Bangkok smog season under way

Five districts in the capital record fine-dust pollution above safe levels

Smog in Bangkok is expected to worsen through Monday due to persistently poor air dispersion, with five districts reporting unsafe levels of fine-dust pollution on Saturday.

The average concentration of particulate matter 2.5 micrometres or less in diameter (PM2.5) in the capital stood at 31.5 microgrammes per cubic metre (µg/m³) at 11am, according to the Bangkok Air Quality Information Centre (AirBKK) website.

The average reading at 7am was 29.2µg/m³, up from 21.6 on Friday. Any reading above 37.5µg/m³ is considered unsafe under Thailand’s national standard.

Air pollution typically increases with the arrival of the cool season. Studies have found that vehicle emissions account for up to 70% of the PM2.5 in Bangkok. Burning of crop residues such as sugarcane and rice straw in nearby provinces is another big contributor.

Of the 50 districts in Bangkok, five exceeded the safety standard on Saturday: Lat Krabang (40.1), Bang Khen (39.4), Pathum Wan and Pom Prap Sattru Phai (both 39) and Yannawa (37.8).

Other districts with high readings were Khlong Sam Wa (37.1), Nong Khaem (36.6), Prawet (36.3), Klong Toey (36.1), Sathon (34.5), Wang Thonglang (34.3) and Bang Khun Thian (34.2).

Air pollution could worsen through Monday due to poor ventilation conditions, which could allow pollutants to accumulate, particularly from nighttime to early morning, AirBKK said.

Weak surface winds and low ventilation rates were contributing to the situation by limiting the dispersal of pollutants.

Conditions could improve in some areas between Nov 17 and 19, with stronger daytime winds and rainfall expected to help reduce dust levels in certain areas.

However, pollution could build up again between Nov 20 and 22 as atmospheric ventilation is expected to deteriorate, it said.