Bioaerosol in composting facilities: occupational health risk assessment

Unlocking the potential of biowaste: Sustainable strategies to produce valuable industrial products

Global solid waste generation is expected to double by 2050 from the present annual level of 2.01 metric ton. Traditional biowaste treatment methods, such as landfilling and incineration, cannot meet the need to deal with gigantic amounts of waste and reduce environmental harm. This review critically evaluates existing sustainable waste management strategies highlighting their role in transitioning to a "reuse and recovery" paradigm. Sustainable waste management refers to conserving resources and protecting human health, society, and the environment. In this context, this review examines the current advancements and potential trends in using widely available biowaste in novel applications to produce key biofuels (such as biogas and biodiesel) and resources such as corrosion inhibitors, asbestos-free brake pads, nutrient-rich functional foods, bio-cement, bio-based fertilizer, and biodegradable plastic. Among these, biowaste-to-energy conversion (e.g., biogas production) and biodegradable plastic synthesis emerge as particularly impactful strategies due to their scalability and potential to address both waste reduction and resource recovery goals. The strategic utilization of biowaste resources into novel products holds significant promise in mitigating sustainability problems, offering renewable alternatives that are biodegradable and free of harmful additives.

A cross-sectional study on occupational hygiene in biowaste plants

Recycling demands are increasing and new biowaste plants are established. The aim of this study is to obtain knowledge about occupational hygiene in biowaste pretreatment plants. At 6 plants, bioaerosol exposure, hand hygiene, and bioaerosol concentrations in work areas were investigated repeatedly. The total inflammatory potential (TIP) of exposures was measured using the human HL-60 cell line. Exposure to airborne bacteria, bacteria able to grow anaerobic, fungi(37°C), endotoxin, and TIP differed between plants and was lowest in a plant transporting waste in closed pipes compared to plants where waste was delivered on the receiving hall floor. Conversely, high exposures were measured in a plant that also processes compost. All microbial components had an impact on TIP of workers' exposure with main effects of fungi and endotoxin. Seasonality was found for several exposures and TIP, and they were lowest in the winter. Concentrations of bacteria and fungi on workers' hands at the end of the workday were 15 times higher for production than for nonproduction workers. In work areas, the concentrations of airborne fungi were highest in the waste-receiving area. Bacteria (3.2 µm) and anaerobic bacteria (4.0 µm) were present as larger airborne particles than fungi (2.8 µm), and bacteria were largest in the waste-receiving area. The microbial community compositions of exposures and work areas differed between plants and work areas. In conclusion, measures to reduce exposure should focus on the waste-receiving area and on the production workers. Differences in exposures and community compositions were found between seasons, work areas, work groups, and plants.

Advances in understanding bioaerosol release characteristics and potential hazards during aerobic composting

Bioaerosol emissions and their associated risks are attracting increasing attention. Bioaerosols are generated during the pretreatment, fermentation, and screening of mature compost when processing various types of solid waste at composting plants (e.g., municipal sludge and animal manure). In this review, we summarize research into bioaerosols at different types of composting plants by focusing on the methods used for sampling bioaerosols, stages when emissions potentially occur, major components of bioaerosols, survival and diffusion factors, and possible control strategies. The six-stage Andersen impactor is the main method used for sampling bioaerosols in composting plants. In addition, different composting management methods mainly affect bioaerosol emissions from composting plants. Studies of the components of bioaerosols produced by composting plants mainly focused on bacteria and fungi, whereas few considered others such as endotoxin. The survival and diffusion of bioaerosols are influenced by seasonal effects due to changes in environmental factors, such as temperature and relative humidity. Finally, three potential strategies have been proposed for controlling bioaerosols in composting plants. Improved policies are required for regulating bioaerosol emissions, as well as bioaerosol concentration diffusion models and measures to protect human health.

Contribution of Particulates to Airborne Disease Transmission and Severity: A Review

The emergence of coronavirus disease 2019 (COVID-19) has catalyzed great interest in the spread of airborne pathogens. Airborne infectious diseases are classified into viral, bacterial, and fungal infections. Environmental factors can elevate their transmission and lethality. Air pollution has been reported as the leading environmental cause of disease and premature death worldwide. Notably, ambient particulates of various components and sizes are harmful pollutants. There are two prominent health effects of particles in the atmosphere: (1) particulate matter (PM) penetrates the respiratory tract and adversely affects health, such as heart and respiratory diseases; and (2) bioaerosols of particles act as a medium for the spread of pathogens in the air. Particulates contribute to the occurrence of infectious diseases by increasing vulnerability to infection through inhalation and spreading disease through interactions with airborne pathogens. Here, we focus on the synergistic effects of airborne particulates on infectious disease. We outline the concepts and characteristics of bioaerosols, from their generation to transformation and circulation on Earth. Considering that microorganisms coexist with other particulates as bioaerosols, we investigate studies examining respiratory infections associated with airborne PM. Furthermore, we discuss four factors (meteorological, biological, physical, and chemical) that may impact the influence of PM on the survival of contagious pathogens in the atmosphere. Our review highlights the significant role of particulates in supporting the transmission of infectious aerosols and emphasizes the need for further research in this area.

