Some local government units (LGUs) in Metro Manila cancelled classes citing the volcanic smog (vog) from Taal Volcano, but the foggy skies may not even be related to the Batangas volcano's activities in the first place.
The likes of Mandaluyong and Quezon City public information offices cited the poor air quality brought about by the Taal vog as the reason behind class suspension. They also reminded residents to wear face masks.
According to the Philippine Institute of Volcanology and Seismology (Phivolcs), the vog over Taal some 90 kilometers south of Metro Manila is drifting in a west-southwest direction, meaning not toward Metro Manila.
So what’s causing the gloomy skies over the Metro?
Read: Taal Vog, Mayon Ash Flow: What You Need to Know
What’s happening over Metro Manila is also being monitored over Calabarzon and parts of Central Luzon, according to the Philippine Atmospheric, Geophysical, and Astronomical Services Administration (PAGASA).
While the agency did not specify what Metro Manila is experiencing, the conditions caused by floating minute particles possibly from smoke, pollutants, or even volcanic aerosols are conducive for the formation of smog or haze.
“This occurs when very small particles get trapped close to the surface due to the presence of a thermal inversion, high humidity, and calm wind conditions,” it said.
What the DENR has to say about the Metro Manila air quality
Heavy vehicular traffic, especially during rush hour, is the main contributing factor as to why air quality in some parts of Metro Manila is on heightened alert, according to the Department of Natural Resources (DENR).
"Air quality varies in time and places and can change anytime depending on pollution sources and meteorological factors," the agency said in a statement on September 22, 2023.
An initial assessment of the skies in Metro Manila showed that Parañaque recorded an Air Quality Index of 217 (acutely unhealthy), while the stations in Makati and Pateros recorded an Air Quality Index of 128 and 141 (unhealthy), respectively, DENR said.
Read: What Fog? Metro Manila's Gray Skies Caused by Haze, PAGASA Says
Fog, Vog, Haze, Smog: What’s the difference?
In case you’re curious, here’s a quick explainer on how to differentiate these terms:
Fog is due to water droplets or moisture in the atmosphere, generally white.
Vog is volcanic smog, or a mix of sulfur dioxide gas and aerosols that causes visible haze. Basically, it’s caused by air pollutants from volcanoes.
Smog is air pollution that happens when smoke and chemical fumes combine.
It is exacerbated by thermal inversion, or when a warm layer of air stops dirty air from dispersing, effectively trapping pollution below.
Haze happens when dust and/or other air pollutants which cannot be seen by the naked eye interact with sunlight. It reduces visibility and gives the sky a grayish hue.