Table 4.
Analysis of the health effects of toner exposure without adjustment for confounders (models 1 and 2)
| Parameters (unit) | Difference in yearly change in each parameter between the toner-handling group and non-toner-handling group (model 1) | Difference in yearly change in each parameter between the toner-handling group and non-toner-handling group (model 2) | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Estimate | 95% CI | P-value | AIC | Estimate | 95% CI | P-value | AIC | |||
| Respiratory function tests | ||||||||||
| VC (l) | 0.0009 | −0.002 | 0.003 | 0.459 | − 3786.6 | − 0.003 | − 0.005 | 0.0002 | 0.067 | − 4375.4 |
| %VC (%) | 0.004 | − 0.05 | 0.06 | 0.892 | 74,963.3 | −0.07 | − 0.1 | − 0.004 | 0.037 | 74,441.0 |
| FEV1 (l) | 0.0001 | −0.002 | 0.002 | 0.925 | − 7999.7 | −0.001 | − 0.004 | 0.001 | 0.272 | − 8462.7 |
| %FEV1 (%) | 0.02 | − 0.05 | 0.08 | 0.608 | 76,776.5 | −0.02 | − 0.09 | 0.05 | 0.568 | 76,306.5 |
| FEV1/FVC (%) | −0.003 | − 0.04 | 0.03 | 0.866 | 60,893.8 | −0.002 | − 0.04 | 0.04 | 0.903 | 60,721.0 |
| %FEV1/FVC (%) | 0.006 | −0.04 | 0.05 | 0.808 | 65,957.3 | 0.008 | −0.04 | 0.06 | 0.727 | 65,790.5 |
| V25 (l/s) | 0.0005 | −0.003 | 0.004 | 0.747 | 4573.4 | 0.0002 | −0.004 | 0.004 | 0.921 | 4303.0 |
| %V25 (%) | −0.06 | − 0.2 | 0.10 | 0.457 | 102,127.6 | −0.02 | − 0.20 | 0.15 | 0.784 | 101,834.2 |
| Biomarkers | ||||||||||
| CRP (mg/dl) | 0.0007 | −0.002 | 0.003 | 0.635 | 3626.3 | 0.0006 | −0.002 | 0.003 | 0.658 | 3620.2 |
| IgE (IU/ml) | 3.2 | −1.6 | 7.9 | 0.190 | 177,623.3 | 4.6 | −1.00 | 10.1 | 0.108 | 175,403.0 |
| 8-OHdG/Creatinine (ng/mg) | −0.01 | − 0.03 | 0.0009 | 0.065 | 45,402.9 | −0.01 | −0.03 | 0.003 | 0.115 | 45,352.5 |
Dependent variables comprised the parameters of respiratory function tests and the values of biomarkers in both models 1 and 2. In model 1, we treated toner-handling work, the survey year, and the interaction between toner-handling work and survey year as fixed effects and treated only the individual differences at baseline as the random effect (random intercept model). In model 2, we treated certain individual differences during the observation period and the individual differences at baseline as random effects (random intercept and slope models)
CI confidence interval, AIC Akaike’s Information Criterion, VC vital capacity, %VC percentage of VC to predicted VC value, FEV1 forced expiratory volume in 1 s, %FEV1 percentage of FEV1 to predicted FEV1 value, FEV1/FVC percentage of forced expiratory volume in 1 s, %FEV1/FVC percentage of FEV1/FVC to predicted FEV1/FVC value, V25 maximal expiratory flow at 25% forced VC, CRP C-reactive protein, IgE immunoglobulin E, 8-OHdG 8-hydroxy-2′-deoxyguanosine