| Ambient Endotoxin Concentrations in PM10 from Southern California Linda Mueller-Anneling,1 Ed Avol,2 John M. Peters,2 and Peter S. Thorne1 1College of Public Health, The University of Iowa, Iowa City, Iowa, USA; 2Department of Preventive Medicine, University of Southern California, Los Angeles, California, USA Abstract
Concentrations of endotoxin in urban air pollution have not previously been extensively characterized. We measured 24-hr levels of PM10 (particulate matter < 10 µm in aerodynamic diameter) and the associated endotoxin component once every 6 weeks for 1 year in 13 communities in Southern California. All the samples collected had detectable PM10 and endotoxin levels. The geometric mean PM10 was 34.6 µg/m3 [geometric SD (GSD) , 2.1 ; range, 3.0-135]. By volume, the endotoxin geometric mean was 0.44 endotoxin units (EU) /m3 (GSD, 3.1 ; range, 0.03-5.44) . Per unit material collected, the geometric mean of endotoxin collected was 13.6 EU/mg (GSD, 3.2 ; range, 0.7-96.8) . No correlation was found between endotoxin concentrations and other ambient pollutants concurrently measured [ozone, nitrogen dioxide, total acids, or PM2.5 (particulate matter < 2.5 µm in aerodynamic diameter]. PM10 and endotoxin concentrations were significantly correlated, most strongly in summer. Samples collected in more rural and agricultural areas had lower PM10 and mid-range endotoxin levels. The high desert and mountain communities had lower PM10 levels but endotoxin levels comparable with or higher than the rural agricultural sites. By volume, endotoxin levels were highest at sites downwind of Los Angeles, California, which were also the locations of highest PM10. Endotoxin concentrations measured in this study were all < 5.5 EU/m3, which is lower than recognized thresholds for acute adverse health effects for occupational exposures but in the same range as indoor household concentrations. This study provides the first extensive characterization of endotoxin concentration across a large metropolitan area in relation to PM10 and other pollutant monitoring, and supports the need for studies of the role of endotoxin in childhood asthma in urban settings. Key words: air pollution, bioaerosol, endotoxin, lipopolysaccharide, particulate matter. Environ Health Perspect 112:583-588 (2004) . doi:10.1289/ehp.6552 available via http://dx.doi.org/ [Online 14 January 2004]
Address correspondence to P.S. Thorne, Department of Occupational and Environmental Health, University of Iowa College of Public Health, 100 Oakdale Campus, IREH, Iowa City, IA 52242-5000 USA. Telephone: (319) 335-4216. Fax: (319) 335-4006. E-mail: peter-thorne@uiowa.edu We thank air monitoring district personnel for their support ; S. Grossman, R. Eden, J. Courtney, J. Cordes, M. Hossain, R. Ramirez, R. Atkinson, P. Wagner, and K. Anderson for their assistance with air sampling ; and K.M. Kelly for providing statistical support. This work was supported by grants P30 ES05605 and P30 ES007048 from the National Institute of Environmental Health Sciences, National Institutes of Health, Department of Health and Human Services. The authors declare they have no competing financial interests. Received 30 June 2003 ; accepted 14 January 2004.
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