McElligott                                                Published on April 22, 2020
Richard McElligott
Director at Future Decisions

The negative health effects of air pollution are well documented by both the medical and academic community [1]. Air quality is also well recognised politically with one of the earliest documented mentions going as far back as Queen Elenor in 1257 (UK) to the passing legislation in 1273 from Parliament banning the burning of sea-coal (bituminous coal). [2] Approximately thirty-seven major elements of legislation on the topic have since been leading to the current day “The Air Quality Strategy for England, Scotland, Wales and Northern Ireland” published in 2000 and followed up with the Clean Air plan issued in 2017. [3] [4]

Prior to SARS-CoV-2 Air quality was already classed as a major environmental risk responsible for 7 million deaths per year worldwide with nine out of ten people worldwide breathing air containing high levels of pollutants (91% of the world’s population). More than 80% of people living in urban areas (that monitor air pollution) are exposed to air quality levels that exceed WHO guideline limits, with low and middle-income countries suffering from the highest exposures, both indoors and outdoors.

WHO - World Health Organisation [5]

Medically, poor air quality is responsible for increased risk of mortality, stroke, heart disease, lung cancer, cardiovascular disease, dementia, obesity, diabetes, asthma and both chronic and acute respiratory diseases, including asthma, autoimmune disorders and neoplastic diseases. [1]

The WHO estimates that some 58% of outdoor air pollution-related premature deaths were due to ischaemic heart disease and strokes with 18% of deaths were due to chronic obstructive pulmonary disease and acute lower respiratory infections respectively, and 6% of deaths were due to lung cancer. The effects of poor quality air are evident from womb to the grave and are aptly detailed in the Royal College of Physicians (RCP) publication “Every breath we take: the lifelong impact of air pollution”. [1]

Placing the effects of poor air quality within the context of the United Kingdom, outdoor air pollution is attributable to 40,000 premature deaths per annum with 9,500 of those in London alone. The cost to the health system for management of the range of air pollution-related diseases is estimated to add up to more than £20 Billion per annum. [6]

The RCP publication also highlights (the often overlooked section of our environment) the risks of indoor air quality. Our own research has shown that buildings both trap and generate pollution and pollution precursors. This type of environment when combined with most common HVAC (heating, ventilation and air conditioning) strategies often aggravates the problem leading to higher levels of outdoor pollutants within the building (higher than the already illegal levels found outside; London). This is particularly true for gas-based pollutants such as NO2 for which HVAC filters are unable to mitigate. [7]

Client Earth has taken the UK to court (successfully) on several occasions in order to enforce and tighten air quality legislation and prevent damaging projects from going ahead. The EU/ECJ (European Court of Justice) has also played its role providing a final warning to the UK, France, Germany, Hungary, Italy and Romania predominantly focused on NOx emissions in 2014 [8] [9]. In 2012 the WHO (IARC) classed diesel exhaust as carcinogenic to humans (Class/Group 1). [10]

The UK government in 2015 issued their initial air quality plan [11] which was deemed inadequate (withdrawn on 26 July 2017 ) with an alternative Clean Air Plan presented the same year [12]. A key output from the new strategy is the ban on petrol and diesel vehicles for sale within the UK from 2040 in combination with other measures such as increased and real-world operational scrutiny of vehicle NOx emissions. 

In addition, in order to tackle some of the worst pollution hotspots, the introduction of lower motorway speed limits was imposed, congestion charges, low emission zones and ultra-low emission zones were also introduced. Broadly the policies aim to reduce the number of the most polluting vehicles in areas that have very poor and often illegal levels of air pollution. Such zones levie a daily charge for any vehicles that do not meet the zones stringent emissions regulations. Typically this is a Euro 6 for diesel cars and Euro 4 for petrol. Petrol cars produce less NOx on average than their diesel counterparts. All fully electric cars are exempt from the charges as they do not generate local NOx emissions. Electric Vehicles combined with the National Grid's increased renewable generation will aid in overall NOx emission reduction. All of these efforts will, however, do little to lessen the overall traffic based generation of Particulate Matter. 

