Allen 2004 - "Estimated Hourly Personal Exposures to Ambient and Nonambient Particulate Matter Among Sensitive Populations in Seattle"

Allen, Ryan; Wallace, Lance; et al.
"Estimated Hourly Personal Exposures to Ambient and Nonambient Particulate Matter Among Sensitive Populations in Seattle"
Journal of Air and Waste Management
September 2004; v.54; n.9; pp.1197-1411
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The authors measured the concentration of particulate matter in various mircoenvironments (home indoors, home outdoors, work, school, in transit, other outdoors, other indoors) and the average exposure for 38 subjects in Seattle. The subjects selected were "sensetive populations" with asthma, coronary heart disease, or advanced age. The major findings were:

• The best air was indoors at home; the worst air was at work, followed by outdoors and in transit.
• Because subjects spend so much time at home, most of their exposure (79%) occured there.
• There was a low correlation between ambient and personal exposures (0.43) compared to findings from other studies. This means that localized sources highly affect personal exposure (i.e. cooking fumes vs.general air quality)

They also found that cooking and being at school increased higher exposure.

The average concentrations (micrograms/m^3) of PM measured in the various microenvironments were:

Location	Geometric Mean	Arithmetic Mean
Home (indoor)	6.5	10.0
Home (outdoors)	12.7	18.1
In transit	10.5	16.2
At work*	18.9	23.1
Outdoors away from home	13.0	17.1
indoors away from home	10.1	16.3

*note that only one subject worked, and his workplace may not be representative.