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DEVELOPMENT OF URINARY METABOLITE BIOMARKERS TO ASSESS POPULATION EXPOSURE TO PM2.5 FROM VARIOUS COMBUSTION SOURCES
Citation:
Lewtas, J, S. Myers, C. Simpson, R. Dills, AND D. Kalman. DEVELOPMENT OF URINARY METABOLITE BIOMARKERS TO ASSESS POPULATION EXPOSURE TO PM2.5 FROM VARIOUS COMBUSTION SOURCES. Presented at 2003 AAAR PM Meeting, Pittsburgh, PA, March 31-April 4, 2002.
Impact/Purpose:
The objective of this task is to develop and evaluate personal exposure and biomarker methods for toxic components associated with PM2.5 and SVOC in population exposures. Specific sub-objectives include the following:
1) Identification and quantification of either toxic or tracer organic chemicals associated with PM2.5 and associated SVOC.
2) Measurement of personal airborne exposure of selected toxic/tracer organic species in population based human exposure studies.
3) Development and application of urinary metabolite and other biomarker methods for these toxic/tracer organic species in human exposure studies.
4) Evaluation of multivariant receptor models for apportioning personal exposure using biomarker data.
Description:
A primary goal of our research is to validate the use of urinary biomarkers to apportion the sources of human exposure to PM2.5. Organic source tracers have been used in source apportionment studies of ambient PM2.5 to distinguish a range of combustion sources. Both gas and particle-phase organic tracer species have been used as biomarkers of exposure to combustion sources. The nicotine urinary metabolite, cotinine, is an example of a well-validated biomarker of exposure to tobacco smoke that has been successfully used in large population studies. Polycyclic aromatic hydrocarbons (PAH) and their urinary metabolites have been used as exposure markers for combustion sources including traffic and coal sources. Levoglucosan (1,6 -anhydro--D-glucose) found in particles and methoxyphenols (lignin combustion products found in both gas and particle phase) are source tracers for woodsmoke. Levoglucosan is a conserved and stable organic tracer for ambient exposure measurements. Methoxyphenols, although less stable when collected on filters, are metabolized and excreted as urinary metabolites. In ongoing ambient and personal exposure studies in Seattle, where woodsmoke and mobile sources (diesel and gasoline) are the major sources of PM2.5, both organic and inorganic source tracers are measured in personal, indoor and outdoor filter samples. Urinary samples are collected and metabolites of these source tracers are measured using GC/MS and HPLC. Validation studies include 1) correlating the exposure to methoxyphenols, levoglucosan and PAH in home-indoor and home-outdoor samples, and 2) examining the relationship between exposure to levoglucosan and PAH in personal air samples and excretion of methoxyphenols and PAH metabolites in urine. Initial studies are examining the time course of exposure and excretion over 10 day sampling periods in susceptible and normal populations. These studies have been conducted in subjects (n=6) that experienced a range of PM2.5 exposure variations over the 10 day period. Mean home-outdoor PM2.5 concentrations for these subjects were 18.8 ug/m3; (range 5.0-41.5 ug/m3), and mean home-outdoor levoglucosan concentrations were 501 ng/m3; (range 88-1214 ng/m3). Studies to determine the half-life of these urinary metabolites are also in progress.
This work has been funded by the U S EPA (Cooperative Agreement #R827177 & EPA Northwest Research Center). It has been subjected to Agency review and approved for publication.