Metro Manilans and those in the Calabarzon region received a generous dose of science education last Friday, Sept. 22, when the hazy atmosphere prompted the suspension of classes. Alerts were also given to those proximately affected by Taal Volcano’s continuing activity.
The Philippine Institute of Volcanology and Seismology (Phivolcs) retracted its initial declaration that volcanic smog, or vog, was the cause of the haze, noting the west-southwest direction of the emissions from Taal Volcano toward other Batangas towns, and not toward Metro Manila.
Another agency, the Department of Environment and Natural Resources’ Environmental Management Bureau (DENR-EMB) stated that “hazy skies in Metro Manila…may be attributed to ground-level and suspended Particulate Matter (PM) concentration. Then, another term — thermal inversion — was injected into the briefing. Thermal inversion occurs when the layers of the atmosphere do not mix, causing aerosols to get trapped.
DENR-EMB explained further: “Normally, air temperature decreases with increasing altitude, but during an inversion, warmer air is held below the cooler air. An inversion can also suppress convection which is the ability of pollutant(s) to move vertically, causing visibly trapped particulate matter closer to the ground.”
The main cause of the phenomenon, therefore, was the presence of significant amounts of Particulate Matter — in simple terms, air pollution — that hovered closer to the ground, instead of drifting into the skies.
The Philippine Atmospheric, Geophysical and Astronomical Services (PAGASA), our good old weather bureau, chimed in to explain the rather unusual “meteorological conditions” last Friday in Metro Manila, Calabarzon and some Central Luzon provinces. It cited “the presence of very small particles…trapped close to the surface (or nearer ground level) due to the presence of a thermal inversion, high humidity, and calm wind conditions.” Usually “the inversion disappears later in the day as heat from the sun allows the mixing of the air, allowing the aerosols to disappear.” But the haze persists when cloudy conditions prevail.
Meanwhile, residents in the immediate vicinity of Taal Volcano, have been warned of the persistent and rising amount of vog whose chemical component is sulfur dioxide, which can irritate the eyes, throat, and respiratory system.
To recap, the smog that blanketed Metro Manila last Friday and through Saturday, was caused by heavy traffic emissions and thermal inversion, not by Taal Volcano’s continuing smoke emission.
This drives home anew the imperative need to curb air pollution to ensure that the air we breathe does not endanger our health.
Law enforcement agencies must intensify and sustain their campaign against smoke belching vehicles. More effective public transport systems such as the EDSA Bus Carousel system should be sustained and further enhanced. The use of hybrid or electric vehicles could also contribute significantly to the mitigation of air pollution. Meantime, if air pollution persists or worsens, commuters will be constrained to wear anew face masks for health protection.
Concerned government agencies must do what is needed to give accurate and reliable public information for the citizenry’s guidance.
