When a greyish blanket settled over Metro Manila in late 2023, many residents immediately suspected Taal Volcano. The assumption was understandable — Taal had been emitting steam and sulfur dioxide for months, and the haze looked similar to the volcanic smog, or vog, that occasionally drifts from Batangas. But the Philippine Institute of Volcanology and Seismology (Phivolcs) offered a different explanation. Director Dr. Teresito Bacolcol clarified that the haze over the capital was likely caused by pollution, not volcanic smog. The distinction matters because it shifts the focus from a natural event to a man-made one — and that changes how the problem gets addressed.
The haze that hung over Metro Manila was a mix of vehicle emissions, industrial smoke, and weather conditions — not volcanic gases drifting north. Phivolcs noted that winds around Taal were moving at less than 1 meter per second, far too slow to carry volcanic material to the capital. That means the real culprit was closer to home: the everyday pollution generated by millions of vehicles, factories, and power plants across the metropolis. For residents wondering whether to worry about their health, the answer depends on which pollutant they are breathing — and for how long.
What the haze actually contains — and why it lingers
Dr. Bacolcol explained that thermal inversion — a meteorological condition where colder air is trapped beneath a layer of warmer air — was a key factor. This inversion prevents pollutants from rising and dispersing, keeping them concentrated near the ground. He noted that this phenomenon was not limited to Metro Manila but also affected nearby provinces, reaching as far as the Tagaytay area. So when you see that greyish layer hanging over the skyline, it is not drifting volcanic ash — it is the city’s own exhaust, trapped by the weather.
The composition of the haze also differs from vog. While volcanic smog contains high levels of sulfur dioxide — an acidic gas that can irritate the eyes and respiratory tract — the Metro Manila haze is dominated by carbon monoxide from vehicle exhaust. Dr. Bacolcol acknowledged that there is some sulfur content from vehicles, but not as substantial as carbon monoxide. That distinction is important for health: carbon monoxide reduces the blood’s ability to carry oxygen, while sulfur dioxide causes immediate irritation to the lungs and throat.
How vog forms — and why it stayed near Taal
Volcanic smog, or vog, follows a different recipe. Dr. Bacolcol explained that vog typically appears as cooler months approach, particularly around December. When hot volcanic materials — abundant at Taal Volcano — come into contact with water, they produce steam. This steaming, combined with the release of sulfur dioxide and volcanic ash, creates the characteristic white-to-grey plume seen rising from the crater. “Kasabay ng puting usok ay paglabas din ng maraming sulfuric dioxide,” Bacolcol said, meaning that along with the white steam comes significant sulfur dioxide emissions.
But in late 2023, that vog stayed put. Phivolcs confirmed that the volcanic smog was mainly found around the Taal Caldera area and was not affecting Metro Manila. The extremely slow wind speeds — less than 1 meter per second — meant the gases had no mechanism to travel north. For context, a gentle breeze is about 3 to 5 meters per second; at less than 1 meter per second, the air around Taal was nearly stagnant.
Taal did have a small phreatic eruption earlier that week — a steam-driven explosion lasting two minutes — but it was minor. The volcano remains under Alert Level 1, indicating low-level unrest. Its last significant eruption was in July 2021, when it was placed under Alert Level 3. For comparison, Mayon Volcano recorded 338 earthquakes in July 2023 but only five by the time of the haze event, suggesting a general decrease in volcanic activity across the country. Kanlaon Volcano sits at Alert Level 1, while Mt. Bulusan is at Alert Level 0.
What gets missed when we blame the volcano
The instinct to attribute the haze to Taal is understandable — the volcano is visible from parts of Metro Manila on clear days, and its activity has disrupted life in the region for years. But that assumption carries a cost. When the public believes the haze is volcanic, attention shifts to monitoring agencies and evacuation protocols rather than to the everyday sources of pollution that are far more persistent and, in many ways, more controllable.
