Last data update: Apr 22, 2024. (Total: 46599 publications since 2009)
Records 1-13 (of 13 Records) |
Query Trace: Martin SB Jr[original query] |
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Large-Format Additive Manufacturing and Machining Using High-Melt-Temperature Polymers. Part I: Real-Time Particulate and Gas-Phase Emissions
Stefaniak AB , Bowers LN , Martin SB Jr , Hammond DR , Ham JE , Wells JR , Fortner AR , Knepp AK , du Preez S , Pretty JR , Roberts JL , du Plessis JL , Schmidt A , Duling MG , Bader A , Virji MA . J Chem Health Saf 2021 28 (3) 190-200 The literature on emissions during material extrusion additive manufacturing with 3-D printers is expanding; however, there is a paucity of data for large-format additive manufacturing (LFAM) machines that can extrude high-melt-temperature polymers. Emissions from two LFAM machines were monitored during extrusion of six polymers: acrylonitrile butadiene styrene (ABS), polycarbonate (PC), high-melt-temperature polysulfone (PSU), poly(ether sulfone) (PESU), polyphenylene sulfide (PPS), and Ultem (poly(ether imide)). Particle number, total volatile organic compound (TVOC), carbon monoxide (CO), and carbon dioxide (CO(2)) concentrations were monitored in real-time. Particle emission rate values (no./min) were as follows: ABS (1.7 × 10(11) to 7.7 × 10(13)), PC (5.2 × 10(11) to 3.6 × 10(13)), Ultem (5.7 × 10(12) to 3.1 × 10(13)), PPS (4.6 × 10(11) to 6.2 × 10(12)), PSU (1.5 × 10(12) to 3.4 × 10(13)), and PESU (2.0 to 5.0 × 10(13)). For print jobs where the mass of extruded polymer was known, particle yield values (g(-1) extruded) were as follows: ABS (4.5 × 10(8) to 2.9 × 10(11)), PC (1.0 × 10(9) to 1.7 × 10(11)), PSU (5.1 × 10(9) to 1.2 × 10(11)), and PESU (0.8 × 10(11) to 1.7 × 10(11)). TVOC emission yields ranged from 0.005 mg/g extruded (PESU) to 0.7 mg/g extruded (ABS). The use of wall-mounted exhaust ventilation fans was insufficient to completely remove airborne particulate and TVOC from the print room. Real-time CO monitoring was not a useful marker of particulate and TVOC emission profiles for Ultem, PPS, or PSU. Average CO(2) and particle concentrations were moderately correlated (r (s) = 0.76) for PC polymer. Extrusion of ABS, PC, and four high-melt-temperature polymers by LFAM machines released particulate and TVOC at levels that could warrant consideration of engineering controls. LFAM particle emission yields for some polymers were similar to those of common desktop-scale 3-D printers. |
Large-Format Additive Manufacturing and Machining Using High-Melt-Temperature Polymers. Part II: Characterization of Particles and Gases
Stefaniak AB , Bowers LN , Martin SB Jr , Hammond DR , Ham JE , Wells JR , Fortner AR , Knepp AK , du Preez S , Pretty JR , Roberts JL , du Plessis JL , Schmidt A , Duling MG , Bader A , Virji MA . J Chem Health Saf 2021 28 (4) 268-278 Extrusion of high-melt-temperature polymers on large-format additive manufacturing (LFAM) machines releases particles and gases, though there is no data describing their physical and chemical characteristics. Emissions from two LFAM machines were monitored during extrusion of acrylonitrile butadiene styrene (ABS) and polycarbonate (PC) polymers as well as high-melt-temperature Ultem (poly(ether imide)), polysulfone (PSU), poly(ether sulfone) (PESU), and polyphenylene sulfide (PPS) polymers. Filter samples of particles were collected for quantification of elements and bisphenol A and S (BPA, BPS) and visualization of morphology. Individual gases were quantified on substance-specific media. Aerosol sampling demonstrated that concentrations of elements were generally low for all polymers, with a maximum of 1.6 mg/m(3) for iron during extrusion of Ultem. BPA, an endocrine disruptor, was released into air during extrusion of PC (range: 0.4 ± 0.1 to 21.3 ± 5.3 μg/m(3)). BPA and BPS (also an endocrine disruptor) were released into air during extrusion of PESU (BPA, 2.0-8.7 μg/m(3); BPS, 0.03-0.07 μg/m(3)). Work surfaces and printed parts were contaminated with BPA (<8-587 ng/100 cm(2)) and BPS (<0.22-2.5 ng/100 cm(2)). Gas-phase sampling quantified low levels of respiratory irritants (phenol, SO(2), toluene, xylenes), possible or known asthmagens (caprolactam, methyl methacrylate, 4-oxopentanal, styrene), and possible occupational carcinogens (benzene, formaldehyde, acetaldehyde) in air. Characteristics of particles and gases released by high-melt-temperature polymers during LFAM varied, which indicated the need for polymer-specific exposure and risk assessments. The presence of BPA and BPS on surfaces revealed a previously unrecognized source of dermal exposure for additive manufacturing workers using PC and PESU polymers. |
Ventilation improvements among K-12 public school districts - United States, August-December 2022
