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Recovery from workplace-induced airway inflammation 1 year after cessation of exposure
  1. Liv Ingunn Bjoner Sikkeland1,
  2. Wijnand Eduard2,
  3. Marit Skogstad3,
  4. Neil E Alexis4,
  5. Johny Kongerud1
  1. 1Department of Respiratory Medicine, Oslo University Hospital, Rikshospitalet, University of Oslo, Oslo, Norway
  2. 2Department of Chemical and Biological Work Environment, National Institute of Occupational Health, Oslo, Norway
  3. 3Department of Occupational Medicine, National Institute of Occupational Health, Oslo, Norway
  4. 4Department of Pediatrics, Centre for Environmental Medicine, Asthma and Lung Biology, University of North Carolina, Chapel Hill, North Carolina, USA
  1. Correspondence to Liv Ingunn Bjoner Sikkeland, Department of Respiratory Medicine, Oslo University Hospital, Rikshospitalet, University of Oslo, Oslo N-0027, Norway; l.i.b.sikkeland{at}


Background Bacterial single-cell protein (BSCP) constitutes of dried bacterial mass which is used as protein enrichment in animal and fish feed. In the production of BSCP, workers are exposed to organic dust containing high levels of endotoxins (arithmetic mean 390 EU/m3 in the moderate exposure and 5800–11 000 EU/m3 in the high exposure groups) and have elevated levels of sputum neutrophils and cytokines associated with exposure.

Objective The aim of the present study was to investigate if airway inflammation among the workers had declined 1 year after cessation of exposure.

Methods Twenty-four non-smoking production workers (age 28–52) with a work history of 2–7 years were included in the study.

Measurements Markers of airways inflammation and innate immune function (using flow cytometry) were assessed in an exposure period and 1 year after cessation of exposure.

Results Sputum neutrophil proportion and numbers were significantly decreased 1 year after cessation of exposure to BSCP (43% vs 71%, 186 vs 598 neutrophils/mg sputum; p<0.001) as were eNO (17 ppb vs 21 ppb (p=0.01) and interleukin-1β (p<0.05) and interleukin-8 (p<0.05). Neutrophils had enhanced expression of CD11b/CR3 (p<0.01) and CD16/FcγRIII (p<0.001) and macrophages had lower expression of CD86 (p<0.01) 1 year after cessation of exposure.

Conclusions One year after closure of the plant airway neutrophils and exhaled NO levels resolved to lower levels and cell surface phenotypes associated with innate immune function recovered to higher levels, indicating that these changes were partly reversible among workers who were no longer exposed to endotoxins in a BSCP plant.

  • Cytokine
  • endotoxins
  • flow cytometry
  • gram-negative bacteria and sputum analysis
  • general expertise
  • cell biology
  • organ system
  • disease
  • disease type
  • respiratory
  • hygiene/occupational hygiene
  • epidemiology
  • methodology
  • specialty
  • exposure monitoring
  • exposure assessment

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  • Funding Financial support was kindly provided by Statoil's Fund for Research in Occupational Medicine, the Research Council of Norway and the Working Environmental Fund granted by the Confederation of Norwegian Enterprise.

  • Competing interests None.

  • Patient consent Obtained.

  • Ethics approval The study protocol was approved by the Regional Committee for Research Ethics, Trondheim, Norway.

  • Provenance and peer review Not commissioned; externally peer reviewed.