The effects of waste sorting in environmental microbiome, THP-1 cell viability and inflammatory responses

Divergent TLR2 and TLR4 Activation by Fungal Spores and Species Diversity in Dust from Waste Sorting Plants

This manuscript presents the results of an exploratory study on the relationships between NF-κB response through Toll-like receptor (TLR) activation by dust characterized by fungal spore concentrations and species diversity. Personal total dust samples were collected from Norwegian waste sorting plants and then characterized for fungal spores and fungal species diversity, as well as for other bioaerosol components, including endotoxins and actinobacteria. The ability of the dust to induce an NF-κB response by activating TLR2 and TLR4 in vitro was evaluated, as well as the relationship between such responses and quantifiable bioaerosol components. The average concentrations of bioaerosols were 7.23 mg total dust m^-3, 4.49 × 10⁵ fungal spores m^-3, 814 endotoxin units m^-3, and 0.6 × 10⁵ actinobacteria m^-3. The mean diversity measurements were 326, 0.59, and 3.39 for fungal richness, evenness, and Shannon index, respectively. Overall, fungal operational taxonomic units (OTUs) belonging to the Ascomycota phylum were most abundant (55%), followed by Basidiomycota (33%) and Mucoromycota (3%). All samples induced significant NF-κB responses through TLR2 and TLR4 activation. While fungal spore levels were positively associated with TLR2 and TLR4 activation, there was a trend that fungal species richness was negatively associated with the activation of these receptors. This observation supports the existence of divergent immunological response relationships between TLR activation and fungal spore levels on one hand and between TLR activation and fungal species diversity on the other. Such relationships seem to be described for the first time for dust from waste facilities. IMPORTANCE This manuscript presents results on multifactorial characterization of bioaerosol exposure in Norwegian waste sorting plants and the potential of such airborne dust to induce NF-κB reactions through TLR2 and TLR4 activations in an in vitro reporter cell model system. Our data revealed that increasing fungal spore levels in the dust is associated with increased activation of TLR2 and TLR4, whereas increasing fungal OTU richness is associated with decreasing activation of these receptors. The NF-κB-induced responses by the collected dust represent, therefore, effective measures of potential key immunological effects induced by a complex mixture of hazardous components, including characterized factors such as endotoxins, fungal spores, bacteria, and many other uncharacterized components. The key immunological events reported here are suggested as holistic alternatives to today's bioaerosol exposure characterization approaches for epidemiological studies in the future.

Microbial contamination and metabolite exposure assessment during waste and recyclable material collection

Waste workers are exposed to bioaerosols when handling, lifting and dumping garbage. Bioaerosol exposure has been linked to health problems such as asthma, airway irritant symptoms, infectious, gastrointestinal and skin diseases, and cancer. Our objective was to characterize the exposure of urban collectors and drivers to inhalable bioaerosols and to measured the cytotoxic effect of air samples in order to evaluate their health risk. Personal and ambient air sampling were conducted during the summer of 2019. Workers from 12 waste trucks collecting recyclables, organic waste or compost were evaluated. Bacteria and fungi were cultured, molecular biology methods were used to detect microbial indicators, cytotoxic assays were performed and endotoxins and mycotoxins were quantified. Domestic waste collectors were exposed to concentrations of bacteria and endotoxins above the recommended limits, and Aspergillus section Fumigati was detected at critical concentrations in their breathing zones. Cytotoxic effects were observed in many samples, demonstrating the potential health risk for these workers. This study establishes evidence that waste workers are exposed to microbial health risks during collection. It also demonstrates the relevance of cytotoxic assays in documenting the general toxic risk found in air samples. Our results also suggest that exposures differ depending on the type of waste, job title and discharge/unloading locations.

Microbial contamination in waste collection: Unveiling this Portuguese occupational exposure scenario