Fungal Colonization of the Airways of Patients with Cystic Fibrosis: the Role of the Environmental Reservoirs

Filamentous fungi frequently colonize the airways of patients with cystic fibrosis and may cause severe diseases, such as the allergic bronchopulmonary aspergillosis. The most common filamentous fungi capable to chronically colonize the respiratory tract of the patients are Aspergillus fumigatus and Scedosporium species. Defining the treatment strategy may be challenging, the number of available drugs being limited and some of the causative agents being multiresistant microorganisms. The knowledge of the fungal niches in the outdoor and indoor environment is needed for understanding the origin of the contamination of the patients. In light of the abundance of some of the causative molds in compost, agricultural and flower fields, occupational activities related to such environments should be discouraged for patients with cystic fibrosis (CF). In addition, the microbiological monitoring of their indoor environment, including analysis of air and dust on surfaces, is essential to propose preventive measures aiming to reduce the exposure to environmental molds. Nevertheless, some specific niches were also identified in the indoor environment, in relation with humidity which favors the growth of thermotolerant molds. Potted plants were reported as indoor reservoirs for Scedosporium species. Likewise, Exophiala dermatitidis may be spread in the kitchen via dishwashers. However, genotype studies are still required to establish the link between dishwashers and colonization of the airways of CF patients by this black yeast. Moreover, as nothing is known regarding the other filamentous fungi associated with CF, further studies should be conducted to identify other potential specific niches in the habitat.

Review of bioaerosols from different sources and their health impacts

The emission of bioaerosols in the ambient atmosphere from different sources is a cause of concern for human health and the environment. Bioaerosols are a combination of biotic matter like microbes and pollens. The present review emphasizes the understanding of various sources of bioaerosols (industries, municipal solid waste, and medical facilities), their components, and their impact on human health. The study of bioaerosols is of great importance as large numbers of people are estimated to be exposed on the global scale. Bioaerosols exposure in different work environments results in health issues such as infectious diseases, allergies, toxic effects, and respiratory problems. Hence, extensive research is urged to establish an effective assessment of bioaerosols exposure in the workplace, risks involved, distribution, and validation. The present review is intended to explore the relationship between bioaerosols exposure to the atmosphere and its impacts on human health. Some of the preliminary findings, based on our analysis of bioaerosols arising from municipal solid waste at a landfill site and a waste transfer station in Hyderabad, India, are also discussed herein.

TFOS Lifestyle Report: Impact of environmental conditions on the ocular surface

Environmental risk factors that have an impact on the ocular surface were reviewed and associations with age and sex, race/ethnicity, geographical area, seasonality, prevalence and possible interactions between risk factors are reviewed. Environmental factors can be (a) climate-related: temperature, humidity, wind speed, altitude, dew point, ultraviolet light, and allergen or (b) outdoor and indoor pollution: gases, particulate matter, and other sources of airborne pollutants. Temperature affects ocular surface homeostasis directly and indirectly, precipitating ocular surface diseases and/or symptoms, including trachoma. Humidity is negatively associated with dry eye disease. There is little data on wind speed and dewpoint. High altitude and ultraviolet light exposure are associated with pterygium, ocular surface degenerations and neoplastic disease. Pollution is associated with dry eye disease and conjunctivitis. Primary Sjögren syndrome is associated with exposure to chemical solvents. Living within a potential zone of active volcanic eruption is associated with eye irritation. Indoor pollution, "sick" building or house can also be associated with eye irritation. Most ocular surface conditions are multifactorial, and several environmental factors may contribute to specific diseases. A systematic review was conducted to answer the following research question: "What are the associations between outdoor environment pollution and signs or symptoms of dry eye disease in humans?" Dry eye disease is associated with air pollution (from NO2) and soil pollution (from chromium), but not from air pollution from CO or PM10. Future research should adequately account for confounders, follow up over time, and report results separately for ocular surface findings, including signs and symptoms.

Health symptoms, inflammation, and bioaerosol exposure in workers at biowaste pretreatment plants

Biowaste pretreatment plants have been built within the last years in Denmark in order to recycle pre-sorted biowaste from houses, restaurants, and industry. We investigated the association between exposure and health at six biowaste pretreatment plants (visited twice) across Denmark. We measured the personal bioaerosol exposure, took blood samples, and administered a questionnaire. Thirty-one persons participated, 17 of them twice, resulting in 45 bioaerosol samples, 40 blood samples, and questionnaire answers from 21 persons. We measured exposure to bacteria, fungi, dust, and endotoxin, the total inflammatory potential of the exposures, and serum levels of the inflammatory markers serum amyloid A (SAA), high sensitivity C-reactive protein (hsCRP), and human club cell protein (CC16). Higher exposures to fungi and endotoxin were found for workers with tasks inside the production area compared to workers with main tasks in the office area. A positive association was found between the concentration of anaerobic bacteria and hsCRP and SAA, whereas bacteria and endotoxin were inversely associated with hsCRP and SAA. A positive association between hsCRP and the fungal species Penicillium digitatum and P. camemberti were found, whereas an inverse association between hsCRP and Aspergillus niger and P. italicum were found. Staff with tasks inside the production area reported more symptoms of the nose than those working in the office area. To conclude, our results indicate that workers with tasks inside the production area are exposed to elevated levels of bioaerosols, and that this may affect workers' health negatively.

Safe use of PHI6 IN the experimental studies

Surrogate viruses theoretically provide an opportunity to study the viral spread in an indoor environment, a highly needed understanding during the pandemic, in a safe manner to humans and the environment. However, the safety of surrogate viruses for humans as an aerosol at high concentrations has not been established. In this study, Phi6 surrogate was aerosolized at high concentration (Particulate matter_2.5: ∼1018 μg m^-3) in the studied indoor space. Participants were closely followed for any symptoms. We measured the bacterial endotoxin concentration of the virus solution used for aerosolization as well as the concentration in the room air containing the aerosolized viruses. In addition, we measured how the bacterial endotoxin concentration of the sample was affected by different traditional virus purification procedures. Despite the purification, bacterial endotoxin concentration of the Phi6 was high (350 EU/ml in solution used for aerosols) with both (two) purification protocols. Bacterial endotoxins were also detected in aerosolized form, but below the occupational exposure limit of 90 EU/m³. Despite these concerns, no symptoms were observed in exposed humans when they were using personal protective equipment. In the future, purification protocols should be developed to reduce associated bacterial endotoxin levels in enveloped bacterial virus specimens to ensure even safer research use of surrogate viruses.

