Correlating indoor and outdoor temperature and humidity in megacities in China

Since people spend much more time indoors, indoor conditions may be better indicators of personal exposure than outdoor. Several studies have explored the associations between indoor and outdoor temperature, humidity in USA or in tropical regions. Few studies examined these associations in China. In this study, we collected the daily indoor temperature and relative humidity (RH) in 1577 household in four megacities across temperate and subtropical regions in China, from March 2017 to July 2018. We use Pearson correlation analysis to examine their correlations with outdoor. We found that the correlation between indoor and outdoor RH was stronger in Northern China (r=0.76 V.S. r=0.58), while the correlation between indoor and outdoor temperature was stronger in Southern China (r=0.92 V.S. r=0.80). In the winter-spring months, there was no statistically significant linear relationship between indoor and outdoor temperature. However, the correlation between indoor and outdoor RH in high urbanized regions in winter-spring was stronger than that in low urbanized regions (r=0.85 V.S. r=0.70). This may be due to the comment use of air conditioning and ground heating in the high urbanized regions. This study provides insight for assessing the indoor-outdoor environment correlations in China.