Skip to main content
PMC home page
Elsevier - PMC COVID-19 Collection logoLink to Elsevier - PMC COVID-19 Collection
. 2020 Jun 25;741:140515. doi: 10.1016/j.scitotenv.2020.140515

A vulnerability-based approach to human-mobility reduction for countering COVID-19 transmission in London while considering local air quality

Manu Sasidharan a,⁎,1, Ajit Singh b,c,⁎,1, Mehran Eskandari Torbaghan d,⁎, Ajith Kumar Parlikad a
PMCID: PMC7315141  PMID: 32887014

Abstract

An ecologic analysis was conducted to explore the correlation between air pollution, and COVID-19 cases and fatality rates in London. The analysis demonstrated a strong correlation (R2 > 0.7) between increment in air pollution and an increase in the risk of COVID-19 transmission within London boroughs. Particularly, strong correlations (R2 > 0.72) between the risk of COVID-19 fatality and nitrogen dioxide and particulate matter pollution concentrations were found. Although this study assumed the same level of air pollution across a particular London borough, it demonstrates the possibility to employ air pollution as an indicator to rapidly identify the city's vulnerable regions. Such an approach can inform the decisions to suspend or reduce the operation of different public transport modes within a city. The methodology and learnings from the study can thus aid in public transport's response to COVID-19 outbreak by adopting different levels of human-mobility reduction strategies based on the vulnerability of a given region.

Keywords: COVID-19, Human mobility, Air pollution, Particulate matter (PM2.5), Nitrogen dioxide (NO2), Transport

Graphical abstract

Unlabelled Image

Open in a new tab

Highlights

  • •

    a strong correlation between increment in NO2 and PM2.5 levels and an increase in the risk of COVID-19 transmission

  • •

    a strong correlation between the risk of COVID-19 fatality and higher NO2 and PM2.5 levels

  • •

    Introduces a vulnerability-based approach to human-mobility reduction strategies.

1. Introduction

The current outbreak of novel coronavirus COVID-19 or severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has resulted in the World Health Organization (WHO) declaring it as a global pandemic (World Health Organization, 2020). Reported first within the city of Wuhan, Hubei Province of China in December 2019, the COVID-19 exhibits high human-to-human transmissibility and has spread rapidly across the world (Qun et al., 2020). The human-to-human transmission of COVID-19 can occur from individuals in the incubation stage or showing symptoms, and also from asymptomatic individuals who remain contagious (Bai et al., 2020). The COVID-19 has been reported to transmit via the inhalation of exhaled respiratory droplets (Guangbo et al., 2020) that remain airborne for up to 3 h (Neeltje et al., 2020). The extent to which COVID-19 induces respiratory stress in infected individuals may also be influenced by underlying respiratory conditions (Wei et al., 2020) like acute respiratory inflammation, asthma and cardiorespiratory diseases (Centers for Disease Control and Prevention, 2020). Various studies have reported an association between air pollution levels and excess morbidity and mortality from respiratory diseases (Adamkiewicz et al., 2004; Dockery, 2001; Yan et al., 2003) with children and elderly people being at most risk (Department for Environment, Food, and Rural Affairs, 2017). 20% of England's population is at risk of mortality from COVID-19 due to underlying conditions and age (Amitava et al., 2020).

The simultaneous exposure to air pollutants such as particulate matter (PM2.5) and Nitrogen dioxide (NO2) alongside COVID-19 virus is also expected to exacerbate the level of COVID-19 infection and risk of fatality (Transport and Environment, 2020; European Public Health Alliance, 2020). Recent studies have also suggested that exposure to NO2 and PM2.5 may be one of the most important contributors to COVID-19 related fatalities (Xiao et al., 2020; Ogen, 2020; Travaglio et al., 2020). Moreover, the adsorption of the COVID-19 virus on PM could also contribute to the long-range transmission of the virus (Guangbo et al., 2020). For example, an ecologic analysis of the 2003 severe acute respiratory syndrome coronavirus 1 (SARS-CoV-1) reported that infected patients who lived in moderate air pollution levels were approximately 84% more likely to die than those in regions with lower air pollution (Yan et al., 2003). The aerosol and surface stability of the COVID-19 or SARS-CoV-2 is reported to be similar to that of SARS-CoV-1 (Neeltje et al., 2020). Given the limited understanding of the epidemiology of COVID-19, social-distancing and human-mobility reduction measures can contribute greatly to tailoring public health interventions (Shengjie et al., 2020).