Characteristics and health effects of particulate matter emitted from a waste sorting plant

Solid waste components can be recycled in waste paper and cardboard sorting plants (WPCSP) through a multistep process. This work collected 15 samples every six days from each of the 9 points selected to study the processes taking place in a WPCSP (135 particulate matter samples total). Examining the concentration and size fraction of particulate matter (i.e., PM₁, PM_2.5 and PM₁₀) in WPCSP is an essential issue to notify policy makers about the health impacts on exposed workers. The major activities for increasing of the concentration of PM in various processing units in the WPCSP, especially in hand-picking routes I and II were related to manual dismantling, mechanical grinding, mechanical agitation, and separation and movement of waste. The results of this work showed that a negative correlation between temperature and particulate matter size followed the order PM₁₀ > PM_2.5 > PM₁. Exposure to PM_2.5 and PM₁₀ in the WPCSP lead to possible risk (HI = 5.561 and LTCRs = 3.41 × 10^-6 to 9.43 × 10^-5 for PM_2.5 and HI = 7.454 for PM₁₀). The exposure duration and the previous concentrations had the most effect on the ILCRs and HQs for PM_2.5 and PM₁₀ in all sampling sites. Hence, because WPCSP are infected indoor environments (I/O ratio > 1), the use of control methods such as isolation of units, misting systems, blower systems equipped with bag houses, protective equipment, a mechanical ventilation system, and additional natural ventilation can reduce the amount of suspended PM, enhance worker safety, and increase the recycling rate.

Characteristics and assessing biological risks of airborne bacteria in waste sorting plant

Examining the concentration and types of airborne bacteria in waste paper and cardboard sorting plants (WPCSP) is an urgent matter to inform policy makers about the health impacts on exposed workers. Herein, we collected 20 samples at 9 points of a WPCSP every 6 winter days, and found that the most abundant airborne bacteria were positively and negatively correlated to relative humidity and temperature, respectively. The most abundant airborne bacteria (in units of CFU m^-3) were: Staphylococcus sp. (72.4) > Micrococcus sp. (52.2) > Bacillus sp. (30.3) > Enterococcus sp. (24.0) > Serratia marcescens (20.1) > E. coli (19.1) > Pseudomonas sp. (16.0) > Nocardia sp. (1.9). The lifetime average daily dose (LADD) for the inhalation and dermal routes for the intake of airborne bacteria ranged from 3.7 × 10^-3 ≤ LADD_Inhalation ≤ 2.07 × 10¹ CFU (kg d)^-1 and 4.75 × 10^-6 ≤ LADD_Dermal ≤ 1.64 × 10^-5 CFU (kg d)^-1, respectively. Based on a sensitivity analysis (SA), the concentration of airborne bacteria (C) and the exposure duration (ED) had the most effect on the LADD_Inhalation and LADD_Dermal for all sampling locations. Although the Hazard Quotient of airborne bacteria was HQ < 1, an acceptable level, the indoor/outdoor ratio (1.5 ≤ I/O ≤ 6.6) of airborne bacteria typically exceeded the threshold value (I/O > 2), indicating worker's exposure to an infected environment. Therefore, in the absence of sufficient natural ventilation the indoor ambient conditions of the WPCSP studied should be controlled by supplying mechanical ventilation.

Inactivation and risk control of pathogenic microorganisms in municipal sludge treatment: A review

The rapid global spread of coronavirus disease 2019 (COVID-19) has promoted concern over human pathogens and their significant threats to public health security. The monitoring and control of human pathogens in public sanitation and health facilities are of great importance. Excessive sludge is an inevitable byproduct of sewage that contains human and animal feces in wastewater treatment plants (WWTPs). It is an important sink of different pollutants and pathogens, and the proper treatment and disposal of sludge are important to minimize potential risks to the environment and public health. However, there is a lack of comprehensive analysis of the diversity, exposure risks, assessment methods and inactivation techniques of pathogenic microorganisms in sludge. Based on this consideration, this review summarizes the control performance of pathogenic microorganisms such as enterovirus, Salmonella spp., and Escherichia coli by different sludge treatment technologies, including composting, anaerobic digestion, aerobic digestion, and microwave irradiation, and the mechanisms of pathogenic microorganism inactivation in sludge treatment processes are discussed. Additionally, this study reviews the diversity, detection methods, and exposure risks of pathogenic microorganisms in sludge. This review advances the quantitative assessment of pathogenic microorganism risks involved in sludge reuse and is practically valuable to optimize the treatment and disposal of sludge for pathogenic microorganism control.

