Exposure to endotoxins and respiratory health in composting facilities
Graphical abstract
Introduction
The impact of municipal solid waste management (MSWM), handling and treating technologies on the environment, workers, and the public is nowadays identified as a growing health concern worldwide (Giusti, 2009). People involving in various MSWM activities are exposed to higher levels of pollutants such as bioaerosols, volatile organic compounds (VOCs), polycyclic aromatic hydrocarbons (PAHs), heavy metals, dioxins and furans and therefore a greater variety of risks compared to the general population (Nabizadeh et al., 2020a, 2020b; Poole and Basu, 2017; Akpeimeh et al., 2019). The composting process as a sustainable waste management technique is a suitable way for recycling organic waste which is considered among major sources of bioaerosols and their constituents such as endotoxins (Rolph et al., 2018; Wéry, 2014). Exposure to endotoxins, as pulmonary immunotoxicants and an inflammatory component of the cell wall of Gram-negative bacteria, was classified as “top 10 emerging biological risks” in occupational environments by The European Agency for Safety and Health at Work (Brun, 2007). Endotoxins can be released following cell growth or death during waste-related activities which may result in adverse respiratory health as the most important hazard caused by this agent (Searl and Crawford, 2012).
Endotoxins absorbed onto the surface of organic dust are precipitated in the lung following inhalation, which is responsible for a variety of acute and chronic clinical effects ranging from respiratory symptoms (including cough, wheezing, dyspnea, upper airways irritation, asthmatic symptoms, and chronic bronchitis) to some gastrointestinal disorders (Rylander, 2002; Smit et al., 2005; Farokhi et al., 2018). Lung function decline or change in respiratory capacities such as FEV1% (Forced Expiratory Volume at 1 s) and FEV1/FVC (ratio of FEV1/Forced Vital Capacity) in compost workers has also been found to be related to endotoxin exposure (Cyprowski et al., 2015; Liebers et al., 2006). In a study conducted in Finland, workers handling solid waste experienced 2.6 times higher risk of allergic pulmonary disease and 2.5 times higher chronic bronchitis (Poulsen et al., 1995). Over the last twenty years, several studies have been conducted concerning the health effects of bioaerosols in developed and high-income countries (Van Kampen et al., 2016a; Basu, 2020; Schlosser et al., 2009; Taha et al., 2006; Pearson et al., 2015). While the risks of exposure to endotoxins are almost well-identified in these countries, the occupational health risks associated with endotoxin exposure are still less well described. In low-income countries, where there is little attention on dust control or personal equipment facilities, and waste-related activities are often conducted manually, reports on the health risks are rare.
Currently, there is no agreement on workplace exposure limits for endotoxin (Duquenne et al., 2013), also exposure limits have not been proposed for the general population for different exposure routes in the ambient air by international agencies such as World Health Organization (WHO) (Shamsollahi et al., 2019). However, occupational exposure limits (OELs) for bacterial endotoxins recommended by the Health Council of the Netherlands as an occupational limit of 90 EU/m3 (8-h time-weighted average) (Health Council of, 2010). It seems insufficient exposure assessment data, and the range of health effects hinder the establishment of exposure limits for this biological agent.
To the best of our knowledge, this study is the first-ever of its kind to investigate the exposure to endotoxin concentrations as a biohazard in composting facilities and adverse health effects in one of the largest solid waste management facilities in the Middle East (Aradkooh Complex). The aim is to evaluate whether there is an association between exposure to endotoxin and lung function, clinical and respiratory symptoms. Based on these results, we can gain insight into the estimation of the level of endotoxin exposure in the composting plant and its health effects in the exposed employee which can help us to recommend capital and operational mitigation measures.
Section snippets
Study area and plant descriptions
Tehran city as one of the biggest world's megacities, with a population of approximately 9 million inhabitants, generates between 5000 and 7000 tons of solid waste every day (Fardi, 2008). All solid wastes produced in Tehran have been transferred to the southern part of Tehran where there is a large site for solid waste processing and disposal (Aradkouh complex) for over 55 years. Daily, tons of solid waste from 22 municipal districts and other sources such as nearby small cities and health
Composition of waste
According to the information obtained from Tehran Waste Management Organization (TWMO), total solid waste entering the preprocessing unites in the Aradkouh complex was about 5400 tons/day in the time of sampling, of which approximately 52% (2800 tons/day) transferred to the composting plant. Fig. 2 shows the composition of the sample taken from waste entered the compost site in which the highest proportion of the collected sample was organic waste (78.2%) as a biodegradable part of the waste
Discussion
In this study, conducted in one of the largest solid waste management facilities in the Middle East, exposure to endotoxin and its association with clinical symptoms and lung function were investigated. Endotoxin exposure was not associated with lung function indices. However, the moderate and high exposure groups suffered more from the majority of the symptoms than the control (office workers) group, and this difference was statistically significant for cough, fatigue, and headache. Other
Conclusion
A cross-sectional study was conducted in one of the largest solid waste management facilities in the Middle East. The increased risk of cough, fatigue, and headache were found in the exposed groups compared to controls. Evidence of association was not found between endotoxin exposure and lung function parameters (FEV1, FVC, FEV1/FVC, PEF, FEF25-75%) despite a relatively high difference in the concentration of endotoxin observed in air samples of different locations. There are several reasons
Credit author contribution statement
Mina Aghaei: Conceptualization, Investigation, Formal analysis, Software, Drafting the manuscript, Kamyar Yghmaeian: Conceptualization, Methodology, Funding acquisition. Mohammad Sadegh Hassanvand: Methodology, Editing the manuscript. Mohammad Hossein Hedayati: Performing the experiments. Fatemeh Yousefian and Hosna janjani: Data collection, Analysis. Ramin Nabizadeh: Conceptualizationand design of study, Supervision, analysis. Masud Yunesian: Conceptualization, Supervision, Funding
Declaration of competing interest
The authors declare that they have no conflict interests.
The authors whose names are listed immediately below certify that they have no affiliations with or involvement in any organization or entity with any financial interest or non-financial interest in the subject matter or materials discussed in this manuscript.
Acknowledgment
This study is part of a PhD thesis that was supported by the Ministry of Health and Medical Education (MOHME), and conducted under the supervision of the Health Technology Development and Industrial Relationship Office of Tehran University of Medical Science, Iran (98-01-159-42073). The authors would like to thanks the subjects who agreed to participate in this study.
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