After the number of days defined as having ‘good’ air quality saw an increase between February and March they returned to previous levels in April, data provided by the Meteorological and Geophysical Bureau (SMG) indicated to Macau News Agency (MNA).
Accoridng to the data 16 ‘good air quality’ days were reported in January – when the Covid-19 pandemic was in the beginning – a number that then increased to 25 in February and March, to again bounce back to 16 in April.
The remaining days of these months were defined as ‘normal’ air quality.
The local air quality index defined by the SMG is based on measurements of the daily concentrations of the pollutant monitoring stations PM10, PM2.5, SO2, NO2, CO, O3 and the degree of influence of each pollutant on the health of the population, with a ‘good air quality’ day showing an index under 50, and ‘average air quality days with an index between 51 and 100.
MNA had previously reported that there has been a reduction in atmospheric pollution in Macau in the first months of this year that coincided with the Covid-19 crisis, but that more detailed studies are required to assess if water pollution has declined.
However, the SMG is known to evaluate the concentration limit of fine particulate matter in Macau considered as safe with standards higher than those set by the WHO of 10 micrograms (μg) per cubic metre annually and 25 µg per cubic metre as the 24-hour standard.
Levels of PM2.5 across China fell by more than 18 per cent between January 20 and April 4 amid city-wide lockdowns and strict travel restrictions, according to China’s environment ministry.
However, Greenpeace China has indicated recently that air pollution seems to have returned in higher levels than before, as Chinese factories rush to ramp up output after going idle during the outbreak, with levels of toxic pollutants including nitrogen dioxide and tiny particles known as PM2.5 all higher in April compared with the same period last year.