2. Human-mobility reduction

Countries across the world have enforced lockdowns and other coordinated efforts to reduce human-mobility (European Commission, 2020; Anderson et al., 2020; Matteo et al., 2020; Edward et al., 2020). The UK's national framework for responding to a pandemic states that public transport should continue to operate normally during a pandemic, but users should adopt good hygiene measures, and stagger journeys where possible (Department of Health, 2007). Within the UK, London has recorded the highest COVID-19 related fatalities (i.e. 30.2% of UK's deaths as of 31 March 2020) (National Health Services, 2020). On 18 March 2020, further to the UK government's advice, Transport for London (TfL) closed 40 out of 270 London Underground (LU) stations that do not serve as interchanges with other lines and announced a reduced service across its network (Transport for London, 2020). This is also because 30% of TfL's drivers, station staff, controllers and maintenance teams were not able to come to work, including those self-isolating or ill with COVID-19 (Transport for London, 2020).

The UK's current human-mobility reduction response reflects the need to maintain business continuity, near-normal functioning of society and enable critical workers to make essential journeys (Department of Health, 2007; Joy et al., 2011). However, a statistically significant association exists between human-mobility through public transport and transmissions of acute respiratory infections (ARI) (Joy et al., 2011; Lara and Anders, 2018). It was found that using public transport in the UK during a pandemic outbreak has an approximately six-fold increased risk of contracting an ARI (Joy et al., 2011). Moreover, the pandemic case rates for London boroughs with access to interchange stations are higher (Lara and Anders, 2018), as individuals would interact with more people in comparison to through stations.

One of the most controversial debates in pandemic countermeasures is the potential benefit of human-mobility reduction and social-distancing attained by the closure of public transport systems. From a public policy perspective, there is a need to achieve a trade-off between the potential public health benefits of closing public transport during a pandemic thereby delaying the community spread, against the socio-economic impacts of curtailing/reducing human mobility. Determining the vulnerability of regions/locations to COVID-19 might help achieve such trade-offs. The proposed approach can be employed to rapidly identify regions that are highly vulnerable to COVID-19 and accordingly inform human-mobility reduction measures across the city's public transport network.

3. Materials and methods

An ecologic analysis was conducted to explore the correlation between short-term air pollution (of PM2.5 and NO2 levels) and COVID-19 cases and fatality rate in each London borough/region. To this end, a linear regression model was fitted to the data for regions with more than 100 reported cases and 10 COVID-19 related deaths as of 31 March 2020. Accordingly, the vulnerabilities of different boroughs in London to COVID-19 was measured.

3.1. Fatality data

As the COVID-19 is an evolving pandemic, the available data as of 31 March 2020 on COVID-19 morbidity and mortality for different boroughs in London was collected (Public Health England, 2020; National Health Services, 2020) The Office of National Statistics (A Baker, personal communication, 2020) confirmed that they are unable to provide COVID-19 related fatality data categorized by each London borough or local authority. To this end, the deaths reported by individual NHS Hospital Trusts in London were employed to inform the reported deaths for each London borough. The fatality rate across each London borough was estimated by dividing the number of reported deaths by the number of reported positive COVID-19 cases.

3.2. Air pollution data

The air pollution data associated with particulate matter (PM2.5) and nitrogen dioxide (NO2) for each London borough was collected from (King's College London, 2020). NO2 data was available for 15 boroughs namely Barking and Dagenham, Bexley, Wandsworth, City of London, Croydon, Greenwich, Havering, Hillingdon, Kensington and Chelsea, Lewisham, Reading, Redbridge, Sutton, Tower Hamlets and Westminster. While, the PM2.5 data was available only for 8 boroughs (Barking and Dagenham, Wandsworth, City of London, Croydon, Hillingdon, Kensington and Chelsea, Lewisham). Time series of available air pollution (PM2.5 and NO2) and COVID-19 cases could be seen in Fig. 1 , which shows that COVID-19 cases increase with increasing air pollution at London boroughs.

Fig. 1.

Fig. 1

Open in a new tab

The average a) NO2 and b) PM2.5 pollution concentrations and reported COVID-19 cases for different boroughs in London for March 2020. The grey bars show the monthly average of NO2 and PM2.5 concentrations and the line represent the cumulative number of reported COVID-19 cases in each London borough.

