Lockdown's Impact: Air Quality Improved, But Is It Lasting?

The COVID-19 pandemic has had a significant impact on air pollution levels globally. In many cities, lockdown restrictions have led to substantial improvements in air quality, with nitrogen dioxide and small particle pollution levels decreasing compared to pre-pandemic times. For instance, London's air pollution levels dropped by a third during the lockdown, and India's air quality index in Delhi fell to 45, a significant improvement from the previous year's reading of 160. However, some studies, such as those conducted in Nigeria, attribute the improved air quality to seasonal changes and favourable meteorological conditions rather than lockdown measures.

Air pollution in London dropped by a third during lockdown

Air pollution in London has dropped significantly since the COVID-19 lockdown, with levels of nitrogen dioxide (NO2) falling by more than a third compared to pre-lockdown readings. This improvement in air quality is largely due to the reduction in traffic and road transport, as well as the decrease in commercial activity.

Data published by the City of London Corporation shows that nitrogen dioxide levels in the Square Mile decreased by around 35% since the start of the lockdown. This improvement is particularly notable at specific locations, such as Sir John Cass Foundation Primary School, where air quality improved by 36%, and Upper Thames Street, which saw a 34% improvement.

The lockdown restrictions on movement and traffic have had a significant impact on air pollution levels, with London experiencing some of the lowest pollution readings since recordings. This improvement in air quality is not limited to London, as other cities around the world have also reported similar reductions in air pollution due to lockdown measures. For example, a study in Dongying, China, found a 24.6% reduction in the monthly average Air Quality Index (AQI) during the lockdown period in February 2020 compared to the previous year.

The drop in air pollution has been welcomed by many, and there are now calls for this cleaner air to become a permanent feature of London's environment. Elizabeth Fonseca, senior air quality manager at EDFE, emphasized the need to target the sources of pollution, stating that "by looking closer at which activities are producing the pollution, we can drive targeted solutions to clean the air."

To maintain these improvements in air quality, the City of London Corporation is taking several measures. One of their main goals is to have 90% of the City meet World Health Organization (WHO) guidelines for nitrogen dioxide levels by 2025. They also plan to collaborate with schools to implement Air Quality Action Plans and accelerate the use of zero-emission vehicle technology. Additionally, the governing body has banned new diesel vehicles from its fleet and is cracking down on idling engines.

Nitrogen dioxide levels in London fell by 35% during lockdown

Nitrogen dioxide levels in London fell by 35% during the lockdown, according to data published by the City of London Corporation. This was compared to the average reading from January 1st to March 22nd, with the lockdown period being from March 23rd to April 28th. The lockdown restrictions on movement meant that traffic in the Square Mile was heavily reduced, leading to a significant improvement in air quality in a matter of weeks.

The City of London, with its dense road network and high buildings, faces a particular challenge when it comes to air quality. Before the lockdown, around half of London's air pollution came from road transport, with diesel engines being a major contributor to nitrogen dioxide levels. The reduction in vehicle emissions during the lockdown period led to a notable decrease in nitrogen dioxide levels, with the air pollutant reaching low concentrations not seen in the past decade.

The improvement in air quality during the lockdown period provides valuable insights into the impact of human behaviour on the environment. It highlights the potential for long-term improvements in air quality through reduced traffic and the embrace of more sustainable modes of transportation, such as cycling and walking.

The City of London Corporation and other governing bodies are using this data to advocate for continued improvements in air quality. They are proposing initiatives such as the roll-out of Air Quality Action Plans in schools and the increased use of zero-emission vehicle technology to ensure that Londoners can breathe cleaner air permanently.

Air pollution in India's cities dropped during lockdown

Air pollution in India's cities dropped significantly during the COVID-19 lockdown, mainly due to the reduction in emissions from vehicles and industrial activities. According to the Centre for Science and Environment (CSE), PM 2.5 levels across major cities like Delhi, Mumbai, Kolkata, Chennai, Hyderabad, and Bengaluru decreased by 45-88% during the lockdown. This decrease can be attributed to the absence of industrial activity, reduced on-road traffic, and a temporary halt on construction projects.

Observational data from York University supports this, showing a drastic decline in air pollution during the initial lockdown phase. However, researchers caution that these numbers might be deceiving as certain pollutants can be invisible and still cause health issues. They found that while some pollutants decreased, ozone (O3) levels increased by up to 30% due to more sunshine.

