title: School Endotoxin Exposure and Asthma Morbidity in Inner-city Children.
abstract: BACKGROUND
  Endotoxin exposure is associated with airway inflammation. Children spend 6 to 8 h/d in school, yet the effect of school-specific endotoxin exposure on asthma morbidity is not well understood.
  
  
  METHODS
  In this longitudinal cohort study, 248 students with asthma, from 38 inner-city schools, underwent baseline phenotyping and follow-up. Clinical outcomes were evaluated throughout the academic school year and linked to classroom-specific dust and air endotoxin levels as well as home dust endotoxin levels. The primary outcome was maximum asthma symptom-days per 2-week period.
  
  
  RESULTS
  Classrooms had higher settled dust endotoxin levels compared with homes (14.3 endotoxin unit/mg vs 11.3 endotoxin unit/mg; P = .02). Airborne endotoxin levels exceeding recommended occupational exposure limits for adults were recorded in 22.0% of classrooms. Classroom air endotoxin levels were independently associated with increased maximum symptom-days in children with nonatopic asthma, but not in those with atopic asthma (interaction P = .03). Adjusting for home exposures, classroom endotoxin exposure was independently associated with a dose-dependent increase in asthma symptom-days for children with nonatopic asthma (adjusted incidence rate ratio, 1.16 [95% CI, 1.03-1.31]; P = .02). In these subjects, maximum symptom-days increased by 1.3 days for each 14-day period when comparing students in classrooms with the lowest endotoxin levels compared with average measured levels.
  
  
  CONCLUSIONS
  Inner-city children with asthma are exposed to high levels of airborne endotoxin at school, resulting in increased asthma symptoms in children with nonatopic asthma. Mitigation of school-related exposures may represent a strategy to decrease asthma morbidity in this population.
  
  
  BACKGROUND
  ClinicalTrials.gov; No.: NCT01756391; URL: www.clinicaltrials.gov.
authors.affiliation: Division of Pulmonary and Critical Care, Massachusetts General Hospital, Boston, MA; Harvard Medical School, Boston, MA.
authors.forename: Peggy S
authors.initials: PS
authors.lastname: Lai
authors.affiliation: Harvard Medical School, Boston, MA; Boston Children's Hospital, Brigham and Women's Hospital, Boston, MA.
authors.forename: William J
authors.initials: WJ
authors.lastname: Sheehan
authors.affiliation: Harvard Medical School, Boston, MA; Boston Children's Hospital, Brigham and Women's Hospital, Boston, MA.
authors.forename: Jonathan M
authors.initials: JM
authors.lastname: Gaffin
authors.affiliation: Boston Children's Hospital, Brigham and Women's Hospital, Boston, MA.
authors.forename: Carter R
authors.initials: CR
authors.lastname: Petty
authors.affiliation: Department of Environmental Health, Harvard School of Public Health, Boston, MA; Department of Biostatistics, Harvard School of Public Health, Boston, MA.
authors.forename: Brent A
authors.initials: BA
authors.lastname: Coull
authors.affiliation: Harvard Medical School, Boston, MA; Boston Children's Hospital, Brigham and Women's Hospital, Boston, MA; Channing Laboratory, Brigham and Women's Hospital, Boston, MA.
authors.forename: Diane R
authors.initials: DR
authors.lastname: Gold
authors.affiliation: Harvard Medical School, Boston, MA; Boston Children's Hospital, Brigham and Women's Hospital, Boston, MA. Electronic address: wanda.phipatanakul@childrens.harvard.edu.
authors.forename: Wanda
authors.initials: W
authors.lastname: Phipatanakul
mesh_terms: D000293:Adolescent; D016902:Air Pollution, Indoor / Q000009:adverse effects*; D001249:Asthma / Q000453:epidemiology*; D001900:Boston / Q000453:epidemiology; D002648:Child; D002675:Child, Preschool; D004731:Endotoxins / Q000009:adverse effects*; D004781:Environmental Exposure / Q000009:adverse effects*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D009017:Morbidity / Q000639:trends; D011446:Prospective Studies; D013334:Students / Q000706:statistics & numerical data; D014505:Urban Population
chemical_list: D004731:Endotoxins