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Table 3 Summary of main results on airborne endotoxin exposure and respiratory outcomes assessed by questionnaires and spirometry

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

Results
Author (year) Population Levels of airborne endotoxin exposure (EU/m3) Conclusion
Non-occupational populations
Rabinovitch et al. (2005) [45] 24 asthmatic school-children Interval 1: median 0.08 EU/m3, IQR 0.09 Higher personal endotoxin exposure was significantly related to more sleep-related asthma complaints and decreased evening FEV1 in children with asthma in a dose-dependent manner.
Interval 2: median 0.37 EU/m3, IQR 0.16
Schiffman et al. (2005) [35] 48 healthy subjects 7.40 EU/m3 No statistical significant effects of the 1 h exposure to endotoxin on lung function changes or respiratory symptoms.
Hoopmann et al. (2006) [37] 3867 children Median 0.064 EU/m3, IQR 0.025–0.141a Increase of asthmatic symptoms and wheezing due to exposure to airborne endotoxin was significant for children of atopic parents.
Horick et al. (2006) [38] 360 children Mean 0.81 EU/m3, range 0.23–5.87 Exposure to airborne endotoxin leads to a significant increase in prevalence of wheeze.
Ramagopal et al. (2014) [61] 75 children SIM: median 0.6 EU/m3, range 0.03–8.6 No significant differences in prevalence of wheeze or asthma symptoms among children exposed to different levels of endotoxin.
PIPER: median 1.0 EU/m3, range 0.09–16
Delfino et al. (2015) [46] 43 asthmatic school-children Mean 2.04 EU/m3 (±3.71), range 0.002–25.3 Personal endotoxin exposure was not associated with acute daily changes in FEV1 overall. Among patients with %predicted FEV1 < 80%, however, daily FEV1 significantly decreased with increase in personal endotoxin exposure with 2.19 EU/m3.
Lai et al. (2015) [47] 248 asthmatic school-children GM 24.7 EU/m3, range 0.2–780.0 (of which 78% < 90 EU/m3) In subjects who were non-atopic, higher concentrations of school air endotoxin were significantly associated with increased daytime wheeze, exercise related symptoms and maximum symptom days in a dose-dependent manner.
Bose et al. (2016) [62] 84 COPD patients Mean 0.55 EU/m3 (±1.3) No significant associations between airborne endotoxin and increased respiratory/COPD morbidity.
Occupational populations
Kawamoto et al. (1987) [48] 128 cotton workers 3 groups: < 17 EU/m3, 17–117 EU/m3 and > 117 EU/m3a A non-significant decrease in FEV1 was seen in workers exposed to more than 17 EU/m3.
Kateman et al. (1990) [32] 40 textile yarn workers exposed to spray-humidifier, 42 controls exposed to other or no humidifier. GM 0.64 EU/m3 (GSD 0.016) for cold-water humidification area, 0.18–0.19 EU/m3 for other areas. Significant cross-work shift decreases in multiple lung function variables were found for the workers in the cold-water humidification area. Also, a decrease in multiple lung function variables was visible over the week for these workers.
Dahlqvist et al. (1992) [52] 28 wood trimmers, 19 controls (office workers) 15–25 EU/m3a Significantly higher prevalence of dry cough, cough with phlegm and breathlessness among exposed workers. Wood trimmers seropositive for precipitating antibodies to moulds showed a significant decrease in FEV1 over a workweek. Subjects with a period of employment > 18 years had a significantly larger change in MEF over the workweek than subjects employed < 6 years.
Sprince et al. (1997) [54] 183 machine workers in automobile industry. 66 assemblers (controls). GM 31 EU/m3, range 2.7–984 Significant difference in prevalence of cough and work-related chest tightness between exposed subjects and controls. Usual phlegm showed a significant association with increasing endotoxin exposure. No significant associations between endotoxin and change in lung function.
Zock et al. (1998) [39] 57 potato processing workers AM 32.9 EU/m3. Low exposed group: AM 21 EU/m3, high exposed group: 56 EU/m3 Significant larger across-work shift decreases in lung function variables were found in subjects exposed to higher levels of endotoxin exposure when compared to lower exposed subjects.
Mandryk et al. (1999) [53] 168 wood workers. 30 maintenance workers (controls). Inhalable endotoxin: GM 24.1–43.0 EU/m3(GSD 15.5–47.7)a Significant differences in prevalence of respiratory symptoms, lung function decline and cross-work shift lung function changes in exposed wood workers when compared to controls. Also significant dose-response relationships between lung function decline/cross work shift changes and personal exposure to airborne endotoxin.
Mahar et al. (2002) [40] 87 refuse derived fuel plant workers 1995: GM 28.5 EU/m3 (GSD 2.77) Pulmonary function values of the exposed are within predicted values and show no decrements over time for the workforce as a whole. No trends indicating reductions in lung functions based on length of employment.
