Indoor air quality has become a topic of interest and concern. Especially changes in construction design and the increased use of synthetic products may result in an increasing of complaints and health effects about the quality of indoor air at home. In this study, nitrogen dioxide($NO_2$) and volatile organic compounds(VOCs) within new and established apartments on the basis of 4 years of building year were measured every 3 days consecutively during 60 days. We selected each 10 house in Seoul, Asan and Daegu, respectively, and produced risk numbers for hazard quotients, and predicted increases in incidence of cancer. The calculations were made for the adult with default exposure values and also made for a worst case scenario using Monte-Carlo simulation as describing the reasonable exposure(RME). Mean of Monte carlo analysis by benzene, in the construction under 4 years (male: $9.2{ imes}10^{-5}$, female: $1.0{ imes}10^{-4}$) and over 4 years (male: $6.8{ imes}10^{-5}$, female: $8.3{ imes}10^{-5}$) exceeded $10^{-6}$ of permitted standards in US EPA, RME of Monte carlo analysis. In construction under 4 yews (male: $9.9{ imes}10^{-3}$, female: $9.6{ imes}10^{-3}$) and over 4 years (male: $9.8{ imes}10^{-3}$, female: $7.8{ imes}10^{-3}$) exceeded $10^{-4}$ of maximum permitted standards in US EPA. The hazard index of non-carcinogenic pollutants by nitrogen dioxide, toluene, m,p-xylene and o-xylene, both male and female in apartment constructed under 4 yews and over 4 years was found less than the permitted standards of hazardous health effects in CTE. Significant cancer risks and non-cancer hazard quotients were predicted in under 4 yews of building year.