Electric vehicles are on average 24% heavier than their internal combustion engine equivalents for which there exists a positive relationship between a vehicle's weight and its non-exhaust emissions. Non-exhaust emissions account for almost 90% of a vehicle's PM10 emissions and 85% of a vehicle's PM2.5 emissions. The amount of PM generated increases with increasing vehicle weight. Non-exhaust particulate matter is generated predominantly by brake wear (16-55%), tyre wear (5-30%) and road dust resuspension (28-59%). [13]

The banning of the sale of petrol and diesel cars by 2040 will at present allow for only EV (electric vehicles) which will certainly help reduce the local emitted NOx levels however will do little to reduce the levels of Particulate Matter. 

The Defra publication on non-exhaust emission projects an upward trend for PM10 and PM2.5 out to 2030 based primarily on an increase in road traffic use. Traffic use is expected to increase by 50% out to 2050.  

Regenerative braking in electric vehicles has been presented as a means to help overcome traditional mechanical breaks (which produce more particulate matter). Such a system allows electric vehicles to recover energy that would otherwise be lost, thereby gaining efficiency and range. It will also help reduce the amount of PM which would have otherwise been emitted by the mechanical braking system. Unfortunately, such a system adds more weight to the vehicle and at present has substantial technical challenges to overcome if it is to operate in the full braking spectrum, particularly at slower city speeds. [14]

WHO Air quality guidelines for particulate matter, ozone, nitrogen dioxide and sulphur dioxide: global update 2005: summary of risk assessment

Particulate Matter is generally considered more of a toxicological health risk than NO2. The health risks shown in the table above provide a guide to levels of exposure to PM10 and PM2.5. [15]

Of the 40,000 premature deaths due to air quality within the UK The Committee on the Medical Effects of Air Pollutants (COMEAP) has attributed 29,000 of those deaths to Particulate Matter. [13]

As of the 16th April due to the coronavirus pandemic, the CAZs (Clean Air Zones) have been postponed until 2021 With London suspending the congestion charge, low emission zones and ultra-low emissions zones. The suspension of charges has rightly been enacted so as not to penalise those providing essential services and deliveries around London and the rest of the country. [16]

Lockdown effects on air quality

The current pandemic is rightly the focus of attention and is by far the biggest threat facing the world at present short of climate change. To date, COVID-19 has infected 2.3 Million people with 160,767 deaths. Within the UK over 114,000 cases with 15,464 deaths (from March 5th to April 18th). [17]

The lock down within London has reduced traffic by almost 73% with 60% less buses, and 40% less HGVs. Rail travel is also down by almost 90% with Tube and Bus transports down 94% and 83 % respectively. 

The lock-down and the resulting reduction in traffic has had an almost immediate effect on the countries and notably the capital's air quality. Areas that would normally have seen the most traffic are similarly seeing the greatest improvements. 

The chart above shows the average daily dop in NO2 per location with red representing the Lock-down periods and blue prior to the restrictions. The levels of NO2 are generally halved in concentration. To put this in context the WHO guidelines state that any average exposure of over 40 μg/m3 per annum is harmful to health. The EU/UK legislation for NO2 is identical for annual exposure. [18] [19] [20]

Particulate Matter has also decreased (PM2.5 shown in the chart above) likely due to the reduction in traffic from the implementation of the lock-down. The extent of the decrease is approximately one third . [21]

Significant time has been devoted to using this period of extraordinary data to provide a glimpse what the world may look like without internal combustion vehicles however as previously stated unless EVs (Electric Vehicles) can make significant progress on regenerative braking and vehicle weight, tire composition with advancement in road surfaces there is unlikely to be significant improvement particulate matter levels. Technological breakthroughs across the board will be required.

SARS-CoV-2 + Air Quality on Health

The effect of poor air quality on human health is well documented as stated in the introduction a myriad of conditions are created or aggravated by long term exposure to air pollution. To reiterate there is an Increased risk of mortality, stroke, heart disease, lung cancer, cardiovascular disease, dementia, obesity, diabetes, asthma and both chronic and acute respiratory diseases, including asthma, autoimmune disorders and neoplastic diseases. [1]

Repeating such a list of diseases makes for uncomfortable reading at the best of times but in the middle of a respiratory pandemic it is even more crucial to understand who is at risk locally, nationally and internationally in order to enact a strategic response. Where should resources be used? Where is careful management required? 

Should preventative measures be taken?

There are two recent publications of note that are combining the data of the pandemic with that of air quality. 