2000: GM 28.1 EU/m3 (GSD 6.65)
Total: GM 28.4 EU/m3 (GSD 3.75)
Wouters et al. (2002) [59] 47 waste collecting workers. 15 office workers (controls). GM 39.4 EU/m3, range 4–7182 No significant differences in prevalence of respiratory symptoms among exposed workers when compared to controls.
Fransman et al. (2003) [55] 112 plywood mill workers. 415 controls of the general population. GM 23.0 EU/m3 (GSD 2.8) Shortness of breath and wheezing were significantly more prevalent among subjects exposed to dust, endotoxin, terpenes and formaldehyde and also significantly more present in workers employed > 6.5 years (all p < 0.05). No clear associations between prevalence of symptoms and exposure to endotoxin alone. 53–83% of respiratory symptoms lessened during holidays.
Heldal et al. (2004) [36] 22 waste collection workers AM 2.5 EU/m3, range 0–7.8 No significant difference in exposure level to endotoxin between subjects with and without respiratory complaints.
Kennedy et al. (2004) [34] 226 glass bottle recycling workers. 212 ferry workers (controls). GM 3.6–4.3 EU/m3, range < 0.14–179 Significantly higher prevalence of chest tightness in the exposed groups vs unexposed subjects. No significant increase found in respiratory symptoms related to personal endotoxin exposure > 4 EU/m3when compared to exposure to lower levels.
Sigsgaard et al. (2004) [34] 97 paper mill workers. 55 water-supply workers (controls). 6–69 EU/m3, range 6–370 No significant decrements in lung function were seen among paper recycling workers exposed to endotoxin levels below 200 EU/m3.
Smit et al. (2005) [41] 371 waste water workers. 97 office staff, 2698 general population members (controls). GM 27 EU/m3 (GSD 3.7) Prevalence of daily cough, shortness of breath and asthma attacks were significantly higher among exposed subjects than in the general population. No significant differences in respiratory symptoms in subjects exposed to higher levels of endotoxin when compared to lower levels. Length of employment > 20 years was significantly associated with LRT and skin symptoms.
Widmeier et al. (2007) [47] 409 wastewater-and garbage workers. 369 public transport and forestry workers (controls). Wastewater workers: winter 8.8–29.7 EU/m3, summer 29.8–52.6 EU/m3; garbage collectors winter 3.43–8.14 EU/m3, summer 3.63–11.03 EU/m3 No significant association between endotoxin exposure and lung function or respiratory symptoms.
Rusca et al. (2008) [60] 111 sawmill workers Range 1–24 EU/m3 No significant relationships between respiratory symptoms or lung function tests and exposure to dust and endotoxin.
Dang et al. (2010) [49] 69 water resort workers, 74 office workers (controls). Mean 45 EU/m3, range 18–84 EU/m3 Workers exposed to (higher levels of) endotoxin and chloramine were significantly more likely to report work-related respiratory symptoms such as cough, wheezing shortness of breath and chest tightness than unexposed colleagues.
Renström et al. (2011) [50] 59 pet shop workers Range 1–100 EU/m3 No significant difference in exposure levels of endotoxin between subjects with work symptoms compared to subjects without symptoms.
Schlunssen et al. (2011) [57] 232 woodchip and straw workers. 107 workers in oil/gas power plants (controls). Woodchip plants: median 1.7 EU/m3, range 0.01–6.5 Significant association between increased asthma symptoms and endotoxin exposure to 12–294 EU/m3. No significant relationship between endotoxin exposure and change in lung function parameters.
Straw plants: median 74 EU/m3, range 1.5–294
Control: median 0.9 EU/m3
Meza et al. (2013) [56] 183 aircraft workers exposed to MWF. 224 office workers (controls). Mean 1.2 EU/m3, range 0.42–2.7 Significantly more respiratory symptoms and asthma among workers exposed to metalworking fluids and endotoxin when compared to controls.
Shiryaeva et al. (2014) [58] 70 salmon processing workers Monday-Thursday GM 1.39–1.65 EU/m3, range 0.30–29.0 Wheeze and chest tightness decreased significantly over the workweek (p < 0.05). Significant decline in cross-work shift %FEV1 was seen on Monday. Models relating separate respiratory variables/lung function to endotoxin exposure showed no significant associations.
Cyprowski et al. (2015) [43] 78 sewage workers AM 38.8 EU/m3, range 0.63–214 Small but significant across-work shift declines in FEV1(p = 0.044) associated with endotoxin exposure, independent of organic dust concentrations or smoking habits.
Heldal et al. (2015) [51] 47 compost workers, 37 office controls. AM 4.0–38 EU/m3, range 0–730 Significant association between cough and exposure to 0.7–2.7 EU/m3 endotoxin. Cough and one or more work-related symptoms were significantly more prevalent in the compost workers when compared to controls. The predicted FVC% measured before work was significantly lower in the compost workers as compared to controls (p < 0.05).
Ghani et al. (2016) [44] 100 textile mill workers, 100 controls. Range 40–300 EU/m3 Significantly decreased mean lung function values amongst workers exposed to airborne endotoxin when compared to control subjects.
  1. aoriginal values were presented in article in mg/m3 or ng/m3