Indoor occurrence and health risk of formaldehyde, toluene, xylene and total volatile organic compounds derived from an extensive monitoring campaign in Harbin, a megacity of China.

Human exposure to formaldehyde, toluene, xylene (FTX) and other volatile organic compounds (VOCs) are associated with negative health impact. To characterize the exposure and health effects of FTX and TVOC from indoor environments, we conducted an extensive monitoring campaign involving 1278 measurements of 472 indoor locations in Harbin, a megacity in China from May 2013 to March 2018. The results showed that household had the highest mean formaldehyde concentration (0.171 ± 0.084 mg m-3) among all types of indoor environments. Meanwhile, there was no significant differences in formaldehyde concentration of the living room, master bedroom, secondary bedroom and study room (p > 0.05), as well as toluene and xylene. The highest mean concentration of toluene, xylene and TVOC was measured in public bath center. Great difference was found between formaldehyde concentrations in 2013 and other years, except 2015. There were great positive nonlinear correlations between the indoor temperature and concentration of formaldehyde (p < 0.01), good negative nonlinear correlations between the finish time of decoration and concentration of formaldehyde (p < 0.01), good positive linear correlations between the relative humidity and concentration of formaldehyde (p < 0.01). A risk assessment methodology was utilized to evaluate the potential adverse health effects of the individual FTX compounds according to their carcinogenicities. The predicted carcinogenic risk of formaldehyde was greater than the threshold value 1E-06 at all environments. The non-carcinogenic risk of TX compounds in the population is negligible. For estimating human health risk exposure, sensitivity analysis showed that more attention should be given to the influential variables such as the level of pollutants.