The news comes as protesters who live around St John’s Road in Corstorphine move to oppose a new supermarket planed for the suburb.
Friends of the Earth Scotland said new government figures from Air Quality Scotland show that air pollution levels on the thoroughfare have worsened.
St John’s Road’s air pollution monitoring station recorded a Nitrogen Dioxide average level of 72 microgrammes per cubic metre in the first half of 2015, set against a 2011 figure of 65 a legal limit of 40.
The second most polluted street for the first six months of this year was Hope Street in Glasgow, which recorded average Nitrogen Dioxide levels of 60 microgrammes per cubic metre.
Edinburgh councillors are expected to determine a planning application for the new supermarket with car park on the corner of St John’s Road and Manse Road, in the heart of a problem zone.
The Corstorphine monitor recorded 35 pollution “spike” incidents between January and June, where pollution levels soared over 200 microgrammes per cubic metre in one hour.
More than 400 people objected to the proposal due to concerns over increased congestion, air pollution, and safety hazards to schoolchildren walking past the site on their way to Corstorphine Primary School.
Promoted storiesRecommended byEmilia Hanna, FoeS air pollution campaigner, said: “These results show that levels of air pollution, which were already at illegal levels, are reaching appalling new heights.
John’s Road is now Scotland’s most polluted road, and traffic congestion is the reason why.
“These worrying figures further the case for refusing planning permission for the supermarket.
“The developer’s plans would see 3000 new vehicle visits to heart of the Pollution Zone each day, worsening traffic congestion and further adding to the soaring levels of pollution.”
Becky Lloyd, a mother-of-two who heads up the Corstorphine Residents Action and Information Group, “These new pollution figures only go to show how critical the committee meeting decision will be.
“We trust the council will come to the same conclusion as residents and rule this development entirely inappropriate for the site.
“Corstorphine is saturated with supermarkets and there is no demand or need for another one.”
Lesley Hinds, Edinburgh transport and environment said: “As a city we recognise improving air quality as a challenge, and continue to work with partners to reduce emissions.
“We are aware that there are improvements which can be made to limit emissions across Edinburgh including at St John’s Road and Clermiston Road junction.”
She added: “Through implementation of the Local Transport Strategy and meetings of the city’s Air Quality Working Group we regularly review Air Quality Management Areas to assess pollution, in order to create a cleaner, greener city for everyone.”
A spokesman for Realis Estates said: “We have submitted a planning application for a new supermarket in Corstophine along with the necessary supporting documentation – including the findings of our own air quality specialist.
“It is anticipated that our application will be considered by the council when it meets next Wednesday and until the application has been determined it would be premature for us to say anything further at this stage.”