Toxic air pollution from vehicle exhausts is worsening at five busy streets in Glasgow, Edinburgh and Dundee, according to the latest official monitoring.
Average levels of nitrogen dioxide gas have shot up on Byres Road in Glasgow from 45 to 54 microgrammes per cubic metre from 2013 to the first half of this year. Over the same period levels have increased at Hope Street in the city centre, at Queensferry Road in Edinburgh and on two streets in Dundee.
There are another seven streets in Scotland where nitrogen dioxide pollution breaches the legal safety limit of 40 microgrammes per cubic metre. At two sites the concentrations have stayed the same, at four places they have dropped and at one site it's unclear.
Nitrogen dioxide belched out by cars, lorries and buses irritates lungs and lowers resistance to respiratory infections, particularly in children. It causes problems for people with asthma.
According to the secretary of Hillhead Community Council, Jean Charsley, in Byres Road people are choking: "It has got worse.
"Asthmatics can't stay very long. One man had to be carted off to hospital last year because he couldn't cope with the pollution." She criticised Glasgow City Council for failing to do enough to curb pollution from cars, taxis and buses. "There has been a systematic lack of action to reduce traffic."
The "dirty dozen" streets that breach pollution limits across Scotland alarm environmentalists. "Air pollution is the biggest environmental threat to our health," said Emilia Hanna, a campaigner with Friends of the Earth Scotland.
"A number of well-visited streets in Scotland have recorded pollution levels which are well above legal limits. In Glasgow, Edinburgh, Aberdeen and Perth, pollution levels this year have not improved since last year."
Glasgow City Council stressed that it was striving to improve air quality with a wide variety of measures. It had introduced a new £600,000 hire scheme for 400 bikes, and was encouraging the use of electric vehicles.
"New signs are also being piloted in the city's west end which flash messages about air pollution to passing motorists - urging them to consider whether they really need to use their car for every journey," said a council spokeswoman.