Mark-Carew M , Kang G , Pampati S , Mead KR , Martin SB Jr , Barrios LC . MMWR Morb Mortal Wkly Rep 2023 72 (14) 372-376 Improving ventilation has been one of several COVID-19 prevention strategies implemented by kindergarten through grade 12 (K-12) schools to stay open for safe in-person learning. Because transmission of SARS-CoV-2 occurs through inhalation of infectious viral particles, it is important to reduce the concentration of and exposure time to infectious aerosols (1-3). CDC examined reported ventilation improvement strategies among U.S. K-12 public school districts using telephone survey data collected during August-December 2022. Maintaining continuous airflow through school buildings during active hours was the most frequently reported strategy by school districts (50.7%); 33.9% of school districts reported replacement or upgrade of heating, ventilation, and air conditioning (HVAC) systems; 28.0% reported installation or use of in-room air cleaners with high-efficiency particulate air (HEPA) filters; and 8.2% reported installation of ultraviolet (UV) germicidal irradiation (UVGI) devices, which use UV light to kill airborne pathogens, including bacteria and viruses. School districts in National Center for Education Statistics (NCES) city locales, the West U.S. Census Bureau region, and those designated by U.S. Census Bureau Small Area Income Poverty Estimates (SAIPE) as high-poverty districts reported the highest percentages of HVAC system upgrades and HEPA-filtered in-room air cleaner use, although 28%-60% of all responses were unknown or missing. Federal funding remains available to school districts to support ventilation improvements. Public health departments can encourage K-12 school officials to use available funding to improve ventilation and help reduce transmission of respiratory diseases in K-12 settings. |
Efficacy of Do-It-Yourself air filtration units in reducing exposure to simulated respiratory aerosols
Derk RC , Coyle JP , Lindsley WG , Blachere FM , Lemons AR , Service SK , Martin SB Jr , Mead KR , Fotta SA , Reynolds JS , McKinney WG , Sinsel EW , Beezhold DH , Noti JD . Build Environ 2023 229 109920 Many respiratory diseases, including COVID-19, can be spread by aerosols expelled by infected people when they cough, talk, sing, or exhale. Exposure to these aerosols indoors can be reduced by portable air filtration units (air cleaners). Homemade or Do-It-Yourself (DIY) air filtration units are a popular alternative to commercially produced devices, but performance data is limited. Our study used a speaker-audience model to examine the efficacy of two popular types of DIY air filtration units, the Corsi-Rosenthal cube and a modified Ford air filtration unit, in reducing exposure to simulated respiratory aerosols within a mock classroom. Experiments were conducted using four breathing simulators at different locations in the room, one acting as the respiratory aerosol source and three as recipients. Optical particle spectrometers monitored simulated respiratory aerosol particles (0.3-3 μm) as they dispersed throughout the room. Using two DIY cubes (in the front and back of the room) increased the air change rate as much as 12.4 over room ventilation, depending on filter thickness and fan airflow. Using multiple linear regression, each unit increase of air change reduced exposure by 10%. Increasing the number of filters, filter thickness, and fan airflow significantly enhanced the air change rate, which resulted in exposure reductions of up to 73%. Our results show DIY air filtration units can be an effective means of reducing aerosol exposure. However, they also show performance of DIY units can vary considerably depending upon their design, construction, and positioning, and users should be mindful of these limitations. |
Towards sustainable additive manufacturing: The need for awareness of particle and vapor releases during polymer recycling, making filament, and fused filament fabrication 3-D printing
Stefaniak AB , Bowers LN , Cottrell G , Erdem E , Knepp AK , Martin SB Jr , Pretty J , Duling MG , Arnold ED , Wilson Z , Krider B , Fortner AR , LeBouf RF , Virji MA , Sirinterlikci A . Resour Conserv Recycl 2022 176 Fused filament fabrication three-dimensional (FFF 3-D) printing is thought to be environmentally sustainable; however, significant amounts of waste can be generated from this technology. One way to improve its sustainability is via distributed recycling of plastics in homes, schools, and libraries to create feedstock filament for printing. Risks from exposures incurred during recycling and reuse of plastics has not been incorporated into life cycle assessments. This study characterized contaminant releases from virgin (unextruded) and recycled plastics from filament production through FFF 3-D printing. Waste polylactic acid (PLA) and acrylonitrile butadiene styrene (ABS) plastics were recycled to create filament; virgin PLA, ABS, high and low density polyethylenes, high impact polystyrene, and polypropylene pellets were also extruded into filament. The release of particles and chemicals into school classrooms was evaluated using standard industrial hygiene methodologies. All tasks released particles that contained hazardous metals (e.g., manganese) and with size capable of depositing in the gas exchange region of the lung, i.e., granulation of waste PLA and ABS (667 to 714 nm) and filament making (608 to 711 nm) and FFF 3-D printing (616 to 731 nm) with waste and virgin plastics. All tasks released vapors, including respiratory irritants and potential carcinogens (benzene and formaldehyde), mucus membrane irritants (acetone, xylenes, ethylbenzene, and methyl methacrylate), and asthmagens (styrene, multiple carbonyl compounds). These data are useful for incorporating risks of exposure to hazardous contaminants in future life cycle evaluations to demonstrate the sustainability and circular economy potential of FFF 3-D printing in distributed spaces. © 2021 |
