Beijing smog: The difference a month makes
China's capital continues to be enveloped in a thick smog that has forced school closures and sparked warnings to some citizens to stay inside.
A reading at the US embassy in Beijing on Tuesday put levels of harmful microscopic particles at 634 micrograms per cubic metre, compared with the World Health Organisation's maximum recommended limit of 25 micrograms per cubic metre.
China's ministry of environmental protection said the smog was due to "unfavourable" weather.
The following images show how different street scenes were a month ago.