Ebelt 2005 - "Exposure to Ambient and Nonambient Components of Particulate Matter"

Ebelt, Stefanie T; Wilson, William E; Brauer, Michael.
"Exposure to Ambient and Nonambient Components of Particulate Matter: A Comparison of Health Effects"
Epidemiology
May 2005; v.16, n.3; pp.396-405
On the Web
Relevance: medium

Intro: Using a small sample of pulmonary patients in Vancouver, the authors measured exposure to particulate matter and health effects, trying to separate out influence of ambient and nonambient particles on lung function, heart rate, and blood pressure.

Findings: They found that ambient exposure was not correlated with nonambient or personal exposure. They also found that ambient exposure was a better predictor of health effects. In contrast nonambient and personal exposures were not associated with health effects, except in the wrong direction for lung function. The authors caution that this is a small study and the results are not conclusive.

Methods: The authors estimated ambient vs nonambient exposure by using activity diaries and by assuming that all sulfate particles were ambient. The authors note that ambient and nonambient PM likely have different compositions, leading to different health effects.

[I wonder about their choice to assign all sulfate particles to ambient exposure. Diesel buses are often a source of sulfur, so if a participant rode the bus that personal exposure is counted as ambient.]