Table 2.

Air toxic combinations identified with statistically significant interactions within members of the combination found to be associated with asthma symptoms across the three exposure periods.

Air toxic combinations	p-value
Most recent year (2019)
ACETALDEHYDE >= 9.168e-01 & 1,1,1-TRICHLOROETHANE >= 2.040e-02	0.0036
2,4,6-TRICHLOROPHENOL >= 6.940e-07 & 1,1,1-TRICHLOROETHANE >= 2.039e-02	0.0036
Last 3 years (2017-2019)
DIESEL PM >= 4.085e-01 & 1,1,1-TRICHLOROETHANE >= 3.981e-02	0.0036
2,4,6-TRICHLOROPHENOL >= 6.265e-07 & 1,1,1-TRICHLOROETHANE >= 3.883e-02	0.0036
Last 5 years (2014-2019)
ETHYLBENZENE >= 1.656e-01 & 1,1,1-TRICHLOROETHANE >= 6.484e-02	0.0036
2,4,6-TRICHLOROPHENOL >= 4.545e-06 & ACETONITRILE >= 1.836e-02	0.0042

Multivariable linear regression models were used to examine the interactions within the XGBoost-identified multi-air toxic combinations and the outcome by using the levels of the constituent air toxics and their product in the models. A significant interaction was identified if the p-value of the corresponding interaction term was lower than 0.05.