Pollution levels will peak on Friday, particularly in areas of south-east England where the government are advising the entire population to reduce physical activity

Harmful levels of air pollution will accompany the warm weather expected across the UK on Friday, triggering government warnings that people with health problems should reduce their physical activity.

Much of central, eastern and northern England will be blanketed in high pollution, according to the official UK Air site, with some of south-east England affected by very high pollution.



The episode is blamed on a combination of dirty air from the continent, the fine weather conditions and Saharan dust, which contributed to several days of serious pollution one year ago. Temperatures are expected to reach almost 20C in some areas on Friday.



Air pollution forecast for 10 April. Photograph: UK Air

This week’s warning comes a day after Islamist hackers took control of UK Air, posting a portrait of former Iraqi dictator Saddam Hussein and criticising the UK government for the 2003 Iraq invasion. The site, which is run by consultancy Ricardo-AEA on the environment department’s behalf, is still offline but a spokeswoman said they were working to get it up again “as soon as possible”. Pollution forecasts are being posted on a holding page.

In regions hit by high pollution on Friday, the official health advice is for adults and children with lung problems to reduce their physical activity, and for all older people to reduce physical exertion. In the very high areas, which include Brighton, Eastbourne and Hastings, the entire population are advised to reduce physical activity.



A Met Office spokeswoman said the settled weather this week meant the pollution episode was likely to happen, but would be blown away by Saturday.



“We do have a weak front crossing the UK late on Friday which is bringing some cooler, fresher air behind it. Until then we have these fairly calm, settled conditions which means any pollution buildup doesn’t move, it’s trapped there,” she said.



Pollution levels are expected to rise throughout Thursday in advance, but the forecast is for largely low levels by Saturday.



Dr Penny Woods, chief executive of the British Lung Foundation, said: “This latest high air pollution episode, coming so soon after the last, is troubling, and could again put people living with respiratory conditions at risk of worsening symptoms.”

She added: “With periods of high pollution often resulting from a combination of domestically-produced pollution and that coming from mainland Europe, we need urgent action from government to clean up the air we breathe, across all government departments at home and at a pan-European level.”

On Wednesday, the Advertising Standards Authority upheld a complaint against a Transport for London newspaper advert that claimed Boris Johnson’s planned ‘ultra low emissions zone’ would cut vehicle pollution by half. The ASA rejected two other complaints but ruled that the advert’s claim was misleading because it only referred to two pollutants, NO2 and NOx, and did not include CO2, PM10 and PM2.5 emissions, which would not be cut by half.



TfL said it would appeal the decision.