Tracing Contributions of Benzene from Outdoor to Indoor Air

Abstract

Regulatory action levels for benzene in indoor air are typically unrealistic because they are commonly less than ambient outdoor concentrations. To trace potential benzene contributions to indoor air from outdoor sources, we evaluated data from 66 air samples collected at three sites with known subsurface impacts. Comparison of benzene:tracer ratios from indoor air, outdoor air, and soil gas samples demonstrated that indoor air benzene was primarily contributed by outdoor air and not by soil-vapor intrusion. Principal components analysis also demonstrated that soil gas had a distinctly different volatiles signature than both indoor and outdoor air. Ignoring ambient outdoor benzene contributions may lead to the erroneous conclusion that soil gas is the source of indoor air benzene.

Keywords:

• indoor air
• benzene
• outdoor air
• soil-vapor intrusion
• source identification

Acknowledgement

Financial support was provided by the American Petroleum Institute (API) and the United States Department of Energy (Cooperative Agreement number DE-FC26-98FT40321). However, any opinions, findings, conclusions, or recommendations expressed herein are those of the authors and do not necessarily reflect the views of the sponsors. Thea Reilkoff's help with the data reduction is appreciated.

Notes

^aThe fraction of variance accounted for by each factor.