Association between indoor environment and common cold among children aged 7-9 years in five typical cities in China

The common cold is an acute, self-limited viral infection of the upper respiratory tract, it is a heterogeneous group of diseases caused by numerous viruses that belong to several different families. A total of 292 households with children aged 7-9 years from Harbin, Xi'an, Ningbo, Nanning, and Shenzhen, China were investigated and 877 air samples from both bedrooms and living rooms in study area were tested to reveal indoor air quality level in 2017. The mean indoor temperature, relative humidity, CO, CO2, NO2, formaldehyde, total count of colonies, and total count of fungi levels were 21.00 + 4.05 degrees C, 54.66 + 16.28%, 0.85+ +2.99 mg/m(3), 0.08 + 0.06%, 0.03 + 0.02 mg/m3, 0.03 + 0.02 mg/m(3), 173.14 +/- 4.28 cfu/m(3), and 241.21 +/- 4.20 cfu/m(3), respectively. Of the 292 children, 1.72% had >5 common colds in the past year, 12.04% 3-5 per year, and rest <3 per year. The average prevalence of the common cold in five cities was 1.68 times per year with an average duration of 5.62 days. The main symptoms of a common cold in children are cough and expectoration, which are significantly influenced by indoor relative humidity, formaldehyde, and total count of fungi. The total count of fungi as well as relative humidity are also significantly correlated with the duration of children common cold. And significant correlation was found between indoor temperature and the prevalence of a common cold. This study systematically analyzed influence of indoor environment, including physical variables, chemical variables, and biological variables, on common cold in children and identified essential indoor risk factors in China.