Hong Kong's air quality will show "dramatic improvement" over the next five years, says undersecretary for the environment Christine Loh Kung-wai.
And she predicts that reductions in pollution should start being measured by the second half of this year
In her most confident pledge so far on the fight for cleaner air, Loh told the South China Morning Post the city is well on target to achieve landmark goals - such as a 20 per cent reduction in sulphur emissions - before 2020.
"There's no question - we will meet these objectives," Loh said.
"Our whole vehicle fleet will be dramatically cleaner in about four or five years … we will see a dramatic improvement in roadside [air quality]."
Recent government data indicates roadside air quality is getting worse, but she insisted the situation would improve.
Objectives set out in last year's seven-year air quality road map had already been met without much political resistance, she said. This was in stark contrast to stalled action on other environmental issues such as waste, energy and conservation.
Loh believes several more air quality measures will be endorsed by Legco before the summer. "We should be able to start measuring reductions by the second half of the year," she said.
A HK$11.4 billion initiative to replace about 82,000 old commercial diesel vehicles will start next month.
A scheme to replace catalytic converters - devices that reduce harmful emissions - on 20,000 taxis and public light buses powered by LPG is expected to be approved by summer, while a plan to retrofit about 1,400 franchised buses with selective catalytic reduction devices is also scheduled for approval this year.
"By 2016, all pre-Euro vehicles will be banned from the street," said Loh, in reference to the "Euro" emission standards introduced progressively by the European Union since 1992.
"Once we start running the scheme, we can see how we can incentivise vehicle owners to replace their vehicles earlier rather than later."
Loh said that the community would have to be "galvanised" for all the measures to succeed.
But tackling roadside pollution is not enough, Loh admitted. Maritime traffic is one of the city's biggest causes of toxic sulphur dioxide emissions.
In 2012, a study found 75 per cent of deaths linked to sulphur dioxide in the Pearl River Delta each year were Hongkongers.
Loh expects legislation for a mandatory fuel switch - which will force all ocean-going vessels berthing at Hong Kong to switch to a lower-sulphur fuel - to be passed in summer and to take effect by early next year.
This will be coupled with an initiative that would require smaller local ships to switch to a cleaner marine diesel, which Loh has pencilled in for April 1.
"We think, after the implementation of both measures, we will see an estimated 20 per cent drop in local sulphur dioxide emissions. This is really quite substantial."
Loh was pleased the much-criticised Air Pollution Index was replaced by the Air Quality Health Index in December. "We now have a much better health-based air quality index," she said.