The Philippine Institute of Volcanology and Seismology (Phivolcs) observed volcanic smog, or vog, coming from Taal Volcano in Batangas province on Monday morning, raising public health concerns and prompting widespread class suspensions.

“In light of the recent eruption of Taal Volcano and the release of volcanic smog in the last 24 hours, the Department of Education (DepEd) is authorizing affected schools to suspend classes in the absence of official [guidance] from the local government units,” read a DepEd memorandum issued by Education Secretary Sonny Angara on Monday, 19 August.

According to DepEd, a total of 41 local government units in Luzon suspended face-to-face classes and shifted to blended learning due to the volcanic smog.

“To ensure learning continuity in affected areas, DepEd instructs schools to employ alternative delivery modalities such as modular or online learning,” the memo added.

Vog consists of fine droplets containing volcanic gas such as sulfur dioxide (SO2) which is acidic and can cause irritation of the eyes, throat, and respiratory tract. The severity of these effects depends on the gas concentrations and the duration of exposure, according to Phivolcs.

Phivolcs recommended that people affected by the vog stay indoors and protect themselves by wearing N95 face masks and drinking plenty of water to reduce throat irritation or constriction.

Further, a voluminous emission of a steam plume shooting up 2,400 meters and drifting north-northwest was observed by the agency’s 24-hour monitoring.

Last Thursday, 15 August, Taal spewed 3,355 tons of SO2 and was observed to have an upwelling of hot volcanic fluids in the main crater lake.

The Taal caldera was also seen to have long-term deflation, along with short-term inflation of the general northern and southeastern flanks of Taal Volcano island. A caldera is the depression formed when a crater collapses on itself, as with Taal which is described as a volcano within a lake within a volcano.

Blended learning

Taal has remained under Alert Level 1 due to its abnormal condition which should not be interpreted as having stopped its unrest or threat of eruption.

Some areas in Luzon, mostly in the Calabarzon region, suspended in-person classes on Monday due to the high levels of vog, the DepEd said Sunday.

In Batangas, the municipalities of Balete, Balayan, Malvar, Laurel, San Jose, Mataas na Kahoy, Agoncillo, San Nicolas, Nasugbu, Lemery, Lian, Talisay, San Luis, Alitagtag, San Pascual, Calatagan, Tuy, Cuenca, Sta. Teresita, Bauan, San Juan, Taal, Padre Garcia, and Ibaan, and the city of Calaca suspended in-person classes at all levels in both public and private schools.

In Cavite, the towns of Silang, Mendez, Indang, Alfonso, Gen. Mariano Alvarez (GMA), Carmona, Gen. Emilio Aguinaldo, Amadeo, Maragondon, Naic and Carmona also suspended in-person classes.

Calamba, Biñan and Los Baños towns in the province of Laguna suspended face-to-face classes on all levels.

Meanwhile, the cities of Muntinlupa and Las Piñas in Metro Manila shifted to blended learning to ensure the safety of learners.

As this developed, the Department of Health (DoH) issued a health advisory amid the presence of vog in Metro Manila and nearby provinces.

The DoH warned that vog may cause irritation in the eyes, throat, and respiratory tract that can be severe depending on the concentration or duration of inhalation.

The health department also cautioned residents near Taal Volcano about “the high level of sulfur dioxide emission that causes volcanic smog or vog.”

To minimize the inhalation of vog, the DoH advised the public to avoid outdoor activities, close doors and windows, cover the nose and mouth, wear an N95 mask, and drink plenty of water.

“Monitor your health and seek help from a doctor or the barangay health unit, if necessary, especially if experiencing serious side effects,” the DoH said.

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

On Monday, the Department of Environment and Natural Resources warned of unhealthy air quality in Caloocan, Parañaque and Pateros. Meanwhile, Makati logged a very unhealthy air quality level.