Removing siloxanes and hydrogen sulfide from landfill gases with biochar and activated carbon filters.

Landfill gas (LFG) is formed by microorganisms within a landfill; it can be utilized as a renewable fuel in power plants. Impurities such as hydrogen sulfide and siloxanes can cause significant damage to gas engines and turbines. The aim of this study was to determine the filtration efficiencies of biochar products made of birch and willow to remove hydrogen sulfides, siloxanes, and volatile organic compounds from the gas streams compared to activated carbon. Experiments were conducted on a laboratory scale with model compounds and in a real LFG power plant where microturbines are used to generate power and heat. The biochar filters removed heavier siloxanes effectively in all of the tests. However, the filtration efficiency for volatile siloxane and hydrogen sulfide declined quickly. Biochars are promising filter materials but require further research to improve their performance.

Volatile organic compound and particulate emissions from the production and use of thermoplastic biocomposite 3D printing filaments.

Biocomposites (BCs) can be used as substitutes for unsustainable polymers in 3D printing, but their safety demands additional investigation as biological fillers may produce altered emissions during thermal processing. Commercial filament extruders can be used to produce custom feedstocks, but they are another source of airborne contaminants and demand further research. These knowledge gaps are targeted in this study. Volatile organic compound (VOC), carbonyl compound, ultrafine particle (UFP), and fine (PM2.5) and coarse (PM10) particle air concentrations were measured in this study as a filament extruder and a 3D printer were operated under an office environment using one PLA and four PLA-based BC feedstocks. Estimates of emission rates (ERs) for total VOCs (TVOC) and UFPs were also calculated. VOCs were analyzed with a GC-MS system, carbonyls were analyzed with an LC-MS/MS system, whereas real-time particle concentrations were monitored with continuously operating instruments. VOC concentrations were low throughout the experiment; TVOC ranged between 34-63 µg/m3 during filament extrusion and 41-56 µg/m3 during 3D printing, which represent calculated TVOC ERs of 2.6‒3.6 × 102 and 2.9‒3.6 × 102 µg/min. Corresponding cumulative carbonyls ranged between 60-91 and 190-253 µg/m3. Lactide and miscellaneous acids and alcohols were the dominant VOCs, while acetone, 2-butanone, and formaldehyde were the dominant carbonyls. Terpenes contributed for ca. 20-40% of TVOC during BC processing. The average UFP levels produced by the filament extruder were 0.85 × 102-1.05 × 103 #/cm3, while the 3D printer generated 6.05 × 102-2.09 × 103 #/cm3 particle levels. Corresponding particle ERs were 5.3 × 108-6.6 × 109 and 3.8 × 109-1.3 × 1010 #/min. PM2.5 and PM10 particles were produced in the following average quantities; PM2.5 levels ranged between 0.2-2.2 µg/m3, while PM10 levels were between 5-20 µg/m3 for all materials. The main difference between the pure PLA and BC feedstock emissions was terpenes, present during all BC extrusion processes. BCs are similar emission sources as pure plastics based on our findings, and a filament extruder produces contaminants at comparable or slightly lower levels in comparison to 3D printers.

Controlling flour dust exposure by an intervention focused on working methods in Finnish bakeries: a case study in two bakeries.

Objectives. The purpose of this study was to examine the effectiveness of intervention strategies to control mass concentrations and peak exposures of flour dust in two Finnish bakeries. The effect of the intervention on the proportion of various particle size fractions of the total particulate matter was also investigated. Methods. Mass concentrations of flour dust were measured during three working days in a pre-intervention and post-intervention study in both an industrial and a traditional bakery. Gravimetric sampling and real-time measurements were performed. Relevant intervention strategies focused on working methods were planned in collaboration with the managers of the bakeries. Results. The average mass concentration of inhalable flour dust reduced in most of the stationary locations post intervention. The reductions in exposure levels were between 39 and 45%. However, the exposure levels increased 28-55% in the breathing zone. Real-time measurements showed reductions in the peak mass concentrations in the traditional bakery post intervention. In both bakeries, the total particulate matter size fraction consisted predominantly of particles with an aerodynamic diameter lower than 1 µm and greater than 10 µm. Conclusion. Further studies are needed to plan more effective intervention measures supplemented by technical control methods in both bakeries.

Organic compound and particle emissions of additive manufacturing with photopolymer resins and chemical outgassing of manufactured resin products.

