EXPLAINER: What is ashfall and why is it dangerous?

When volcanoes such as Mount Mayon erupts, lava flows and pyroclastic currents are not the only threats communities need to watch out for: there is also the danger posed by ashfall.

One of the biggest dangers during volcanic unrest is ashfall—the fine volcanic particles that can reduce visibility to near zero, damage homes and vehicles, and pose serious risks to human health, animals, and crops.

According to the Albay Provincial Information Office, at least 195,363 individuals or 55,991 families have been affected by heavy ashfall as of May 4.

Among the hardest-hit areas were 53 villages in the town of Oas, 41 in Guinobatan, 19 in Ligao City, and 16 in Camalig.

The Philippine Institute of Volcanology and Seismology (PHIVOLCS) defines ashfall as volcanic particles measuring no more than two millimeters in diameter. Unlike ordinary ash from burned wood, volcanic ash is made up of tiny but abrasive fragments of rock, minerals, and volcanic glass expelled during an eruption.

Since these particles are so fine, ashfall can easily be carried by the wind and spread far beyond the volcano’s crater. This is why visibility can quickly drop in affected areas, creating dangerous conditions for motorists and nearby residents.

But beyond travel disruptions, ashfall presents more serious safety risks.

When ash accumulates on rooftops and structures, it becomes a thick and heavy layer that can damage or even cause homes and buildings to collapse. It can also contaminate drinking water and damage vehicle engines, air vents, and other machinery.

Ashfall is also hazardous to human health, especially when inhaled.

According to the explainer, volcanic ash can cause irritation in the nose and throat, coughing, difficulty breathing, and asthma attacks. Long-term exposure may also lead to more serious lung disease.

Animals are also at risk.

Livestock and pets can die from inhaling volcanic ash or consuming grass and feed contaminated by sharp ash particles. In agriculture, ashfall can also pollute the soil because of its acidity and toxic chemicals, damaging farmland and killing crops.

Authorities advise the public to wear N95 masks or to cover their nose and mouth with a damp cloth to reduce inhalation of ash particles. Residents are also urged to keep doors and windows closed, place wet cloth in gaps where ash may enter, and drink plenty of water if they experience throat or nasal irritation.

Above all, residents are urged to stay alert and closely monitor advisories from PHIVOLCS and local government units as Mayon’s unrest continues.

DOH also listed some safety measures in the event of ashfall:

• Wear a mask (preferably N95) or use a damp cloth to filter fine ash particles that may irritate the nose, throat, and lungs.
• Avoid going near the volcano’s Permanent Danger Zone, where harmful gases and hazards are more concentrated.
• Keep doors and windows closed, and seal gaps with damp cloths to prevent ash from entering.
• Stay hydrated to help ease irritation in the throat and respiratory tract.
• Monitor official advisories from PHIVOLCS and local government units.

For emergencies, the public may contact the DOH through the national emergency hotline (911) or DOH Bicol at 0992-811-0733. — With information and research from GMA News Feed