Air pollution will hit "dangerous" levels across much of Scotland in the next few days, environmental campaigners have warned.

Friends of the Earth Scotland said the pollution will hit parts of the country on Thursday, peak on Friday, and in some areas will still be an issue on Saturday.

Toxic levels of particulate matter from car exhausts and other pollutants are predicted to break World Health Organisation safety standards in 15 areas across Scotland.

Emilia Hanna, Friends of the Earth Scotland air pollution campaigner, said: "Air pollution is expected to blow in from the east and combine with the heavy air pollution pouring out of car and lorry exhausts on our streets.

"The weather is expected to be still and calm on Friday, which means that the air pollution will have nowhere to go, creating dangerous conditions, with our air much more damaging than usual.

"People with lung or heart problems and older people will be especially vulnerable to this toxic stew. The expected pollution levels will be exceptionally high and in some places will be potentially dangerous for people who are otherwise healthy, as well as at-risk individuals."

She called on the Scottish Government to advise motorists to avoid driving on Thursday and Friday and adding to the pollution.

She added: "Toxic air pollution episodes like this show that the Scottish Government is not doing enough to address the public health crisis of our dirty air. This kind of air pollution causes over 2000 early deaths each year and costs the Scottish economy over £1.1bn."

Official health advice for Clackmannanshire, East Dunbartonshire, Falkirk, Fife, Glasgow, North Lanarkshire, South Lanarkshire and Stirling on Friday - where pollution levels are classed as high - is that adults and children with lung problems, and adults with heart problems, should reduce strenuous physical exertion, particularly outdoors, and if they experience symptoms.

Asthma sufferers should make sure they are carrying their inhalers as they may need to use them more often. Older people should also reduce physical exertion.

Anyone experiencing discomfort such as sore eyes, a cough or sore throat should also consider reducing activity, particularly outdoors.

Health advice for the expected "moderate" pollution levels in East Ayrshire, East Renfrewshire, North Ayrshire, Perth and Kinross, Renfrewshire, South Ayrshire and West Lothian on Friday is that adults and children with lung problems, and adults with heart problems, who experience symptoms should consider reducing strenuous physical activity.

A Scottish Government spokeswoman said: "Much progress has been made over recent years in improving air quality and Scotland is pressing ahead with world-leading climate change targets.

"However, areas of poorer air quality related to emissions from transport remain in many of our urban areas and we continue to work closely with local authorities and other partners to improve air quality and the lives and well-being of communities and individuals across the country."