Photopolymer resins are applied at an increasing rate in additive manufacturing (AM) industry as vat photopolymerization (VP) and material jetting (MJ) methods gain more popularity. The aim of this study was to measure volatile organic compound (VOC), carbonyl compound, ultrafine particle (UFP), and particulate matter (PM10) air concentrations emitted in 3D printer operations. Individual chemicals were identified when multiple photopolymer resin feedstocks were used in various VP and MJ printers. The size distributions of UFPs, and indoor air parameters were also monitored. Finally, the VOC outgassing of the cured resin materials was determined over 84 days. The data demonstrated that 3D printer operators were exposed to low concentrations of airborne exposure agents as follows: average concentrations of VOCs were between 41 and 87 µg/m3, UFP number levels ranged between 0.19 and 3.62 × 103 number/cm3; however, no impact was detected on air parameters or PM10 concentrations. A majority of the UFPs existed in the 10-45 nm size range. The identified compounds included hazardous species included sensitizing acrylates and carcinogenic formaldehyde. The outgassed products included similar compounds that were encountered during the AM processes, and post-processing solvents. Products heated to 37°C emitted 1.4‒2.9-fold more VOCs than at room temperature. Total emissions were reduced by 84‒96% after 28 days roughly from 3000-14000 to 100-1000 µg/m2/hr. In conclusion, resin printer operators are exposed to low concentrations of hazardous emissions, which might result in adverse health outcomes during prolonged exposure. Manufactured resin products are suggested to be stored for 4 weeks after their production to reduce potential consumer VOC hazards.

A Comparative Study of Pyrolysis Liquids by Slow Pyrolysis of Industrial Hemp Leaves, Hurds and Roots.

This study assessed the pyrolysis liquids obtained by slow pyrolysis of industrial hemp leaves, hurds, and roots. The liquids recovered between a pyrolysis temperature of 275-350 °C, at two condensation temperatures 130 °C and 70 °C, were analyzed. Aqueous and bio-oil pyrolysis liquids were produced and analyzed by proton nuclear magnetic resonance (NMR), gas chromatography-mass spectrometry (GC-MS), and atmospheric pressure photoionization Fourier transform ion cyclotron resonance mass spectrometry (APPI FT-ICR MS). NMR revealed quantitative concentrations of the most abundant compounds in the aqueous fractions and compound groups in the oily fractions. In the aqueous fractions, the concentration range of acetic acid was 50-241 gL-1, methanol 2-30 gL-1, propanoic acid 5-20 gL-1, and 1-hydroxybutan-2-one 2 gL-1. GC-MS was used to compare the compositions of the volatile compounds and APPI FT-ICR MS was utilized to determine the most abundant higher molecular weight compounds. The different obtained pyrolysis liquids (aqueous and oily) had various volatile and nonvolatile compounds such as acetic acid, 2,6-dimethoxyphenol, 2-methoxyphenol, and cannabidiol. This study provides a detailed understanding of the chemical composition of pyrolysis liquids from different parts of the industrial hemp plant and assesses their possible economic potential.

Weathering of Antibacterial Melt-Spun Polyfilaments Modified by Pine Rosin.

For many antibacterial polymer fibres, especially for those with natural functional additives, the antibacterial response might not last over time. Moreover, the mechanical performance of polymeric fibres degrades significantly during the intended operation, such as usage in textile and industrial filter applications. The degradation process and overall ageing can lead to emitted volatile organic compounds (VOCs). This work focused on the usage of pine rosin as natural antibacterial chemical and analysed the weathering of melt-spun polyethylene (PE) and poly lactic acid (PLA) polyfilaments. A selected copolymer surfactant, as an additional chemical, was studied to better integrate rosin with the molecular structure of the plastics. The results reveal that a high 20 w-% of rosin content can be obtained by surfactant addition in non-oriented PE and PLA melt-spun polyfilaments. According to the VOC analysis, interestingly, the total emissions from the melt-spun PE and PLA fibres were lower for rosin-modified (10 w-%) fibres and when analysed below 60 ℃. The PE fibres of the polyfilaments were found to be clearly more durable in terms of the entire weathering study, i.e., five weeks of ultraviolet radiation, thermal ageing and standard washing. The antibacterial response against Gram-positive Staphylococcus aureus by the rosin-containing fibres was determined to be at the same level (decrease of 3-5 logs cfu/mL) as when using 1.0 w-% of commercial silver-containing antimicrobial. For the PE polyfilaments with rosin (10 w-%), full killing response (decrease of 3-5 logs cfu/mL) remained after four weeks of accelerated ageing at 60 ℃.

Emissions, airflow patterns and modeling of test compounds in controlled hospital environments.

