title: Personal endotoxin exposure in a panel study of school children with asthma.
abstract: BACKGROUND
  Endotoxin exposure has been associated with asthma exacerbations and increased asthma prevalence. However, there is little data regarding personal exposure to endotoxin in children at risk, or the relation of personal endotoxin exposure to residential or ambient airborne endotoxin. The relation between personal endotoxin and personal air pollution exposures is also unknown.
  
  
  METHODS
  We characterized personal endotoxin exposures in 45 school children with asthma ages 9-18 years using 376 repeated measurements from a PM2.5 active personal exposure monitor. We also assayed endotoxin in PM2.5 samples collected from ambient regional sites (N = 97 days) and from a subset of 12 indoor and outdoor subject home sites (N = 109 and 111 days, respectively) in Riverside and Whittier, California. Endotoxin was measured using the Limulus Amoebocyte Lysate kinetic chromogenic assay. At the same time, we measured personal, home and ambient exposure to PM2.5 mass, elemental carbon (EC), and organic carbon (OC). To assess exposure relations we used both rank correlations and mixed linear regression models, adjusted for personal temperature and relative humidity.
  
  
  RESULTS
  We found small positive correlations of personal endotoxin with personal PM2.5 EC and OC, but not personal PM2.5 mass or stationary site air pollutant measurements. Outdoor home, indoor home and ambient endotoxin were moderately to strongly correlated with each other. However, in mixed models, personal endotoxin was not associated with indoor home or outdoor home endotoxin, but was associated with ambient endotoxin. Dog and cat ownership were significantly associated with increased personal but not indoor endotoxin.
  
  
  CONCLUSIONS
  Daily fixed site measurements of endotoxin in the home environment may not predict daily personal exposure, although a larger sample size may be needed to assess this. This conclusion is relevant to short-term exposures involved in the acute exacerbation of asthma.
authors.affiliation: Department of Epidemiology, School of Medicine, University of California, Irvine, Irvine, CA 92617-7555, USA. rdelfino@uci.edu
authors.forename: Ralph J
authors.initials: RJ
authors.lastname: Delfino
authors.forename: Norbert
authors.initials: N
authors.lastname: Staimer
authors.forename: Thomas
authors.initials: T
authors.lastname: Tjoa
mesh_terms: D000293:Adolescent; D000393:Air Pollutants / Q000009:adverse effects / Q000032:analysis*; D000818:Animals; D001249:Asthma / Q000139:chemically induced* / Q000453:epidemiology; D002140:California / Q000453:epidemiology; D002244:Carbon / Q000032:analysis / Q000633:toxicity; D002415:Cats; D002648:Child; D004285:Dogs; D004731:Endotoxins / Q000032:analysis* / Q000633:toxicity; D004784:Environmental Monitoring; D062665:Epidemiological Monitoring; D005260:Female; D006801:Humans; D019570:Inhalation Exposure / Q000009:adverse effects / Q000032:analysis*; D016014:Linear Models; D008137:Longitudinal Studies; D008297:Male; D009585:Nitrogen Dioxide / Q000032:analysis / Q000633:toxicity; D052638:Particulate Matter / Q000032:analysis* / Q000633:toxicity; D057805:Pets; D015203:Reproducibility of Results; D012111:Residence Characteristics; D012621:Seasons; D018709:Statistics, Nonparametric; D013997:Time Factors
chemical_list: D000393:Air Pollutants; D004731:Endotoxins; D052638:Particulate Matter; D002244:Carbon; D009585:Nitrogen Dioxide