title: Endotoxin exposure is a risk factor for asthma: the national survey of endotoxin in United States housing.
abstract: BACKGROUND
  Although research has shown that early life exposure to household endotoxin protects against development of allergies, studies are less clear on the relationship between household endotoxin exposure and prevalence of wheezing and asthma. We assayed 2,552 house dust samples in a representative nationwide sam- ple to explore relationships between endotoxin exposures and risk factors for asthma, asthma symptoms, and medication use.
  
  
  METHODS
  House dust was vacuum-sampled from five locations within homes and assayed for endotoxin. Health, demographic, and housing information was assessed through questionnaire and on-site evaluation of 2,456 residents of 831 homes selected to represent the demographics of the United States.
  
  
  RESULTS
  Endotoxin concentration (EU/mg) and load (EU/m(2)) were highly correlated (r = 0.73-0.79). Geometric mean endotoxin concentrations were as follows (in EU/mg): bedroom floors, 35.3 (5th-95th percentile, 5.0-260); bedding, 18.7 (2.0-142); family room floors, 63.9 (11.5-331); sofas, 44.8 (6.4-240); and kitchen floors, 80.5 (9.8-512). Multivariate analysis demonstrated significant relationships between increasing endotoxin levels and diagnosed asthma, asthma symptoms in the past year, current use of asthma medications, and wheezing among residents of the homes. These relationships were strongest for bedroom floor and bedding dust and were observed in adults only. Modeling the joint effect of bedding and bedroom floor endotoxin on recent asthma symptoms yielded an adjusted odds ratio of 2.83 (95% confidence interval, 1.01-7.87). When stratified by allergy status, allergic subjects with higher endotoxin exposure were no more likely to have diagnosed asthma or asthma symptoms than nonallergic subjects.
  
  
  CONCLUSIONS
  This study demonstrates that household endotoxin exposure is a significant risk factor for increased asthma prevalence.
authors.affiliation: Department of Occupational and Environmental Health, College of Public Health, University of Iowa, 100 Oakdale Campus, 176 IREH, Iowa City, IA 52242-5000, USA. peter-thorne@uiowa.edu
authors.forename: Peter S
authors.initials: PS
authors.lastname: Thorne
authors.forename: Katarina
authors.initials: K
authors.lastname: Kulhánková
authors.forename: Ming
authors.initials: M
authors.lastname: Yin
authors.forename: Richard
authors.initials: R
authors.lastname: Cohn
authors.forename: Samuel J
authors.initials: SJ
authors.lastname: Arbes
authors.forename: Darryl C
authors.initials: DC
authors.lastname: Zeldin
mesh_terms: D000328:Adult; D000393:Air Pollutants / Q000009:adverse effects* / Q000737:chemistry; D001249:Asthma / Q000139:chemically induced* / Q000453:epidemiology; D004391:Dust / Q000032:analysis; D004731:Endotoxins / Q000009:adverse effects* / Q000032:analysis; D006306:Health Surveys; D006798:Housing; D006801:Humans; D016017:Odds Ratio; D015995:Prevalence; D012307:Risk Factors; D011795:Surveys and Questionnaires; D014481:United States / Q000453:epidemiology
chemical_list: D000393:Air Pollutants; D004391:Dust; D004731:Endotoxins