Could electric cars reduce China's smog?
"Particulate Matter 2.5" is now, it seems, officially an enemy of the people.
The harmful, tiny pieces of matter, up to 2.5 microns in diameter (PM2.5 for short), are too small to be seen by the naked eye, but big enough to make it into the outgoing Chinese premier's final speech to parliament this week.
In his swansong after a decade in power, Wen Jiabao noted that the government had started releasing PM2.5 data and said more needed to be done to bring China's serious air quality problem under control.
So with the issue of pollution so high on the agenda at the annual parliamentary session, some are wondering what possible solutions might be in the pipeline.
One might very well be a renewed effort to kick-start the electric car industry.
Some reports suggest that the generous subsidy scheme for battery-driven vehicles will be expanded from the present five cities to 20 more.
But so far no country in the world has succeeded in making the dream of emission-free driving a reality.
Despite the lofty ideal, the electric car has so far been a sputtering disappointment, accounting for only a fraction of 1% of global car sales.
And the same is true in China. There is an existing target to put five million on the road by 2020 but the Chinese consumer is so far very much unconvinced.
But BYD Auto Company in the southern city of Shenzhen is just one electric vehicle maker hoping that the time is now ripe for the government to step up its efforts.
The company rose to global prominence in 2008 when venture capitalist Warren Buffett bought a 9.9% stake.
He was betting that if anyone could make the technology work then China's central planners would be the ones to do it.
They have certainly tried. In Shanghai, for example, the total amount of subsidy on offer, including an exemption from the city's expensive licence plate system, is worth up to $30,000 (£20,000).
But that would still leave more than $40,000 to be paid before you could drive away in a BYD e6.
Electric cars are not cheap and buyers have worries other than price.
"I think that when you talk to a regular Joe about electric vehicles he is excited but when you ask Mr Joe to buy one, he's nervous," said Isbrand Ho from BYD's Auto Export Trade Division.
"We call that 'range anxiety'. How far will my vehicle go?"
The answer for an e6 is well in excess of 300 km (190 miles) on one charge.
That is the sort of number that might just start looking attractive to less price-sensitive customers but China still doesn't have anything like enough charging stations to make the car a practical choice.
Last year, BYD sold only 1,700 electric cars in China. Isbrand Ho tells me that at that volume the car is inherently expensive, due to the economy of scale.
What they need, he says, is for production to get above a certain threshold, and then costs will come down.
And there may yet be one way to do that. When it comes to deciding what kind of cars are on the road China has a number of advantages over some other governments.
Firstly, the luxury of unchallenged, centralised decision-making power. They can easily just build more charging stations. And secondly, an awful lot of vehicles.
In Shenzhen, BYD has found one willing customer; the public transport system.
The company aims to triple its sales this year by selling 2,000 electric buses and 6,000 e6 cars to the city's partly state-owned taxi companies.
If copied nationwide, then China's sales of battery cars might not look quite so weedy.
For China, the costs of its decades-long economic rise are beginning to loom very large indeed.
Public discontent over a range of grievances is mounting; income disparity, corruption and pollution are often cited as the main ones.
The issues are complex and structural and there are no quick fixes, but the government needs to be seen to be doing something.
More than one million new fuel-engine cars pour onto China's roads every month, and vehicle exhaust now accounts for up to a half of those PM2.5 particles.
That is why they made it into Wen Jiabao's speech and why, as leaders meet for the annual parliament, some are expecting the Communist Party to make a renewed effort to give battery power a boost.