Here is what the data actually shows about the haze and its causes:
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| Factor | Haze (Metro Manila) | Vog (Taal Caldera) |
|---|---|---|
| Primary cause | Vehicle emissions, industrial pollution | Volcanic sulfur dioxide + steam |
| Main pollutant | Carbon monoxide | Sulfur dioxide |
| Weather role | Thermal inversion traps pollution | Cooler months trigger steaming |
| Wind dependency | Low winds worsen concentration | Winds <1 m/s kept it local |
| Health effect | Reduced oxygen in blood | Eye, nose, throat irritation |
| Geographic reach | Metro Manila + nearby provinces | Taal Caldera area only |
One nuance that often gets overlooked is the role of climate change. Dr. Bacolcol listed it among the factors influencing the haze, alongside humidity and sunlight intensity. Warmer temperatures can intensify the chemical reactions that turn vehicle exhaust into visible smog, while changing wind patterns may make thermal inversions more frequent. This is not a simple story of “too many cars” — it is a layered problem where weather, geography, and human activity intersect.
Another point worth considering: the same thermal inversion that trapped pollution in Metro Manila also affected areas like Tagaytay, which is closer to Taal. If the haze had been volcanic, Tagaytay would have experienced it more intensely than Metro Manila. Instead, both areas saw similar conditions, reinforcing the conclusion that the source was urban pollution, not volcanic emissions.
What you can actually do about the haze
Knowing that the haze is pollution-driven rather than volcanic changes what actions make sense. Here are practical steps based on the evidence.
Check real-time air quality before planning your day
Phivolcs and the Department of Environment and Natural Resources (DENR) monitor air quality through stations across Metro Manila. Before heading out, check readings for PM2.5 — fine particulate matter that penetrates deep into the lungs. When levels are elevated, limit outdoor exercise, especially in the morning when thermal inversion is strongest. If you must go out, wear an N95 or KN95 mask; surgical masks do little to filter fine particles.
Reduce personal contribution during inversion days
On days when haze is visible, vehicle emissions are the dominant source. Consider carpooling, taking public transport, or working from home if possible. Idling your engine while waiting — even for a few minutes — adds to the problem. The Metro Manila air crisis is driven largely by the sheer volume of vehicles, so any reduction in traffic during inversion events helps lower the concentration of pollutants near ground level.
Protect indoor air when haze is thick
Keep windows and doors closed during peak haze hours, typically early morning and late afternoon. Use an air purifier with a HEPA filter if available. If you do not have one, placing a damp cloth over window gaps can reduce the amount of outdoor air seeping in. Avoid burning candles, incense, or cooking methods that produce smoke indoors — these add to the particulate load.
Know the difference between haze symptoms and vog symptoms
If you experience eye irritation, throat burning, or coughing that starts suddenly, it could be sulfur dioxide from vog — but only if you are near Taal or downwind of it. For most Metro Manila residents, symptoms like headaches, fatigue, or shortness of breath are more likely from carbon monoxide and fine particles. If symptoms persist, consult a doctor rather than assuming it is volcanic. The treatment differs: for vog exposure, rinsing eyes and throat with clean water helps; for carbon monoxide, fresh air and rest are the first steps.
Frequently asked questions about the Metro Manila haze
Is the haze dangerous to breathe? ▾
How long does thermal inversion usually last? ▾
Can Taal’s vog still reach Metro Manila under different wind conditions? ▾
Does the DENR issue health advisories for haze? ▾
Why does the haze look worse some days than others? ▾
What to watch for next
The distinction between haze and vog is not just academic — it determines whether the solution lies in traffic management and industrial regulation or in volcano monitoring and evacuation planning. For Metro Manila, the evidence points squarely at the former. As cooler months approach and thermal inversions become more frequent, the haze will likely return. The question is whether the response will focus on the actual source: the emissions from millions of vehicles and factories that the city generates every day. If this was useful, you might also want to read how environmental degradation affects the Philippine economy.
Sources
Metro Manila’s air crisis: a deeper look — A comprehensive analysis of the sources, health impacts, and policy challenges behind the capital’s air quality problem.
Phivolcs explains Metro Manila haze vs. Taal volcano smog. DZRH, 2023.
Phivolcs confirms: smog in Metro Manila not caused by Taal Volcano. Planet Philippines UK, 2023.
