In pictures: Air pollution around the world

Air pollution in London
Pollution levels across parts of England, including London, are set to get worse

A rise in emergency calls over health problems has been reported as high levels of air pollution continue to affect parts of the UK.

London Ambulance Service reported a 14% rise in 999 calls relating to breathing difficulties on Wednesday.

Man wearing an anti-pollution mask riding a bicycle
Cyclists have been wearing masks to protect themselves from the pollution

Data from Defra shows London and south-east England experiencing "very high" pollution levels on Thursday.

Yesterday, government health advice was issued amid warnings of air pollution spreading across England.

The view out to sea from the Long Hole in Bangor was very hazy
The view from the Long Hole in Bangor was unusually hazy at the weekend

Defra put them out after high pollution levels were recorded on Tuesday.

The pollution - a mix of British and European emissions and dust blown in from the Sahara desert - were forecast in parts of south England, the Midlands and East Anglia.

Pollution dust on David Cameron's car
Prime Minister David Cameron's car has been covered in Sahara dust

The low pressure in the Atlantic Ocean and high pressure to the east of the UK, combined with a south-easterly breeze, have pulled in pollutants from across Europe.

Pollution dust on a car
Health experts said the "vast majority" would suffer no harm from the pollution

Defra has a 10-point scale for measuring air quality - with 1 meaning there is a "low" risk of air pollution and 10 warning of "very high" levels.

A layer of smog covered London in April 2011
A layer of smog covered London in April 2011

On Wednesday morning levels were recorded at 5 - meaning moderate - in the South East, north-east England and East Anglia.

Foggy Piccadilly Circus in December 1952
Thousands died following 1952's Great Smog in London

Other countries around the world have experienced poor air quality recently, too.

Paris

Paris

Last month, police monitored traffic in Paris after high pollution levels prompted the French government to impose major restrictions.

Only motorists with odd-numbered number plates were allowed to drive, the next day even numbered cars were let on the roads.

The smoggy conditions have been caused by a combination of cold nights and warm days, which have prevented pollution from dispersing.

A police officer inspects a vehicle in Paris (17 March 2014)
Drivers ignoring the instructions were fined and some had their cars impounded

Ministers acted after air pollution exceeded safe levels for five days running in Paris and surrounding areas.

The environment ministry said lower traffic levels and a change in weather conditions had significantly improved the smog.

Beijing

Beijing

In February, particulate readings soared 15 times above the daily maximum recommended by the World Health Organization in the Chinese capital, Beijing.

In response, city authorities used a new smog alert system - a series of emergency measures meant to quickly reduce pollution levels and protect city dwellers.

Cars drive on the Three Ring Road amid heavy haze in Beijing in this February
Cars drive on the Three Ring Road amid heavy haze in Beijing in February

Residents were warned to stay indoors as much as possible to avoid outdoor air pollution.

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