The first paper was published (in BioMed Central) in 2003 by the Department of Epidemiology, School of Public Health, University of California titled “Air pollution and case fatality of SARS in the People's Republic of China: an ecologic study”. [22]

This paper presented a positive association between levels of air pollution and the SARS case fatality. While the paper stresses that statistical correlation is not causation such results merit further investigation and the paper stresses as much. Severe acute respiratory syndrome (SARS) claimed 349 lives with an estimated 5,327 cases reported in mainland China (since November 2002). The SARS case fatality varied across geographical areas, which might be partially explained by air pollution levels. The correlation coefficient between air pollution index and SARS fatality was 0.8568 (p = 0.0636). 

The second paper of note was published in MedRxiv and updated on the 5th of April 2020 from the Department of Biostatistics, Harvard. The paper is titled “Exposure to air pollution and COVID-19 mortality in the United States”. [23] [24] While the paper is not yet peer reviewed the results are significant again and are related to the current SARS-CoV-2 pandemic.

The results presented show that with only 1 ug/m3 increase in PM2.5 (long-term exposure) increases the mortality rate by 15% for those infected with SARS-CoV-2. These results are statistically significant with a confidence interval of 95%. In short, “A small increase in long-term exposure to PM2.5 leads to a large increase in COVID-19 death rate, with the magnitude of increase 20 times that observed for PM2.5 and all-cause mortality”.

While more research is needed to prove causation the data presented makes logical sense and in similar fashion to the time delay between the proven link between cigarettes and lung cancer it would seem prudent to take a safety first approach. [25]The advent of EVs will not solve the particulate matter issue and should be considered in policy going forward. 

The current SARS-CoV-2 pandemic is only four months old; it is likely that there will be more peaks to come depending on the strategies enacted by governments. A key point even given the application of the planet's resources in fighting the virus is that at present there is simply not enough known to make concrete policy decisions particularly with respect to softening or removing the lockdown. The current narrative in the use of antibody tests to determine immunity after someone has survived exposure is flawed until such time there are accurate and standardised tests and the level of immunity post exposure is determined. At time of writing the WHO (WHO - coronavirus - COVID-19 daily press briefing 17 April 2020) stated that antibody tests are currently not standardised and thus unreliable. 

Secondly the preliminary data points to a case where only a low proportion of the population have seroconverted (seroconversion is the time period during which a specific antibody develops and becomes detectable in the blood. After seroconversion has occurred, the disease can be detected in blood tests for the antibody). Without the antibody at detectable levels it is not possible to know if you have been exposed or have any form of immunity. [26]

While the data may change as the detection capability improves as will the understanding of the virus (and the immune response) it is clear that making data and evidence based decisions is the only method which can be trusted. 

The initial discussions of UK herd immunity without the facts would have amounted to let's see what happens and we will deal with who is left alive at the end. Herd immunity has only ever truly been achieved where vaccination is possible and a full understanding of the contagion. 

Immunity without vaccination is possible such as with chicken pox where once you have been exposed you are protected for future exposures. With chicken pox while you have immunity to the virus your body does not clear it 100% and as such the virus remains latent within the body's nerve cells. Should your immune system become reduced you can again catch chicken pox. In about one third of cases the virus reactivates at a later date and results in shingles.

Dr. Seema Yasmin (Doctor & Journalist) - https://www.wired.com/story/covid-19-immunity/

With respect to H1N1 which was classed as a pandemic in 2009 the research shows that once recovered immunity lasted between two to ten years. With respect to SARS-CoV-1 a genetically similar virus to SARS-CoV-2 the immunity response provided two to three years immunity. [27]

In short without a data and evidence driven approach poor decision making will occur aggravating the problem you are trying to solve. Without standardised sensor equipment you can not produce quality trustworthy data. In the poor quality sensor scenario you may make the correct decisions given the data however the data is at fault. The result is the same resulting in poor quality decisions.

Trustworthy Data from Trustworthy Sensors Requires Standards

There are a myriad of air quality sensors available on the market from low cost at a few hundred dollars to eye wateringly expensive laboratory equipment at tens of thousands. The laboratory grade equipment must adhere to a range of EU & BSI standards. Such equipment must undergo regular testing and provide auditable results. [28]

Unfortunately for 99% of the non laboratory equipment available on the market no such standards exist. This has resulted in a significant amount of new super cheap sensors that are sold to Health and Well-being initiatives that are at best indicative of the air quality or at worst simply random number generators.  

