Results from the categorical principal component analysis
| Environmental determinants (daily values) | Weight for* | ||
| Factor 1 | Factor 2 | Factor 3 | |
| PETmean | 0.98 | 0.51 | 0.15 |
| PETmax | 0.93 | 0.58 | 0.25 |
| PETmin | 0.97 | 0.35 | 0.00 |
| Mean relative humidity | −0.34 | −0.92 | 0.07 |
| Mean vapour pressure | 0.97 | 0.24 | 0.02 |
| Mean wind speed | −0.26 | 0.16 | −0.80 |
| NO concentrations | −0.16 | −0.58 | 0.79 |
| PM10 concentrations | 0.02 | −0.02 | 0.70 |
| O3 concentrations | 0.36 | 0.89 | −0.55 |
| Factors interpreted as | Thermal conditions | High ozone levels | High air pollution |
*Highest loadings of the variables are depicted in bold.
NO, nitric oxide; O3, ozone; PET, physiological equivalent temperature; PM10, particulate matter with an aerodynamic diameter of ≤10 µm; PM10, particulate matter with an aerodynamic diameter of ≤10 µm.