Ozone and dust particles could be the main factors worsening air pollution in Bangkok over the next decade if the government fails to raise minimum standards for vehicle fuel emissions, an air quality expert says.
Standards need to be raised from the current minimum Euro 4 to Euro 5 and Euro 6, according to Supat Wangwongwattana, an air quality expert from Thammasat University's Faculty of Public Health.
He was speaking at a gathering on emissions hosted by the Bangkok Metropolitan Administration, the Department of Pollution Control and the Thailand Environment Institute.
Raising standards means a stronger capacity to deal with pollution and to enjoy cleaner air, said Mr Supat, a former chief of the Department of Pollution Control.
He said many indicators have shown that Bangkok has better air quality now than 10 years ago.
This is the result of strong efforts by authorities to improve emission standards at the current level of Euro 4, where sulphur dioxide in the air was reduced from 10,000 ppm from 1993 to 50 ppm in 2012.
The European emission standards are used for setting acceptable limits for exhaust emissions of new vehicles sold in the EU and European Economic Area member states.
Beyond a reduction of sulphur dioxide, agencies succeeded in phasing out lead in gasoline at the end of 1995, together with reducing benzene content in fuel from 5% in 1991 to 1% in 2012, Mr Supat said.
This was done under the country's first-ever implementation of emission standards under Euro 4 required for both fuel and vehicles in 2012.
However, he said dust particles and ozone remain major factors causing problems in Bangkok's air quality.
Mr Supat explained that high rise buildings have blocked air flows and hindered the dispersal capacity of ozone, which makes smog linger over an extended period of time, especially at the start of summer in February and March.
"Clean fuel and new vehicles [producing less pollution] contribute to cleaner Bangkok air. But if we do not progress beyond Euro 4, I'm afraid serious air pollution that choked Bangkok in the past might return by the year 2035," he said.
"We need to go to the next level and achieve even better standards," he said. In vehicles, the amount of nitrogen dioxide reduces from 3.5 gramme per kilowatt-hour in Euro 4 to 2.0 in Euro 5. The emission amount will be even less for Euro 6.
He said the Euro 4 standard in vehicles has no effective function to capture nitrogen dioxide, a key element of ozone, and dust particles. That is the reason why they remain an air quality problem now, he added.