In the absence of standards for non laboratory equipment sensors need to fall back onto scientific method. This means that in order for the sensors to be trustworthy both at install time and over their lifetime (most will drift over time) they need to be both independently reviewed by subject matter experts and that data published with respect to laboratory grade equipment. To my knowledge there is currently only one sensor on the market to date that provides such data.

Without traceability and trustworthy sensor data you can not make informed decisions. The same predicament is true for building control systems. If the sensors are not of sufficient quality you will not have correct control. Poor control can be derived from decisions made due to poor quality data. Where good quality data is available poor results can be down to flawed decisions making (control) where a lack of domain knowledge hinders the interpretation of the data. It can of course be a mixture of both.

Building Health and Wellness programs understand the need to monitor indoor air quality. The benefits of a good working environment are well understood with respect to health, morale and productivity. [29]–[31] To achieve a positive healthy environment there are various Health and Well-being certifications with comfort, temperature, humidity, lighting, air quality (CO2, SO2, NO, NO2, CO, O3, PM1, PM2.5, PM10 ) at a minimum to consider. 

Ultimately it is not possible to be a subject matter expert in all categories and nor can someone be expected to be such. This is why guidelines, standards and certification bodies exist. Unfortunately without adequate standards when the order for air quality sensors are passed off to the facilities manager or integrator all too often the primary goal is not the resolution, accuracy, reliability and repeatability of the sensor that is analysed.  

The primary driver tends to be what will work with my existing equipment and recommendations will be made to that effect rather than is the data this sensor produces fit for purpose. The sensor say they measure air quality and for some reason there is implicit trust. 

This is not an indictment on any individual or service provider, rather a failure in standards organisations to set out what is or is not acceptable for non laboratory air quality sensors. Bad sensors and bad data will equate to poor decision making even for building control systems.


[1]   ‘Every breath we take: the lifelong impact of air pollution’, RCP London, Feb. 23, 2016. https://www.rcplondon.ac.uk/projects/outputs/every-breath-we-take-lifelong-impact-air-pollution (accessed Feb. 13, 2020).

[2]   W. G. Christy, ‘HISTORY of the Air Pollution Control Association’, J. Air Pollut. Control Assoc., vol. 10, no. 2, pp. 126–174, Apr. 1960, doi: 10.1080/00022470.1960.10467911.

[3]   ‘Air Quality | History of Air Pollution in the UK’. http://www.air-quality.org.uk/02.php (accessed Apr. 20, 2020).

[4]   ‘Brief history - Defra, UK’. https://uk-air.defra.gov.uk/networks/brief-history (accessed Apr. 20, 2020).

[5]   ‘WHO | Ambient air pollution: Pollutants’, WHO. http://www.who.int/airpollution/ambient/pollutants/en/ (accessed Feb. 13, 2020).

[6]   L. Pimpin et al., ‘Estimating the costs of air pollution to the National Health Service and social care: An assessment and forecast up to 2035’, PLOS Med., vol. 15, no. 7, p. e1002602, Jul. 2018, doi: 10.1371/journal.pmed.1002602.

[7]   N. Glover, R. McElligott, C. Muller, and D. Bennett, ‘Does Control of Indoor CO2 Levels Negatively Impact IAQ?’, p. 11.

[8]   ‘UK Government loses third air pollution case as judge rules air pollution plans “unlawful”’, ClientEarth, Feb. 21, 2018. https://www.clientearth.org/government-loses-third-air-pollution-case-judge-rules-air-pollution-plans-unlawful/ (accessed Apr. 20, 2020).

[9]   ‘Air quality: Commission takes action to protect citizens from air pollution’, European Commission - European Commission. https://ec.europa.eu/commission/presscorner/detail/en/IP_18_3450 (accessed Apr. 20, 2020).

[10]   ‘IARC: DIESEL ENGINE EXHAUST CARCINOGENIC – IARC’. https://www.iarc.fr/news-events/iarc-diesel-engine-exhaust-carcinogenic/ (accessed Apr. 20, 2020).

[11]   ‘Tackling nitrogen dioxide in our towns and cities: UK overview document’, p. 70.

[12]   ‘UK plan for tackling roadside nitrogen dioxide concentrations: An overview’, p. 11.

[13]   ‘Non-exhaust traffic related emissions. Brake and tyre wear PM’. JRC Science and Policy Reports, Accessed: Apr. 19, 2020. [Online]. Available: https://publications.jrc.ec.europa.eu/repository/bitstream/JRC89231/jrc89231-online%20final%20version%202.pdf.