Exposure to endotoxins and respiratory health in composting facilities

The impact of bioaerosols in municipal solid waste management is nowadays identified as a growing health concern worldwide. In this study, exposure to endotoxin in composting facilities and its association with lung function and clinical symptoms was investigated in Tehran municipal solid waste management complex (Aradkooh) as one of the largest solid waste management facilities in the Middle East. Airborne endotoxins were collected between June and July 2019 and the concentrations were determined by Limulus Amebocyte Lysate (LAL) method. Healthy workers with no history of respiratory disease were recruited and data on clinical symptoms (cough, phlegm, wheezing, dyspnea, fatigue, headache, eye irritation, runny nose, runny eyes, and sore throat) was obtained by the modified American Thoracic Society questionnaire, and spirometric measurement was performed by an expert. The binary logistic regression test was used and adjusted for confounding variables. The results didn't show any difference in lung function parameters (FEV₁, FVC, FEV₁/FVC, PEF, FEF_25-75%), and most of the respiratory symptoms despite a relatively high difference in the concentration of endotoxin observed in air samples of different locations. Only the increased risk of cough (OR 10.5, 95% CI: 2.4 to 44.8 in the moderately exposed group and 7.8, 95% CI: 1.6 to 39.1 in highly exposed ones), fatigue (OR 3.7, 95% CI: 1.2 to 11.7), and headache (OR 6.02, 95% CI: 1.4 to 24.5) were found in the exposed groups compared to controls after adjusting for age, active and passive smoking. However, findings of the study might be underestimated due to some issues including healthy worker effect, intra and intersubject variability, and self-reporting bias, thereby the results should be interpreted with caution. Although we did not find any relationship, due to the high concentrations of endotoxins observed in some sites, it is recommended to consider some possible prevention measures such as using personal protective equipment to reduce the exposure of workers at an acceptable level.

Airborne mycotoxins in waste recycling and recovery facilities: Occupational exposure and health risk assessment

Mycotoxins are metabolites secreted by certain types of moulds, and some of them can be harmful to health. The objective of this study was to estimate the level of exposure to airborne aflatoxin B1, ochratoxin A, gliotoxin and sterigmatocystin in waste recycling and recovery facilities. An additional goal was to assess the related health risks for workers. Targeted mycotoxins were analysed quantitatively in 94 air samples collected in five sites using ultra-performance liquid chromatography coupled with high resolution mass spectrometry. The level of exposure to mycotoxin during working day scenarios was compared to benchmark values, either health-based guidelines when available or the concentration of no toxicological concern (CoNTC) when not. Eleven per cent of samples showed quantifiable measurement results. Aflatoxin B1 and sterigmatocystin were quantified at the mechanical separation area in mechanical-biological treatment (MBT) facilities and in the materials recovery facility (MRF), but not in composting plants and composting units in MBT facilities. The levels of exposure were all below 1 ng m^-3. This is the first time exposure to sterigmatocystin in waste management facilities is reported and quantified. Ochratoxin A and gliotoxin were not quantified in any of the air samples. Health risk assessment approaches did not suggest a significant threat to workers' health. These data do not suggest the need for specific prevention measures in addition to those against other airborne biological agents.

Genomewide and Enzymatic Analysis Reveals Efficient d-Galacturonic Acid Metabolism in the Basidiomycete Yeast Rhodosporidium toruloides

Biorefining of renewable feedstocks is one of the most promising routes to replace fossil-based products. Since many common fermentation hosts, such as Saccharomyces cerevisiae, are naturally unable to convert many component plant cell wall polysaccharides, the identification of organisms with broad catabolism capabilities represents an opportunity to expand the range of substrates used in fermentation biorefinery approaches. The red basidiomycete yeast Rhodosporidium toruloides is a promising and robust host for lipid- and terpene-derived chemicals. Previous studies demonstrated assimilation of a range of substrates, from C₅/C₆ sugars to aromatic molecules similar to lignin monomers. In the current study, we analyzed the potential of R. toruloides to assimilate d-galacturonic acid, a major sugar in many pectin-rich agricultural waste streams, including sugar beet pulp and citrus peels. d-Galacturonic acid is not a preferred substrate for many fungi, but its metabolism was found to be on par with those of d-glucose and d-xylose in R. toruloides A genomewide analysis by combined transcriptome sequencing (RNA-seq) and RB-TDNA-seq revealed those genes with high relevance for fitness on d-galacturonic acid. While R. toruloides was found to utilize the nonphosphorylative catabolic pathway known from ascomycetes, the maximal velocities of several enzymes exceeded those previously reported. In addition, an efficient downstream glycerol catabolism and a novel transcription factor were found to be important for d-galacturonic acid utilization. These results set the basis for use of R. toruloides as a potential host for pectin-rich waste conversions and demonstrate its suitability as a model for metabolic studies with basidiomycetes.IMPORTANCE The switch from the traditional fossil-based industry to a green and sustainable bioeconomy demands the complete utilization of renewable feedstocks. Many currently used bioconversion hosts are unable to utilize major components of plant biomass, warranting the identification of microorganisms with broader catabolic capacity and characterization of their unique biochemical pathways. d-Galacturonic acid is a plant component of bioconversion interest and is the major backbone sugar of pectin, a plant cell wall polysaccharide abundant in soft and young plant tissues. The red basidiomycete and oleaginous yeast Rhodosporidium toruloides has been previously shown to utilize a range of sugars and aromatic molecules. Using state-of-the-art functional genomic methods and physiological and biochemical assays, we elucidated the molecular basis underlying the efficient metabolism of d-galacturonic acid. This study identified an efficient pathway for uronic acid conversion to guide future engineering efforts and represents the first detailed metabolic analysis of pectin metabolism in a basidiomycete fungus.

Effects of plant features on symptoms and airway inflammation in compost workers followed over 18 months

This study investigated the plant features associated with increased irritation symptoms and levels of inflammation markers among compost workers (CWs). Ninety CWs were followed over 18 months, using questionnaires on respiratory symptoms, fractional exhaled nitric oxide measurements, spirometry, a methacholine bronchial challenge test, and quantification of specific immunoglobulins E (IgE) and G. CWs in plants processing the highest quantities of waste exhibited more airway irritation symptoms. So did the CWs in partially and fully indoor plants as compared to those in plants entirely outdoors. Working in sewage sludge versus green waste plants and having a high level of exposure were associated with higher levels of different IgE. The duration of employment decreased the FEV₁ by 16 ml per year. Working in an indoor plant is linked to symptoms and inflammation markers in CWs.

