Several areas in Metro Manila recorded elevated PM2.5 levels, with air quality reaching “Very Unhealthy” to “Acutely Unhealthy” levels, the Department of Environment and Natural Resources–Environmental Management Bureau (DENR-EMB) reported Tuesday.

“The elevated PM2.5 may be associated with smoke and haze from ongoing fires in Kalimantan, Indonesia, transported by prevailing winds toward the Philippines,” the EMB National Capital Region (EMB-NCR) said in a public service advisory.

Areas classified under the “Acutely Unhealthy” category, with an Air Quality Index (AQI) of 201 to 300 as of 6 a.m. on September 1, include Parañaque (296), Quezon City (241), Las Piñas (237), Manila (231), Malabon (229), Taguig (224), Valenzuela (224), Marikina (217), Muntinlupa (216), San Juan (213), and Mandaluyong (207). 

Other areas such as Navotas and Pateros recorded “Very Unhealthy” air quality, with AQI readings of 153 and 172, respectively, while Makati observed “Unhealthy for Sensitive Groups” air quality with an AQI of 111.

Rain as natural mechanism

EMB-NCR Chief of the Environmental Quality Management Division (EQMD) Engr. Jundy del Socorro said the haze situation is largely beyond the Philippines’ control as it depends on several factors outside the country, including the intensity of forest fires in Kalimantan, prevailing wind patterns, and rainfall across the region.

“From September 1 to September 3, haze may continue to affect parts of the Philippines because smoke from Kalimantan is still being transported by the prevailing southwest monsoon (Habagat) while fires remain active,” Socorro said.

“However, periods of rain can help reduce pollution levels by washing smoke particles and fine particulate matter (PM2.5) out of the atmosphere,” he added.

Socorro said air quality could gradually improve between September 4 and 6 if rainfall remains widespread and wind patterns begin to shift.

He noted that rain is one of the most effective natural mechanisms for removing suspended particles from the atmosphere, which can improve visibility and reduce haze concentrations.

“Beyond September 6, conditions will depend primarily on whether the fires in Kalimantan continue to generate smoke, whether new hotspots emerge, and whether winds continue to carry smoke toward the Philippines,” Socorro said.

The agency said sustained rainy conditions would generally favor a gradual reduction in haze, while a drier monsoon pattern could allow smoke to travel farther and linger longer.

The DENR-EMB NCR advised the public to limit prolonged outdoor activities, particularly those sensitive to air pollution, and to wear masks for protection as it continues to monitor the haze situation.

UP, ADMU issue advisories 

The University of the Philippines (UP) Diliman advised members of the UP community to wear well-fitting face masks, particularly when commuting or going outdoors, amid degraded air quality caused by haze from wildfires in Indonesia.

In an announcement Tuesday, the UP Diliman Office of the Chancellor said the degraded air quality was affecting Quezon City and the National Capital Region and was expected to persist over the coming days.

The university urged members of the community to prioritize their health and well-being and visit the University Health Service (UHS) if they experience any medical discomfort.

Meanwhile, the Ateneo de Manila University (ADMU) suspended onsite work at its Loyola Heights Campus on Tuesday due to air quality concerns.

“Following the assessment by the Ateneo Institute for Sustainability and the Office of the University Physician and Clinic, [onsite work] at the Loyola Heights Campus [was suspended] starting at 2:30 p.m. today due to air quality concerns,” the ADMU said in its advisory.

In its Memorandum No. UHR2627-25R, the university reminded its employees to wear well-fitted masks, preferably KN95 or equivalent, particularly when traveling via non-air-conditioned vehicles.

The institution also advised employees to avoid staying outdoors unnecessarily.

Employees who need to complete their work onsite may remain in their offices until the end of their work schedule, the memorandum stated.