Phivolcs clarification: Metro Manila smog contains Taal vog, after all

Thick haze envelopes the metropolis on Tuesday, June 29. The Philippine Institute of Volcanology and Seismology (Philvolcs) clarified that the haze in Metro Manila was brought about by “human activity” or pollution and not from Taal Volcano. -INQUIRER/GRIG C. MONTEGRANDE

MANILA, Philippines — It was volcanic smog or “vog” after all, not just vehicle emissions, that clouded Metro Manila and nearby provinces earlier this week.

Following a routine check of open satellite data, the Philippine Institute of Volcanology and Seismology (Phivolcs) on Wednesday confirmed that sulfur dioxide (SO2) emissions from Taal Volcano reached Metro Manila and produced a haze over it.

Phivolcs said data released by the National Aeronautics and Space Administration (Nasa) on Tuesday afternoon showed that Taal’s plumes extended from the planetary boundary layer to the upper troposphere at almost 20 kilometers above sea levels, and mostly spread over Metro Manila and the provinces of Batangas, Laguna, Cavite, Rizal, Bulacan, Pampanga, Bataan and Zambales.

“In view of the scientific data from above satellite platforms, Phivolcs stands to acknowledge evidence of the wider extents that volcanic SO2 has actually spread over the National Capital Region and adjoining provinces,” Phivolcs said in a statement.

The satellite data “gives credence” to observations pointed out by the public on the haze enveloping Metro Manila in the past few days, the agency added.

Smog made worse

But Science Undersecretary Renato Solidum Jr., who serves as officer in charge of Phivolcs, said that even with vog spreading to Metro Manila and nearby provinces, smog from vehicle emissions and human activities still result in poor air quality in the capital region.

“The smog was already present in Metro Manila and this would be due to human activities, … made worse by temperature inversion,” Solidum said. “The dispersed sulfur dioxide on [June] 28th contributed to the haze.”

Temperature inversion, which was recorded by the weather bureau from June 26 to 29, happens when the cold air closer to the ground is trapped by a layer of warm air above it, preventing smoke and other pollutants from rising and dispersing as temperature increases throughout the day.

Monitoring by the Philippine Atmospheric, Geophysical and Astronomical Services Administration (Pagasa), however, showed that there was no temperature inversion on Wednesday morning, and that aerosols and other pollutants were able to rise and dissipate, leading to better air quality over the capital region, Solidum said.

Lack of evidence

Phivolcs said that it had initially denied the presence of vog over the capital region due to the lack of substantiating evidence and the general direction of wind and SO2 dispersal from Taal since Monday.

“As a scientific institution, we have been reminded again of the value of uncertainty and the limitations of our data, the value of citizen observation and the need to constantly challenge our own perceptions, interpretations and ideas,” the agency said.

Environment group Greenpeace Philippines said the haze over Metro Manila should push the government to prioritize and invest in better air pollution monitoring devices.

“Without adequate and working air quality monitoring systems, the government will be stuck in an air pollution guessing game,” Greenpeace campaigner Khevin Yu said.