Inhalable dust as a marker of exposure to airborne biological agents in composting facilities

OBJECTIVES

Industrial composting is associated with high levels of worker exposure to bioaerosols. Measurement of airborne microorganisms and endotoxin is complex and the related cost is high. The objective was therefore to examine whether dust measurement could be used as a marker of exposure to bioaerosols in composting facilities.

METHODS

A dataset of 110 measurements carried out in eight sludge composting plants was explored. Mixed-effects models were constructed to explain between-site and within-site variability in concentration of endotoxin and culturable mesophilic bacteria, mesophilic moulds and thermophilic actinomycetes in air. Fixed-effects variables were inhalable dust concentration, the season, the outdoor/indoor location of sampling and the process area.

RESULTS

The level of dust was a highly significant determinant of concentration for all biological agents. Within-site variability was always larger than between-site variability. The proportion of within-site variability explained by determinants was 68%, 65%, 56% and 60% for endotoxin, bacteria, moulds and actinomycetes, respectively. Inclusion of dust in the final model resulted in an increase of 24, 20, 12 and 17 points of percentage within-site variability, respectively. Inclusion of season resulted in an increase of 9, 12, 12 and 15 points, respectively. Within-site variability was less influenced by outdoor/indoor location and process area, except for moulds.

CONCLUSION

Dust was the factor that most influenced within-site variability in endotoxin and culturable bacteria concentration. Measurement of dust can efficiently assist decision making for prevention measures against endotoxin and bacteria in sludge composting plants. Our results are not as conclusive for actinomycetes and especially for moulds.

Bioaerosols concentrations in working areas in biomethanization facilities

This study sought to fill the gap in information about the type and the concentration of bioaerosols present in the air of biomethanization facilities (BF). Evaluation of bioaerosol composition and concentration was achieved in two biomethanization facilities located in Eastern Canada, during summer and winter. In order to have a thorough understanding of the studied environment, the methodology combined culture of bacteria and molds, qualitiative polymerase chain reaction (qPCR) for specific microorganisms, endotoxin quantification, and next-generation sequencing (NGS) for bacterial diversity. Results revealed that workers in biomethanization facilities are exposed to bioaerosols and pathogenic microorganisms similar to those found in composting plants. However, human exposure levels to bioaerosols are lower in BF than in composting plants. Despite these differences, use of personal protective equipment is recommended to lower the risks of health problems.

IMPLICATIONS

Biomethanization is a new technology used in eastern Canada for waste management. In the next few years, it is expected that there will be an expansion of facilities in response of tight governmental regulations. Workers in biomethanization facilities are exposed to various amounts of bioaerosols composed of some harmful microorganisms. Therefore, monitoring this occupational exposure could be an interesting tool for improving worker's health.

Respiratory hospital admission risk near large composting facilities

BACKGROUND

Large-scale composting can release bioaerosols in elevated quantities, but there are few studies of health effects on nearby communities.

METHODS

A cross-sectional ecological small area design was used to examine risk of respiratory hospital admissions within 2500m of all 148 English large-scale composting facilities in 2008-10. Statistical analyses used a random intercept Poisson regression model at Census Output Area (COA) level (mean population 310). Models were adjusted for age, sex, deprivation and tobacco sales.

RESULTS

Analysing 34,963 respiratory hospital admissions in 4656 COAs within 250-2500m of a site, there were no significant trends using pre-defined distance bands of >250-750m, >750-1500m and >1500-2500m. Using a continuous measure of distance, there was a small non-statistically significant (p=0.054) association with total respiratory admissions corresponding to a 1.5% (95% CI: 0.0-2.9%) decrease in risk if moving from 251m to 501m. There were no significant associations for subgroups of respiratory infections, asthma or chronic obstructive pulmonary disease.

CONCLUSION

This national study does not provide evidence for increased risks of respiratory hospital admissions in those living beyond 250m of an outdoor composting area perimeter. Further work using better measures of exposure and exploring associations with symptoms and disease prevalence, especially in vulnerable groups, is recommended to support regulatory approaches.

Field evaluation of personal sampling methods for multiple bioaerosols

Ambient bioaerosols are ubiquitous in the daily environment and can affect health in various ways. However, few studies have been conducted to comprehensively evaluate personal bioaerosol exposure in occupational and indoor environments because of the complex composition of bioaerosols and the lack of standardized sampling/analysis methods. We conducted a study to determine the most efficient collection/analysis method for the personal exposure assessment of multiple bioaerosols. The sampling efficiencies of three filters and four samplers were compared. According to our results, polycarbonate (PC) filters had the highest relative efficiency, particularly for bacteria. Side-by-side sampling was conducted to evaluate the three filter samplers (with PC filters) and the NIOSH Personal Bioaerosol Cyclone Sampler. According to the results, the Button Aerosol Sampler and the IOM Inhalable Dust Sampler had the highest relative efficiencies for fungi and bacteria, followed by the NIOSH sampler. Personal sampling was performed in a pig farm to assess occupational bioaerosol exposure and to evaluate the sampling/analysis methods. The Button and IOM samplers yielded a similar performance for personal bioaerosol sampling at the pig farm. However, the Button sampler is more likely to be clogged at high airborne dust concentrations because of its higher flow rate (4 L/min). Therefore, the IOM sampler is a more appropriate choice for performing personal sampling in environments with high dust levels. In summary, the Button and IOM samplers with PC filters are efficient sampling/analysis methods for the personal exposure assessment of multiple bioaerosols.

