Assessing the Impact of Traffic Emissions on Fine Particulate Matter and Carbon Monoxide Levels in Hanoi through COVID-19 Social Distancing Periods

Abstract

Hanoi, Vietnam, is usually ranked as one of the most polluted capital cities in terms of air quality, particularly PM2.5. However, there has not been enough data to determine the main source of this pollution. In this study, we utilized the rare opportunity of the COVID-19 social distancing to assess the contribution of traffic emission to PM2.5 and CO levels when traffic volume was reduced significantly in Hanoi. Hourly PM2.5 and CO concentrations were measured from nine urban and traffic monitoring stations during pre-, soft, hard, and post-social distancing periods. As a result, we observed large reductions in both PM2.5 and CO levels during social distancing periods. PM2.5 concentrations were 14-18% lower during the social distancing than before this period, while CO concentrations had a more considerable drop by 28-41%. It is known that meteorological conditions can have significant effects on the ambient levels of air pollutants. To overcome this challenge, weather normalized concentrations of those pollutants were estimated using the random forest model, a machine learning technique. The normalized weather concentrations showed smaller reductions by 7-10% for PM2.5 and 5-11% for CO, indicating the presence of favorable weather conditions for better air quality during the social distancing period. In further analysis, the apparent improvement of air quality in Hanoi during the social distancing period could be attributed mainly to reducing traffic emissions while emissions from coal-fired power plants remained relatively stable.

Interrupting Effect of Social Distancing on Ischemic Heart Disease, Asthma, Stroke, and Suicide Attempt Patients by PM2.5 Exposure

“…The mean percentage of IHD patients increased significantly in Incheon and Gwangju, whereas it decreased in Seoul and Suwon after SD. This decline in patient visits after SD can be attributed to the government’s implementation of quarantine measures to prevent COVID-19 infections, which was more strictly enforced during this period than before SD to further reduce air pollution 19 20 21 22 23 and curb the spread of infectious diseases. 26 The WHO reported that “each suicide in a population is accompanied by more than 20 suicide attempts.” 29 Therefore, we can estimate that the same patients visited EDs several times for treatment after suicide attempts.…”

“…21 Several studies reported a decrease in PM 2.5 levels as a result of the lockdown and the implementation of SD measures in response to the COVID-19 epidemic. 22 23 24 These measures represented a public health infection control strategy aimed at minimizing individual or group contact to reduce the transmission of infectious diseases. The measures are considered non-pharmaceutical interventions, meaning they do not involve the use of treatments or vaccines.…”

Change in Air Quality during 2014–2021 in Jinan City in China and Its Influencing Factors

“…NO 2 concentrations during the COVID-19 lockdown period decreased slightly by 8.2% over the urban ambient station in the Metro of Atlanta, USA [ 21 ]. PM 2.5 concentrations in Hanoi, Vietnam, were about 14–18% lower during the COVID-19 epoch than before this era, but CO concentrations had a significant decline by about 28–41% [ 22 ]. The control measures during the COVID-19 pandemic reduced NO 2 levels in China [ 23 ].…”

The Effect of COVID-19 Pandemic on Emitted PM2.5 in Urban Road Networks: Using Loop Data and Kriging Method for Passenger Cars in the Central Part of the City of Lodz

“…Countries have taken various actions to control and confront this infectious disease such as: staying at home and keeping social distancing (Şahin, 2020). Furthermore, many regions imposed lockdown and movement restrictions as one of the most effective measures for minimizing the risk of virus contractions (Le et al, 2021). Execution of the lockdown policy not only has had implications for curbing the pandemic but also highly impacted the transportation system worldwide (Ranjbari et al, 2021), and consequently, improvement of the air quality in different parts of the world (Gautam, 2020;Chen et al, 2021).…”

“…Aside from the city and regional scale studies which considered the effect of lockdowns on the pollution emitted by the transportation system (Gualtieri et al, 2020;Şahin, 2020;Wang et al, 2020a;Chen et al, 2021;Le et al, 2021), some research has been done at the intra-urban level. Xiang et al (2020) conducted research to examine the impacts of the COVID-19 responses on traffic-related air pollution utilizing flow data collected by the loop sensors for several links in the street network along with the pollution data gathered from a roadside monitoring station.…”