In 2012, there were toxic concentrations and tiny particles of nitrogen dioxide emitted by cars, lorries and buses in Glasgow, Edinburgh, Aberdeen, Dundee, Paisley, Bearsden, Rutherglen, Perth, Falkirk and several other towns. The worst pollution was at Hope Street in the centre of Glasgow.
According to experts, the high levels can cause breathing problems and heart attacks. Up to 3000 people are estimated to die every year from air pollution in Scotland, compared to 190 deaths from road accidents.
"Air pollution is the biggest environmental threat to health," said Dr Richard Dixon, director of Friends of the Earth Scotland. "Fumes from cars, lorries and buses kill at least 10 times the number who die in road crashes every year."
Some of the targets to cut air pollution, set in the late 1990s, should have been met by 2005. "Yet we still have air pollution at dangerous levels on streets across Scotland," he told the Sunday Herald. "The Scottish Government and local authorities have failed to take this issue seriously, and between them need to do more than make promises. We need action on traffic levels and the types of vehicles allowed on our most polluted streets."
Professor James Curran, chief executive of Sepa, urged travellers to walk, cycle or use public transport, all of which have lower emissions.
''If you really have to drive, try car-sharing, choose the cleanest car you can, and drive it as economically as you can," he said.
Dr Sean Semple, a University of Aberdeen air pollution expert, said there is good evidence that the tiny particles produced by combustion engines are harmful to health: "Those with heart or breathing problems are particularly vulnerable." He said pollution was monitored in only a few places. "The current number and location of sampling sites can lead to areas with particularly high levels being missed," he warned.
The Scottish Government accepted there were "localised hot spots of poorer air quality in a number of urban areas", but insisted air pollution targets are being met across most of Scotland.
"We recognise we must build on achievements and continue to take action to improve air quality," said a Government spokesman, who said it was investing more than £1 billion per year to encourage people out of their cars. "This is a long-term delivery agenda to reflect the fact that changes steadily take effect within society over time."
The Convention of Scottish Local Authorities (Cosla) said councils are working to reduce pollution levels: "City councils have participated in Scottish Government funding programmes for retrofitting buses in the four cities covered by air quality management areas."
Multinational car companies are facing new curbs to silence the excessive traffic noise that blights the lives of nearly one million people across Scotland.
The European Parliament will vote this week on proposals to force manufacturers to produce quieter engines and exhausts, amid evidence of their damaging impact on health.
MEPs are being urged by environmental campaigners in Scotland and Brussels to back the moves which are being fiercely opposed by car manufacturers, including Porsche.
According to official figures, as many as 945,100 people in Scotland are exposed to daytime noise levels from traffic above 55 decibels. The World Health Organisation says this will damage performance at work and school, disturb sleep, and impair hearing and heart functions.
"This legislation is critical to tackle the problem at source," said Colin Howden, director of campaign group Transform Scotland. More than 40% of people in Europe are exposed to noise levels which posed a "serious risk to health", he said.
However, the European Automobile Manufacturers' Association said the proposals would be "damagingly costly to implement" and "could weaken the industry's competitiveness in the face of its global rivals".
Reducing speed limits to 40mph would cut climate-wrecking carbon emissions, according to a report from the Government-funded Transport Research Laboratory.
It also says such a move would cut injuries and deaths from traffic accidents, as well as noise and air pollution, and warns that motorists often over-estimate the time they will save by driving faster.
The report was commissioned by the university-backed Edinburgh Centre for Carbon Innovation for a seminar on speed limits and climate change taking place this week. Organised by the Scottish Government's high-ranking 2020 Climate Group, it is aimed at addressing one of the "more challenging" barriers to cutting climate pollution.
"Reducing speed really will reduce emissions," said Professor James Curran, chief executive of Sepa. "It will also save money, as well as improving road safety and increasing road capacity, so you may actually get to your destination faster."
However, one of the speakers at this week's seminar will argue that more radical steps are needed. "How deft we are with our accelerator pedals is interesting," said Ed Gillespie, co-founder of the Futerra communications agency.
"But, in the scale and urgency of our climate change challenge, we need to think bigger, smarter, bolder. From rail freight to relocalisation, car clubs to cycling – we need to not just think better, but think different."