Blogs
Weekly Air Quality in Selected Towns of Sri Lanka (17 – 23 November 2025)
Summary for 17–23 November 2025:
After a week of poor Air quality the previous week (9-16 Nov), AQ has improved this week (17-23 November, 2025). Last week polluted air was transported from the northern parts of the Indian peninsula and travelled across the Arabian Sea and the Bay of Bengal to Sri Lanka at times.
In contrast, from 17-23 November, winds coming from the northeast helped clear polluted air by the beginning of the week. Although some polluted air entered Sri Lanka again in the middle of the last week, AQI levels remained improved compared to the previous week across the country.
During the week, overall air quality across Sri Lanka ranged from “Good” to “Unhealthy for Sensitive Groups”. On 20 November, the AQI in Chilaw rose to 106, placing it in the Unhealthy for Sensitive Groups category. Mirihana (Cleanco) reported the highest AQI of the week at 67, while Ambalantota recorded the lowest value at 30, indicating the cleanest air during this period. Most locations recorded Good to Moderate conditions, indicating generally favourable air quality.
Weekly Air Quality Index (AQI) Levels:
- Good (AQI 0-50): Kurunegala, Ambalantota, Puttalam, Trincomalee, Jaffna, Anuradhapura
- Moderate (AQI 51-100): Akurana-AV-Outdoor, Digana, Colombo(Gregory’s Road), Mirihana(Cleanco), Battaramulla(CEA), Chilaw(CEA), Ambalangoda
Observed fine particulate measurements by the hour for the last week.
Air Quality impact on human health
Fine particulate matter (PM 2.5) are generally 2.5 microns and smaller in size. Such particles are inhalable and easily lodges inside the lungs reducing capacity. PM2.5 is a concern for people’s health when levels in the air are high. The levels of risk are shown in the dial shown against the US EPA air quality standards. AQ has a scale that run from 0-500, that tells you how clean or polluted your air is. Each level on the scale corresponds to a different level of health concern.
AIR QUALITY BASICS
Air pollution, a widely- talked and argued topic today has been a primary cause of unforeseen climatic changes, many health problems associated with respiratory diseases and ecosystem damage. Vehicular and industrial emissions, dust, burning of fossil fuels, open burning of garbage waste and natural phenomena such as volcanoes, wildfires and pollen contribute to air pollution. Polluted air consists of both particulate matter of fine dimensions and gaseous matter. The presence of these impurities decreases the pureness of the air we breathe.
AQI
United States Environmental Protection Agency (US EPA) has set up a standard to measure the level of air pollution by the following 5 major air pollutants:
- Ground- level ozone (O3)
- Particle pollution (PM2.5 and PM10)
- Carbon monoxide (CO)
- Sulphur dioxide (SO2)
- Nitrogen dioxide (NO2)
Particulate matter of diameter less than 2.5 micrometers (PM2.5) and diameter less than 10 micrometers (PM10) and gases, ozone, carbon monoxide, sulphur dioxide and nitrogen dioxide have been identified as major air pollutants.
The AQI standard for ozone and particle pollution according to US EPA comprises of six categories. Each category is assigned a specific colour and corresponds to a different level of health concern. As the scale grows the air quality turns from good to extremely unhealthy.
Access to real- time air quality data from laser air quality sensoring instruments operated by FECT is available at www.cleanair.lk
