In an interview with the Philippine News Agency, Solidum said the haze was primarily due to vehicle emissions, and the water vapor from rains.
"Vehicle emissions will be the major contributor. (Also), because of thunderstorms, there have been frequent rains all over (Metro Manila). Water has been evaporating since morning as the sun heats the ground," Solidum said.
He said the steam and gas plume over the Taal Volcano is heading towards the northeast, and not towards Metro Manila. "Hence, the haze or smog in Metro Manila is not from Taal," he said.
He added that the haze was likely caused by "human activities".
"The volume of vehicles is increasing. You can see this pollution clearly in the morning when temperature is cooler as the sun has just risen. The haze is from the ground and moving up, and very evident in major roads. The smog would eventually rise farther up as air temperature would increase during the day," he said.
Phivolcs issued an advisory on Monday saying that volcanic smog or vog has been observed over the Taal Caldera.
Vog is a type of air pollution caused by volcanoes. It consists of fine droplets containing volcanic gas such as SO2 (sulfur dioxide) which is acidic and can cause irritation of the eyes, throat, and respiratory tract in severities depending on the gas concentrations and durations of exposure.
As such, Phivolcs advised people surrounding Taal Lake to protect themselves and to stay indoors.
According to the United States Geological Survey (USGS), vog poses a health hazard by aggravating preexisting respiratory ailments. SO2 gas could irritate the skin, eyes, nose, throat. Further, the aerosol particles in vog could penetrate the lungs and could induce the symptoms of asthma.
Phivolcs advised those who have health conditions such as asthma, lung disease, and heart disease, as well as the elderly, pregnant women and children to take necessary precautions against the ill effects of vog. (PNA)