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Table 2 Study characteristics of studies with occupational populations

From: Respiratory health effects of exposure to low levels of airborne endotoxin – a systematic review

Occupational populations
Author (Year) Country Study designa Population Ageb,c Endotoxin assessment methods Exposure variables measured Duration of exposured Spirometry Questionnaire Confounders accounted for
Kawamoto et al. (1987) US [48] CS 128 cotton workers 35.6–38.6 (±2.47–2.90) -Area sampling
-breathing zone height
-LAL assay
Total dust, endotoxin, oil mist and boric acid 6.3–13.1 (±1.28–2.03) FVC and FEV1 Standardized questionnaire Age, smoking
Kateman et al. (1990) Netherlands [32] L: follow up 5 days 40 textile yarn workers exposed to spray-humidifier, 42 controls exposed to other or no humidifier 30 -Personal sampling
-Glass fibre filter
- 2.0 L/min
-LAL assay
Dust, endotoxin, fungi, bacteria FVC, FEV1, PEF, MEF75, MEF50, MEF25, MMEF Modified MRC questionnaire Smoking, age, height, standing height
Dahlqvist et al. (1992) Sweden [52] CS 28 wood trimmers, 19 office workers (controls) S: 37 (±11), C:42 (±8) -Personal sampling
-Millipore filter
- 2 L/min
-LAL assay
Dust, endotoxin, moulds and bacteria, terpenes 13 (±11) FEV1 and FVC, MEF50, MEF25 Modified MRC questionnaire Smoking
Sprince et al. (1997) US [54] CS 183 machine workers in automobile industry, 66 assemblers (controls) 43.2–43.7 (± 7.6–8.4) -Area and personal sampling
-MCE filters
-LAL assay
MWF, total aerosol, endotoxin, total fungi, total bacteria, total organisms S: 12 (±9) years, C: 8 (±8) years (p = 0.023) FEV1 and FVC Modified ATS-DLD questionnaire Smoking status, gender, age, race
Zock et al. (1998) Netherlands [39] CS 57 potato processing workers 39–41 (±7–10) -Personal sampling
-Glass fibre filter
- 2.0 L/min
-LAL assay
Endotoxin exposure 13–14 years (± 7–9) FVC, FEV1, MMEF and PEF MRC questionnaire Smoking
Mandryk et al. (1999) Australia [53] CS 168 wood workers, 30 maintenance workers (controls) S: 37 (± 12.8), C:39 (±11.7) -Personal sampling
-Polycarbonate filter 25 mm
-LAL assay
Airborne dust, endotoxin, micro-organisms, (1- > 3)-B-D-glucan 11 (±10.6 years) VC, FEV1 and FVC Combination of the Organic Dust Questionnaire and the MRC respiratory questionnaire Age, height, smoking, number of years of exposure
Mahar et al. (2002) UK [40] L: follow up 5 years 87 refuse derived fuel plant workers 39.9–41.4 (SD 8.0–8.1) -Personal and area sampling
-0.45 μm endotoxin free filters
-LAL assay
Airborne endotoxin 7.7–11 years (SD 5.4–5.9) FEV1 and FVC Questionnaire Smoking, length of employment
Wouters et al. (2002) Netherlands [59] CS 47 waste collecting workers, 15 controls S:34.0 (SD 10.2) C: 36.4 (SD 6.4) -Personal sampling -Glass fibre filter
-3.5 L/min
-LAL assay
Dust, endotoxin, β(1-- > 3)-glucan Median 5 years Modified MRC questionnaire -
Fransman et al. (2003) New Zealand [55] CS 112 plywood mill workers, 415 controls of the general population S: 34.5 (±9.1), C: 32.5 (±7.2) -Personal sampling
-Glass fibre filter
-2.0 L/min
-LAL assay
Inhalable dust, endotoxin, abietic acid, terpenes, formaldehyde 4.7 years (±3.5) Combination of ISAAC, MRC and ECRHS questionnaires Age, gender, ethnicity
Heldal et al. (2004) Norway [36] CS 22 waste collection workers AM: 32 (range 20–62) -Personal sampling
-25 mm polycarbonate filter
-2 L/min -LAL assay
Total dust, endotoxin, bacteria, fungal spores Questionnaire Age, smoking
Kennedy et al. (2004) Canada [34] Ee: follow up 1 month 226 glass bottle recycling workers, 212 ferry workers (controls) S: 41.2–45.5 (±8.4–9.0) -Personal sampling -2 L/min
-LAL assay
Endotoxin, dust, fungi 12.0–17.3 years (±7.4–8.4) Modified ATS questionnaire Age, gender, race, smoking status, history of hay fever and asthma
