The Labour transport convener of the capital has suggested a low-emission zone (LEZ) will inevitably cover the entire city as rules tighten up in the coming years.

Edinburgh will roll out its LEZ in June, with the area covering some of the city centre – but key routes such as Queen Street do not fall into the zone.

Vehicles entering the LEZ must meet certain Euro emission standards or face fines.

Edinburgh City Council’s transport convener, Scott Arthur, has raised the possibility of the LEZ rules being strengthened or even using a ‘pay-as-you-drive’ model for a more targeted approach.

The suggestion comes as Environmental Standards Scotland (ESS) calls for a tightening of the air pollution limits for particulate matter (PM) to safeguard the population’s health.

In a new report, ESS has investigated new World Health Organisation (WHO) guidance, advising that more stringent limits for particulate matter should be introduced to safeguard public health.

ESS’s analysis sets out that Scotland, along with most other countries, does not currently meet the new WHO guidelines advised for particulate matter and recommends legal targets are tightened.

The European Union is already proposing a tightening of limits and the Scottish Government will need to take action if it wants to maintain alignment with European legislation, as is SNP policy.

Mark Roberts, chief executive of ESS, said: “Scotland has made significant progress in recent decades in reducing emissions of particulate matter and is currently largely meeting its objectives and limit values for concentrations of particulate matter.

“However, the scientific evidence has strengthened about the damage to human health caused by particulate matter. This is why it is important that the Scottish Government updates the limits for particulate matter in Scotland to reflect this evidence.

“Emissions from transport have rightly been the focus of recent decades. Attention now needs to be widened to include other sectors. Our analysis concludes that emissions from industry, agriculture and residential combustion now need attention to make further improvements.”

Looking ahead to Edinburgh’s LEZ rolling out in June, Mr Arthur said the policy is not “going to have any more than an incremental impact” on traffic levels in the city centre.

He said: “It will clean up air quality because we already know lots of people have upgraded their vehicles or moved to other transport modes in advance of it.

“We’ve seen compliance levels are quite high, particularly amongst petrol vehicles.

“Things are heading in the right direction, air quality is improving already.”

Mr Arthur added that the Scottish Government “set the standards” of air quality for LEZs, stressing the council cannot set the limits.

He said: “We have no power to change the limits including moving to cleaner vehicles.

“The Scottish Government based it on Euro standards, which I think was a mistake – they should have based it on actual emissions from the vehicles.

“If you have a tiny little car that might be quite efficient, you could be banned because it’s older – yet you could still drive in your 5L Range Rover.

“There’s something not quite right there.”

The transport and environment convener acknowledged that the plan, which was watered down from the original plan to cover the entire city boundary, “was the least popular option”.

Mr Arthur said: “It was the option we could get people to agree with rather than everybody was delighted.”

"The (current) one itself isn’t going to get smaller. The emission standards are only going to get stricter.”

Asked if the entire city will eventually be covered by an LEZ, Mr Arthur sad: “That’s going to happen anyway.”

He added: “I think we’re moving that way.

“The challenge was the LEZ encourages people to switch but the outer zone would have been too much of a jump for people. It would have really impacted on the economy.”

Mr Arthur pointed to pay-as-you drive road-charging model The Herald previously revealed the council is in discussions with the Scottish Government over.

He said: “ You could choose more polluting vehicles and make it more expensive for them to come into the city. You might not have to have that outer LEZ proposal anymore.”