Previous studies anticipated that microorganisms and their metabolites in waste will increase as a consequence of a decreased collection frequency and due to differences in what kind of waste is bagged before collection leading to an increased exposure of workers handling the waste. This study aim was to investigate the microbial contamination present in the waste collection trucks (WCT) and in the support facilities (waste collection station - WCS). It was applied a multi-approach protocol using active (air sampling by impingement and impaction) and passive (surface swabs, electrostatic dust cloths and settled dust) sampling methods. The screening of azole-resistance, the investigation of mycotoxins and the assessment of the elicited biological responses in vitro were also carried out aiming recognizing the possible health effects of waste collection drivers. SARS-CoV-2 detection was also performed. In WCS only air samples had contamination in all the four sampling sites (canteen, operational removal core, operational removal center, and administrative service). Among all the analyzed matrices from the WCT a higher percentage of total bacterial counts and Gram-was detected in swabs (66.93%; 99.36%). In WCS the most common species were Penicillium sp. (43.98%) and Cladosporium sp. (24.68%), while on WCT Aspergillus sp. (4.18%) was also one of the most found. In the azole resistance screening Aspergillus genera was not observed in the azole-supplemented media. SARS-CoV-2 was not detected in any of the environmental samples collected, but Aspergillus section Fumigati was detected in 5 samples. Mycotoxins were not detected in EDC from WCS, while in WCT they were detected in filters (N = 1) and in settled dust samples (N = 16). In conclusion, our study reveals that a comprehensive sampling approach using active and passive sampling (e.g. settled dust sampling for a representative mycotoxin evaluation) and combined analytic methods (i.e., culture-based and molecular) is an important asset in microbial exposure assessments. Concerning the waste collection exposure scenario, the results of this study unveiled a complex exposure, particularly to fungi and their metabolites. Aspergillus section Fumigati highlight the significance of targeting this section in the waste management industry as an indicator of occupational health risk.

Peptides Regulating Proliferative Activity and Inflammatory Pathways in the Monocyte/Macrophage THP-1 Cell Line

This study evaluates the effects of five different peptides, the Epitalon^® tetrapeptide, the Vilon^® dipeptide, the Thymogen^® dipeptide, the Thymalin^® peptide complex, and the Chonluten^® tripeptide, as regulators of inflammatory and proliferative processes in the human monocytic THP-1, which is a human leukemia monocytic cell line capable of differentiating into macrophages by PMA in vitro. These peptides (Khavinson Peptides^®), characterized by Prof. Khavinson from 1973 onwards, were initially isolated from animal tissues and found to be organ specific. We tested the capacity of the five peptides to influence cell cultures in vitro by incubating THP-1 cells with peptides at certain concentrations known for being effective on recipient cells in culture. We found that all five peptides can modulate key proliferative patterns, increasing tyrosine phosphorylation of mitogen-activated cytoplasmic kinases. In addition, the Chonluten tripeptide, derived from bronchial epithelial cells, inhibited in vitro tumor necrosis factor (TNF) production of monocytes exposed to pro-inflammatory bacterial lipopolysaccharide (LPS). The low TNF release by monocytes is linked to a documented mechanism of TNF tolerance, promoting attenuation of inflammatory action. Therefore, all peptides inhibited the expression of TNF and pro-inflammatory IL-6 cytokine stimulated by LPS on terminally differentiated THP-1 cells. Lastly, by incubating the THP1 cells, treated with the peptides, on a layer of activated endothelial cells (HUVECs activated by LPS), we observed a reduction in cell adhesion, a typical pro-inflammatory mechanism. Overall, the results suggest that the Khavinson Peptides^® cooperate as natural inducers of TNF tolerance in monocyte, and act on macrophages as anti-inflammatory molecules during inflammatory and microbial-mediated activity.

Are In Vitro Cytotoxicity Assessments of Environmental Samples Useful for Characterizing the Risk of Exposure to Multiple Contaminants at the Workplace? A Systematic Review

In some occupational environments risk characterization is challenging or impossible to achieve due to the presence of multiple pollutants and contaminants. Thus, in vitro testing using the most relevant cell lines will provide information concerning health effects due to the co-exposure to multiple stressors. The aim of this review article is to identify studies where the cytotoxicity assessment was performed in environmental samples, as well as to describe the main outputs and challenges regarding risk characterization and management. This study is based on a study of the available information/data on cytotoxicity assessment performed on environmental samples following the PRISMA methodology. Different cell lines were used depending on the environment assessed and exposure routes implicated. The A549 alveolar epithelial cell line was applied in four studies for occupational exposure in the waste sorting industry and for outdoor environments; lymphocytes were used in two studies for occupational and outdoor environments; swine kidney cells were used in three studies performed in the waste industry and hepatocellular/Hep G2 in one study in the waste industry. Cytotoxicity assessments in environmental samples should have a more prominent role due to their contribution for identifying and better understanding the associations between co-exposure to environmental contaminants and adverse human health effects as a prioritization for risk management.