[14]   P. Fajri, S. Heydari, and N. Lotfi, ‘Optimum low speed control of regenerative braking for electric vehicles’, in 2017 IEEE 6th International Conference on Renewable Energy Research and Applications (ICRERA), San Diego, CA, Nov. 2017, pp. 875–879, doi: 10.1109/ICRERA.2017.8191185.

[15]   ‘WHO Air quality guidelines for particulate matter, ozone, nitrogen dioxide and sulfur dioxide Global update 2005 Summary of risk assessment’, WHO World Health Organ., 2005, [Online]. Available: https://apps.who.int/iris/bitstream/handle/10665/69477/WHO_SDE_PHE_OEH_06.02_eng.pdf;jsessionid=FCAACD4CDAFD5CADE1F9EFD2DC6F7455?sequence=1.

[16]   ‘Coronavirus delays cleaner air plans in cities’, BBC News, Mar. 26, 2020.

[17]   ‘COVID-19 situation reports’. https://www.who.int/emergencies/diseases/novel-coronavirus-2019/situation-reports (accessed Apr. 21, 2020).

[18]   ‘Standards - Air Quality - Environment - European Commission’. http://ec.europa.eu/environment/air/quality/standards.htm (accessed Jun. 10, 2016).

[19]   ‘Ambient (outdoor) air pollution’. https://www.who.int/news-room/fact-sheets/detail/ambient-(outdoor)-air-quality-and-health (accessed Feb. 13, 2020).

[20]   A. Khoo, ‘Air pollution plummets across UK amid lockdown’, BBC News, Apr. 08, 2020.

[21]   J. Amos, ‘Lockdown prompts clear fall in UK air pollution’, BBC News, Mar. 31, 2020.

[22]   Y. Cui et al., ‘Air pollution and case fatality of SARS in the People’s Republic of China: an ecologic study’, Environ. Health, vol. 2, no. 1, p. 15, Dec. 2003, doi: 10.1186/1476-069X-2-15.

[23]   X. Wu, R. C. Nethery, B. M. Sabath, D. Braun, and F. Dominici, ‘Exposure to air pollution and COVID-19 mortality in the United States’, Epidemiology, preprint, Apr. 2020. doi: 10.1101/2020.04.05.20054502.

[24]   L. Friedman, ‘New Research Links Air Pollution to Higher Coronavirus Death Rates’, The New York Times, Apr. 07, 2020.

[25]   R. N. Proctor, ‘The history of the discovery of the cigarette–lung cancer link: evidentiary traditions, corporate denial, global toll: Table 1’, Tob. Control, vol. 21, no. 2, pp. 87–91, Mar. 2012, doi: 10.1136/tobaccocontrol-2011-050338.

[26]   Live from WHO Headquarters - coronavirus - COVID-19 daily press briefing 17 April 2020. .

[27]   ‘Here’s How Covid-19 Immunity Compares to Other Diseases’, Wired.

[28]   8am to 6pm 0370 8506 506 From outside the UK +44 1709 389 201, ‘Monitoring emissions to air, land and water (MCERTS)’, GOV.UK. https://www.gov.uk/government/collections/monitoring-emissions-to-air-land-and-water-mcerts (accessed Apr. 21, 2020).

[29]   R. Harris, ‘Defining and measuring the productive office’, J. Corp. Real Estate, vol. 21, no. 1, pp. 55–71, Apr. 2019, doi: 10.1108/JCRE-05-2018-0016.

[30]   P. Wargocki, D. P. Wyon, Y. K. Baik, G. Clausen, and P. O. Fanger, ‘Perceived Air Quality, Sick Building Syndrome (SBS) Symptoms and Productivity in an Office with Two Different Pollution Loads’, Indoor Air, vol. 9, no. 3, pp. 165–179, 1999, doi: 10.1111/j.1600-0668.1999.t01-1-00003.x.

[31]   ‘Productivity effects of air pollution_ Evidence from professional soccer | Elsevier Enhanced Reader’. https://reader.elsevier.com/reader/sd/pii/S0927537117302658?token=012A6A89FDEBE4C6EC1AA867654115B530E693F37235C7D5CD2EA29C6A1E54DEC4E690DC398D5CD35E358CD456DF49E1 (accessed Feb. 13, 2020).