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

Abstract

BackgroundElevated endotoxin levels have been measured in ambient air around livestock farms, which is a cause of concern for neighbouring residents. There is clear evidence that occupational exposure to high concentrations of airborne endotoxin causes respiratory inflammation, respiratory symptoms and lung function decline. However, health effects of exposure to low levels of endotoxin are less well described. The aim of this systematic review is to summarize published associations between exposure to relatively low levels of airborne endotoxin and respiratory health endpoints.MethodsStudies investigating respiratory effects of measured or modelled exposure to low levels of airborne endotoxin (average < 100 EU/m3) were eligible for inclusion. In total, 1362 articles were identified through a Pubmed database search, of which 31 articles were included in this review. Studies were included up to February 2017. Overview tables and forest plots were created, and study quality was assessed.ResultsTwenty-two included studies had a cross-sectional design, others were designed as longitudinal observational (n = 7) or experimental (n = 2) studies. Most studies (n = 23) were conducted in an occupational setting, some involved domestic or experimental exposure. Several studies reported statistically significant effects of exposure to low levels of endotoxin on respiratory symptoms and lung function. However, considerable heterogeneity existed in the outcomes of the included studies and no overall estimate could be provided by meta-analysis to quantify the possible relationship. Instead, a best evidence synthesis was performed among studies examining the exposure-response relationship between endotoxin and respiratory outcomes. Significant exposure-response relationships between endotoxin and symptoms and FEV1 were shown in several studies, with no conflicting findings in the studies included in the best evidence synthesis. Significantly different effects of endotoxin exposure were also seen in vulnerable subgroups (atopics and patients with broncho-obstructive disease) and smokers.ConclusionsRespiratory health effects of exposure to low levels of airborne endotoxin (< 100 EU/m3) seem plausible. Future studies are needed to investigate ambient exposure to endotoxin and potential respiratory health effects, especially in vulnerable subgroups of the population.Electronic supplementary materialThe online version of this article (10.1186/s12940-018-0360-7) contains supplementary material, which is available to authorized users.

Potential occupational and respiratory hazards in a Minnesota cannabis cultivation and processing facility

“…Exposure to organic dust and high concentrations of endotoxin cause respiratory inflammation, respiratory symptoms, and declinations in lung function . There is variable evidence about the health effects associated with exposure to low endotoxin concentrations (less than 100 EU/m 3 ) but it has been reported that levels as low as 45 EU/m 3 may cause acute airflow obstruction, mucous membrane irritation, chest tightness, cough, shortness of breath, fever, and wheezing .…”

On the interpretation of bioaerosol exposure measurements and impacts on health

“…Cardiopulmonary markers including blood pressure, pulse, and heart rate variability are often considered (Cole-Hunter et al 2018). Lung function is evaluated using spirometry and often the Tiffeneau-Pinelli index (FEV 1 /FVC; forced expiratory volume in the first second/forced vital capacity) to compare exposed subjects with nonexposed controls (Farokhi, Heederik, and Smit 2018;Magzamen et al 2018). Blood samples from exposed subjects are commonly used to investigate inflammatory mechanisms or as exposure markers, either by measuring total and specific immunoglobins (IgE and IgG) or by determining blood levels of neutrophils, cytokines (tumor necrosis factor-α [TNF-α], interleukin-1β [IL-1β], or interleukin-6 [IL-6]).…”

Evaluation of a thermal drying process at a wastewater treatment plant.

“…Endotoxins produce a wide range of biological responses including blood vessel changes, inflammation, and allergic reactions. Airborne endotoxin exposures between 45 and 400 EU/m 3 have been associated with symptoms of cough, wheeze, shortness of breath, chest tightness, and mucous membrane irritation, and signs of acute airflow obstruction [Castellan et al 1987;Farokhi et al 2018;Milton et al 1996;Smid et al 1994]. Chronic health effects that have been associated with airborne endotoxin exposures include chronic bronchitis, bronchial hyperreactivity, chronic airways obstruction, hypersensitivity pneumonitis, and emphysema [Castellan 1995;Liebers et al 2008].…”