Spreading and distribution of selected volatile organic compounds (VOCs) released as point source emissions in a hospital environment were investigated in two office rooms and two patient rooms. Six tracer compounds were released from six locations and their concentrations were measured in five sampling sites during two consecutive days. The air flow rates, velocity and flow direction, air temperature, pressure differences between adjacent rooms, and relative humidity and concentrations of the tracer compounds were measured. The results revealed that the size of the examined space and ventilation rates, the monitoring point should be either close to the exhaust terminal device or in the middle of the occupied zone the way that supply air flows do not interfere the measurements. Depending on the inlet terminal device and its location, the air is either delivered parallel to the ceiling or it can be directed to a desired spot into the occupied zone. The tracer compounds did spread evenly within the room and their concentrations decreased inversely with the distance. In rooms with a good ventilation, the concentrations at the exhaust air terminal units were close to those measured near the source point. The results obtained from modeling were consistent with the measurements.

Predicting Indoor Concentrations of Black Carbon in Residential Environments.

Black carbon (BC) is a descriptive term that refers to light-absorbing particulate matter (PM) produced by incomplete combustion and is often used as a surrogate for traffic-related air pollution. Exposure to BC has been linked to adverse health effects. Penetration of ambient BC is typically the primary source of indoor BC in the developed world. Other sources of indoor BC include biomass and kerosene stoves, lit candles, and charring food during cooking. Home characteristics can influence the levels of indoor BC. As people spend most of their time indoors, human exposure to BC can be associated to a large extent with indoor environments. At the same time, due to the cost of environmental monitoring, it is often not feasible to directly measure BC inside multiple individual homes in large-scale population-based studies. Thus, a predictive model for indoor BC is needed to support risk assessment in public health. In this study, home characteristics and occupant activities that potentially modify indoor levels of BC were documented in 23 homes, and indoor and outdoor BC concentrations were measured twice. The homes were located in the Cincinnati-Kentucky-Indiana tristate region and measurements occurred from September 2015 through August 2017. A linear mixed-effect model was developed to predict BC concentration in residential environments. The measured outdoor BC concentrations and the documented home characteristics were utilized as predictors of indoor BC concentrations. After the model was developed, a leave-one-out cross-validation algorithm was deployed to assess the predictive accuracy of the output. The following home characteristics and occupant activities significantly modified the concentration of indoor BC: outdoor BC, lit candles and electrostatic or high efficiency particulate air (HEPA) filters in heating, ventilation and air conditioning (HVAC) systems. Predicted indoor BC concentrations explained 78% of the variability in the measured indoor BC concentrations. The data show that outdoor BC combined with home characteristics can be used to predict indoor BC levels with reasonable accuracy.

Cleaning workers' exposure to volatile organic compounds and particulate matter during floor polish removal and reapplication.

The floor polish removal (FPR) and reapplication (FPA) are important cleaning tasks in public buildings that have hard floor surfaces. Usually, the FPR and FPA are conducted once or twice a year, during the periodic cleaning of these buildings. The FPR can be performed either chemically (CFPR) or by using dry scrubber (DFPR), when the polish is ground from the floor. In this study, cleaning workers' exposure to volatile organic compounds (VOCs) and particulate matter (PM) during the FPR and FPA, and the differences in the exposures between the two FPR methods were investigated. In total, three buildings located in Central Finland were included, and total of six cleaning workers (two per building) participated in the study. In Buildings 1 and 2, the CFPR and FPA were performed and in Building 3, the DFPR was conducted. TVOC (total volatile organic compounds) concentrations in the breathing zone of the workers during the CFPR were 8,740 and 390 µg/m3 (SD 3,290 and 180 µg/m3) for Buildings 1 and 2, respectively. During the DFPR in Building 3, the average TVOC concentration was 400 µg/m3 (SD 180 µg/m3, stationary sampling). The TVOC concentrations during the FPA were high, 1,640 and 2,170 µg/m3 on average (SD 1,570 and 930 µg/m3) for Buildings 1 and 2, respectively. Glycol ethers were the most prominent VOCs during the CFPR and FPA, whereas carboxylic acids were the most common during the DFPR. The inhalable dust concentrations in the workers' breathing zone were noticeably higher during the DFPR (1.55 mg/m3 on average, SD 0.01 mg/m3) than the CFPR (0.24 mg/m3 on average, SD 0.05 mg/m3). Finnish occupational exposure limit value for organic inhalable dust is 5 mg/m3. As the products used during the CFPR and FPA contain glycol ethers and ethanolamines that are absorbed via the skin as well, the use of skin protection is recommended. Whereas the use of FFP3 respirators and skin protection are recommended during the DFPR to prevent the PM exposure.

Indoor air-related symptoms and volatile organic compounds in materials and air in the hospital environment.

