Health warnings have been issued in parts of the UK as air pollution has hit "high" or "very high" levels.
Adults and children with lung problems, adults with heart problems and older people are being warned to take extra precautions if they are in a high-risk area.
The Government's Daily Air Quality Index reveals air pollution levels across the country and provides recommended actions and health advice.
Areas with high pollution levels marked in pink and red, while very high is marked in purple.
The Department for Environment, Food and Rural Affairs (Defra) has urged people to:
Determine whether you (or your children) are likely to be at-risk from air pollution
If you may be at-risk, and are planning strenuous activity outdoors, check the air pollution forecast
Use the health messages corresponding to the highest forecast level of pollution as a guide
Should you find you are living in an area experiencing "very high" pollution levels, the following advice is given:
Adults and children with lung problems, adults with heart problems, and older people, should avoid strenuous physical activity
People with asthma may find they need to use their reliever inhaler more often
Reduce physical exertion, particularly outdoors, especially if you have a cough or sore throat
The charity Asthma UK has issued further advice for asthma sufferers should they find they are in an area with high pollution levels:
Avoid strenuous exercise outside
Keep on top of asthma symptoms with an asthma action plan
Have your reliever inhaler with you at all times
If you think that you may be having an asthma attack, take one to two puffs of your reliever inhaler (usually blue), immediately.
Sit down and try to take slow, steady breaths - if you do not feel any better, take another two puffs of the reliever inhaler every two minutes, up to ten puffs.