Extension of the sorting instructions for household plastic packaging and changes in exposure to bioaerosols at materials recovery facilities

Analyzing the territorial dimensions of work through a comparative study of waste recovery facilities in France and Brazil

BACKGROUND

Waste production and management from residents and collection for sorting are systems heavily dependent on territorial dimensions. Ergonomic research needs to better integrate such territorial determinants to improve work conditions and design sustainable work systems.

OBJECTIVE

Through studies in France and Brazil, this paper analyzes the territorial relations that raise work systems' sustainability challenges for materials recovery facilities (MRFs) and waste management in both countries and examines the links between work activity and territory in MRFs.

METHODS

Both studies were based on the principles of activity-oriented ergonomics and used analyses of work activity and sociotechnical systems. The French study focused on interventions conducted over a 42-month period in five MRFs. The Brazilian study was based on a 20-month longitudinal qualitative and quantitative study.

RESULTS

In this paper, we argue that territory is a key determining factor in waste production and work. Notably, the consumption patterns of residents and the economic flows within a geographic space determine the waste composition; and the territorially specified public policies, which define technical and social dimensions of waste collection and sorting. However, the territorial dimensions of waste are poorly considered in facility design. Workers' health and sorting system performance are thus affected and negatively compromising plant performance.

CONCLUSION

The territory appears as a blind spot in the design of work systems. One of the challenges is to create interfaces and devices that could help to integrate better human activity and waste territorialized anchorage, in a multilevel organization, from local communities to the global recycling chains.

Exposure levels of dust, endotoxin, and microorganisms in the Danish recycling industry

INTRODUCTION

Recycling of domestic waste and a number of employees in the recycling industry is expected to increase. This study aims to quantify current exposure levels of inhalable dust, endotoxin, and microorganisms and to identify determinants of exposure among recycling workers.

METHODS

This cross-sectional study included 170 full-shift measurements from 88 production workers and 14 administrative workers from 12 recycling companies in Denmark. The companies recycle domestic waste (sorting, shredding, and extracting materials from waste). We collected inhalable dust with personal samplers that were analysed for endotoxin (n = 170) and microorganisms (n = 101). Exposure levels of inhalable dust, endotoxin, and microorganisms and potential determinants of exposure were explored by mixed-effects models.

RESULTS

The production workers were 7-fold or higher exposed to inhalable dust, endotoxin, bacteria, and fungi than the administrative workers. Among production workers recycling domestic waste, the geometric mean exposure level was 0.6 mg/m3 for inhalable dust, 10.7 endotoxin unit (EU)/m3 for endotoxin, 1.6 × 104 colony forming units (CFU)/m³ of bacteria, 4.4 × 104 CFU/m³ of fungi (25 °C), and 1.0 × 103 CFU/m³ of fungi (37 °C). Workers handling paper or cardboard had higher exposure levels than workers handling other waste fractions. The temperature did not affect exposure levels, although there was a tendency toward increased exposure to bacteria and fungi with higher temperatures. For inhalable dust and endotoxin, exposure levels during outdoor work were low compared to indoor work. For bacteria and fungi, indoor ventilation decreased exposure. The work task, waste fraction, temperature, location, mechanical ventilation, and the company size explained around half of the variance of levels of inhalable dust, endotoxin, bacteria, and fungi.

CONCLUSION

The production workers of the Danish recycling industry participating in this study had higher exposure levels of inhalable dust, endotoxin, bacteria, and fungi than the administrative workers. Exposure levels of inhalable dust and endotoxin among recycling workers in Denmark were generally below established or suggested occupational exposure limits (OEL). However, 43% to 58% of the individual measurements of bacteria and fungi were above the suggested OEL. The waste fraction was the most influential determinant for exposure, and the highest exposure levels were seen during handling paper or cardboard. Future studies should examine the relationship between exposure levels and health effects among workers recycling domestic waste.

