Coronavirus: How lockdowns have caused drop in air pollution across the world

Meanwhile, CO2 emissions in China were down by at least 30% between 3 February and 1 March, according to the Center for Research on Energy and Clean Air (CREA).

CREA estimates this is equivalent to 200 million tons of carbon dioxide.

In Hong Kong, key air pollutants dropped by nearly a third from January to February, according to data from Hong Kong University School of Public Health.

South Korea also appears to have seen a drop in nitrogen dioxide levels, despite avoiding putting entire regions under lockdown.

However, it has taken an aggressive approach to tracing and isolating suspected cases.

Researchers in New York said that early findings showed carbon monoxide had been reduced by nearly 50% compared with the previous year.

The scientists, from Columbia University, said they estimated traffic levels in the city were down 35%.

Countries that went into lockdown later – such as Britain, which did so on 23 March – look set for a pollution reprieve in coming weeks.

Air pollution can cause or exacerbate lung cancer, pulmonary disease and strokes. It causes around 400,000 premature deaths each year in Europe.