PM2.5 | Overall pooled effect estimate | | | | | | |
| Fixed effects model | 1.005 | 1.003 | 1.007 | 1.28 | <0.025 | 6 |
| Random effects model | 1.010 | 1.005 | 1.016 | 1.64 | | |
PM10 | Overall pooled effect estimate | | | | | | |
| Fixed effects model | 1.000 | 0.999 | 1.001 | 1.00 | <0.001 | 12 |
| Random effects model | 1.004 | 1.002 | 1.006 | 1.22 | | 12 |
| Subgroups based on outcome measures (fixed effects models) | | | | | | |
| Symptom prevalence only | 1.000 | 0.999 | 1.001 | 1.00 | <0.001 | 8 |
| Subgroups based on the population studied (fixed effects models) | | | | | | |
| Asthmatic or symptomatic children | 1.000 | 0.999 | 1.001 | 1.00 | <0.001 | 9* |
| Non-symptomatic children | 1.002 | 1.001 | 1.004 | 1.11 | <0.025 | 5* |
| Subgroups based on environmental conditions (fixed effects models) | | | | | | |
| High ozone levels | 1.010 | 1.006 | 1.014 | 1.64 | <0.001 | 3 |
| High SO2 levels | 1.001 | 1.000 | 1.002 | 1.05 | <0.025 | 2 |
| High PM10 levels only | 1.000 | 1.000 | 1.000 | 1.00 | <0.001 | 8 |
| Subgroups based on pollutant lag (fixed effects models) | | | | | | |
| Same day or prior two days | 1.000 | 0.999 | 1.001 | 1.00 | <0.001 | 8 |
| Subgroups based on analytical approach (fixed effects models) | | | | | | |
| Use of a two-stage approach | 1.005 | 1.003 | 1.007 | 1.28 | <0.001 | 3 |
| Use of a population daily average outcome | 1.000 | 0.999 | 1.001 | 1.00 | <0.001 | 9 |
| Autocorrelation modelled using GEE | 1.005 | 1.004 | 1.007 | 1.28 | <0.001 | 6 |
| Autocorrelation not modelled using GEE | 1.000 | 0.999 | 1.001 | 1.00 | <0.001 | 6 |