Air pollution both inside and outside is contributing to the deaths of 9,500 Londoners each year.
A new report by the Royal College of Physicians and the Royal College of Paediatrics and Child Health shows the major health impact of outdoor pollution, but also the less understood impact of indoor pollution.
When outside - it's nitrogen dioxide, an invisible toxic gas, which is of most concern. You can't see it, but its there - given off by diesel vehicles.
We are now seeing the medical evidence to tell us that air pollution is seriously damaging our health. we've got to take action, it's down to all of us to work together to improve the air. We've got to get rid of polluting vehicles like diesels. We've also got to think about being more active, but we've got to know where the air is to avoid.
Air pollution is a particular concern for Shazia Ali Webber, her asthmatic children go to a school next to a busy road in Hackney.
Where there is a continual flow of traffic, even on quiet roads, as long as there is a continual flow of traffic, there nitrogen dioxide levels are sometimes 2,3 or 4 times over the legal limit which is prescribed for human health.
The increase in nitrogen dioxide pollution is down to the increase in diesel vehicles.
Successive governments have made them cheaper to tax because they release fewer carbon emissions. But they're worse for our health, and there's more of them on our roads than ever before.
In the 1980s, fewer than 10% of new cars were diesel. By 2000 it was 14% but now, half of the cars on London's roads are diesel.
Wherever you are in London air pollution is high, and it's been found to reduce children's lung capacity, affect the development of unborn babies, and increase the chances of someone suffering from a heart attack.
The study also found that the air quality inside homes can be low due to things like cleaning products. So what should people do if they live next to a busy road?
I would recommend everybody should ventilate their houses once a day just for a short period, to blow the pollutants that have accumulated over 24 hours, and then shut it again.
The report calls for the government and local councils to do more to improve the air we breathe.