Sigsgaard et al. (2004) Denmark [33] L: follow up 11 years 97 paper mill workers, 55 water-supply workers (controls) 39–43 (±7–9) -Personal sampling
- 37 micropore filters
-LAL assay
Total dust, endotoxin, micro-organisms FVC and FEV1 Age, smoking, atopy
Smit et al. (2005) Netherlands [41] CS 371 waste water workers; 97 office staff, 2698 general population members (controls) 43.4–47.3 (± 9.9–10.1) -Personal sampling
-Glass fibre filter
- 3.5 L/min
-LAL assay
Endotoxin 12.6–14.9 years (±9.0–10.2) Questionnaire specifically developed for bioaerosol related health effects in waste recycling and composting industry Age, gender and smoking habits
Widmeier et al. (2007) Switzerland [42] CS 409 wastewater-and garbage workers, 369 public transport and forestry workers (controls) median 41–47 (5th–95th% 22–58) -Personal and area sampling
-LAL assay
Endotoxin exposure FVC and FEV1 Questions from SAPALDIA-study questionnaire Age, gender, height, packyears, BMI, serum creatinine, job change, smoking history
Rusca et al. (2008) Switzerland [60] CS 111 sawmill workers group 1: 26.5 (±9.5), group 2: 36.7 (±8.5), group 3: 47.7 (±8.2) -Area sampling
-Glass fibre filter
- 2.0 L/min
-LAL assay
Airborne dust, endotoxin, fungi and bacteria group 1: 1–5 years, group 2: 5–20 years, group 3: > 20 years FVC and FEV1 Combination of the Organic Dust Questionnaire and the MRC respiratory questionnaire Height and packyears of cigarette smoking
Dang et al. (2010) US [49] CS 69 water resort workers, 74 office workers (controls) S: 20 (range 16–50), C: 31 (range 15-61) -Area sampling
-Polyvinyl-chloride filters
- 2 L/min
- LAL assay
Chloramines, endotoxin, Legionella, Mycobacterium 2.8 months Questionnaire Smoking, asthma status
Renström et al. (2011) Sweden [50] CS 59 pet shop workers 31.4 (±9.9) -Personal sampling
-1 μm filter
- 2.0 L/min
-LAL assay
Endotoxin and aeroallergens 9.4 (±7.4) VC, FVC and FEV1 Questionnaire Smoking, gender,
Schlünssen et al. (2011) Denmark [57] CS 232 woodchip and straw workers, 107 workers in oil/gas power plants (controls) S: 45.9–47.7(SD 8.6–9.3), C:48.1 (SD 10.0) -Stationary air sampling
-Teflon filters
- 1.9 L/min
-LAL assay
Endotoxin, total dust and fungi 7–10.9 years FVC and FEV1 Modified ECRHS questionnaire Gender, height, weight, atopy, age and smoking
Meza et al. (2013) US [56] CS 183 aircraft workers exposed to MWF, 224 office workers (controls) S: 95% > 45 C: 92% > 45 -Area air sampling
- 0.45 μm filter
-2 L/min
-LAL assay
Metal working fluids, endotoxin, bacteria Questionnaire based on the ECRHS Age, gender, smoking status and hours worked per week
Shiryaeva et al. (2014) Norway [58] CS 70 salmon processing workers 40.1 (±11.5) -Personal sampling
-Glass fibre filter
- 2.5 L/min
-LAL assay
Endotoxin, parvalbumin and total protein FEV1 Modified MRC questionnaire Age, gender, asthma, smoking and height
Cyprowski et al. (2015) Poland [43] CS 78 sewage workers 43 -Personal sampling
-25 mm glass-fibre filter
-2 L/min
-LAL assay
Endotoxin in inhalable dust 8.5 years FEV1 and FVC Inhalable dust, smoking habits
Heldal et al. (2015) Norway [51] CS 47 compost workers, 37 office controls S: 41–42 (± 9–11), C: 43 (±10) -Personal sampling
-Glass fibre filter
- 2.0 L/min
-LAL assay
Dust, endotoxin, bacteria, fungal spores, actinomycetes FEV1/FVC and FEV1 Questionnaire Smoking packyears, age, atopy
Ghani et al. (2016) Pakistan [44] CS 100 textile mill workers, 100 controls 3 groups: < 30, 30–40, > 40 -Area air sampling
-Glass fibre filter
-LAL assay
Airborne endotoxin ≥5 years FEV1, FVC, FEV1/FVC, PEF Modified ATS questionnaire Age, duration of exposure
  1. aCS cross-sectional, L longitudinal, E experimental
  2. bS exposed subjects, C controls
  3. cAge: mean, presented as range if mean age is presented for subgroups only
  4. dPresented as mean, unless stated otherwise
  5. eHalf of the participating shops shut down glass-breaking activity during this experiment