The Ministry of Environment said on Tuesday that the PM2.5 concentration levels marking air quality returned to normal at 50.

Ministry spokesman Neth Pheaktra said according to tests on the air quality conducted across the country, the PM2.5 air quality index remained at 50 on Tuesday afternoon.

“The air quality has returned to normal,” he said, adding that the ministry would keep the public informed.

The ministry does not follow an international standard for defining air quality but lists a PM2.5 reading of above 50 as the level at which concerns arise.

On Friday, the ministry warned the public about rising levels of pollution across the country.

It said the main sources and activities that caused PM2.5 levels to increase were rising plumes of smoke from industrial factories, diesel-powered vehicles and forest fires.

Burning grass, rice stubble, and solid waste in open locations and at dumpsites and construction sites also contributed to the problem, it said.

It also announced a strategy to tackle the pollution, instructing environmental departments in the capital and provinces to work together in its implementation.

As part of this plan, environment departments were asked to cooperate to stop forest fires and waste incineration in open locations and dumpsites and reduce the amount of dust from construction sites.

Pheaktra said on Sunday that the PM2.5 concentration was over 50 but dropping and noted on Tuesday that the hard work of officials played a major role.

“The Ministry of Environment thanks all specialists at the ministry and relevant authorities, particularly those at the sub-national level at environment departments, and the public, for following the ministry’s measures.

“We urged them to follow this instruction to protect air quality in Cambodia and they have done a great job,” he said.

PM2.5 refers to atmospheric particulate matter that has a diameter of less than 2.5 micrometres, which is about three per cent the diameter of a human hair.

If inhaled, these particles can make their way into the lungs and even blood vessels, eventually causing damage to the body.