Exposures and health outcomes in relation to bioaerosol emissions from composting facilities: a systematic review of occupational and community studies

The number of composting sites in Europe is rapidly increasing, due to efforts to reduce the fraction of waste destined for landfill, but evidence on possible health impacts is limited. This article systematically reviews studies related to bioaerosol exposures within and near composting facilities and associated health effects in both community and occupational health settings. Six electronic databases and bibliographies from January 1960 to July 2014 were searched for studies reporting on health outcomes and/or bioaerosol emissions related to composting sites. Risk of bias was assessed using a customized score. Five hundred and thirty-six papers were identified and reviewed, and 66 articles met the inclusion criteria (48 exposure studies, 9 health studies, 9 health and exposure studies). Exposure information was limited, with most measurements taken in occupational settings and for limited time periods. Bioaerosol concentrations were highest on-site during agitation activities (turning, shredding, and screening). Six studies detected concentrations of either Aspergillus fumigatus or total bacteria above the English Environment Agency's recommended threshold levels beyond 250 m from the site. Occupational studies of compost workers suggested elevated risks of respiratory illnesses with higher bioaerosol exposures. Elevated airway irritation was reported in residents near composting sites, but this may have been affected by reporting bias. The evidence base on health effects of bioaerosol emissions from composting facilities is still limited, although there is sufficient evidence to support a precautionary approach for regulatory purposes. While data to date are suggestive of possible respiratory effects, further study is needed to confirm this and to explore other health outcomes.

Concentration of bioaerosols in composting plants using different quantification methods

BACKGROUND

Bioaerosols (organic dusts) containing viable and non-viable microorganisms and their metabolic products can lead to adverse health effects in exposed workers. Standard quantification methods of airborne microorganisms are mainly based on cultivation, which often underestimates the microbial burden. The aim of the study was to determine the microbial load in German composting plants with different, mainly cultivation-independent, methods. Second purpose was to evaluate which working areas are associated with higher or lower bioaerosol concentrations.

METHODS

A total of 124 inhalable dust samples were collected at different workplaces in 31 composting plants. Besides the determination of inhalable dust, particles, and total cell numbers, antigen quantification for moulds (Aspergillus fumigatus, Aspergillus versicolor, Penicillium chrysogenum, and Cladosporium spp.) and mites was performed. Concentrations of β-glucans as well as endotoxin and pyrogenic activities were also measured. The number of colony forming units (cfu) was determined by cultivation of moulds and actinomycetes in 36 additional dust samples.

RESULTS

With the exception of particle numbers, concentrations of all determined parameters showed significant correlations (P < 0.0001; r Spearman: 0.40-0.80), indicating a close association between these exposure markers. Colony numbers of mesophilic moulds and actinomycetes correlated also significantly with data of cultivation-independent methods. Exposure levels showed generally large variations. However, all parameters were measured highest in dusty working areas like next to the shredder and during processing with the exception of Cladosporium antigens that were found in the highest concentrations in the delivery area. The lowest concentrations of dust, particles, antigens, and pyrogenic activity were determined in wheel loader cabins (WLCs), which were equipped with an air filtration system.

CONCLUSION

It was possible to assess the microbial load of air in composting plants with different quantification methods. Since allergic and toxic reactions may be also caused by nonliving microorganisms, cultivation-independent methods may provide additional information about bioaerosol composition. In general, air filtration reduced the bioaerosol exposure shown in WLCs. Due to the fact that the mechanical processing of compost material, e.g. by shredding or sieving is associated with the generation of high bioaerosol concentrations, there is still a need of improved risk assessment and state-of-the-art protective measures in composting plants.

Bioaerosols from composting facilities--a review

Bioaerosols generated at composting plants are released during processes that involve the vigorous movement of material such as shredding, compost pile turning, or compost screening. Such bioaerosols are a cause of concern because of their potential impact on both occupational health and the public living in close proximity to such facilities. The biological hazards potentially associated with bioaerosol emissions from composting activities include fungi, bacteria, endotoxin, and 1-3 β-glucans. There is a major lack of knowledge concerning the dispersal of airborne microorganisms emitted by composting plants as well as the potential exposure of nearby residents. This is due in part to the difficulty of tracing specifically these microorganisms in air. In recent years, molecular tools have been used to develop new tracers which should help in risk assessments. This review summarizes current knowledge of microbial diversity in composting aerosols and of the associated risks to health. It also considers methodologies introduced recently to enhance understanding of bioaerosol dispersal, including new molecular indicators and modeling.

Occupational allergic respiratory diseases in garbage workers: relevance of molds and actinomycetes

Exposures to molds and bacteria (especially actinomycetes) at workplaces are common in garbage workers, but allergic respiratory diseases due to these microorganisms have been described rarely. The aim of our study was a detailed analysis of mold or bacteria-associated occupational respiratory diseases in garbage workers. From 2002 to 2011 four cases of occupational respiratory diseases related to garbage handling were identified in our institute (IPA). Hypersensitivity pneumonitis (HP) was diagnosed in three subjects (cases 1-3, one smoker, two non-smokers), occupational asthma (OA) was diagnosed in one subject (case 4, smoker), but could not be excluded completely in case 2. Cases 1 and 2 worked in composting sites, while cases 3 and 4 worked in packaging recycling plants. Exposure periods were 2-4 years. Molds and actinomycetes were identified as allergens in all cases. Specific IgE antibodies to Aspergillus fumigatus were detected exclusively in case 4. Diagnoses of HP were essentially based on symptoms and the detection of specific IgG serum antibodies to molds and actinomycetes. OA was confirmed by bronchial provocation test with Aspergillus fumigatus in case 4. In conclusion, occupational HP and OA due to molds occur rarely in garbage workers. Technical prevention measures are insufficient and the diagnosis of HP is often inconclusive. Therefore, it is recommended to implement the full repertoire of diagnostic tools including bronchoalveolar lavage and high resolution computed tomography in the baseline examination.

