The main reason why the Scottish Government should intervene and stop the Edinburgh tram project is the same reason why the Westminster Government should have intervened to stop the financial boom and mortgage crisis: the potential indebtedness is too great ("Call for tram public inquiry", The Herald, June 24).

Individual banks had neither the reserves nor profitability to underpin their balance sheets, and so the liability inevitably fell on the UK taxpayer. In the case of the trams, the potential indebtedness is so great that Edinburgh City Council cannot underpin potential future liabilities.

The real problem is not the few hundred million pounds of overspend now contemplated, but potentially tens of thousands of claims in the long term for compensation for health damage and even deaths caused by traffic pollution resulting from traffic being rerouted through residential districts. Potentially, these could far exceed the capacity of Edinburgh City Council to fund. The liability would inevitably fall on the Scottish taxpayer, making this a matter for the Scottish Government.

The council claims that the trams will enhance Edinburgh’s air quality along its route. That is clearly true of Princes Street, which has few basements and an open aspect to the south which disperses traffic pollution. But what about damage to air quality elsewhere?

The New Town, through which the council now plans permanently to reroute heavy traffic, has many basements in streets with buildings on both sides rising to many storeys. Traffic pollution is known to be trapped by such “street canyons”, making the residents’ exposure to these pollutants on a 24-hour, seven-day-a-week basis far greater than that of the travelling and pedestrian public.

The public health impacts of this project have been ignored in the presentation of the tram as “clean and green”. No-one disputes that the tram is cleaner and greener than petrol and diesel engine vehicles. The council is deluding itself by relying on this irrelevant and undisputed fact. The Scottish Government Traffic Analysis Report (the 2003 STAG report) predicted that when the proposed line was completed, some 134,500 homes (275,000 people approximately) would be exposed to a worse level of air pollution from nitrogen dioxide and particulates. This STAG report assumed that traffic would share Shandwick Place with the tram, so the current diversion of traffic through the New Town would have increased those numbers.

Measurement at city basement level in streets along which traffic is rerouted is clearly essential and is only now being started by the council, and the results from the first street to be monitored is only expected to be available in 2012, well after the course of this project has been fixed.

The residents of basement flats exposed to heavier-than-air pollutant gases and particulates have a great interest in this; grandparents, parents, children and as-yet-unborn babies will be subjected to additional pollution in their homes.

Only a public inquiry in which potential future pollution damage claims are assessed can determine whether the allegedly pollution-saving tram scheme should be allowed to proceed. The probable total true cost must be assessed realistically. The Edinburgh tram scheme must be stopped in its tracks and an urgent public inquiry instituted.

Michael Hamilton,

5 Stodrig Cottages,

Kelso.