title: Exposure to high endotoxin concentration increases wheezing prevalence among laboratory animal workers: a cross-sectional study.
abstract: BACKGROUND
  Endotoxin from Gram-negative bacteria are found in different concentrations in dust and on the ground of laboratories dealing with small animals and animal houses.
  
  
  METHODS
  Cross-sectional study performed in workplaces of two universities. Dust samples were collected from laboratories and animal facilities housing rats, mice, guinea pigs, rabbits or hamsters and analyzed by the "Limulus amebocyte lysate" (LAL) method. We also sampled workplaces without animals. The concentrations of endotoxin detected in the workplaces were tested for association with wheezing in the last 12 months, asthma defined by self-reported diagnosis and asthma confirmed by bronchial hyperresponsiveness (BHR) to mannitol.
  
  
  RESULTS
  Dust samples were obtained at 145 workplaces, 92 with exposure to animals and 53 with no exposure. Exposed group comprised 412 subjects and non-exposed group comprised 339 subjects. Animal-exposed workplaces had higher concentrations of endotoxin, median of 34.2 endotoxin units (EU) per mg of dust (interquartile range, 12.6-65.4), as compared to the non-exposed group, median of 10.2 EU/mg of dust (interquartile range, 2.6-22.2) (p < 0.001). The high concentration of endotoxin (above whole sample median, 20.4 EU/mg) was associated with increased wheezing prevalence (p < 0.001), i.e., 61 % of workers exposed to high endotoxin concentration reported wheezing in the last 12 months compared to 29 % of workers exposed to low endotoxin concentration. The concentration of endotoxin was not associated with asthma report or with BHR confirmed asthma.
  
  
  CONCLUSIONS
  Exposure to endotoxin is associated with a higher prevalence of wheezing, but not with asthma as defined by the mannitol bronchial challenge test or by self-reported asthma. Preventive measures are necessary for these workers.
authors.affiliation: Department of Social Medicine, Medical School of Ribeirão Preto, University of São Paulo, Ribeirão Preto, Brazil.
authors.forename: Amanda Souza
authors.initials: AS
authors.lastname: Freitas
authors.affiliation: Department of Medicine, Medical School of Ribeirão Preto, University of São Paulo, Ribeirão Preto, Brazil.
authors.forename: Christian Silva
authors.initials: CS
authors.lastname: Simoneti
authors.affiliation: Department of Medicine, Medical School of Ribeirão Preto, University of São Paulo, Ribeirão Preto, Brazil.
authors.forename: Erica
authors.initials: E
authors.lastname: Ferraz
authors.affiliation: Department of Preventive and Social Medicine, State University of Campinas, Campinas, Brazil.
authors.forename: Ericson
authors.initials: E
authors.lastname: Bagatin
authors.affiliation: Department of Biochemistry and Immunology, Medical School of Ribeirão Preto, University of São Paulo, Ribeirão Preto, Brazil.
authors.forename: Izaira Tincani
authors.initials: IT
authors.lastname: Brandão
authors.affiliation: Department of Biochemistry and Immunology, Medical School of Ribeirão Preto, University of São Paulo, Ribeirão Preto, Brazil.
authors.forename: Celio Lopes
authors.initials: CL
authors.lastname: Silva
authors.affiliation: Department of Medicine, Medical School of Ribeirão Preto, University of São Paulo, Ribeirão Preto, Brazil.
authors.forename: Marcos Carvalho
authors.initials: MC
authors.lastname: Borges
authors.affiliation: Department of Medicine, Medical School of Ribeirão Preto, University of São Paulo, Ribeirão Preto, Brazil. evianna@fmrp.usp.br.
authors.forename: Elcio Oliveira
authors.initials: EO
authors.lastname: Vianna
mesh_terms: D000328:Adult; D016902:Air Pollution, Indoor / Q000009:adverse effects*; D000818:Animals; D001249:Asthma / Q000150:complications / Q000453:epidemiology*; D001938:Brazil / Q000453:epidemiology; D016535:Bronchial Hyperreactivity; D006224:Cricetinae; D003430:Cross-Sectional Studies; D004731:Endotoxins / Q000009:adverse effects*; D005260:Female; D006168:Guinea Pigs; D006801:Humans; D008297:Male; D051379:Mice; D009784:Occupational Diseases / Q000453:epidemiology* / Q000209:etiology; D016273:Occupational Exposure / Q000009:adverse effects*; D015995:Prevalence; D011817:Rabbits; D051381:Rats; D012135:Respiratory Sounds / Q000209:etiology*
chemical_list: D004731:Endotoxins
keywords: Animal handler; Endotoxin; Occupational disease; Wheezing