On a mission: A pilot flying next to another aircraft from the Royal Rainmaking department taking part in an atmospheric modification mission to displace pollution by spraying icy water in the air. — AFP
Flying through Bangkok’s cloudless blue skies, a small aircraft sprays a white mist over a thick haze of pea soup smog below.
This is Thailand’s desperate, unproven attempt at reducing the oppressive air pollution over its capital, which reached eight times the World Health Organisation’s recommended daily maximum average.
The scourge has made more than a million people ill since late 2023 and cost Thailand more than US$88mil (RM390mil) in medical expenses, the public health ministry said earlier this month.
According to Bangkok governor Chadchart Sittipunt, the main culprits are vehicle emissions, crop burning in the wider region and “closed” weather conditions – a warm atmospheric lid covering the dust, preventing it from dispersing.
Known as a temperature inversion, the kingdom is trying to deal with the phenomenon using a homegrown experimental method to displace the pollution.
Twice a day, the Royal Rainmaking department sends aircraft up to spray cold water or dry ice into the layer of warm air to cool it down.
Critics say there is little to no evidence it works.
AFP was granted exclusive access on board a flight over the outskirts of Bangkok.
Inside the small craft – which climbed to an altitude of around 1,500m – a scientist tracks the flight path on an iPad as two crew members release icy water from a pair of large blue containers that sprays out from the craft’s belly.
The theory is that reducing the temperature difference between the levels makes it easier for the trapped particles, known as PM2.5, to disperse into the upper atmosphere.
It is an unconventional method the department says is only used in Thailand.
“This is not the usual cloud seeding,” said programme head Chanti Detyothin.
Countries have long tried “cloud seeding” – injecting chemicals such as silver iodide into clouds to trigger rain or snowfall – in attempts to alleviate drought and, increasingly, air pollution.
But its effectiveness is open to question and scientists say it has been shown to only be marginally useful in creating rain and absorbing pollutants.
Thailand’s worst smog happens during the dry season between December and April, when it is too windy and cloudless to induce precipitation.
The new technique was first used last year and is still in its testing stages.
Another aircraft measures pollutant concentrations before and after spraying to gauge the difference in air quality.
“The concentration (of PM 2.5) is less,” said Chanti.
“The data suggests that at the level of our area of focus, the dust cleared up,” though he admits they cannot “make the pollution go away entirely. Even with this new technology, there are limitations.”
Ekbordin Winijkul of the Asian Institute of Technology said it is more cost-effective for Bangkok to address the causes of pollution with proven measures such as low-emissions traffic zones.
City authorities are already pursuing many of these, he said, like banning some heavy-duty vehicles and working with other provinces to control agricultural burning.
“Before we try to do something,” he said, “at least we should have confidence in the data first.” — AFP