Aspergillus Section Fumigati in Firefighter Headquarters

Background: Aspergillus section Fumigati is one of the Aspergillus sections more frequently related to respiratory symptoms and by other health outcomes. This study aimed to characterize Aspergillus section Fumigati distribution in eleven firefighter headquarters (FFHs) to obtain an accurate occupational exposure assessment. Methods: A sampling approach protocol was performed using active (impaction method) and passive sampling methods (floor surfaces swabs, electrostatic dust collectors (EDCs), and settled dust). All samples were analysed by culture-based methods and passive sampling was used for molecular detection of Aspergillus section Fumigati. Results: Of all the matrices, the highest counts of Aspergillus sp. were obtained on settled dust filters (3.37% malt extract agar—MEA, 19.09% dichloran glycerol—DG18) followed by cleaning cloths (1.67% MEA; 7.07% DG18). Among the Aspergillus genus, the Fumigati section was predominant in Millipore and EDC samples in MEA (79.77% and 28.57%, respectively), and in swabs and settled dust filters in DG18 (44.76% and 30%, respectively). The Fumigati section was detected more frequently in DG18 (33.01%) compared to MEA (0.33%). The Fumigati section was observed in azole supplemented media (itraconazole and voriconazole) in several passive sampling methods employed and detected by qPCR in almost all passive samples, with EDCs being the matrix with the highest prevalence (n = 61; 67.8%). Conclusion: This study confirms that Aspergillus sp. is widespread and the Fumigati section is present in all FFHs. The presence of fungi potentially resistant to azoles in the FFHs was also observed. Further studies are needed to identify the best corrective and preventive measures to avoid this section contamination in this specific occupational environment.

Cytotoxicity of filtering respiratory protective devices from the waste sorting industry: A comparative study between interior layer and exhalation valve

Filtering respiratory protection devices (FRPD) are mandatory for workers to wear in the Portuguese waste-sorting industry. Previous results regarding microbial contamination found on FRPD interior layer raised the question of whether microbial contamination from the exhalation valve would also have cytotoxicity effects. Since the FRPD exhalation valves are very close to workers' nose and mouth, they represent a source of exposure to bioburden by inhalation. This study aimed to evaluate the cytotoxicity of the microbial contamination present in the FRPD exhalation valves. For this purpose, the cytotoxicity effects were determined through the MTT assay in two different cell lines (human A549 epithelial lung cells, and swine kidney cells) and compared with previous results obtained with FRPD interior layers. The contamination present in the FRPD exhalation valves presented some cytotoxicity on epithelial lung cells, suggesting the inhalation route as a potential route of exposure through the use of FRPD in the waste-sorting industry. Half-maximal (50%) inhibitory concentration (IC50) values were lower for FRPD interior layer than exhalation valves in lung cells, with overall cytotoxicity lower in exhalation valves when compared to interior layer (z = -4.455, p = 0.000). Higher bacterial counts in TSA were correlated with lower IC50 values, thus, higher cytotoxicity effect in lung cells. No statistically significant differences were detected among different workplaces.

Bioaerosol Exposure and in vitro Activation of Toll-like Receptors in a Norwegian Waste Sorting Plant

Background

The global shift toward greener societies demands new technologies and work operations in the waste-management sector. However, progressive industrial methods do not necessarily consider workers’ health. This study characterized workers' exposure to bioaerosols and investigated the bioaerosols’ potential to engage the immune system in vitro.

Methods

Full shift personal aerosol sampling was conducted over three consecutive days. Dust load was analyzed by gravimetry, fungal and actinobacterial spores were analyzed by scanning electron microscopy, and endotoxin by limulus amebocyte lysate (LAL) assay. In vitro exposure of HEK cells to airborne dust samples was used to investigate the potential of inducing an inflammatory reaction.

Results

The total dust exposure level exceeded the recommended occupational exposure limit (OEL) of 5.0 mg/m³ in 3 out of 15 samples. The inhalable endotoxin level exceeded the recommended exposure level by a 7-fold, whereas the fungal spore level exceeded the recommended exposure level by an 11-fold. Actinobacterial spores were identified in 8 out of 14 samples. In vitro experiments revealed significant TLR2 activation in 9 out of 14 samples vs. significant TLR4 activation in all samples.

Conclusion

The present study showed that the dust samples contained potentially health-impairing endotoxin, fungi, and actinobacterial levels. Furthermore, the sampled dust contained microbial components capable of inducing TLR activation and thus have the potential to evoke an inflammatory response in exposed individuals.

Bioburden contamination and Staphylococcus aureus colonization associated with firefighter's ambulances

Ambulance vehicles are an essential part of emergency clinical services. Bioburden control in ambulances, through cleaning and disinfection, is crucial to minimize hospital-acquired infections, cross contamination and exposure of patients and ambulances' crew. In Portugal, firefighter crews are responsible, besides fire extinction, for first aid and urgent pre-hospital treatment. This study assessed the bioburden in Portuguese firefighters' ambulances with a multi-approach protocol using active and passive sampling methods. Fungal resistance profile and mycotoxins detection in ambulances' ambient, and S. aureus (SA) prevalence and resistance profile in ambulances' ambient and colonization in workers were also investigated. Toxigenic fungi with clinical relevance, namely Aspergillus section Fumigati, were found on ambulance's air in the hazardous dimension range. Interestingly, surface contamination was higher after cleaning in several sampling sites. Prevalence of S. aureus was 3% in environmental samples, of which 2% were methicillin-sensitive (MSSA) and 1% methicillin-resistant (MRSA). About 2.07 fungal species were able to grow in at least one azole, ranging from one (44% samples) to five (6% samples) species in each azole. Mycotoxins were detected in mops and electrostatic dust cloths. Colonization by S. aureus in the firefighter crew was observed with a high associated prevalence, namely 48%, with a 24% prevalence of MSSA (8/33) and 21% of MRSA (7/33). Additional studies are needed to determine the potential risk of infection transmission between different vehicle fleets and under varying conditions of use. This will strengthen the paramedic sector's mission to save lives without putting their own health and safety at risk.