The average NO2 concentration within the LU network was reported to be 51 μg m−3 (James David et al., 2016). The PM2.5 concentration within different LU stations was recorded by Smith et al. (2020) with an average concentration of was 88 μg m−3.

4. Results

A strong correlation between short-term NO2 and PM2.5 pollution concentrations and COVID- 19 cases with R2 values of 0.82 (COVID-19 cases = −29.345 + 10.306*NO2 concentration) and 0.72 (COVID-19 cases = −215.63 + 40.997*PM2.5 level) were observed respectively (see.

Fig. 2 ). In particular, COVID-19 fatality rate increased with increase in short-term air pollution, where a significant correlation between COVID-19 fatality and NO2 and PM2.5 pollution concentrations with R2 of 0.90 (fatality rate = 1.864+ 0.5787*NO2 level) and 0.67 (fatality rate = −7.733+ 2.3399*PM2.5 level) were found (see.

Fig. 2.

Fig. 2

Open in a new tab

Relationship between a) NO2 and b) PM2.5 pollution concentrations and reported COVID-19 cases at London boroughs using data during March 2020.

Fig. 3 ).

Fig. 3.

Fig. 3

Open in a new tab

Relationship between a) NO2 and b) PM2.5 pollution concentrations and the COVID-19 fatality rate for each London borough. The fatality rate was calculated by dividing the number of reported deaths by the number of reported positive COVID-19 cases.

The median PM2.5 levels recorded for 27 of 40 closed LU stations range from 0 to 50 μg m−3 (5 stations), 50–100 μg m−3 (9 stations), 100–200 μg m−3 (5 stations), 200–300 μg m−3(6 stations) and greater than 300 μg m−3 (2 stations) (see Table A1). Of the 230 operating stations, the median PM2.5 levels recorded for 219 stations range from 0 to 50 μg m−3 (56 stations), 50–100 μg m−3 (15 stations), 100–200 μg m−3 (15 stations), 200–300 μg m−3 (18 stations) and greater than 300 μg m−3 (7 stations) (Smith et al., 2020) (see Table A1). This suggests that approximately 40% of the stations in operation during the current COVID-19 outbreak in London are up to 26 times more polluted than the ambient background locations and the roadside environment which has a median PM2.5 level of 14 μg m−3 (Smith et al., 2020). Moreover, the average NO2 concentrations across the LU network is 27.5% higher than the NO2 limit values for the protection of human health (European Environment Agency, 2014).

5. Concluding discussion

Our analysis shows that short-term exposure to air pollution (both NO2 and PM2.5) is significantly correlated with an increased risk of contracting and dying from COVID-19, expanding on previous evidence linking high mortality rates in England (Travaglio et al., 2020), Northern Italy (Ogen, 2020) and USA (Xiao et al., 2020). Biologically, either long-term or short-term exposure to air pollutants such as PM2.5 and NO2 can compromise lung function and therefore increase the risk of dying from COVID-19 (Wei et al., 2020). Given that the immunity to the 2003 SARS-CoV-1 was reported to be relatively short-lived (around 2 years) (Li-Ping et al., 2007), achieving herd immunity for diseases like COVID-19 or SARS-CoV-2 would be unlikely without overwhelming the healthcare system (Edward et al., 2020). Human-mobility reduction measures provide the greatest benefit to COVID-19 mitigation (Matteo et al., 2020; Anderson et al., 2020) as prevention is potentially cost-effective than cure (Lara and Anders, 2018) or death.

The results from this study demonstrate that the air pollution levels can serve as one of the indicators to assess a region's vulnerability to COVID-19 and accordingly adopting human-mobility reduction strategies. For instance, the London Borough of Kensington and Chelsea is seen to be highly vulnerable to COVID-19 fatality from our analysis (see Fig. 3a). Table A1 shows that all the through stations and 3 out of 4 interchange stations (South Kensington, Sloane Square, Earl's Court, Notting Hill gate) in this borough are currently operational. Such a vulnerability-based assessment might aid decision-makers in selecting appropriate human-mobility reduction measures to COVID-19 in London's different local authorities/boroughs (such as apportion of transport staff across railway stations, arranging dedicated shuttling services for key workers, scheduling bus operations etc.) while adhering to the UK's national framework for response to pandemic outbreaks (Department of Health, 2007) of not isolating towns or even cities (Department of Health and Social Care, 2020).

