BANGKOK, Oct 9 — Air pollution in Bangkok breached Thailand’s safety threshold in five districts this morning, prompting warnings for residents to wear protective masks and limit outdoor activities as fine particle levels showed an upward trend.

PM2.5 readings exceeded the national threshold of 37.5 micrograms per cubic metre (µg/m³) in several busy commercial and transport districts, The Nation reported.

According to the Bangkok Air Quality Information Centre, Yan Nawa recorded the highest concentration at 48 µg/m³ at 7am, followed by Prawet at 40.4 µg/m³ and Khlong Toei at 40 µg/m³.

Pathum Wan, home to some of Bangkok’s busiest shopping and commercial areas, registered 39.5 µg/m³, while Bang Khun Thian recorded 38.5 µg/m³.

All five districts fell into Thailand’s orange air quality category, indicating pollution levels that are beginning to affect health.

Despite the elevated readings, Bangkok’s citywide average stood at 29.2 µg/m³, below the national threshold, with overall air quality classified as moderate.

Other districts also recorded elevated concentrations, including Bang Na at 35.5 µg/m³, Sathon at 34.9 µg/m³ and Rat Burana at 34.5 µg/m³.

With pollution levels trending upwards, authorities urged residents to wear protective masks, such as N95 respirators, when outdoors and avoid strenuous activities, including running and other outdoor exercise.

They were also advised to watch for symptoms such as coughing, breathing difficulties, chest tightness and eye irritation.

Additional precautions were recommended for vulnerable groups, including young children, older people, pregnant women and those with chronic respiratory or heart conditions.

Those at higher risk were advised to avoid outdoor activities wherever possible, minimise time spent outside and seek medical attention if unusual symptoms developed.

PM2.5 refers to airborne particles measuring 2.5 micrometres or smaller in diameter, which can penetrate deep into the lungs and enter the bloodstream.

Exposure has been linked to respiratory and cardiovascular problems, particularly among people with existing health conditions.

Thailand has long struggled with recurring air pollution, driven by vehicle emissions, industrial activity, agricultural burning and weather conditions that trap pollutants close to the ground.