In pictures: Beijing pollution-watch

The BBC is sampling pollution levels in Beijing before and during the Olympics. The daily readings measure air particles known as PM10. The error margin is 20%.

26 August PM10 reading: 93 micrograms per cubic metre. (The World Health Organisation guideline maximum is 50 micrograms per cubic metre, averaged over 24 hours.)

25 August PM10 reading: 70 micrograms per cubic metre. We test for 10 minutes at midday from a seventh floor balcony in central Beijing.

24 August PM10 reading: 99 micrograms per cubic metre.

23 August PM10 reading: 12 micrograms per cubic metre.

22 August PM10 reading: 21 micrograms per cubic metre.

21 August PM10 reading: 56 micrograms per cubic metre.

20 August PM10 reading: 87 micrograms per cubic metre.

19 August PM10 reading: 39 micrograms per cubic metre.

18 August PM10 reading: 18 micrograms per cubic metre. Blue skies over Beijing after a hazy Sunday.

17 August PM10 reading: 54 micrograms per cubic metre.

16 August PM10 reading: 7 micrograms per cubic metre. (The World Health Organisation guideline maximum is 50 micrograms per cubic metre, averaged over 24 hours.)

15 August PM10 reading: 12 micrograms per cubic metre.

14 August PM10 reading: 46 micrograms per cubic metre.

13 August PM10 reading: 128 micrograms per cubic metre.

12 August PM10 reading: 41 micrograms per cubic metre.

11 August PM10 reading: 54 micrograms per cubic metre.

10 August PM10 reading: 278 micrograms per cubic metre.

9 August PM10 reading: 110 micrograms per cubic metre.

8 August PM10 reading: 156 micrograms per cubic metre.

7 August PM10 reading: 191 micrograms per cubic metre.

6 August PM10 reading: 186 micrograms per cubic metre.

5 August PM10 reading: 104 micrograms per cubic metre.

4 August PM10 reading: 292 micrograms per cubic metre.

3 August PM10 reading: 79 micrograms per cubic metre.

2 August PM10 reading: 15 micrograms per cubic metre.

1 August PM10 reading: 19 micrograms per cubic metre.

31 July PM10 reading: 56 micrograms per cubic metre.

30 July PM10 reading: 78 micrograms per cubic metre.

29 July PM10 reading: 8 micrograms per cubic metre.

28 July PM10 reading: 134 micrograms per cubic metre.

27 July PM10 reading: 269 micrograms per cubic metre.

26 July PM10 reading: 165 micrograms per cubic metre.

25 July PM10 reading: 261 micrograms per cubic metre.

24 July PM10 reading: 254 micrograms per cubic metre.