In this case study, hospital workers did suffer from symptoms related to the poor indoor air quality. To investigate reasons for symptoms MM40-survey and house inspection methods were performed. The study consisted of 49 operating rooms and 470 employees. MM-40 survey revealed that over 40% of the staff suffered from skin reactions, over 50% had upper respiratory tract symptoms and 25% suffered headaches. No reason for the staff's symptom could be found in the structural studies of workplaces. The mean air exchange rate of the rooms was 5.51/h. In total 61 materials and 49 indoor air samples were taken. The most frequently found compounds in the material samples were 2-ethyl-1-hexanol and aliphatic hydrocarbons. VOC emissions were high in some of the material samples and they presumably were the one reason for the workers' symptoms observed in some in of the rooms. However, indoor air VOC concentrations were low in most of the cases. According to the linear regression model emissions from flooring material couldn't explain the indoor air concentration of the VOCs. One reason for that was the high ventilation rates of the rooms, which presumably kept VOC levels in indoors low. In addition, VOC concentrations indoors were strongly related to the ongoing healthcare activities in the hospital.

Occupational exposure to gaseous and particulate contaminants originating from additive manufacturing of liquid, powdered, and filament plastic materials and related post-processes.

The aim of this study was to measure the concentrations of gaseous and particulate contaminants originated from additive manufacturing operations and post-processes in an occupational setting when plastics were used as feedstock materials. Secondary aims were to evaluate the concentration levels based on proposed exposure limits and target values and to propose means to reduce exposure to contaminants released in additive manufacturing processes. Volatile organic compounds were sampled with Tenax TA adsorption tubes and analyzed with a thermo desorption gas chromatography-mass spectrometry instrument. Carbonyl compounds were sampled with DNPH-Silica cartridges and analyzed with a high-performance liquid chromatography device. Particles were measured with P-Trak instrument and indoor air quality was sampled with IAQ-Calc instrument. Dust mass concentrations were measured simultaneously with a DustTrak DRX instrument and IOM-samplers. Particle concentrations were highest (2070-81 890 #/cm3 mean) during manufacturing with methods where plastics were thermally processed. Total volatile organic compounds concentrations, in contrast, were low (113-317 µg/m3 mean) during manufacturing with such methods, and vat photopolymerization. However, total volatile organic compounds concentrations of material jetting and multi jet fusion methods were higher (1,114-2,496 µg/m3 mean), perhaps because of material and binder spraying, where part of the spray can become aerosolized. Chemical treatment of manufactured objects was found to be a severe volatile organic compounds source as well. Formaldehyde was detected in low concentrations (3-40 µg/m3) in all methods except for material jetting method, in addition to several other carbonyl compounds. Notable dust concentrations (1.4-9.1 mg/m3) were detected only during post-processing of powder bed fusion and multi jet fusion manufactured objects. Indoor air quality parameters were not found to be notably impacted by manufacturing operations. Only low concentrations (below 2 ppm) of CO were detected during several manufacturing processes. All studied additive manufacturing operations emitted potentially harmful contaminants into their environments, which should be considered in occupational additive manufacturing and workplace design. According to the measured contaminant levels it is possible that adverse additive manufacturing related health effects may occur among exposed workers.

Evaluation of the use of low flow passive sampling technique in offset printing plants.

OBJECTIVES: The aim of this study was to evaluate the suitability and applicability of low-flow passive tubes for sampling of organic solvents in occupational environment. MATERIALS AND METHODS: Laboratory and field studies were conducted to continue the evaluation of low-flow diffusive sampling combined with thermal desorption and gas chromatographic/mass spectrometric analysis in occupational hygiene surveys. Passive sampler tubes with Tenax GR adsorbent were employed to assess exposures to organic solvents in 10 small sheet-fed offset printing plants in Finland. The retention of the solvent compounds in the samplers was investigated using laboratory chamber studies. Active sampling with activated carbon tubes served as the control method. RESULTS: The laboratory tests showed that passive tubes had good retention, stability and reproducibility for the solvent compounds. Parallel passive and active sampling in both breathing zone and area monitoring in the printing plants yielded similar measurements though passive sampling tended to give slightly higher concentrations (by 5 to 12%). The suitability of passive sampling to be done by workers was also confirmed. The study also shows that exposure to organic solvents can be effectively reduced by the use of vegetable oil-based cleaning fluids. Especially, since ventilation and other protective measures are often inadequate in small facilities, the use of toxic cleaning solutions should be avoided. CONCLUSIONS: Passive sampling tubes with capillary orifice analyzed with thermal desorption GC-MS are well suited for measuring occupational solvent exposure. Method is well suited for sampling done by workers.