The first readings of the capital’s PM2.5 concentration, a major indicator of air quality, show that levels of the harmful particulates are “still low”, said Thiv Sophearith, chief of the Ministry of Environment’s Air Quality, Noise and Vibration Office, though an environmental specialist yesterday challenged how representative the readings were.

In April Cambodia received its first air quality monitor, which detects ultra-fine airborne particles that contribute to dangerous forms of air pollution.

According to data provided by the Ministry of Environment, the daily average concentration in April was 19.8 micrograms per cubic metre of air, and 12.9 micrograms per cubic metre in May. The World Health Organization’s guidelines recommend a level of 25 micrograms per cubic metre or less.

The ministry’s readings showed particulate levels exceeded that benchmark on just one day in April, when the mean was 25.8 micrograms per cubic metre.

While PM2.5 data are now available, national guidelines setting goals are not yet in place, Sophearith said.

“We don’t have the national standards for PM2.5 yet. However, we can see by using standards for our neighbouring countries that our results are still low,” he said.

The figures recorded by the monitor, installed at the top of the ministry’s building located near the river, likely underestimated pollution levels, said Chhinh Nyda, a lecturer and researcher in environmental studies at the Royal University of Phnom Penh.

“There is a lot of open space near the river so the air will generally be quite good,” he said, adding that the location near parks and greenery may have contributed to the low readings.

While Sophearith defended the monitor’s location – saying that the ministry is located near construction sites and would “get both clean air and polluted air” – Nyda explained that air particles from these sources “will still be carried away by the wind from the river”. More representative, he said, would be readings in built-up areas where air is stagnant.

According to Sophearith, levels of toxic gases, including carbon monoxide, sulfur dioxide and nitrogen dioxide – have been consistently below the maximum levels laid out in a 2000 air pollution control sub-decree.

However, he conceded that PM10 – particles most commonly associated with construction activities and road dust – are important air quality indicators yet to be monitored in the country.

“Because Phnom Penh is a developing city, we have a lot of infrastructure development and construction,” he said. “However, I think it’s temporary pollution. After construction, the pollution will be over.”

Nonetheless, he said, more should be done to reduce vehicle emissions.

“These two years the number of vehicles has increased dramatically. We have to find a solution to reduce pollution from transportation.”