We support the UK government's existing COVID-19 guidance (Department of Health and Social Care, 2020) to exercise good hygiene and to avoid unnecessary travel. While considering the evidence that COVID-19 can be transmitted from an asymptomatic individual (Bai et al., 2020), the currently implemented countermeasure of suspending operations only on the stations that do not serve as interchanges is not effective. This is because of the statistically significant risk of contracting ARI's on UK's public transport and higher pandemic case rates within London boroughs that have comparatively easier access to interchange stations. Moreover, the PM2.5 and NO2 levels, potential contributors to COVID-19 transmission and fatalities, are relatively higher in LU stations than other transport environments. E.g. the median level of airborne PM2.5 in LU stations is several times higher than cycling (35 μg m−3), bus (30.9 μg m−3), cars (23.7 μg m−3) (Vania et al., 2015; Smith et al., 2020).

It has to be noted that the number of positive COVID-19 cases considered within this study are only those reported at the hospitals and does not include the growing number of people who are self-isolating at home due to mild COVID-19. While the individual risk of contracting and dying from COVID-19 is dependent on various factors (including age, underlying conditions, availability of health care, population density etc.), these results are informative for both scientists and decision-makers in their efforts to reduce the transmission and socio-economic impact of the ongoing COVID-19 outbreak through appropriate human-mobility reduction strategies. It is also recommended to expand the study further to understand the effect (if any) of other air quality parameters such as volatile organic compounds (VOCs) and nitrogen oxides (NOx), on COVID-19 transmission and fatality rate.

CRediT authorship contribution statement

Manu Sasidharan:Conceptualization, Formal analysis, Writing - original draft, Writing - review & editing.Ajit Singh:Conceptualization, Formal analysis, Writing - original draft, Writing - review & editing.Mehran Eskandari Torbaghan:Conceptualization, Writing - original draft, Writing - review & editing.Ajith Kumar Parlikad:Conceptualization, Writing - review & editing.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgments

Acknowledgements

We would like to thank Anne Baker from the Office for National Statistics for very kindly providing her input to the COVID-19 related fatality data. We appreciate the work of J.D. Smith, B.M. Barratt, G.W. Fuller and team that captured the levels of PM2.5 exposure in London Underground.

Funding

This work was supported by the Engineering and Physical Science Research Council (EPSRC) through the grant EP/N021614/1 (CSIC Innovation and Knowledge Centre Phase 2) and EP/N010523/1 (Balancing the Impact of City Infrastructure Engineering on Natural Systems using Robots), and Innovate UK through the grant 920035 (Centre for Smart Infrastructure and Construction).

Contributor Information

Manu Sasidharan, Email: mp979@cam.ac.uk.

Ajit Singh, Email: a.singh.2@bham.ac.uk.

Mehran Eskandari Torbaghan, Email: m.eskandaritorbaghan@bham.ac.uk.

Appendix A.

Table A1.

Status of LU stations (as of 31 March 2020) and their mean PM2.5 levels adapted from (Smith et al., 2020; Transport for London, 2020a, Transport for London, 2020b, Transport for London, 2020c).

