# The Combined Effect of Indoor Air Quality and Socioeconomic Factors on Health in Northeast China
## 4 Discussion  
### Link Between Socioeconomic Factors, Indoor Air Quality, and Health  
This paper confirmed the complex relationship between socioeconomic factors, indoor air quality and occupants' health (Figure 4). Socioeconomic factors (0.413) had a stronger direct impact on health than indoor air quality (0.105). Although, there is no literature that specifically indicates the relative weight of socioeconomic factors or indoor air quality to health, research has increasingly pointed out that the contribution of socioeconomic factors (e.g., education, income, and work conditions) was beyond physical environment (e.g., air quality and drinking water). For example, America's Health Rankings estimated that the weight of socioeconomic factors (0.27) to health was three times as great for physical environment (0.09) [45]. County Health Rankings established the relative contribution of socioeconomic factors (0.4) and physical environment (0.1) on health [46]. The University of Wisconsin Population Health Institute assigned weights to health as follows: Socioeconomic factors, 0.4; physical environment, 0.05 [47]. Unfortunately, there is no consensus on the relative contribution of socioeconomic factors or physical environment on health. But the weight of physical environment is rather weaker than socioeconomic factors. Income level (0.595 \(\times\) 0.413 = 0.246), education level (0.551 \(\times\) 0.413 = 0.228), and occupation prestige (0.508 \(\times\) 0.413 = 0.209) delivered the similar weight to health. This may be due to the interplay among the three factors. More education level is usually connected to higher income level and better employment options [48]. It is estimated that each additional year of schooling can increase approximately 11% more income every year [49]. Higher income jobs usually provide not only a safe work environment, but also health insurance and paid sick leave [50]. As for indoor air quality, PM\({}_{2.5}\) concentration (0.813 \(\times\) 0.105 = 0.085) was the major indicator contributing to health, followed by CO\({}_{2}\) (0.385 \(\times\) 0.105 = 0.04), TVOC (0.218 \(\times\) 0.105 = 0.02) and formaldehyde (0.142 \(\times\) 0.105 = 0.01). The weighting distributions can be explained as follows. Approximately 61.7% of the average PM\({}_{2.5}\) concentration exceeded 35 \(\mathrm{\SIUnitSymbolMicro m}^{3}\) specified by WHO air quality guidelines [51], as shown in Figure 3. The average CO\({}_{2}\) level were above 1000 ppm (National Indoor Air Quality Standard GB18883-2002 [30]) \begin{table}
\begin{tabular}{l c c c c c c} \hline \hline \multicolumn{6}{c}{**Formative Measurement Model**} \\ \hline
**Latent** & **Indicators** & **Outer** & **VIF** & **Latent** & **Indicators** & **Outer** & **VIF** \\ \hline \multirow{4}{*}{SES} & education level & 0.551 * & 1.011 & \multirow{4}{*}{Air quality} & PM\({}_{2.5}\) & 0.813 * & 1.039 \\  & occupation prestige & 0.508 * & 1.005 & & CO\({}_{2}\) & 0.385 * & 1.055 \\  & income level & 0.595 * & 1.009 & & HCHO & 0.142 * & 1.050 \\  & & & & TVOC & 0.218 * & 1.072 \\ \hline \multicolumn{6}{c}{**Reflective Measurement Model**} \\ \hline
**Latent** & **Indicators** & **Outer** & **Composite** & **Discriminant** & **Viality** & **AVE** \\ \hline \multirow{4}{*}{Health} & physical functioning & 0.849 & \multirow{4}{*}{0.853} & \multirow{4}{*}{YES} & \multirow{4}{*}{0.637} \\  & role physical & 0.677 & & & \\  & bodily pain & 0.545 & & & \\  & general health & 0.564 & & & \\  & vitality & 0.736 & & & \\  & social functioning & 0.491 & & & \\  & role emotional & 0.773 & & & \\  & mental health & 0.565 & & & \\ \hline \multicolumn{6}{c}{**Structural Model**} \\ \hline
**Relation** & **Path Coefficient** & **VIF** & **Coefficient of** & **Predictive Relevance** \\ \hline IAQ\(\rightarrow\)Health & 0.105 * & 1.136 & 0.305 & 0.283 \\ SES\(\rightarrow\)Health & 0.413 * & 1.216 & 0.305 & 0.283 \\ SES\(\rightarrow\)IAQ & 0.381 * & 1.272 & 0.220 & 0.110 \\ \hline \hline \end{tabular} Note. * represents the \(P\) value \(<\) 0.01.  
\end{table}