An assessment of occupational exposure to bioaerosols in automated versus manual waste sorting plants

Occupational exposure during waste sorting is associated with several health outcomes. This study obtained knowledge about the impact of work in fully automated waste sorting plants (AWSP; n = 3) vs manual waste sorting plants (MWSP; n = 3) on personal exposure (n = 71) to bioaerosols and exposure-related health effects. Personal full-shift air samples were collected using various filter-based active sampling devices that were placed in the workers' breathing zone. Personal exposure to inhalable and thoracic dust, endotoxin and microorganisms varied considerably between and within types of waste sorting plants (WSP). Workers at AWSP were on average exposed to 0.34 mg/m³ inhalable dust, 0.15 mg/m³ thoracic dust, and 51 EU/m³ endotoxins (geometric mean (GM) levels), whereas GM exposure levels at MWSP were 0.66 mg/m³ for inhalable dust, 0.44 mg/m³ for thoracic dust, and 32 EU/m³ for endotoxins. Exposure to submicronic fungal fragments did not differ between types of plants and ranged from levels below the detection limit (limit of detection, LOD) to levels in the order of 10⁶ fragments/m³. Higher levels of fungal fragments and fungal spores were found at AWSP compared to MWSP with a GM of 2.1 × 10⁵ spores/m³and with a GM of 1.2 × 10⁵ spores/m³, respectively. Actinobacterial spores were found in samples from AWSP only, with exposure levels ranging from 1.9 × 10⁴ to 1.1 × 10⁷ spores/m³. Exposure to microbial DNA varied within and between WSP and was on average in the order of 10⁴ copies/m³ for fungi and 10⁵ copies/m³ for bacteria. Health symptoms, such as sneezing, congested nose and runny nose were significantly more common among exposed workers compared to the unexposed control group.

Cytotoxicity of Aspergillus Section Fumigati Isolates Recovered from Protection Devices Used on Waste Sorting Industry

Safe working conditions must be guaranteed during waste sorting, which is crucial to maximizing recycling and reuse, in order to minimize workers’ exposure to chemical and biological hazards. This study determines the contribution of Aspergillus section Fumigati to the overall cytotoxicity of filtering respiratory protection devices (FRPD) and mechanic protection gloves (MPG) collected in 2019 from different workstations in one waste sorting industry in Portugal. The cytotoxicity of 133 Aspergillus section Fumigati isolates was determined as IC50 in human A549 epithelial lung cells and swine kidney cells, using the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay. Aspergillus section Fumigati cytotoxicity results were compared with previous total cytotoxicity data from FRPD and MPG samples. A significant correlation was detected between the total cytotoxicity of samples and cytotoxicity of Aspergillus section Fumigati isolates in A549 cells (rS = −0.339, p = 0.030). The cytotoxicity of Aspergillus section Fumigati isolates explained 10.7% of the total cytotoxicity of the sample. On the basis of the comparison of cytotoxicity levels, it was possible to determine the contribution of Aspergillus section Fumigati isolates for the total cytotoxicity of protection devices used in the waste sorting industry. The results support in vitro toxicology as a relevant approach in risk assessments regarding cytotoxicity in passive sampling, and thus, useful in determining the contribution of relevant microbial contaminants to overall cytotoxicity. This approach can provide valuable answers in dose/response studies, and support innovations in risk characterization and their translation into occupational policies.

Review of biological risks associated with the collection of municipal wastes

In many countries, the management of household waste has recently changed with an increased focus upon waste sorting resulting in lower collection frequency for some waste fractions. A consequence of this is the potential for increased growth of microorganisms in the waste before collection, which can lead to an increased exposure via inhalation for waste collection workers. Through a review of the literature, we aimed to evaluate risks caused by waste collecting workers' exposure to bioaerosols and to illuminate potential measures to reduce the exposure. Across countries and waste types, median exposure to fungi, bacteria, and endotoxin were typically around 10⁴ colony forming units (cfu)/m³, 10⁴ cfu/m³, and 10 EU/m³, respectively. However, some studies found 10-20+ times higher or lower median exposure levels. It was not clear how different types of waste influence the occupational exposure levels. Factors such as high loading, ventilation in and cleaning of drivers' cabs, increased collection frequency, waste in sealed sacks, and use of hand sanitizer reduce exposure. Incidences of gastrointestinal problems, irritation of the eye and skin and symptoms of organic dust toxic syndrome have been reported in workers engaged in waste collection. Several studies reported a correlation between bioaerosol exposure level and reduced lung function as either a short or a long term effect; exposure to fungi and endotoxin is often associated with an inflammatory response in exposed workers. However, a better understanding of the effect of specific microbial species on health outcomes is needed to proceed to more reliable risk assessments. Due to the increasing recycling effort and to the effects of global warming, exposure to biological agents in this working sector is expected to increase. Therefore, it is important to look ahead and plan future measures as well as improve methods to prevent long and short-term health effects.

