Warning over high air pollution over Newry
High to very high levels of air pollution in the Newry area have been detected, the Department of Environment has said.
Moderate levels are also being recorded in Armagh, Londonderry and north Down.
It is likely being caused by a build-up of emissions from vehicles and home heating during the calm, cold weather conditions, the department said.
It has warned that the symptoms of people with lung or heart disease may worsen due to the pollution.
Healthy people are unlikely to experience any ill effects.
"Although not forecast to continue or increase, it is possible that high levels of air pollution could continue to be seen in urban areas across Northern Ireland while current weather conditions last," the department said.
Hourly updates on levels of particulate matter (PM10), sulphur dioxide, nitrogen dioxide, ozone and carbon monoxide are available on the department's website.
There is also a helpline (0800 556677), which also offers health advice to those who may be particularly sensitive to air pollution.