Where in London has the worst smog, what is toxic air pollution and how has the heatwave affected health levels?
Mayor of London Sadiq Khan has declared the capital's 'filthy air' a health crisis
TOXIC air pollution can lead to serious health problems including stunted lung growth and cancer, experts say.
But what causes the toxic air and what measures could tackle it? Here's the latest.
Where in London has the worst smog?
Central London tends to have the worst smog as it is the most heavily built-up area.
Pollution can build up in London when it becomes trapped between buildings, especially during still weather.
Enclosed streets with large amounts of diesel traffic tend to be the worst-hit.
The City of London is the worst-hit area, with 8.3 per cent of deaths caused by man-made pollution in 2013 and 14.
Surrounding boroughs Camden, Islington, Hackney, Tower Hamlets and Southwark all came in around the 7 per cent mark.
Westminster and Kensington and Chelsea also neared 8 per cent each.
Boroughs furthest from the city centre are the least at risk of smog.
What is toxic air pollution and how is it caused?
Hazardous pollutants from industrial facilities can have serious negative health impacts as they are released into the air.
The main pollution problem in both developed and and rapidly industrialising countries has been high levels of smoke and sulphur dioxide - emitted through the combustion of sulphur-containing fossil fuels such as coal.
Petrol and diesel-engine vehicles emit several types of pollutants such as carbon monoxide, oxides of nitrogen, volatile organic compounds, and particulate matter.
In general pollution from industry is steady or improving with time, however the consequences of traffic pollution are worsening with time.
By January 19, 2017, London had already breached its legal limits for toxic air for the entire year.
The quality of air pollution in London is thought to be contributing to about 9,000 deaths every year.
What does smog do to your lungs?
Toxic air pollution can lead to several short-term health problems because its ozone content.
Lung damage is the most likely with symptoms including:
- Difficulty breathing
- Lung damage
- Worsening of asthma symptoms
- Coughing and throat or chest irritation
Scientists say evidence proves children’s lung growth can be stunted by toxic air.
And if someone has been breathing in polluted air for a long period of time, lung cancer and death becomes more likely.
Experts have warned air pollution is also responsible for a 10 per cent increase in cancer cases.
American researchers have discovered a link between cumulative exposure to pollution and an increased rate of the disease.
What are the different levels of toxic air alerts and what do they mean?
The London Air website operated by King's College in London has four different levels of alert which apply to a 1 -10 scale.
A black alert warning is issued when the figure reaches 10.
These alerts were issued in London in January 2017 and forced some schools to suspend outdoor playtime because of the dangerous levels of pollution in the air.
A red alert is issued when the scale stands between seven and nine out of ten.
Between a two and six is classed as a moderate alert and anything less than 2 is classed as "low".
What do the Government advise we do to reduce air pollution?
Air quality is largely due to road transport emissions.
Using fewer vehicles or cleaner transport such as bicycles can therefore help to reduce emissions.
Tightening of standards for vehicle emissions means that modern vehicles should cause less population than older ones.
Vehicles that run on electricity are now available.
Using less-polluting transport can also be cheaper and faster too.
How has the heatwave affected health levels?
There are three main risks posed by a heatwave, according to NHS Choices - dehydration, overheating which can worsen existing conditions mainly connected to heart and breathing problems, and heat exhaustion/heatstroke.
Both the young and old, especially those over 75, are most at risk as well as anyone with a chronic condition.
People with serious mental health problems can also be badly affected and those with mobility problems.
Why are people warned to stay indoors?
When toxic air reaches a "red alert", millions are warned to stay indoors in central and west London.
This is because pollution is expected to reach a "high" level - which could have deadly consequences.
People are also urged to avoid busy roads if possible, where polluted air is already a concern.
Asthma sufferers and others who are vulnerable to breathing difficulties are most at risk.
Theresa May has signalled tough new measures would be introduced as she replied to a letter from more than 220 doctors, who warned time is “running out” to solve the UK’s pollution problem.
She said: “Poor air quality is the fourth largest risk to public health, behind only cancer, obesity and cardiovascular disease.
“It disproportionately affects some of the most vulnerable in our society, including the elderly, people with lung and heart conditions, and the very young.”
Replying to doctors, Mrs May wrote: “I agree with you that one of the main reasons our cities continue to face pollution problems is the significant levels of NOx emissions that diesel vehicles produce.
“Harmful emissions from transport contribute significantly to the air quality challenge we face.”
Why has Sadiq Khan called for a wood-burning stove ban?
Wood burning could be banned in London's most polluted areas in a bid to tackle air pollution, under proposals suggested by Sadiq Khan.
Open fireplaces, bonfires and wood burning stoves would be prohibited and only sales of low-emission stoves allowed.
London Mayor Khan wrote to Environment Secretary Michael Gove seeking the new laws.
The move comes after it was revealed that up to a third of all fine particle pollution in London comes from domestic wood burning.
Mr Khan wants to “protect those who have bought stoves in good faith” but requested powers to ban the burning of any wood or coal in “zero-emission zones”.
Zones could be created in 187 areas of the capital where pollution exceeds European limits.
In a statement Mr Khan said: "With more than 400 schools located in areas exceeding legal pollution levels, and such significant health impacts on our most vulnerable communities, we cannot wait any longer and I am calling on government to provide the capital with the necessary powers to effectively tackle harmful emissions from a variety of sources."
What is the Mayor of London Sadiq Khan doing to tackle toxic air pollution in the capital?
Sadiq Khan has announced £250,000 will go to 50 schools in London boroughs where levels of pollutant nitrogen oxide exceed legal limits.
The funding is part of a move where schools will carry out audits of the toxic air in their surrounding area.
He said it will help schools identify solutions to protect pupils from toxic fumes.
Recommended measures for schools include moving entrances and play areas to reduce exposure to busy roads.
The most heavily-polluting vehicles may also been banned from driving near schools.
"Green infrastructure" such as bushes and hedges may be built around school buildings to block out fumes.
The Mayor is also planning to charge the most polluting vehicles £10 to drive into central London.
Diesel drivers in Westminster will be charged 50 per cent more to park in the Marylebone area.
Mr Khan said: "Every child deserves the right to breathe clean air in London and it is a shameful fact that more than 360 of our primary schools are in areas breaching legal pollution limits.
“London’s filthy air is a health crisis and our children are particularly vulnerable to the toxic effects of air pollution.”
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Why has Khan implemented a high air pollution alert?
The Mayor of London has issued another high pollution alert due to the “illegal state” of “toxic air” in the capital.
He tweeted: “London: the shocking & illegal state of our toxic air means another high air pollution alert.”
Khan posted a link to which details why the alert has been implemented.
A high pressure system over northern Scandinavia is “resulting in an easterly air feed from the continent.”
This air feed will travel slowly and at low altitude across “industrialised parts of Europe giving it time to pick up emissions on the way.”
This polluted air mixed with London’s own high emissions will “likely produce 'High' levels of PM2.5 and 'Moderate' levels of PM10 particulate pollution across areas of London and the South East.”