Borough Line Station Mean PM2.5 level in the station (μg m−3) Status (as of 31/03/2020)
Barking and Dagenham District Becontree tube station 6 Open
Barking and Dagenham District Dagenham Heathway tube station 4 Open
Barking and Dagenham District Upney tube station 3 Open
City of Westminster Central Bond Street tube station 367 Open
City of Westminster Central Oxford Circus tube station 338 Open
City of Westminster Northern Embankment tube station 316 Open
City of Westminster Bakerloo Edgware Road tube station (Bakerloo line) 311 Open
City of Westminster Victoria Green Park tube station 308 Open
City of Westminster Central Marble Arch tube station 307 Open
City of Westminster Central Tottenham Court Road tube station 298 Open
City of Westminster Victoria Oxford Circus tube station 296 Open
City of Westminster Northern Leicester Square tube station 287 Open
City of Westminster Bakerloo Baker Street tube station 273 Open
City of Westminster Bakerloo Maida Vale tube station 268 Open
City of Westminster Bakerloo Oxford Circus tube station 263 Open
City of Westminster Victoria London Victoria station 253 Open
City of Westminster Jubilee Bond Street tube station 245 Open
City of Westminster Bakerloo Piccadilly Circus tube station 244 Open
City of Westminster Jubilee Westminster tube station 242 Open
City of Westminster Northern Tottenham Court Road tube station 239 Open
City of Westminster Jubilee Green Park tube station 236 Open
City of Westminster Bakerloo Embankment tube station 227 Open
City of Westminster Piccadilly Piccadilly Circus tube station 176 Open
City of Westminster Jubilee Baker Street tube station 174 Open
City of Westminster Piccadilly Leicester Square tube station 148 Open
City of Westminster Piccadilly Green Park tube station 144 Open
City of Westminster Jubilee St. John's Wood tube station 131 Open
City of Westminster District Embankment tube station 104 Open
City of Westminster District Westminster tube station 104 Open
City of Westminster Circle Westminster tube station 89 Open
City of Westminster District London Victoria station 75 Open
City of Westminster Circle Embankment tube station 61 Open
City of Westminster Hammersmith & City Baker Street tube station 57 Open
City of Westminster Circle Baker Street tube station 50 Open
City of Westminster Metropolitan Baker Street tube station 42 Open
City of Westminster Circle London Victoria station 42 Open
City of Westminster Hammersmith & City Edgware Road tube station (Hammersmith & City lines) 39 Open
City of Westminster Hammersmith & City Paddington tube station (Hammersmith & City lines) 19 Open
City of Westminster Circle Edgware Road tube station (Circle, District and Hammersmith & City lines) 10 Open
City of Westminster Hammersmith & City Royal Oak tube station 9 Open
City of Westminster Circle Paddington tube station (Circle) 6 Open
City of Westminster Circle Royal Oak tube station 4 Open
City of Westminster Hammersmith & City Westbourne Park tube station 4 Open
City of Westminster Circle Westbourne Park tube station 3 Open
City of Westminster Circle Bayswater tube station 3 Closed
City of Westminster Piccadilly Covent Garden tube station 132 Closed
City of Westminster Circle Great Portland Street tube station 91 Closed
City of Westminster Metropolitan Great Portland Street tube station 48 Closed
City of Westminster Hammersmith & City Great Portland Street tube station 99 Closed
City of Westminster Piccadilly Hyde Park Corner tube station 148 Closed
City of Westminster Central Lancaster Gate tube station 260 Closed
City of Westminster Victoria Pimlico tube station 460 Closed
City of Westminster Central Queensway tube station 277 Closed
City of Westminster Bakerloo Regent's Park tube station 243 Closed
City of Westminster Circle St. James's Park tube station 53 Closed
City of Westminster District St. James's Park tube station 94 Closed
City of Westminster District Temple tube station 82 Closed
