title: Environmental exposure to endotoxin in rural and urban Egyptian school children and its relation to asthma and atopy.
abstract: OBJECTIVE
  The environmental exposure of farm children to micro-organisms in dust has been related to a reduced prevalence of asthma and atopy. The aim of this study was to evaluate the relation between settled dust endotoxin and development of asthma and/or atopy in rural and urban school children.
  
  
  METHODS
  A comparative study was conducted on 40 rural and 40 urban school children (6-12 years). Parental self-reported allergic symptoms questionnaires were distributed. Forced expiratory volume in the first second (FEV1), forced vital capacity (FVC) were measured using MIR spirobank and FVE1% was calculated. Skin prick testing with the most common aeroallergens was performed. Limulus amebocyte lysate endotoxin content was measured in settled dust samples.
  
  
  RESULTS
  The rural group which has higher exposure to farm animals and feeding on farm milk has less allergic symptoms. Rural students showed highly significant FEV1, FEV1% and significant FVC versus urban students (110.9±19.7, 103.8±12.2, 105.8±24.3 vs. 92.3±24.2, 98.4±18.9, 92.7±23.2, respectively). Rural school dust contains significantly higher level of endotoxin (2-3 EU/mg) than urban school (0-0.1 EU/mg). Urban residence was associated with increase risk of asthma after age and sex adjustments ([ORadj], 5.16; 95% [CI], 0.95-28).
  
  
  CONCLUSIONS
  Our results support the hygiene theory, i.e., endotoxin exposure could be protective to asthma and atopy in school children.
authors.affiliation: Child Health Department, National Research Centre, Cairo, Egypt. m4morcos@yahoo.com
authors.forename: M M
authors.initials: MM
authors.lastname: Morcos
authors.forename: W M
authors.initials: WM
authors.lastname: Morcos
authors.forename: M A
authors.initials: MA
authors.lastname: Ibrahim
authors.forename: M A
authors.initials: MA
authors.lastname: Shaheen
mesh_terms: D000465:Algorithms; D000485:Allergens / Q000032:analysis; D000818:Animals; D001249:Asthma / Q000175:diagnosis; D002648:Child; D004391:Dust / Q000032:analysis; D004534:Egypt / Q000453:epidemiology; D004731:Endotoxins / Q000032:analysis* / Q000276:immunology; D004781:Environmental Exposure / Q000009:adverse effects / Q000032:analysis*; D005260:Female; D006798:Housing; D006801:Humans; D006969:Hypersensitivity, Immediate / Q000175:diagnosis* / Q000453:epidemiology / Q000276:immunology / Q000517:prevention & control; D008033:Limulus Test; D008297:Male; D015995:Prevalence; D012129:Respiratory Function Tests; D012307:Risk Factors; D012424:Rural Population / Q000706:statistics & numerical data*; D012574:Schools; D012882:Skin Tests; D013334:Students / Q000706:statistics & numerical data*; D011795:Surveys and Questionnaires; D014505:Urban Population / Q000706:statistics & numerical data*
chemical_list: D000485:Allergens; D004391:Dust; D004731:Endotoxins