EDITORIAL - Smothered by smog

The last time Metro Manila and neighboring provinces were blanketed by ashfall, grounding flights, forcing the cancellation of classes and disrupting office work was in January 2020 when Taal Volcano erupted.

Yesterday, several local government units in southern Metro Manila as well as in neighboring areas in Cavite, Laguna, Rizal and much of Batangas also suspended classes in all levels, after the sky turned a murky brownish gray with poor visibility. Taal Volcano’s unrest was initially blamed, with warnings raised about the health risks posed by toxic vog or volcanic smog.

It turned out, however, that the reason for the poor visibility was a more common one. According to government scientists, it was plain smog, mostly from vehicular emissions, and aggravated by “thermal inversion.”

As explained by Science and Technology Secretary Renato Solidum, the air, as it goes higher in the atmosphere, should be cooler. In the case of thermal inversion, the cool air is at a higher altitude. The Philippine Institute of Volcanology and Seismology, which Solidum used to head, also clarified that the vog from Taal was drifting west-southwest, away from Metro Manila.

Solidum doused speculation that fine sand used in the controversial reclamation activities in Manila Bay had aggravated the smog from vehicular emissions. The speculation arose from the unusually dense smog, which was alarming enough to cause the suspension of classes in many areas. Solidum said sand is too heavy to be part of smog.

Vehicle emissions have long been a bane in air quality, despite the requirement that all motor vehicles must pass a smoke emission test before registration. There was no particular spike in vehicle density in Metro Manila and the neighboring