A worried Pollution Control Department (PCD) and City Hall are considering declaring Bangkok a "pollution control zone" after haze in the capital worsened on Monday.

Chatri Watthanakhechon, director of the Bangkok Metropolitan Administration's (BMA) Environment Office, said the fine particulate matter known as PM 2.5, exceeded the 50 microgrammes per cubic metre (µg/m³) safety limit in all the capital's districts.

According to Mr Chatri, the BMA was scheduled to hold talks with the PCD Monday afternoon to come up with emergency measures to deal with the pollution.

The talks were to look into the possibility of declaring Bangkok a pollution control zone, Mr Chatri said.

The declaration would authorise local administrative bodies to find ways to deal with pollution in their areas, ranging from conducting studies to implementing specific measures to deal with the problem.

Thammarat Phutthai, a lecturer in Mahidol University's Faculty of Environment and Resource Studies, said he supported such a declaration since the capital is currently blanketed with harmful dust particles.

Measures that could be rolled out include suspending classes for students or avoiding outdoor activities, he said.

The lecturer said the BMA's road cleaning may not be of much help, noting they should impose stringent measures to regulate fuel to curb the amount of exhaust emissions by vehicles.

A PCD source said the impacts on the economy and society must also be taken into account before any pollution control declaration is made.

The Department of Disaster Prevention and Mitigation (DDPM) said that Bangkok and its surrounding provinces are being choked by fine dust particles at levels that are affecting human health.

Its director-general, Chayapol Thitisak, said the agency is working with provincial authorities to tackle toxic haze by spraying water as well as assigning officials to monitor air quality closely.

Residents were also being urged to use public transport and refrain from burning rubbish, he noted.

They are also advised to avoid outdoor activities and wear face masks, he said.

Motorists are also being warned to drive carefully as road visibility may be poor in some areas, he said, adding people can contact Hotline 1784 around the clock to ask for help related to the haze.

As of 4pm Monday, PM 2.5 levels rose to between 56 and 85 microgrammes per cubic metre (µg/m³), according to readings taken by 10 air quality stations in Bangkok. The air quality index at 4am on Tuesday was "hazardous" at 183 and rising in Bangkok as a whole.

However, the PCD said the dust could ease slightly today due to better air circulation and wind.