Special Issue on COVID-19 Aerosol Drivers, Impacts and Mitigation (XI)

Eliani Ezani This email address is being protected from spambots. You need JavaScript enabled to view it.1, Peter Brimblecombe2,3, Zulfa Hanan Asha’ari4, Amirul Aiman Fazil1, Sharifah Norkhadijah Syed Ismail1, Zamzam Tuah Ahmad Ramly4, Md Firoz Khan5 

1 Department of Environmental and Occupational Health, Faculty of Medicine and Health Sciences, Universiti Putra Malaysia, 43400 Serdang Selangor, Malaysia
2 Department of Marine Environment and Engineering, National Sun Yat-Sen University, Kaohsiung 80424, Taiwan
3 Aerosol Science Research Center, National Sun Yat-Sen University, Kaohsiung 80424, Taiwan
4 Department of Environment, Faculty of Forestry and Environment, Universiti Putra Malaysia, 43400 Serdang Selangor, Malaysia
5 Department of Chemistry, Faculty of Science, University of Malaya, 50603 Kuala Lumpur, Malaysia

Received: July 31, 2020
Revised: October 28, 2020
Accepted: October 28, 2020

 Copyright The Author(s). This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are cited.

Download Citation: ||https://doi.org/10.4209/aaqr.2020.07.0476  

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Cite this article:

Ezani, E., Brimblecombe, P., Hanan Asha’ari, Z., Fazil, A.A., Syed Ismail, S.N., Ahmad Ramly, Z.T., Khan, M.F. (2021). Indoor and Outdoor Exposure to PM2.5 during COVID-19 Lockdown in Suburban Malaysia. Aerosol Air Qual. Res. 21, 200476. https://doi.org/10.4209/aaqr.2020.07.0476


  • Reduction in concentration of PM2.5 was observed in suburban Malaysia during lockdown.
  • Potential for higher exposure to fine particles indoors than outdoors under lockdown.
  • Calculated an enhanced risk from PM2.5 from short term exposures under lockdown.
  • Increased working from home raises concerns about future indoor exposures.


During the COVID-19 pandemic, key policies aimed at reducing exposure to the virus from social distancing, restrictions on travel through to strongly enforced lockdowns. However, COVID-19 restrictions required people to spend more time at home so the exposure to air pollutants shifted to being derived from that of domestic interiors, rather than outdoors or the workplace environment. This study aims to characterise the influence of lockdown intervention on the balance of indoor and outdoor PM2.5 exposure in a Malaysian suburb. We also calculate the potential health risk from exposure to both indoor and outdoor PM2.5 to give context to personal exposure assessment in different microenvironments during the COVID-19 lockdown, known locally as Movement Control Orders (MCO). The implementation of the MCOs slightly reduced daily average of outdoor PM2.5 concentrations (median of 12.63 µg m–3 before and 11.72 µg m–3). In the Malaysian apartment considered here, cooking led to a substantial increase in exposure from increasing concentrations in PM2.5 during a COVID-19 lockdown (maximum average concentration at 52.2 µg m–3). The estimated excess risk to health was about 25% for lung cancer from staying indoor. Thus, there seems a potential for greater exposure to fine particles indoors under lockdown, so it is likely premature to suggest that more lives were saved through a reduction of outdoor pollutants than lost in the pandemic. Unfortunately, little is known about the toxicity of indoor particles and the types of exposures that result where people increase the amount of time they spend working from home or staying indoors, especially during periods of lockdown.

Keywords: Cancer, Cardio-respiratory diseases, Cooking, Indoor air quality, Lockdown

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