By Amy Sawitta Lefevre
BANGKOK (Reuters) - Residents in Bangkok, one of the world's top tourist destinations, were warned on Thursday the city's air quality had hit dangerous levels just days after the country's pollution control agency appealed to residents to wear face masks.
Air pollution in the Thai capital has come under increasing scrutiny in recent weeks with residents complaining of smog and respiratory problems. Some schools were closed on Thursday or kept children indoors.
Air Quality Index (AQI) formulas usually include up to six main pollutants including PM2.5, PM10, carbon monoxide, sulfur dioxide, nitrogen dioxide and ground level ozone.
"The Pollution Control Department would like to report the situation of PM2.5 dust in the Bangkok Metropolitan area on February 8. At 12:00 hours it was measured at 72-95 micrograms per m3. Dust is likely to increase in all areas," the Pollution Control Department warned in a statement on Thursday.
That compares with a World Health Organization (WHO)guideline of an annual average of no more than 10 micrograms. PM 2.5 is a mixture of liquid droplets and solid particles that can include dust, dirt, soot and smoke.
The Air Quality Index (AQI) in central Bangkok area as measured by the Pollution Control Department on Thursday at 1:30 p.m. showed a 135 AQI or "unhealthy" level.
The Air4Thai mobile phone application, which shows Pollution Control Department readings, does not factor in PM 2.5 or fine particulate matter that pose the greatest risk to human health.
Data from the American AirVisual smartphone application showed a 154 AQI reading for Bangkok.
"We've received information from my daughter's school that they are monitoring pollution levels and will be keeping the children indoors until it improves," Joanna Lorgrailers, 32, a mother of two who lives in Bangkok, told Reuters.
Some international schools in the city have installed their own air pollution measuring devices, said parents, and are in touch with other international schools in cities with high air pollution levels to discuss ways to limit childrens' exposure.
The Pollution Control Department did not immediately reply to a Reuters request for comment.
(Additional reporting by Panarat Thepgumpanat; Editing by Michael Perry)