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. 2010 Oct;118(10):1490-6.
doi: 10.1289/ehp.0901602. Epub 2010 May 21.

Temporal and spatial patterns of ambient endotoxin concentrations in Fresno, California

Ira B Tager  1 , Frederick W Lurmann, Thaddeus Haight, Siana Alcorn, Bryan Penfold, S Katharine Hammond
Affiliations

Temporal and spatial patterns of ambient endotoxin concentrations in Fresno, California

Ira B Tager et al. Environ Health Perspect. 2010 Oct.

Abstract

Background: Endotoxins are found in indoor dust generated by human activity and pets, in soil, and adsorbed onto the surfaces of ambient combustion particles. Endotoxin concentrations have been associated with respiratory symptoms and the risk of atopy and asthma in children.

Objective: We characterized the temporal and spatial variability of ambient endotoxin in Fresno/Clovis, California, located in California's Central Valley, to identify correlates and potential predictors of ambient endotoxin concentrations in a cohort of children with asthma [Fresno Asthmatic Children's Environment Study (FACES)].

Methods: Between May 2001 and October 2004, daily ambient endotoxin and air pollutants were collected at the central ambient monitoring site of the California Air Resources Board in Fresno and, for shorter time periods, at 10 schools and indoors and outdoors at 84 residences in the community. Analyses were restricted to May-October, the dry months during which endotoxin concentrations are highest.

Results: Daily endotoxin concentration patterns were determined mainly by meteorologic factors, particularly the degree of air stagnation. Overall concentrations were lowest in areas distant from agricultural activities. Highest concentrations were found in areas immediately downwind from agricultural/pasture land. Among three other measured air pollutants [fine particulate matter, elemental carbon (a marker of traffic in Fresno), and coarse particulate matter (PMc)], PMc was the only pollutant correlated with endotoxin. Endotoxin, however, was the most spatially variable.

Conclusions: Our data support the need to evaluate the spatial/temporal variability of endotoxin concentrations, rather than relying on a few measurements made at one location, in studies of exposure and and respiratory health effects, particularly in children with asthma and other chronic respiratory diseases.

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Figures

Figure 1
Figure 1
Map of study area with air quality (AQ) monitoring locations, major roadways, and agricultural land use. CAFO, concentrated animal feeding operations.
Figure 2
Figure 2
(A) Average endotoxin concentrations during the warm season in Fresno; (B) average PM2.5 concentrations during the warm season in Fresno; (C) average PMc concentrations during the warm season in Fresno; (D) average EC concentrations during the warm season in Fresno. Colors represent different scaling for each pollutant. Bias for all pollutants ranged between 1% to 5%, on average, but measurements were less accurate for the pollutants with more spatial variability (e.g., endotoxin). The average errors in daily mapped concentrations were ± 12%, ± 20%, ± 25%, and ± 28% for PM2.5, PMc, EC, and endotoxin. The coefficients of determination (r2) were 0.86, 0.58, 0.48, and 0.34 for PM2.5, EC, PM2.5–10, and endotoxin, respectively. Dotted lines divide study area into quadrants.
See this image and copyright information in PMC

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