Taal ‘Vog’ Stirs Public Confusion About Poor Air Quality in Metro Manila Last Week

Small but restive Taal Volcano in Batangas City, Batangas, emitted above-average sulfur dioxide and volcanic smog last week. At the same time, parts of Metro Manila experienced poor quality due to thermal inversion and heavy pollution, prompting authorities to suspend classes and issue health warnings to the public.

Philippine Institute of Volcanology and Seismology (Phivolcs) released an advisory on Thursday afternoon, September 21, after state volcanologists observed a noticeable amount of volcanic smog or vog from the Taal Main Crater. The emission recorded a total of 4,569 tonnes per day of volcanic sulfur dioxide gas (SO2) from the volcano. Satellite monitors have also detected a large cloud of SO2 over Taal Lake drifting in the west-southwest direction (towards the area of Batangas and Cavite). In addition, Phivolcs noted that Taal Volcano has already been releasing “average of 3,402 tons of SO2 per day” since the first week of September.

The relative amount of volcanic smog prevailing in nearby provinces of Batangas, Laguna, and Cavite, enabled authorities to suspend work and classes at all levels and issue a health warning on Friday, September 22 due to the toxic gas emissions from Taal.

During the same period, parts of Metro Manila were enveloped by heavy smog on Friday morning, September 22, mainly caused by heavy traffic and “thermal inversion,” a naturally occurring event. However, several news sites initially reported that the thick smog caused poor air quality in Metro Manila originated from the volcanic smog emitted by Taal.

Officials from Phivolcs, the Department of Natural Resources- Environmental Management Bureau (DENR-EMB), and the Department of Science and Technology (DOST) later clarified that the smog in Metro Manila is “not likely due to the [volcanic smog] drifting over Taal Volcano” since initial wind patterns suggest that the volcanic smog is going west southwest direction and not going towards the Metro Manila area. Nevertheless, the thick haze forced all 17 local government units in Metro Manila to suspend classes at all levels, in both private and public schools on Friday afternoon due to poor air quality observed.

In an advisory, the state weather bureau PAGASA said the meteorological conditions on Friday morning in Metro Manila, Region 4A (Calabarzon), and parts of Central Luzon were conducive for haze or smog formation. “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. These floating minute particles in the air could be from smoke, pollutants, or volcanic aerosols,” PAGASA said.

According to the Batangas provincial government, the majority of vog in Batangas had already dissipated as of Monday, September 25, and only a thin layer of vog was reportedly logged over the town of Agoncillo but was significantly less dense than previous days.

PSA notes that Taal Volcano remains at Alert Level 1 on a five-level scale, which denotes a “low-level of volcanic unrest,” and no hazardous eruption is possible within weeks or even days. Individuals residing in this area are still advised to limit outdoor activities, keep doors and windows closed, and wear facemask if possible to cover their nose and mouth.