City of Westminster Circle Temple tube station 14 Closed
City of Westminster Bakerloo Warwick Avenue tube station 277 Closed
Greenwich Jubilee North Greenwich tube station 103 Open
Hammersmith & City Circle Ladbroke Grove tube station 5 Open
Havering District Elm Park tube station 5 Open
Havering District Hornchurch tube station 3 Open
Havering District Upminster Bridge tube station 2 Open
Hillingdon Piccadilly Heathrow Terminals 2 & 3 tube station 50 Open
Hillingdon Piccadilly Heathrow Terminal 4 tube station 47 Open
Hillingdon Piccadilly Hatton Cross tube station 44 Open
Hillingdon Metropolitan Uxbridge tube station 31 Open
Hillingdon Metropolitan Ruislip Manor tube station 30 Open
Hillingdon Metropolitan Eastcote tube station 29 Open
Hillingdon Metropolitan Ruislip tube station 29 Open
Hillingdon Metropolitan Hillingdon tube station 28 Open
Hillingdon Metropolitan Ickenham tube station 28 Open
Hillingdon Metropolitan Northwood Hills tube station 23 Open
Hillingdon Metropolitan Northwood tube station 23 Open
Hillingdon Central Ruislip Gardens tube station 19 Open
Kensington and Chelsea Piccadilly Gloucester Road tube station 147 Closed
Kensington and Chelsea Circle Gloucester Road tube station 5 Closed
Kensington and Chelsea District Gloucester Road tube station 24 Closed
Kensington and Chelsea Central Holland Park tube station 123 Closed
Kensington and Chelsea Central Notting Hill Gate tube station 200 Open
Kensington and Chelsea Piccadilly South Kensington tube station 178 Open
Kensington and Chelsea Piccadilly Knightsbridge tube station 137 Open
Kensington and Chelsea Piccadilly Earl's Court tube station 105 Open
Kensington and Chelsea District Sloane Square tube station 57 Open
Kensington and Chelsea District South Kensington tube station 45 Open
Kensington and Chelsea Circle Sloane Square tube station 33 Open
Kensington and Chelsea District Earl's Court tube station 21 Open
Kensington and Chelsea Circle South Kensington tube station 18 Open
Kensington and Chelsea Circle High Street Kensington tube station 4 Open
Kensington and Chelsea Hammersmith & City Latimer Road tube station 4 Open
Kensington and Chelsea Circle Notting Hill Gate tube station 3 Open
Kensington and Chelsea Circle Ladbroke Grove tube station 2 Open
Kensington and Chelsea Circle Latimer Road tube station 2 Open
Redbridge Central Newbury Park tube station 56 Open
Redbridge Central Gants Hill tube station 55 Open
Redbridge Central Redbridge tube station 75 Closed
Redbridge Central Wanstead tube station 35 Open
Redbridge Central Barkingside tube station 31 Open
Redbridge Central Fairlop tube station 12 Open
Redbridge Central Hainault tube station 9 Open
Redbridge Snaresbrook tube station Open
Redbridge South Woodford tube station Open
Redbridge Woodford tube station Open
Tower Hamlets Central Mile End tube station 186 Open
Tower Hamlets District Tower Hill tube station 91 Open
Tower Hamlets District Mile End tube station 82 Open
Tower Hamlets District Aldgate East tube station 64 Open
Tower Hamlets Circle Tower Hill tube station 59 Open
Tower Hamlets District Bromley-by-Bow tube station 56 Open
Tower Hamlets Hammersmith & City Mile End tube station 45 Open
Tower Hamlets Hammersmith & City Aldgate East tube station 42 Open
Tower Hamlets Hammersmith & City Bromley-by-Bow tube station 40 Open
Tower Hamlets Hammersmith & City Bow Road tube station 76 Closed
Tower Hamlets District Bow Road tube station 80 Closed
Tower Hamlets District Stepney Green tube station 127 Closed
Tower Hamlets Hammersmith & City Stepney Green tube station 74 Closed
Tower Hamlets Millwall tube station Open
Tower Hamlets St Katharine Docks tube station Open
Wandsworth Northern Tooting Broadway tube station 284 Open
Wandsworth Northern Tooting Bec tube station 234 Open
Wandsworth Northern Clapham South tube station 203 Closed
Wandsworth East Putney tube station Open
Wandsworth Southfields tube station Open
Open in a new tab

