The prevailing thick smog observed in Manila on Tuesday is risky, especially to the elderly, children, and those with underlying conditions.

The Manila Department of Public Service (DPS) said based on their air quality monitoring, the smog was primarily caused by pollution from mobile vehicles and other industrial sources.

The DPS also refuted the rumor that the haze was caused by the unstable condition of Taal Volcano.

DPS Director Kenneth Amurao said an increasing concentration of Particulate Matter (PM) 2.5 has been recorded in the city since June 25.

DPS air quality monitoring report from 10 a.m. on Monday until 9 a.m. Tuesday showed that the Air Quality Index City was observed to be unhealthy for sensitive groups, Amurao said.

PM2.5 is described as “fine inhalable particles, with diameters that are generally 2.5 micrometers and smaller”, according to experts.

“Low wind speeds have been observed in the city since Sunday, which also contributes to lower dispersion of particulates in the atmosphere,” the DPS report read.

The DPS warned that people with lung and heart disease, older adults, and children are at greater risk from air pollution exposure.

Amurao advised wearing surgical masks, like N95 or KF94, or any tight-fitting masks when going outdoors.

Manila has five air quality sensors installed at the Freedom Triangle roadside beside the City Hall, Mehan Garden, Rizal Park, Barangay 128 roadside in Tondo, and Aurora Boulevard intersection in Sta. Cruz.