London is facing moderate air pollution as the Olympics kick off, following several days of hot sunny weather.
The latest UK air pollution forecast from the Environment Department said pollution would be at moderate levels over the next 24 hours in London and southern England as the current weather conditions continue. Other parts of the UK are forecast to experience low air pollution levels.
The situation is predicted to remain unchanged over the next two days as the Games get under way.
The main concern is ground level ozone, which forms from traffic fumes in warm sunny weather, and can cause breathing difficulties.
At moderate levels of air pollution, adults and children with lung problems and adults with heart problems who experience symptoms are advised to consider reducing strenuous physical activity, particularly outdoors.
However, other people should not be affected and do not need to take precautions.