References

  1. Adamkiewicz G., Ebelt S., Syring M., Slater J., Speizer F.E., Schwartz J.…Gold D.R. Association between air pollution exposure and exhaled nitric oxide in an elderly population. Environmental Exposure. 2004;59:204–209. doi: 10.1136/thorax.2003.006445. [DOI] [PMC free article] [PubMed] [Google Scholar]
  2. Amitava, B., Laura, P., Steve, H., Arturo, G.-I., Ana, T., Laura, S., … Harry, H. (2020). Estimating excess 1- year mortality from COVID-19 according to underlying conditions and age in England: a rapid analysis using NHS health records in 3.8 million adults. medRxiv(doi.org/ 10.1101/2020.03.22.20040287). [DOI]
  3. Anderson R.M., Heesterbeek H., Klinkenberg D., Hollingsworth T.D. How will country-based mitigation measures influence the course of the COVID-19 epidemic? Lancet. 2020;395(10028):931–934. doi: 10.1016/S0140-6736(20)30567-5. [DOI] [PMC free article] [PubMed] [Google Scholar]
  4. Bai Y., Yao L., Wei T., Tian F., Jin D.Y., Chen L., Wang M. Presumed asymptomatic carrier transmission of COVID-19. JAMA. 2020 doi: 10.1001/jama.2020.2565. [DOI] [PMC free article] [PubMed] [Google Scholar]
  5. Centers for Disease Control and Prevention. (2020). People who are at higher risk for severe illness. Retrieved March 31, 2020, from https://www.cdc.gov/coronavirus/2019-ncov/need-extra-precautions/people-at-higher-risk.html?CDC_AA_refVal=https%3A%2F%2Fwww.cdc.gov%2Fcoronavirus%2F2019-ncov%2Fspecific-groups%2Fhigh-risk-complications.html.
  6. Department for Environment, Food & Rural Affairs . DEFRA; London: 2017. Air Quality: A Briefing for Directors of Public Health. [Google Scholar]
  7. Department of Health . Department of Health; London: 2007. Pandemic Flu – A National Framework for Responding to an Influenza Pandemic. [Google Scholar]
  8. Department of Health & Social Care . 2020. Coronavirus: Action Plan. [Google Scholar]
  9. Dockery D.W. Epidemiologic evidence of cardiovascular effects of particulate air pollution. Environmental Health Perspective. 2001;109(4):483–486. doi: 10.1289/ehp.01109s4483. [DOI] [PMC free article] [PubMed] [Google Scholar]
  10. Edward, D. B., Daniele, R., & Yves, M. (2020). Modeling the COVID-19 outbreaks and the effectiveness of the containment measures adopted across countries. medRxiv(doi.org/ 10.1101/2020.04.02.20046375). [DOI]
  11. European Commission. (2020, March 26). Coronavirus response: travel and transportation. Retrieved March 31, 2020, from https://ec.europa.eu/info/live-work-travel-eu/health/coronavirus-response/travel-and-transportation_en.
  12. European Environment Agency. (2014, August 22). Nitrogen dioxide - annual limit values for the protection of human health. Retrieved March 31, 2020, from https://www.eea.europa.eu/data-and-maps/figures/nitrogen-dioxide-annual-limit-values-for-the-protection-of-human-health.
  13. European Public Health Alliance. (2020, March 16). Coronavirus threat greater for polluted cities. Retrieved March 31, 2020, from https://epha.org/coronavirus-threat-greater-for-polluted-cities/.
  14. Guangbo Q., Xiangdong L., Ligang H., Guibin J. An imperative need for research on the role of environmental factors in transmission of novel coronavirus (COVID-19) Environmental Science & Technology. 2020;54(7):3730–3732. doi: 10.1021/acs.est.0c01102. [DOI] [PubMed] [Google Scholar]
  15. James David S., Christina M., Nutthida K., Ben M.B., Heather A.W., Jonathon G.T.…Sean D.B. London Hybrid Exposure Model: Improving Human Exposure Estimates to NO2 and PM2.5 in an Urban Setting. Environmental Science & Technology. 2016;50:11760–11768. doi: 10.1021/acs.est.6b01817. [DOI] [PubMed] [Google Scholar]
  16. Joy T., Puja M., Jack G., Ahmed H., Joanne E., Susan K.…Jonathan Nguyen V.-T. Is public transport a risk factor for acute respiratory infection. BMC Infectious Diseases. 2011;11(16) doi: 10.1186/1471-2334-11-16. [DOI] [PMC free article] [PubMed] [Google Scholar]
  17. King's College London Data feeds for London air quality. 2020. http://www.londonair.org.uk/LondonAir/API/ Retrieved March 31, 2020, from.
  18. Lara G., Anders J. Analysing the link between public transport use and airborne transmission: mobility and contagion in the London underground. Environ. Health. 2018;17(84):1–11. doi: 10.1186/s12940-018-0427-5. [DOI] [PMC free article] [PubMed] [Google Scholar]
  19. Li-Ping W., Nai-Chang W., Yi-Hua C., Xiang-Yi T., Dan-Yu N., Li-Yuan Z.…Guo-Dong L. Duration of antibody responses after severe acute respiratory syndrome. Emerging infectious diseases. 2007;13(10):1562–1564. doi: 10.3201/eid1310.070576. [DOI] [PMC free article] [PubMed] [Google Scholar]
