With air pollution responsible for the deaths of about 10,000 Londoners per year, activists are ramping up efforts to take on the growing public health crisis.

Key points: Levels of NO2 in some areas of London breached EU standards in 2016

Levels of NO2 in some areas of London breached EU standards in 2016 A 2015 study found about 9,500 people died each year due to the pollution

A 2015 study found about 9,500 people died each year due to the pollution London pollution is less visible than smog in China or India making it harder to raise awareness among Londoners

The city's Mayor Sadiq Khan has issued several warnings, including telling public transport passengers to stay away from bus stops when pollution is high.

The levels of toxic nitrogen dioxide (NO2) in some areas regularly breached European Union standards in 2016.

Shazia Ali-Webber became an anti-pollution campaigner in London after worrying about the damage being done to her young sons' lungs on their walk to school.

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The 41-year-old, who helped form I Like Clean Air, started measuring the pollution level at intersections where the staggered traffic lights meant she and her children often spent long periods waiting in the middle of busy roads.

"There are trucks and buses and concrete mixers and lorries and most of them run on diesel and we're stuck in the middle of the road," Mrs Ali-Webber said.

"We do know from the studies that children's lungs are being stunted.

"And the worst thing is that stunting stays with them into their adult lives so the respiratory problems that occur will stay with them."

In 2015, a study by researchers at London's Kings College found about 9,500 people died each year due to long-term exposure to the pollution.

Paul Drayson, a former Labour Party science minister and the CEO of Drayson Technologies, has come up with a product he hopes will provide the most complete digital map of the city's air.

A personal tag sends information to an application on people's smart phones about the pollution they encounter. ( ABC News: Lisa Millar )

A personal tag the size of a smart phone and a third of the weight sends information to an app measuring the pollution they encounter.

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It also combines to create a bigger picture of London's situation.

"If you have a device that tells you where the air is good and where it is not so good you can avoid those pollution hot spots and you can look after your health," Lord Drayson said.

"Whilst people are hopefully getting on with removing the internal combustion engine from our cities and improving the air, people can actually make a difference for themselves."

While the tag does not measure nitrogen oxides, it does track carbon monoxide (CO).

"More CO indicates higher levels of more harmful substances, such as nitrogen oxides and tiny soot particles that lodge in the lungs," Lord Drayson said.

The app developers are working with bicycle couriers who zip around the city with the tags in their backpacks adding to the pollution statistics being fed into the digital map.

London pollution 'less obvious' than smog in India, China

Simon Birkett is another passionate anti-pollution agitator.

The former banker retired early to campaign full time against poor air quality.

"Particle levels are much higher in China, India or even Eastern Europe than they are here," he said.

"But for gases like NO2, a toxic gas, scientists say London has the highest level in the world, so that is what we are really worried about."

He said people were still coming to terms with the dangers London's bad air poses, especially because clear skies make them think the problem is not as serious as it is in Beijing or Delhi.

"I think when you spend time in those cities it's obvious they've been living with it for years. You don't have to convince them that they have a serious problem," he says.

"Here in London it's less obvious but … it is having a significant effect on our health and we don't want it to get as bad as it is on those cities.

"Nitrogen dioxide will affect everyone to a greater or lesser extent but it certainly exacerbates respiratory problems.

"It's also been associated with heart attacks and strokes, so it is a serious problem."

Diesel cars and other heavy vehicles are blamed for much of London's air problems.

Mr Khan has said he will more than double funding to clear up the capital's dirty air, improving the quality of buses and encouraging taxi drivers to switch from the older black cabs to new ones with zero emissions.