One-year follow-up of microbial diversity in bioaerosols emitted in a waste sorting plant in France

Bioaerosols emitted in waste sorting plants (WSP) can induce some adverse health effects on the workers such as rhinitis, asthma and hypersensitivity pneumonitis. The composition of these bioaerosols is scarcely known and most of the time assessed using culture-dependent methods. Due to the well-known limitations of cultural methods, these biodiversity measurements underestimate the actual microbial taxon richness. The aim of the study was to assess the airborne microbial biodiversity by using a sequencing method in a French waste sorting plant (WSP) for one year and to investigate the main factors of variability of this biodiversity. Static sampling was performed in five areas in the plant and compared to an indoor reference (IR), using closed-face cassettes (10 L.min^-1) with polycarbonate membranes, every month for one year. Environmental data was measured (temperature, relative humidity). After DNA extraction, microbial biodiversity was assessed by means of sequencing. Bacterial genera Staphylococcus, Streptococcus, Prevotella, Lactococcus, Lactobacillus, Pseudomonas and fungal genera Wallemia, Cladosporium, Debaryomyces, Penicillium, Alternaria were the most predominant airborne microorganisms. Microbial biodiversity was different in the plant compared to the IR and seemed to be influenced by the season.

Assessment of airborne particles and bioaerosols concentrations in a waste recycling environment in Brazil

This study aims to assess the concentrations of size-fractioned particle mass (PM_1.0, PM_2.5, PM_4.0, PM₁₀) and number (PNC_0.3, PNC_0.5, PNC_1.0, PNC_2.5), bacteria, and fungi in a Materials Recycling Facility (MRF) in Brazil. The measurements were performed inside the waste processing shed (P1) and in the outdoor environment (P2) during working days in winter and spring of 2017, and summer of 2019. A total of 2,400 min of PM, 1,440 min of PNC, and 216 samples of bioaerosols were collected in the morning and afternoon. P1 has the strongest air contamination with mean values of 475.5 ± 563.7 µg m⁻³ for PM₁₀, 58.6 ± 36.0 cm⁻³ for PNC_0.3, 1,088.8 ± 825.2 colony-forming units per cubic meter (CFU m⁻³) for bacteria, and 2,738.3 ± 1,381.3 CFU m⁻³ for fungi. The indoor/outdoor ratios indicated the large influence of indoor sources due to the activities performed inside P1 that promote the generation and resuspension of pollutants. Gram-positive bacteria dominated with 58.6% of indoor samples. Overall, our results show a critical indoor air quality situation in a Brazilian MRF, which may cause several health risks for waste pickers. Finally, we call attention to the lack of occupational exposure limits for bioaerosols in industrial workplaces and mainly in MRFs.

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.

Are workers from waste sorting industry really protected by wearing Filtering Respiratory Protective Devices? The gap between the myth and reality

One of the solutions for decreasing the workers' exposure to bioburden is the use of Filtering Respiratory Protective Devices (FRPD). As such it is important to determine whether these devices are fulfilling their protective role. This is the basis of the current study, aimed at characterizing bioburden retained by 120 FRPD (both in interior layers and in exhalation valves) through culture based-methods and molecular tools and also via analysis of antifungal resistance and mycotoxins profile. Our results show that Gram - Bacteria are present at a higher prevalence than total bacteria in both matrixes. Regarding fungal identification, Chrysonilia sitophila presented the highest prevalence on interior layers (55.1% on malt extract agar (MEA) supplemented with chloramphenicol (0.05%); 59.6% on dichloran-glycerol agar (DG18)), whereas on exhalation valves Aspergillus sp. presented the highest prevalence on MEA (6.8%) and C. sitophila on DG18 (36.3%). Among Aspergillus genera, section Fumigati was the one with the highest prevalence in both matrices. Aspergillus sp. was the most prevalent on exhalation valves (75.0% ITRA) in the screening of azole resistance. Fumigati section was the most abundant Aspergillus sp. detected on the interior layers (33.33%, 40 samples out of 120) and on the exhalation valves (1.66%, 2 samples out of 120). The interior layers and exhalation valves from workers with more waste contact showed an increased exposure to bioburden. This study showed that FRPD can have high levels of bioburden, toxigenic fungal strains and Aspergillus sections with reduced susceptibility to the tested azoles and can be used as a passive sampling method since it mimics the results obtained by active methods in previous studies. The gathered information will be useful to prioritize multiple interventions on workers' education or even on FRPD replacement frequency.

