Key points from article :
Breathing polluted air in UK's most polluted cities is equivalent to smoking 150 cigarettes a year.
This level of air pollution needs to be declared "a public health emergency".
Increases the risk of heart attack and stroke and worsens existing health problems.
Newham, Westminster, Kensington and Chelsea, and Islington areas of London are most polluted.
Government needs to introduce WHO air pollution limits which are way tougher than EU limits.
