Predictors of Endotoxin Levels in U.S. Housing

Environmental Health Sciences Research Center, College of Public Health, University of Iowa, Iowa City, Iowa 52242-5000, USA.
Environmental Health Perspectives (Impact Factor: 7.98). 06/2009; 117(5):763-71. DOI: 10.1289/ehp.11759
Source: PubMed


The relationship of domestic endotoxin exposure to allergy and asthma has been widely investigated. However, few studies have evaluated predictors of household endotoxin, and none have done so for multiple locations within homes and on a national scale.
We assayed 2,552 house dust samples in a nationwide study to understand the predictors of household endotoxin in bedroom floors, family room floors, beds, kitchen floors, and family room sofas.
Reservoir house dust from five locations within homes was assayed for endotoxin and demographic and housing information was assessed through questionnaire and onsite evaluation of 2,456 residents of 831 homes selected to represent national demographics. We performed repeated-measures analysis of variance (rANOVA) for 37 candidate variables to identify independent predictors of endotoxin. Meteorologic data were obtained for each primary sampling unit and tested as predictors of indoor endotoxin to determine if wetter or warmer microclimates were associated with higher endotoxin levels.
Weighted geometric mean endotoxin concentration ranged from 18.7 to 80.5 endotoxin units (EU)/mg for the five sampling locations, and endotoxin load ranged from 4,160 to 19,500 EU/m(2). Bivariate analyses and rANOVA demonstrated that major predictors of endotoxin concentration were sampling location in the home, census division, educational attainment, presence of children, current dog ownership, resident-described problems with cockroaches, food debris, cockroach stains, and evidence of smoking observed by field staff. Low household income entered the model if educational attainment was removed.
Increased endotoxin in household reservoir dust is principally associated with poverty, people, pets, household cleanliness, and geography.

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    • "Samples were analyzed for endotoxin, a cell wall component of gram-negative bacteria and a potent inflammatory agent and asthma trigger (Thorne et al. 2009). Samples were also analyzed for (1→3)-β-D-glucans, non-allergenic structural wall components of most fungi and certain bacteria that may play a role in the development of respiratory symptoms (Douwes 2005). "
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    ABSTRACT: Exposures to particulate matter (PM) re-suspended by traffic from paved roads are ubiquitous, but little is known about the variability in composition of paved road dust (PRD). This knowledge gap hinders estimates of exposure to PM components near roadways. Respirable fractions of PRD collected from multiple U.S. regions and site types were analyzed to explore chemical composition and variability. Fifty samples were collected from streets, traffic arterials, street canyons, freeways, and industrial sites in six urban regions in the southwestern, Southern California, northeastern, and southeastern U.S. regions and five rural sites. Samples were sieved, aerosolized, and size-classified into fine (PM2.5) and coarse (PM10-2.5) fractions. Analyses included metals and other elements, organic and elemental carbon, inorganic ions, endotoxin and glucan. Crustal elements, organic carbon, and reactive metals comprised the PRD mass with smaller fractions of elemental carbon and inorganic ions. Proportions of many inorganic components were strongly correlated between particle sizes, but fine and coarse organic carbon poorly correlated. Composition varied both among and within regions and site types, with evidence that chemical signatures varied more systematically by region than by site type. Local sources strongly influenced some samples. Samples from large urban areas had greater contents of reactive metals, but these comprised less than 0.2 % of the mass. Near-feedlot samples had high levels of endotoxin. The results provide insight into the variability of PRD composition, differences between re-suspended PRD and regional airborne PM, and improved source signatures for estimates of exposure to different PM components near roadways.
    Air Quality Atmosphere & Health 09/2013; 6(3). DOI:10.1007/s11869-013-0200-4 · 1.80 Impact Factor
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    • "Many other studies have also assessed respiratory and allergic health effects of endotoxin using only house dust samples as a surrogate of subject exposures to airborne endotoxin, often with only one measurement. However, exposure studies have shown considerable within-home, and temporal variability of house dust endotoxin [6-8]. Furthermore, the exposures of interest come from resuspended indoor dust and endotoxin infiltrated from outdoor air that both determine indoor airborne concentrations. "
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