  20. Matteo C., Jessica T.D., Marco A., Corrado G., Maria L., Stefano M.…Ira M.L. The effect of travel restrictions on the spread of the 2019 novel coronavirus (COVID-19) outbreak. Science. 2020 doi: 10.1126/science.aba9757. [DOI] [PMC free article] [PubMed] [Google Scholar]
  21. National Health Services COVID-19 daily deaths. 2020. https://www.england.nhs.uk/statistics/statistical-work-areas/covid-19-daily-deaths/ Retrieved March 31, 2020, from.
  22. Neeltje v.D., Trenton B., Dylan H.M. Aerosol and surface stability of SARS-CoV-2 as compared with SARS-CoV-1. N. Engl. J. Med. 2020 doi: 10.1056/NEJMc2004973. [DOI] [PMC free article] [PubMed] [Google Scholar]
  23. Ogen Y. Assessing nitrogen dioxide (NO2) levels as a contributing factor to coronavirus (COVID-19) fatality. Sci. Total Environ. 2020;382(16):1564–1567. doi: 10.1016/j.scitotenv.2020.138605. [DOI] [PMC free article] [PubMed] [Google Scholar]
  24. Public Health England. (2020, March). Retrieved March 31, 2020, from https://www.gov.uk/government/publications/covid-19-track-coronavirus-cases.
  25. Qun L., Xuhua G., Peng W., Xiaoye W., Lei Z., Yeqing T.…Chuding C. Early Transmission Dynamics in Wuhan, China, of Novel Coronavirus–Infected Pneumonia. The New England Journal of Medicine. 2020;382:1199–1207. doi: 10.1056/NEJMoa2001316. [DOI] [PMC free article] [PubMed] [Google Scholar]
  26. Shengjie L., Isaac B., Nick R., Alexander W., Xin L., Weizhong Y.…Andrew J.T. Assessing spread risk of Wuhan novel coronavirus within and beyond China, January-April 2020: a travel network-based modelling study. Health Sciences. 2020 doi: 10.1101/2020.02.04.20020479. [DOI] [Google Scholar]
  27. Smith J., Barratt B., Fuller G., Kelly F., Loxham M., Nicolosi E., Green D. PM2.5 on the London underground. Environ. Int. 2020;134 doi: 10.1016/j.envint.2019.105188. [DOI] [PMC free article] [PubMed] [Google Scholar]
  28. Transport & Environment. (2020, March 19). Air pollution probably increasing coronavirus death rates - experts. Retrieved March 31, 2020, from https://www.transportenvironment.org/news/air-pollution-probably-increasing-coronavirus-death-rates-experts.
  29. Transport for London. (2020a, March). Coronavirus (COVID-19). Retrieved March 31, 2020, from https://tfl.gov.uk/campaign/coronavirus-covid-.
  30. Transport for London. (2020b, March 26). London's transport commissioner Mike Brown on our response to coronavirus. Retrieved March 31, 2020, from https://tfl.gov.uk/info-for/media/press-releases/2020/march/london-s-transport-commissioner-mike-brown-on-our-response-to-coronavirus.
  31. Transport for London. (2020c, March 18). Planned services to support London's critical workers. Retrieved March 31, 2020, from https://tfl.gov.uk/info-for/media/press-releases/2020/march/planned-services-to-support-london-s-critical-workers.
  32. Travaglio M., Popovic R., Yu Y., Leal N., Martins L.M. Links between air pollution and COVID-19 in England. 2020. Retrieved from. [DOI] [PMC free article] [PubMed]
  33. Vania M., Teresa M., Maria Cruz M., Fulvio A., Eladio d.M., Marta C., Xavier Q. Exposure to airborne particulate matter in the subway system. Sci. Total Environ. 2015;511:711–722. doi: 10.1016/j.scitotenv.2014.12.013. [DOI] [PubMed] [Google Scholar]
  34. Wei L., Zhao-Wu T., Lei W., Ming-Li Y., Kui L., Ling Z.…Yi H. Analysis of factors associated with disease outcomes in hospitalized patients with 2019 novel coronavirus disease. Chinese Medical Journal. 2020 doi: 10.1097/CM9.0000000000000775. [DOI] [PMC free article] [PubMed] [Google Scholar]
  35. World Health Organization. (2020, March 11). WHO director-General's opening remarks at the media briefing on COVID-19 - 11 March 2020. Retrieved March 31, 2020, from https://www.who.int/dg/speeches/detail/who-director-general-s-opening-remarks-at-the-media-briefing-on-covid-19---11-march-2020.
  36. Xiao, W., Rachel C. N., Benjamin M. S., Danielle, B., & Francesca, D. (2020). Exposure to Air Pollution and COVID-19 Mortality in the United States. (doi.org/ 10.1101/2020.04.05.20054502). [DOI]
  37. Yan C., Zuo-Feng Z., John F., Jinkou Z., Hua W., Shun-Zhang Y., Roger D. Air pollution and case fatality of SARS in the People's Republic of China: an ecologic study. Environmental Health: A Global Access Science Source. 2003;2(15):1–5. doi: 10.1186/1476-069X-2-15. [DOI] [PMC free article] [PubMed] [Google Scholar]

Articles from The Science of the Total Environment are provided here courtesy of Elsevier

RESOURCES