Sexton 2004 - "Comparison of Personal, Indoor, and Outdoor Exposures to Hazardous Air Pollutants in Three Urban Communities"

Sexton, Ken; Adgate, John L; et al.
"Comparison of Personal, Indoor, and Outdoor Exposures to Hazardous Air Pollutants in Three Urban Communities"
Environmental Science and Technology
2004; v.38, n.2; pp.423-430
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The authors measure personal, indoor, and outdoor exposures to 15 VOCs in three different neighborhoods of Minneapolis/St. Paul, MN. They found that outdoor community air monitors greatly underestimate personal exposures and that even indoor monitors underestimate personal exposure. For example, for benzene, the personal/outdoor (P/O) ratio of estimated relative concentrations is 6.8, while the personal/indoor concentration (P/I) is 1.6.

The Personal/Outdoor and Personal/Indoor estimated concentrations are:

VOC	P/O	P/I
Benzene	6.9	1.6
Toluene	27.1	1.3
Ethylbenzene	18.8	1.6
m-lp-xylene	19.2	1.5
o-xylene	18.0	1.6

The authors also state that people spend 90% of their time indoors and that VOCs tend to come from indoor sources, so personal exposure is more correlated with indoor than with outdoor concentrations. "For the majority of people, the highest personal VOC exposures are likely to occur away from home (for example, filling the car at a self-service station, working in a poorly ventilated office, sitting next to an average smoker, commuting in heavy traffic, visiting a dry cleaner)."