At the current rate of change, levels of nitrogen dioxide in our air will not fall below the legal limit until 2030 for most UK cities and until after 2030 for London. http://www.clientearth.org/news/latest-news/new-figures-for-uk-air-pollution-show-the-results-of-government-inaction-2655 

Nitrogen dioxide is caused predominantly but not exclusively by diesel fumes from traffic. Exposure to high levels of nitrogen dioxide lowers lung function in growing children, increases respiratory problems including bronchitis, exacerbates asthma in children and adults and increases hospitalisations for respiratory issues.

The presence of nitrogen dioxide in the air is a strong indicator of the presence of diesel particulates. Particulates are categorised as a class 1 carcinogen no amount of which is safe for human health. They can cause lung cancer, heart disease and they have been connected to higher rates of autism. http://www.who.int/mediacentre/factsheets/fs313/en/

Most roads in London with a moderate level of traffic have air quality which breaches legal limits.http://www.londonair.org.uk/london/asp/annualmaps.asp

Our campaign tested the air in South Hackney and found that most roads tested were over the legal limit often by as much as 50-100%. http://www.ilikecleanair.org.uk/news

So government policy which will achieve air pollution targets by or after 2030 is 15 years too late for pre-schoolers and primary school children and 15 years too late for thousands of elderly people who will suffer and die prematurely as a result of poor air quality.

We want the Mayor of London to reduce air pollution levels in inner London boroughs on the streets around our homes and schools with an ambitious and far reaching scheme just as he has proposed for the congestion zone.  https://www.tfl.gov.uk/modes/driving/low-emission-zone/ultra-low-emission-zone