The lockdown provided a unique opportunity to study the contribution of local sources of air pollutants. Researchers from Crilley and Young focused on nitrogen oxides (NOx), fine particulate matter (PM2.5), and ozone (O3) in Delhi and Hyderabad. They found that when only observational data was considered, NOx and PM2.5 levels dropped by up to 57% and 75%, respectively. However, when meteorological factors were included, the reductions were less significant, and O3 levels increased.

Despite the overall improvement in air quality during the lockdown, the challenge remains to ensure that pollution levels do not return to pre-lockdown levels. Centre's Executive Director, Anumita Roychowdhury, emphasized the importance of maintaining the gains made during the lockdown and preventing a return to "normal" pollution levels. As India gradually opened up, pollution levels began to rise again, underscoring the need for long-term solutions to combat air pollution.

Air pollution in Nigeria improved during lockdown

Air pollution is a significant issue in Nigeria, causing around 160,000 premature deaths in the country's big cities in a single year, according to an NGO. The COVID-19 lockdown presented a unique opportunity to study air pollution under reduced human activity. While some studies reported substantial improvements in air quality during lockdowns compared to pre-lockdown values, the impact of the lockdown on air pollution in Nigeria is debated.

Some sources argue that the COVID-19 lockdown improved air quality in Nigeria. During 2020, a 21% or 26% decline in average AODf levels was observed across Nigeria during the lockdown month of April compared to the pre-lockdown month of March. Additionally, the city of Port Harcourt saw a decrease of 1.1% and 215.5% in NO2 and SO2 levels, respectively, during the lockdown. These reductions in air pollution are significant and suggest that the lockdown played a role in improving air quality.

However, other sources argue that the improvements in air quality during the COVID-19 lockdown in Nigeria were primarily due to seasonal changes and local meteorological conditions rather than the lockdown measures themselves. One study found that the change in pollution levels during the lockdown period was similar in magnitude to reductions observed during the same period in previous years. Additionally, the lockdown coincided with the onset of the rainy season in Nigeria, which may have contributed to the improved air quality.

Overall, while there were reported declines in some air pollutant levels during the COVID-19 lockdown in Nigeria, the improvements were likely due to a combination of factors, including seasonal changes, meteorological conditions, and reduced human activities associated with the lockdown. Further analysis is needed to disentangle the effects of the lockdown from natural variations in air quality. Nonetheless, the lockdown provided a valuable opportunity to study the impact of reduced human activities on air pollution in Nigeria and highlighted the importance of investing in renewable energy and clean energy generation to improve air quality sustainably.

Air pollution in New York and Los Angeles improved during lockdown

The COVID-19 pandemic and the subsequent lockdown restrictions imposed by governments worldwide have had a significant impact on air pollution levels. The restrictions on movement and human activity have resulted in a substantial reduction in air pollution in many cities, including New York and Los Angeles.

New York City, despite being the most populous city in the United States, has relatively clean air on average. In 2019, the US Environmental Protection Agency (EPA) awarded the city $9.35 million to improve air safety, with a focus on regulating stationary and mobile emission sources. During the COVID-19 lockdown in March 2020, New York observed a 25% reduction in fine particle pollution (PM2.5) compared to the same period in 2019. Chauhan and Singh attributed about a 20% reduction in PM2.5 pollution levels during the lockdown to rainfall.

Los Angeles, a city known for its air pollution issues, also experienced improvements during the COVID-19 lockdown. Chauhan et al. recorded a 4% reduction in PM2.5 in March 2020 compared to March 2019, and they attributed this change primarily to meteorological factors such as wind speed and wind direction. Additionally, Chauhan and Singh noted a 30% reduction in PM2.5 pollution levels during the lockdown, which they associated with rainfall.

The improvements in air quality during the lockdown periods in New York and Los Angeles were influenced by various factors, including reduced traffic volume, decreased industrial emissions, and changes in domestic energy use. These cities saw significant reductions in nitrogen dioxide levels, which are closely linked to vehicle emissions and industrial activities. The lockdown restrictions limited motorized traffic, a key source of urban air pollution, leading to cleaner air in these metropolitan areas.

While the COVID-19 lockdown played a role in reducing air pollution, it is important to acknowledge the influence of seasonal changes and previous environmental interventions. Studies have shown that local meteorological conditions and seasonal variations can significantly impact PM2.5 levels. For example, in Nigeria, it was found that the improvement in air quality during the COVID-19 State of Emergency was primarily due to seasonal changes rather than the lockdown itself.

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