Estimation of fungal contamination and mycotoxin production at workplaces in composting plants, tanneries, archives and libraries

The aim of this research was to estimate fungal contamination at workplaces in composting plants, tanneries, libraries and archives. The influence of raw material processed or stored at these workplaces (compost, leather, cellulose) on the toxigenicity and cytotoxicity of fungi was also investigated. Qualitative and quantitative mycological analysis confirmed a high contamination in composting plants and tanneries, while materials in archives and libraries were less contaminated. Among the 74 fungal species present in the studied work environments, 15 species were identified as useful indicators of microbial contamination based on their presence at the workplace, frequency of occurrence and harmfulness to health. For nine Aspergillus and Penicillium isolates, identification was confirmed on the basis of molecular techniques, i.e. internal transcribed spacer region and β-tubulin gene sequencing, and the obtained nucleotide sequences were deposited into the NCBI GenBank Database. Five strains were cytotoxic to swine kidney cells. Strains of Aspergillus fumigatus originating from a composting plant produced large quantities of fumitremorgin C, fumiquinazoline F, fumagillin, fumigaclavine, helvolic acid, methylsulochrin, pyripyropene A, brevianamid F, verruculogen and others, as analysed by high performance liquid chromatography-tandem mass spectrometry. In the case of Penicillium chrysogenum originating from a tannery, meleagrin, secalonic acid D, roquefortine C, emodin and other metabolites were detected. These findings confirmed the hypothesis that these species may be a health risk factor to workers. Interestingly, the presence of compost extract, leather or cellulose in the culture medium apparently affected the ability of the selected fungi to produce (cytotoxic) mycotoxins.

Quantification of Saccharopolyspora rectivirgula in composting plants: assessment of the relevance of S. rectivirgula

Exposure to bioaerosols in composting plants can lead to negative health effects on compost workers. Health complaints vary between cough, irritation of the eyes and the skin, sinusitis, or dyspnea among others. It is fact that compost materials harbor high concentrations of microorganisms, which were aerosolized during handling compost. Within the present study, total cell numbers between 3.4 × 10(4) and 1.6 × 10(8) cell counts per m(3) air were determined after 4',6-Diamidin-2-phenylindol DAPI staining in 124 samples from German composting plants. Special attention should be paid to some specific microorganisms, which are able to cause health complaints. Saccharopolyspora rectivirgula, known to be one of the major causes of extrinsic allergic alveolitis (EAA, also called hypersensitivity pneumonitis, HP), was often found in environments of agricultural production, where the classical form of EAA ('farmer's lung disease') is common, but also in composting plants. In Germany, cases are known where workers had to terminate their work due to this disease. However, up to now, the relevance of S. rectivirgula at composting plants is unexplained. This study showed that high concentrations of airborne S. rectivirgula were found in composting plants similar to that found in agricultural production. Altogether, in 86.7% of the 124 analyzed samples, S. rectivirgula was detected using quantitative real-time polymerase chain reaction (PCR). Estimated concentrations ranged between 1.24 × 10(2) cell counts of S. rectivirgula per cubic meter air next to the rotted residues and 1.5 × 10(7) cell counts next to a converter. Furthermore, our methodical proceedings were verified. To analyze DNA extraction limits through the amount of cells within one sample, the DNA concentration was compared with total cell counts (TCCs). Altogether, when TCC was <1.4 × 10(5) cells per DNA extraction assay, no DNA was measurable; when TCC reached 3.5 × 10(6) cells, DNA was always detectable by fluorometric method. To overcome limitation of DNA measurement using fluorometric method, samples without measurable DNA were inserted in a PCR assay with universal primers. Results showed that a gain of 37% was possible, when samples were additionally analyzed by universal PCR. Hence, cell counts >2.0 × 10(6) cells were necessary to measure DNA concentrations in 90% of the analyzed samples, whereas cell counts <3.0 × 10(5) are sufficient to detect PCR products. Therefore, sampling of bioaerosols should be done in consideration of the expected cell count per cubic meter air. Note, to get measurable DNA using a fluorometer, >3.5 × 10(6) cells must be sampled for one DNA extraction assay. With this study, the real-time PCR approach for the detection of S. rectivirgula at workplaces in compost plants was revised, and the results revealed that this method is suitable for occupational exposure measurements.

Measurement of endotoxins in bioaerosols at workplace: a critical review of literature and a standardization issue

Endotoxins are lipopolysaccharides found in the outer membrane of most Gram-negative bacteria and cyanobacteria. Worker exposure to endotoxins has been shown in a number of work situations and is associated with both respiratory and systemic pathologies. The lack of an occupational exposure limit is mainly due to the absence of a standard protocol at the international level for sampling and analyzing airborne endotoxins. The bibliographic review in this article takes an exhaustive look at the current knowledge on measuring airborne endotoxins. It shows that, despite several reference documents at the international level, the methods used to measure endotoxin exposure differ considerably from one laboratory to another. Standardization is necessary to reduce interlaboratory variability and, ultimately, to improve the use of interstudy data. The bibliographic review presents the current status of standardization for airborne endotoxin measurement methods in the workplace and summarizes areas for further research. This article is both a reference document for all operators wishing to use such methods and a working document to build international consensus around the measurement of airborne endotoxins.

