After issuing a warning over the country’s air quality on Friday, the Ministry of Environment said on Sunday that the PM2.5 concentration levels in the country were returning to normal.

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

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

The ministry’s secretary of state and spokesman Neth Pheaktra said on Sunday that PM2.5 concentration, a major indicator of air quality, was still over 50 but dropping.

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

“According to the ministry, the air quality in the capital and the provinces seems to be returning to normal, with PM2.5 at just over 50,” he said, noting that particles in the air were now 10 times smaller than a strand of hair.

Pheaktra said ministry experts will continue to monitor the air quality situation and inform the public of any development. He said citizens who spend a lot of time outside should wear protective masks.

He noted that PM2.5 concentrations were rising across theregion as the climate dries.

A ministry press release on Friday 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.

On Friday, the ministry also announced a strategy to tackle the pollution, instructing environmental departments in the capital and provinces to work together to implement it.

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

Officers were also asked to instruct residents to stop burning rubbish, solid waste, grass, rice stubble and other agricultural waste.