Urban air pollution reduction: evidence from phase-wise analysis of COVID-19 pandemic lockdown

Until 31 May 2020, more than six million confirm COVID-19 cases had been reported worldwide. Lockdown has resulted in significant air quality improvement, especially in urban regions. The lockdown has acted as a natural experiment empowering researchers, policymakers, and governing bodies. The present study focuses on quantifying and analysing the effect of lockdown on India’s metropolitan cities, namely New Delhi, Mumbai, Kolkata, Chennai, and Bangalore. The study analyses the phase-wise and diurnal variations in the air quality from 24 March 2020 to 31 May 2020 while focussing on-peak and off-peak duration concentrations. To investigate the reason behind pollutant reduction, correlation of drop percentages in pollutant concentrations with vehicle population, extent of construction activity, and meteorological parameters are analysed. The 24-h drop in PM10 and PM2.5 showed a high correlation (R2 = 0.97 and 0.72, respectively) with the city’s vehicle population. During peak hours, the inland cities (Delhi and Bangalore), with a more extensive vehicle fleet, recorded a higher drop in PM10 and PM2.5 concentrations than coastal cities (Mumbai, Chennai, and Kolkata). With respect to 2019 concentration, the maximum decrease in pollutant concentrations averaged across the five study locations was recorded in NO2 (46%), followed by PM2.5 (40%), PM10 (37%), and CO (19%). SO2 and O3 contrarily recorded an overall increase of 40% and 41%. These results wherein vehicular pollutants recorded the maximum drop indicate that reduced vehicular traffic primarily influenced air quality improvement during the lockdown.

Aerosol number concentrations and new particle formation events over a polluted megacity during the COVID-19 lockdown

The present study investigates the particle number concentrations and size distributions in the ultrafine and fine-sized regimes over a polluted megacity, New Delhi (28.75° N, 77.12° E), India. The experiments were conducted during the periods (April-May 2020) of strict social and travel restrictions (lockdown) imposed by the Government of India aiming to contain the spread of Coronavirus Disease 19 (COVID-19) pandemic. The different phases of the COVID-19 lockdown witnessed restrictions of varying magnitudes with the significant cessation of anthropogenic sources, viz., industrial, road, railways, and air traffic emissions. Using this unique opportunity, the impact of varying urban emissions on particle number size distributions and new particle formation events were examined. The mean total number concentrations were in the range of ∼ (2 to 3.5) x 104 cm-3 and depicted a gradual increase (∼26%) with progressive unlock of the anthropogenic activities. At the same time, accumulation particle concentrations were doubled. However, ultrafine particles (UFP) (diameter < 100 nm) dominated (50-88%) the total number concentrations during most of the days and several new particle formation (NPF) events resulting in elevated (2 - 5 fold) UFP concentrations were observed. Subsequently, the particles grew to larger sizes with rates ∼3.31- 8.37 nm hr-1. The NPF events occurred during the daytime, and during the events, a clear enhancement in the concentrations of [H2SO4] proxy (2 to 3.5 x 107 molecules cm-3;2-3 orders higher than the non-event values) suggesting the role of strong gas-phase photochemistry. Also, some of the NPF events were associated with increased odd oxygen concentrations [Ox = O3+NO2], indicating the regional nature of the precursors and participation of VOC precursors in nucleation/growth. Interestingly, different classes of NPF events were seen during the strictest lockdown period, whereas more frequent and well-defined NPF events were witnessed when anthropogenic activities were opened up with conditional relaxations. These events demonstrated the competition between source strengths of precursor vapors from anthropogenic activities and primary particles acting as condensation sink restricting NPF. This study highlighted that urban pollution mitigation policies need to consider ultrafine particles emanating from the secondary aerosol formation process from traffic emissions.

Incidence and pattern of dental emergencies and their management during Covid-19 pandemic : An experience of Nepali dentists working during lock down

Introduction: Corona Virus Disease-2019 (COVID-19) is highly contagious nature of disease which has spread all over the world in short span of time leading to significant number of death. WHO has declared pandemic and every nation is fighting with their all possible resources to control this disease. The impact of COVID-19 in dentistry is enormous. Most of the dental hospitals and clinic are providing emergency dental services only. So the aim of this research is to find out the nature of dental emergency during the initial month of lock down in Nepal. Additionally this research will try to find out the number of dental emergencies as well as perception of dentists on impact of COVID-19 on dentistry. Materials and Method : A set of electronic questionnaires were sent to 150 Nepal Medical Council registered Nepalese dentists out of which only 122 dentists responded. A consent was obtained prior to collecting data for research purpose. All the quantitative answers were recorded in SPSS spread sheet where as qualitative data were collected in Microsoft word. Descriptive statistics were applied to explain the responses whenever applicable. Result: Out of 122 respondents, maximum were from province 3 and 4 (50% and 34%). Almost half of the respondents were general dental practioners and similar percentage of respondents were working at dental/medical colleges and government centers. 90% of the doctors had consulted patients during lock down period. Average 5-20 cases were seen during the lock down by majority of doctors. Nearly 58% of the doctors had done only virtual consultation and most common emergency was dental pain(n= 92) and swelling( n= 37). Majority of the respondents thought that standard of dental disinfection and sterilization will increase after pandemic, however most of the dentists thought they will be using PPE for dental work and cost of dental treatment will be increased because of the added cost of extra precaution. 90% of the dentists believed that they are going to change the way they practice dentistry after they reopen their clinic. Conclusion: The most common type of dental emergency during lock down is dental pain ,swelling, dento-maxillofacial trauma and broken orthodontic appliances. Virtual dental consultation is gaining popularity among dentists in Nepal and Nepalese dentists are going to change the way of dental practice because of COVID-19.

Comparative study on air quality status in Indian and Chinese cities before and during the COVID-19 lockdown period.

Amidst COVID-19 pandemic, extreme steps have been taken by countries globally. Lockdown enforcement has emerged as one of the mitigating measures to reduce the community spread of the virus. With a reduction in major anthropogenic activities, a visible improvement in air quality has been recorded in urban centres. Hazardous air quality in countries like India and China leads to high mortality rates from cardiovascular diseases. The present article deals with 6 megacities in India and 6 cities in Hubei province, China, where strict lockdown measures were imposed. The real-time concentration of PM2.5 and NO2 were recorded at different monitoring stations in the cities for 3 months, i.e. January, February, and March for China and February, March, and April for India. The concentration data is converted into AQI according to US EPA parameters and the monthly and weekly averages are calculated for all the cities. Cities in China and India after 1 week of lockdown recorded an average drop in AQIPM2.5 and AQINO2 of 11.32% and 48.61% and 20.21% and 59.26%, respectively. The results indicate that the drop in AQINO2 was instantaneous as compared with the gradual drop in AQIPM2.5. The lockdown in China and India led to a final drop in AQIPM2.5 of 45.25% and 64.65% and in AQINO2 of 37.42% and 65.80%, respectively. This study will assist the policymakers in devising a pathway to curb down air pollutant concentration in various urban cities by utilising the benchmark levels of air pollution.