Pollution levels per year in the patient cohort
| Year | SO2 (μg/m3) | NO2 (μg/m3) | PM10 (μg/m3) | Ozone (μg/m3.h) |
| 1997 | 7.81 (0.34) | 34.06 (0.71) | 18.25 (0.17) | |
| 1998 | 6.26 (0.25) | 31.01 (0.63) | 16.92 (0.13) | |
| 1999 | 5.01 (0.21) | 29.71 (0.62) | 16.31 (0.11) | |
| 2000 | 4.35 (0.19) | 27.89 (0.61) | 15.91 (0.12) | |
| 2001 | 3.75 (0.11) | 26.07 (0.60) | 15.51 (0.13) | |
| 2002 | 3.82 (0.16) | 20.87 (0.51) | 14.98 (0.14) | |
| 2003 | 4.13 (0.16) | 23.81 (0.55) | 17.56 (0.14) | 9887.97 (219.51) |
| 2004 | 3.47 (0.15) | 18.25 (0.50) | 20.43 (0.22) | 3236.36 (78.84) |
| 2005 | 3.38 (0.13) | 18.88 (0.51) | 22.04 (0.18) | 4335.35 (103.81) |
| 2006 | 3.49 (0.16) | 17.71 (0.48) | 21.35 (0.20) | 12468.94 (198.86) |
| Mean per year of decline | 4.12 (0.17) | 24.20 (0.64) | 17.31 (0.21) | 6517.70 (271.94) |
Data are shown as mean (SE) for each calendar year for which values were available, with the mean per year of calculation of decline in the final row of the table.