Air pollution levels remain high across South Holland but are expected to reduce later today.
The Department for Environment, Food and Rural Affairs (Defra) reported the district was still gripped by high levels of pollution this morning.
But a fresh air mass arriving later today is expected to push the pollution eastwards over the North Sea, weather forecasters have said.
Residents with asthma or other breathing and heart problems have been advised to stay inside.
The Munro Medical Centre in Spalding said there had been a rise in the number of patients visiting this week with breathing complaints.