Expanded cardboard waste sorting and occupational exposure to microbial species

Member states of the European Union have to maximize recycling. The current, Danish cardboard recycling system can be improved by increasing the kinds of cardboard products that can be recycled to include e.g. used beverage cartons and pizza boxes (i.e. an expanded cardboard fraction (ECF)). This study aims to obtain knowledge about exposure to airborne endotoxin and microorganisms at species level at different collection frequencies of ECF, and whether an increase in waste sorted fractions means that each waste fraction is collected less frequently. Bacterial and endotoxin concentrations were associated significantly with temperature inside the waste containers and endotoxin and fungal exposures with collection frequency. The concentration of fungi was highest at the truck back and for reduced collection frequencies. The geometric mean diameters of particles with bacteria were between 3.0 and 5.2 μm and with fungi between 3.8 μm and 6.0 μm. In total, 81 and 25 different bacterial and fungal species were found at the waste receiving plant, respectively. Work with ECF caused exposures to food-related microorganisms (e.g. Arthrobacter arilaitensis and Penicillium camemberti), potential pathogens (e.g. Bacillus cereus, Salmonella sp. and P. expansum), and commensal bacteria. Bacillus cereus and Salmonella were found in the particle size fraction often being swallowed. Workers collecting EFC will be at risk of being exposed to microbial species that normally are related to residual waste. It seems to be advisable with an EFC collection frequency shorter than eight weeks. However, introduction of new waste fractions has generally been associated with reduced collection frequencies.

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.

Evaluation of performance indicators applied to a material recovery facility fed by mixed packaging waste

Most of the integrated systems for municipal solid waste management aim to increase the recycling of secondary materials by means of physical processes including sorting, shredding and reprocessing. Several restrictions prevent from reaching a very high material recycling efficiency: the variability of the composition of new-marketed materials used for packaging production and its shape and complexity are critical issues. The packaging goods are in fact made of different materials (aluminium, polymers, paper, etc.), possibly assembled, having different shape (flat, cylindrical, one-dimensional, etc.), density, colours, optical properties and so on. These aspects limit the effectiveness and efficiency of the sorting and reprocessing plants. The scope of this study was to evaluate the performance of a large scale Material Recovery Facility (MRF) by utilizing data collected during a long period of monitoring. The database resulted from the measured data has been organized in four sections: (1) data related to the amount and type of inlet waste; (2) amount and composition of output products and waste; (3) operating data (such as worked hours for shift, planned and unscheduled maintenance time, setting parameters of the equipment, and energy consumption for shift); (4) economic data (value of each product, disposal price for the produced waste, penalty for non-compliance of products and waste, etc.). A part of this database has been utilized to build an executive dashboard composed by a set of performance indicators suitable to measure the effectiveness and the efficiency of the MRF operations. The dashboard revealed itself as a powerful tool to support managers and engineers in their decisions in respect to the market demand or compliance regulation variation as well as in the designing of the lay-out improvements. The results indicated that the 40% of the input waste was recovered as valuable products and that a large part of these (88%) complied with the standards of the recycling companies. The evaluation of the indicators led to the decision to modify the layout to improve the interception of some polymers for which the performance indicators were poor. In particular, two additional optical sorters have to be inserted to increase the yield indicator and to the overall performance of the facility. Definitely, the results of the work allowed to: increase the yield and purity of products' flows; ensure the compliance of waste flows; increase the workability.