What is PM2.5 and why is it such a cause for health concern?

Following the massive fire at the Navotas Sanitary Landfill over the weekend, thick smog has caused the deterioration of air quality in several Metro Manila areas and nearby provinces like Bulacan.

Apart from unpleasant odor, there is the more pressing concern about health problems that the haze from the smoke can cause. 

According to Department of Health (DOH) Spokesperson Undersecretary Albert Domingo, smog is caused by air pollutants called PM2.5, which is "napakaliit na alikabok na maaaring pumasok sa ating baga at makaapekto sa ating respiratory system,” he said.

(In better terms, [these are] the really small particles of dust that can enter our lungs and affect the respiratory system.)

The California Air Resources Board characterizes PM2.5 as “fine particulate matter” sized 2.5 microns or less in diameter that is formed from different sources of air pollution and chemicals, all of which can be inhaled through outdoor air.

The United States Environmental Protection Agency (EPA) said that PM2.5 poses the greatest risk to health.

Short-term exposure of PM2.5 have been observed to have caused some of the following issues previously:

• premature death in people with heart or lung disease
• nonfatal heart attacks
• irregular heartbeat
• aggravated asthma
• decreased lung function
• increased respiratory symptoms, such as irritation of the airways, coughing or difficulty breathing.

“Over the long term, kapag masyado akong nai-expose doon, like months, years, merong epekto rin yan sa ating cardiovascular system,” said Domingo.

(Over the long term, if you get exposed too much, like months or years, that can also affect your cardiovascular system.)

According to IQAir, the Philippines was found with a score of 69 with the US Air Quality Index (AQI) in 2025, with 19µg/m³ of PM2.5. That's 3.8 times the annual guideline value of the World Health Organization.

Following the Navotas Landfill fire, DOH recommended tostay indoors and to wear face masks as protection from the effects of smog.

While the Department of Environment and Natural Resources (DENR) had confirmed that air quality has shifted back to normal on Thursday morning, Domingo said it is important to remain aware of the dangers of smog and pollution, and to seek advisories from local health centers to verify the safety and quality of air in your specific areas. — LA, GMA News