Londoners should avoid strenuous physical activity on Friday due to “very high” levels of pollution, experts have warned. The poor air quality is the result of an intense area of high pressure covering western Europe. The associated lack of air movement means emissions from vehicles and other pollutants are not blown away as they usually would be. The government’s forecast predicts pollution levels will hit band 10, the highest level on the scale. The last time pollution levels hit this mark was in March 2018. Older people and those with lung or heart problems should avoid strenuous physical activity, the government’s official advice stated, while people with asthma may need to use inhalers more often. Even healthy people should “reduce physical exertion, particularly outdoors, especially if you experience symptoms such as a cough or sore throat”. The worst pollution is forecast to be in the city centre, with the dirtiest air stretching from Stratford in the east to Hammersmith in the west, though pollution levels are expected to be high throughout the entire city. Earlier this week Sadiq Khan, the mayor of London, said car use had returned to close to pre-pandemic levels, and that the effect on residents could be disastrous. “If we do not double down on our efforts to deliver a greener, more sustainable future, we will replace one public health crisis with another – caused by filthy air and gridlocked roads.” Pollution levels are expected to return to normal by Saturday.