A dirty toxic cloud of air heading over the English Channel is heading towards Huddersfield for the end of the week.

A warning of “moderate” air pollution for the south of England from Thursday has been issued by The Department for Food, Agriculture and Rural Affairs (Defra).

The toxic cloud will spread to northern parts of England by Friday, with a risk of “high” air pollution in some areas according to forecasters.

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In Huddersfield the conditions will be “moderate” and a health warning has been issued by officials for people suffering with lung problems.

A forecast on the Defra Air Quality Index website said: “Moderate air pollution is likely to become more widespread on Thursday, potentially affecting much of England and Wales.

“Scotland and Northern Ireland, meanwhile, should retain predominately low air pollution levels.”

The DEFRA air pollution index – Green is low and yellow is moderate. L-R: Wednesday, Thursday, Friday

The forecast for Friday said: “With southeasterly winds from the Continent dominating, the risk of Moderate air pollution is likely to be widespread through this three-day period, with localised areas of High air pollution also possible.”

Health advice states adults and children with lung problems, and adults with heart problems, should reduce physical exertion particularly if they are outdoors.

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People with asthma may find they need to the use their reliever inhaler more often, while older people should also reduce physical exertion.

The dust cloud, formed from the Saharan desert, is expected to become widespread affecting much of England and Wales by Thursday.

It is expected to continue from Friday to Sunday.

FACT BOX

The dust phenomenon is formed when air pollution levels are high and there is not much wind, during pleasant weather conditions.

This causes a combination of nitrogen dioxide (NO2), particulate matter (PM10 and PM2.5) and ground level ozone to build up.

A yellowish or black fog is created, which can cause respiratory problems when breathed in.

Those suffering with lung and heart problems are particularly at risk.