Occupational exposure to Aspergillus section Fumigati: Tackling the knowledge gap in Portugal

Aspergillus section Fumigati is one of the sections of the Aspergillus genus most often associated with respiratory symptoms. The azole-resistant clinical isolates in this section have been widely described worldwide. More recently, the environmental origin of azole resistance has been correlated with the development of fungal diseases and therapeutic failure. This paper presents a review of several studies performed in Portuguese occupational environments focusing on occupational exposure to this section and give guidance to exposure assessors and industrial hygienists to ensure an accurate exposure assessment. Future studies should tackle the limitations concerning the assessment of occupational exposure to the Fumigati section, in order to allow the implementation of adequate risk management measures. In the light of the results of previous studies, the following approach is proposed to ensure an accurate exposure assessment: a) a combination of active and passive sampling methods appropriate to each occupational environment; b) the use, in parallel, of culture-based methods and molecular tools to overcome the limitations of each method; c) evaluation of the mycobiota azole resistance profile; and d) consider the possible simultaneous presence of mycotoxins produced by this section when assessing workers occupational exposure. In sum, preventing the development of fungal strains resistant to azoles will only be achieved with a holistic approach. An adequate "One Health approach" can contribute positively to concerted actions in different sectors, by reducing the use of fungicides through the introduction of crops and agricultural practices that prevent fungal colonization, and by promoting the rational use of antifungal drugs in human and animal health.

Assessment of the microbial contamination of mechanical protection gloves used on waste sorting industry: A contribution for the risk characterization

In Portugal, mechanical protection gloves (MPG) are of mandatory use and during their use sweat is released and, consequently, the humidity of the material increases leading to conditions favorable to the growth of microorganisms. However, no studies have been conducted in MPG to assess the bioburden. This study intended to determine the bioburden present in MPG and their biological effects, and to discuss the possibility to use MPG as a passive method to assess occupational exposure to microbial contamination. Fungal burden was characterized through molecular tools for fungal toxigenic species, and antifungal resistance and mycotoxins profiles were determined. Cell viability was determined in swine kidney (SK) monolayer and hepatocellular carcinoma (Hep G2) cell lines. All MPG samples presented Gram-negative bacteria. The fungal contamination ranged from 0 CFU.m^-2 in both MEA and DG18, to 5.09 × 10⁶ and 2.75 × 10⁶ and the most commonly fungi found was Aspergillus spp. (50.46%). Azole resistant Aspergillus sections were found in azole supplemented media. Aspergillus sections (Circumdati, Flavi, Fumigati and Versicolores) were detected by molecular tools in 66 out of 67 samples. The most reported mycotoxin was mycophenolic acid (89.6%). HepG2 cells appear to be more sensitive to MPG contamination, with high cytotoxicity (IC50 < 0.05 mm2/ml) observed for 18 out of 57 gloves. MPG can be used in passive sampling to assess occupational exposure to bioburden in waste sorting industries and contribute for risk characterization. Some contaminants of MPG had cytotoxic potential and affected the biology of hepatic cells more than renal cells.

Occupational Exposure to Mycotoxins-Different Sampling Strategies Telling a Common Story Regarding Occupational Studies Performed in Portugal (2012-2020)

In occupational settings where exposure to organic dust occurs (e.g., intensive animal production, waste management, farming and many others) workers can also be exposed to mycotoxins. However, recognizing exposure to mycotoxins in workplace environments does not happen commonly and, consequently, remains as a not identified occupational risk factor. In the last decade, work developed in different occupational settings, using different sampling approaches reported that occupational exposure to mycotoxins occurs and it's of upmost importance to be seen as an occupational concern that needs to be tackled. This paper intends to discuss the several possibilities available for assessing and characterizing the occupational exposure to mycotoxins through the description of the advantages and limitations of the different sampling strategies. Overviewing the approaches and the main achievements used in several field campaigns developed in Portugal, the knowledge obtained will be used to support the identification of the main aspects to consider when designing new occupational studies. The need for additional research work will also be discussed where new directions to follow will be debated.