title: Endotoxin exposure and atopic sensitization in adult pig farmers.
abstract: BACKGROUND
  Recent studies have reported a low prevalence of atopic sensitization and respiratory allergy in children growing up on farms.
  
  
  OBJECTIVE
  We sought to evaluate the dose-response relationship between endotoxin and atopic sensitization in adult farmers and to assess the effect on respiratory health outcomes.
  
  
  METHODS
  Data on endotoxin exposure and serum IgE levels were available for 162 pig farmers from a cross-sectional case-control study, with case selection on the basis of respiratory symptoms. Exposure to endotoxin was modeled in detail, and respiratory health effects were assessed during a medical examination. Exploratory analysis was done by using nonparametric modeling and was followed by classical parametric regression.
  
  
  RESULTS
  IgE to one or more common allergens was detected in sera from 28 (17%) farmers. The average (geometric mean) total serum IgE levels was 37 IU/mL (geometric SD, 4 IU/mL). A strong inverse relationship was found between endotoxin and sensitization to common allergens for exposures of 75 ng/m 3 or less, with an odds ratio of 0.03 (95% CI, 0.0-0.34) for a 2-fold increase in endotoxin. For endotoxin exposure of greater than 75 ng/m 3 , the association was weak (odds ratio, 1.2 [95% CI, 0.38-3.6]). No association was found between endotoxin exposure and total serum IgE levels. Endotoxin was associated with increased airway hyperresponsiveness to histamine and lower lung function in sensitized farmers, without evidence of a nonlinear relationship.
  
  
  CONCLUSIONS
  The prevalence of atopic sensitization in adult pig farmers is low. Endotoxin or related exposures might protect from sensitization, even in an adult working population exposed to high levels of endotoxin, but is a risk factor for increased airway hyperresponsiveness and low lung function.
authors.affiliation: Institute for Risk Assessment Sciences, University of Utrecht, PO Box 80176, 3508 TD Utrecht, The Netherlands. L.Portengen@iras.uu.nl
authors.forename: Lützen
authors.initials: L
authors.lastname: Portengen
authors.forename: Liesbeth
authors.initials: L
authors.lastname: Preller
authors.forename: Martin
authors.initials: M
authors.lastname: Tielen
authors.forename: Gert
authors.initials: G
authors.lastname: Doekes
authors.forename: Dick
authors.initials: D
authors.lastname: Heederik
mesh_terms: D000328:Adult; D000382:Agricultural Workers' Diseases / Q000453:epidemiology* / Q000276:immunology; D000383:Agriculture; D000818:Animals; D001985:Bronchial Provocation Tests; D004731:Endotoxins / Q000276:immunology*; D006801:Humans; D006969:Hypersensitivity, Immediate / Q000453:epidemiology* / Q000276:immunology; D007073:Immunoglobulin E / Q000097:blood; D016273:Occupational Exposure; D015995:Prevalence; D012129:Respiratory Function Tests; D034421:Sus scrofa
chemical_list: D004731:Endotoxins; D007073:Immunoglobulin E