Severe air pollution is set to sweep through parts of Wirral tomorrow threatening the health of the sick and vulnerable.
The Department for Environment, Food and Rural Affairs (Defra) has warned people to be braced for "very high" levels of air pollution over the next few days.
Defra ranks air pollution from one to 10, with one being the lowest and 10 the highest.
Across most of England, moderate to high air pollution levels are forecast, with level 7 to 8 expected in Wirral.
The elevated pollution levels have been caused by a combination of light south-easterly winds, the continental air flow and dust which has blown up from the Sahara desert, a Defra spokeswoman said.
People suffering the effects of high levels of pollution - including sore eyes, coughs and sore throats - should cut down the amount of activity they take outside, experts have warned.
Asthmatics might need to use their blue reliever inhalers more often as they could be prone to attacks today and over the next few days.
Other people with lung and heart problems, and those who are older, should also avoid strenuous exercise or activity.
The advice, from Public Health England (PHE), Asthma UK and Defra, comes after a warning that people in parts of England should be braced for the highest level of air pollution recorded by Defra.
The Defra warning for Thursday states: “High levels of air pollution are forecast for East Anglia, the Midlands, including Lincolnshire, easternmost parts of Wales, through Wirral and the north coast of Wales…”
Defra's weather forecast for tomorrow, Thursday, shows Wirral is expected to see high levels of air pollution.
The Defra forecast added: "The current elevated pollution levels over parts of the UK are caused by light winds allowing the build-up of pollution, plus dust from the Sahara contributing to pollution levels."
The high levels of pollution are expected to continue across East Anglia and the Midlands on Thursday.
But the air pollution is expected to ebb away by Friday.
However, people with heart and lung conditions have been warned to avoid strenuous activity.
This week people in the south east havefound their cars to be covered in a light coating of red dust.
The Met Office said that a large amount of sand and dust was swept up by storm winds in the Sahara Desert.
A Defra spokeswoman said: "The high level of air pollution this week is due to a combination of local emissions, light winds, pollution from the continent and dust blown over from the Sahara.
"We want to keep improving air quality and have introduced a new five-day forecast service in addition to investing heavily in local and transport initiatives to tackle this issue head-on."
Sotiris Vardoulakis, head of air pollution at PHE's centre for radiation, chemical and environmental hazards, said: "Whilst most people will not be affected by short-term peaks in air pollution, some individuals, particularly vulnerable groups such as those with existing heart or lung conditions, may experience increased symptoms.
"On occasions where levels are high, adults and children with lung problems, and adults with heart problems, should reduce strenuous physical exertion, particularly outdoors, and particularly if they experience symptoms.
"People with asthma may find they need to use their reliever inhaler more often. Older people should also reduce physical exertion.
"Anyone experiencing discomfort such as sore eyes, cough or sore throat should consider reducing activity, particularly outdoors."