SINGAPORE - To escape the scourge of a contagious, microscopic foe, various nations went into lockdown earlier this year.
As people were confined to their homes, cars stowed away and industrial activities slowed, it was as though an invisible broom had swept away the pall of smog, soot and harmful pollutants, to reveal clear skies.
Singapore saw improvements in its air quality before and during the two-month circuit breaker, as key pollutants plummeted to levels within the World Health Organisation's air quality guidelines, some of which the country previously could not meet.
In April, for the first time in decades, people in Punjab could view the Himalayan mountain range about 200km away as India enforced a nationwide lockdown.