Protection of the vehicle cab environment against bacteria, fungi and endotoxins in composting facilities

Microbial quality of air inside vehicle cabs is a major occupational health risk management issue in composting facilities. Large differences and discrepancies in protection factors between vehicles and between biological agents have been reported. This study aimed at estimating the mean protection efficiency of the vehicle cab environment against bioaerosols with higher precision. In-cab measurement results were also analysed to ascertain whether or not these protection systems reduce workers' exposure to tolerable levels. Five front-end loaders, one mobile mixer and two agricultural tractors pulling windrow turners were investigated. Four vehicles were fitted with a pressurisation and high efficiency particulate air (HEPA) filtration system. The four others were only equipped with pleated paper filter without pressurisation. Bacteria, fungi and endotoxins were measured in 72 pairs of air samples, simultaneously collected inside the cab and on the outside of the cab with a CIP 10-M sampler. A front-end loader, purchased a few weeks previously, fitted with a pressurisation and high efficiency particulate air (HEPA) filtration system, and with a clean cab, exhibited a mean protection efficiency of between 99.47% CI 95% [98.58-99.97%] and 99.91% [99.78-99.98%] depending on the biological agent. It is likely that the lower protection efficiency demonstrated in other vehicles was caused by penetration through the only moderately efficient filters, by the absence of pressurisation, by leakage in the filter-sealing system, and by re-suspension of particles which accumulated in dirty cabs. Mean protection efficiency in regards to bacteria and endotoxins ranged between 92.64% [81.87-97.89%] and 98.61% [97.41-99.38%], and between 92.68% [88.11-96.08%] and 98.43% [97.44-99.22%], respectively. The mean protection efficiency was the lowest when confronted with fungal spores, from 59.76% [4.19-90.75%] to 94.71% [91.07-97.37%]. The probability that in-cab exposure to fungi exceeded the benchmark value for short-term respiratory effects suggests that front-end loaders and mobile mixers in composting facilities should be fitted with a pressurisation and HEPA filtration system, regardless of whether or not the facility is indoors or outdoors. Regarding the tractors, exposure inside the cabs was not significantly reduced. However, in this study, there was a less than 0.01% risk of exceeding the bench mark value associated with fungi related short-term respiratory effects during an 1-h per day windrow turning operation. Pressurisation and a HEPA filtration system can provide safe working conditions inside loaders and mobile mixer with regard to airborne bacteria, fungi and endotoxins in composting facilities. However, regular thorough cleaning of the vehicle cab, as well as overalls and shoes cleaning, and mitigation of leakage in the filter-sealing system are necessary to achieve high levels of protection efficiency.

Symptoms, spirometry, and serum antibody concentrations among compost workers exposed to organic dust

Work-related symptoms and diseases of 190 currently exposed compost workers, 59 former compost workers, and 38 nonexposed control subjects were investigated in a cross-sectional study. Using a standardized questionnaire, participants were asked for work-related symptoms, exposures to bioaerosols, atopic diseases, and smoking habits. The subjects underwent a physical examination and a lung function test. In addition, total immunoglobulin (Ig) E, IgE specific to environmental allergens and moulds, and IgG specific to molds and actinomycetes were quantified. Compared to controls, compost workers suffered more often from cough and irritation of the eyes in terms of mucosal membrane irritation (MMI). Former compost workers reported similar work-related complaints, but most MMI symptoms had improved after termination of bioaerosol exposure. In contrast, cough and dyspnea persisted, indicating a chronic process. Lung function parameters of compost workers were within the reference ranges. Nevertheless, forced vital capacity (FVC) was significantly lower than for controls. Specific IgE to environmental allergens and molds was positive in 25.3% and 7.4%, respectively, of currently exposed compost workers. There were no marked differences in IgE and IgG concentrations among the three groups. Compost workers suffered with a higher frequency from cough and MMI symptoms. The findings that MMI symptoms improved in former compost workers after leaving the job confirmed the association with bioaerosol exposure. Further, the reduced FVC may be produced by this exposure. There was no higher frequency of mold sensitization in the group of compost workers compared to controls, which may be an indication of a healthy worker survivor effect.

Assessment of airborne exposure to endotoxin and pyrogenic active dust using electrostatic dustfall collectors (EDCs)

Passive airborne dust sampling using electrostatic dustfall collectors (EDCs) is one possibility especially for long sampling periods. In this study, EDCs were deposited in living rooms of private households and in social rooms of composting plants. The aim of the study was to determine whether endotoxin and pyrogenic activity are measurable using EDCs. In all extracts, endotoxin (via Limulus amebocyte lysate [LAL] assay) and pyrogenic activity (interleukin [IL]-1β release via whole blood assay) were detectable. In addition, the monocyte chemotactic protein (MCP-1; CCL-2) as a secondary proinflammatory marker was measured with whole blood assay. Endotoxin activity and proinflammatory/pyrogenic activity of EDC extracts from social rooms in composting plants were higher compared to extracts obtained from EDCs in private household rooms. A significant correlation between LAL assay and whole blood assay was detectable. In conclusion, EDC sampling is an applicable method to evaluate settled dust from airborne bioaerosols displaying a longer period of exposure. The extraction of EDC without Tween enables one to measure endotoxin as well as proinflammatory/pyrogenic activity using the same sample for parallel detection and more reliable characterization of the airborne bioaerosol contamination.

Levels of chemical and microbiological pollutants in the vicinity of a waste incineration plant and human health risks: temporal trends

In 2007, a program was initiated to monitor air levels of volatile organic compounds (VOCs) and bioaerosols in the vicinity of a municipal solid waste incinerator (MSWI) (Tarragona, Catalonia, Spain). To investigate the temporal trends of chemical and microbiological pollutants, four 6-monthly campaigns were performed. Air samples were collected at different distances and directions from the facility, as well as in reference sites. In general terms, the concentrations of microbiological agents were very similar to those found in urban zones worldwide. The seasonal evaluation of the results showed higher levels of gram-negative bacteria in winter, contrasting with the increase of the airborne amount of total bacteria in summer. On the other hand, the concentrations of VOCs (mean range: 7.6-18.2 μg m(-3)) were typical of suburban zones. The current exposure to those compounds should not mean additional health risks for the population living nearby.