Matched pairs of indoor and outdoor air samples from residences in Greensboro, NC; Baton Rouge/ Geismar, LA; Deer Park/Pasadena, TX; Elizabeth/Bayonne, NJ: Antioch/W. Pittsburg, CA; and several small communities in the Los Angeles area were collected and analyzed for over 20 volatile organic compounds during the period from 1981 to 1984. Indoor (I) medians and maximum levels were higher than the corresponding outdoor (O) concentrations over the large majority of chemicals studied. In some cases, e.g., chloroform, dichlorobenzenes, and tetrachloroethylene, the median ratios (I/O) were greater than 10.
Comparison of indoor and outdoor residential levels of volatile organic chemicals in five U.S. geographical areas
Pellizzari, E., Hartwell, T., Perritt, R., Sparacino, C., Sheldon, L., Zelon, H., ... Wallace, L. (1986). Comparison of indoor and outdoor residential levels of volatile organic chemicals in five U.S. geographical areas. Environment International, 12(6), 619-623. https://doi.org/10.1016/0160-4120(86)90104-2