The Philippine Institute of Volcanology and Seismology (Phivolcs) warned of volcanic smog or “vog” from Taal Volcano after sulfur dioxide (SO2) emission reached over 10,000 tons on Thursday, Sept. 29.

In an advisory issued on Thursday evening, Phivolcs said that 10,718 tons per day of SO2 had been recorded in the morning.

The SO2 emission from Taal Volcano “produced significant volcanic smog or vog over Taal Caldera.”

Phivolcs said that residents in the municipalities of Laurel, Agoncillo, and Sta. Teresita in Batangas have reported vog on Thursday morning.

“Airborne volcanic gas is expected to be drifted to the general west of Taal Volcano Island or TVI (Taal Volcano Island) based on air parcel trajectory data from PAGASA (Philippine Atmospheric, Geophysical and Astronomical Services Administration),” Phivolcs said.

It pointed out that SO2 flux averaged 6,612 tons per day in September, in a continuing trend of high emissions since July 15, 2022.

“Since the beginning of August 2022, there was also an increase in degassing activity in the form of visible upwelling of volcanic fluids in the Main Crater Lake and emission of voluminous steam-rich plumes of up to 2,500 meters rise above TVI,” Phivolcs said.

According to Phivolcs, vog consists of fine droplets containing volcanic gas such as SO2, which is acidic and can cause irritation of the eyes, throat and respiratory tract with severities depending on the gas concentrations and durations of exposure.

People with asthma, lung disease, and heart disease, the elderly, pregnant women, and children, may be particularly sensitive to vog.

For communities that can be affected by vog, Phivolcs advised the people to limit their exposure by avoiding outdoor activities, staying indoors, and shutting doors and windows to block out the vog.

It also asked the public to cover their nose, ideally with an N95 facemask, and drink plenty of water to reduce any throat irritation or constriction.

“If belonging to the particularly sensitive group of people above, watch over yourself and seek help from a doctor or the barangay health unit if needed, especially if serious effects are experienced,” Phivolcs said.

In addition, it warned of acid rain that may be generated during periods of rainfall and volcanic gas emission over areas where the plume disperses.

Acid rain can damage crops and metals roofs.

Phivolcs said Taal Volcano remains under Alert Level 1, which means it is still in an abnormal condition and should not be interpreted to have ceased unrest nor ceased the threat of eruptive activity.

Sudden steam-driven or phreatic explosions, volcanic earthquakes, minor ashfall and lethal accumulations or expulsions of volcanic gas can occur and threaten areas within the TVI.

“Should an uptrend or pronounced change in monitored parameters forewarn of renewed unrest, the alert level may be raised back to Alert Level 2,” it said.

Phivolcs said that entry into TVI, which is Taal’s permanent danger zone or PDZ, especially the vicinities of the main crater and the Daang Kastila fissure, must remain strictly prohibited.