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Londoners cycling to work on high pollution days may be doing themselves far more harm than good, Europe’s Environment Commissioner warned today.

Janez Potocnik also advised people to be wary of jogging in the capital when air quality is very poor.

With the Mayor of London and Government facing criticism for not doing more to publicise pollution peaks, Mr Potocnik told The Standard: “It is wrong that people should be anything other than fully aware and informed when pollutant levels are high.

“Medical advice suggests that people should not exert themselves physically during episodes of high pollution - when that jog in the park or cycle to work could be doing considerably more harm than good.”

With more than 3,000 deaths estimated to be linked to air pollution in London a year, former Slovenian minister Mr Potocnik urged people in the capital to use websites and apps which give regular updates on air quality in each borough.

But Boris Johnson rejected the Commisioner’s warning on cycling and jogging.

“The sensible advice given to healthy Londoners by medical professionals is to continue their normal daily activity,” said a spokeswoman for the Mayor.

“Recent research from Barcelona published in the British Medical Journal suggests the health benefits of cycling on normal healthy people greatly outweigh the health risk of air pollution 77 fold.”

Mr Johnson is encouraging people to sign up to a free air text service - www.airtext.info - to receive daily updates on pollution levels.

The Department for Environment, Food and Rural Affairs’s website includes a Daily Air Quality Index forecast with a one to three rating for low pollution, four to six moderate, seven to nine high, and ten very high.

Public Health England advises that on high pollution days, anyone experiencing discomfort such as sore eyes, cough or sore throat should consider reducing activity, particularly outdoors.

Adults and children with lung problems, and adults with heart problems, should reduce strenuous physical exertion, particularly outdoors. Older people should also reduce physical exertion.

Britain is facing legal action by the European Commission for breaching EU rules on nitrogen dioxide levels, with many of the blackspots in London.

Boris Johnson has criticised Brussels, arguing it has developed EU vehicle emissions standards which manufacturers have been able to “diddle”.

The Mayor said this made it “doubly absurd” that the Commission was threatening to fine the UK £300 million for excess NO2.

But Mr Potocnik hit back, claiming Mr Johnson had “romanticised the dust of London” after his comments following recent freak weather which saw Saharan sand, as well as smog, descend on the capital.

Without naming the Mayor, he accused him of an “intellectual sleight of hand” with his criticism of Brussels, stressing member states ultimately make decisions and they had “hampered” Commission moves for cleaner engines in a short timeframe.

However, a spokesman for the Mayor stressed he had “the most ambitious and comprehensive package of measures to tackle pollution”.