Volcanic smog or "vog" has been observed over Taal Volcano's caldera brought about by the high levels of sulfur dioxide gas emissions from the restive volcano in Batangas, the Philippine Institute of Volcanology and Seismology (Phivolcs) said on Monday, June 28.

"For the past two days, high levels of volcanic sulfur dioxide or SO2 gas emissions and steam-rich plumes that rose as much as three kilometers high have been observed from the Taal Main Crater," Phivolcs said.

It noted that Taal Volcano's sulfur dioxide emission averaged 4,771 tonnes daily on Sunday, June 27.

Phivolcs explained that vog is a type of air pollution caused by volcanoes, consisting of fine droplets containing volcanic gas, such as sulfur dioxide, which is acidic and can cause irritation of the eyes, throat, and respiratory tract in severities depending on the gas concentrations and durations of exposure

The atmospheric conditions, especially the near-absence of air movement, over the Taal Volcano "resulted in the formation of volcanic smog or vog that brought a pronounced haze over the Taal Caldera region," it said.

"Should SO2 gas emission continue at the same rate (past week average of ~4,330 tonnes/day) or increase and atmospheric conditions promote the formation of vog, communities surrounding Taal Lake are advised to take necessary precautions," it added.

People particularly sensitive to such ill effects are those with health conditions such as asthma, lung disease, and heart disease, the elderly, pregnant women, and children.

Phivolcs advised that those exposed to vog should stay indoors and "shut doors and windows to block out vog."

"Protect yourself. Cover nose, ideally with an N95 facemask. Drink plenty of water to reduce any throat irritation or constriction," it added.

"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. If serious effects are experienced, call the doctor or the barangay health unit," it also said.

Phivolcs reminded that Taal Volcano remains under Alert Level 2 due to continuous "increased unrest."

This means that the threat of sudden steam- or gas-driven explosions and lethal accumulations or expulsions of volcanic gas can occur and threaten areas within and around the Taal Volcano Island (TVI).

"Venturing into TVI must therefore remain strictly prohibited," Phivolcs said.