Particle and organic vapor emissions from children's 3-D pen and 3-D printer toys
Yi J , Duling MG , Bowers LN , Knepp AK , LeBouf RF , Nurkiewicz TR , Ranpara A , Luxton T , Martin SB Jr , Burns DA , Peloquin DM , Baumann EJ , Virji MA , Stefaniak AB . Inhal Toxicol 2019 31 1-14 Objective: Fused filament fabrication "3-dimensional (3-D)" printing has expanded beyond the workplace to 3-D printers and pens for use by children as toys to create objects.Materials and methods: Emissions from two brands of toy 3-D pens and one brand of toy 3-D printer were characterized in a 0.6 m(3) chamber (particle number, size, elemental composition; concentrations of individual and total volatile organic compounds (TVOC)). The effects of print parameters on these emission metrics were evaluated using mixed-effects models. Emissions data were used to model particle lung deposition and TVOC exposure potential.Results: Geometric mean particle yields (10(6)-10(10) particles/g printed) and sizes (30-300 nm) and TVOC yields (<detectable to 590 microg TVOC/g printed) for the toys were similar to those from 3-D printers used in workplaces. Metal emissions included manganese (1.6-92.3 ng/g printed) and lead (0.13-1.2 ng/g printed). Among toys, extruder nozzle conditions (diameter, temperature) and filament (type, color, and extrusion speed) significantly influenced particle and TVOC emissions. Dose modeling indicated that emitted particles would deposit in the lung alveoli of children. Exposure modeling indicated that TVOC concentration from use of a single toy would be 1-31 microg/m(3) in a classroom and 3-154 microg/m(3) in a residential living room.Discussion: Potential exists for inhalation of organic vapors and metal-containing particles during use of these toys.Conclusions: If deemed appropriate, e.g. where multiple toys are used in a poorly ventilated area or a toy is positioned near a child's breathing zone, control technologies should be implemented to reduce emissions and exposure risk. |
Ambulance disinfection using Ultraviolet Germicidal Irradiation (UVGI): Effects of fixture location and surface reflectivity
Lindsley WG , McClelland TL , Neu DT , Martin SB Jr , Mead KR , Thewlis RE , Noti JD . J Occup Environ Hyg 2017 15 (1) 0 Ambulances are frequently contaminated with infectious microorganisms shed by patients during transport that can be transferred to subsequent patients and emergency medical service workers. Manual decontamination is tedious and time-consuming, and persistent contamination is common even after cleaning. Ultraviolet germicidal irradiation (UVGI) has been proposed as a terminal disinfection method for ambulance patient compartments. However, no published studies have tested the use of UVGI in ambulances. The objectives of this study were to investigate the efficacy of a UVGI system in an ambulance patient compartment and to examine the impact of UVGI fixture position and the UV reflectivity of interior surfaces on the time required for disinfection. A UVGI fixture was placed in the front, middle or back of an ambulance patient compartment, and the UV irradiance was measured at 49 locations. Aluminum sheets and UV-reflective paint were added to examine the effects of increasing surface reflectivity on disinfection time. Disinfection tests were conducted using Bacillus subtilis spores as a surrogate for pathogens. Our results showed that the UV irradiance varied considerably depending upon the surface location. For example, with the UVGI fixture in the back position and without the addition of UV-reflective surfaces, the most irradiated location received a dose of UVGI sufficient for disinfection in 16 seconds, but the least irradiated location required 15 hours. Because the overall time required to disinfect all of the interior surfaces is determined by the time required to disinfect the surfaces receiving the lowest irradiation levels, the patient compartment disinfection times for different UVGI configurations ranged from 16.5 hours to 59 minutes depending upon the UVGI fixture position and the interior surface reflectivity. These results indicate that UVGI systems can reduce microbial surface contamination in ambulance compartments, but the systems must be rigorously validated before deployment. Optimizing the UVGI fixture position and increasing the UV reflectivity of the interior surfaces can substantially improve the performance of a UVGI system and reduce the time required for disinfection. |
Characterization of chemical contaminants generated by a desktop fused deposition modeling 3-dimensional printer
Stefaniak AB , LeBouf RF , Yi J , Ham J , Nurkewicz T , Schwegler-Berry DE , Chen BT , Wells JR , Duling MG , Lawrence RB , Martin SB Jr , Johnson AR , Virji MA . J Occup Environ Hyg 2017 14 (7) 0 Printing devices are known to emit chemicals into the indoor atmosphere. Understanding factors that influence release of chemical contaminants from printers is necessary to develop effective exposure assessment and control strategies. In this study, a desktop fused deposition modeling (FDM) 3-D printer using acrylonitrile butadiene styrene (ABS) or polylactic acid (PLA) filaments and two monochrome laser printers were evaluated in a 0.5 m3 chamber. During printing, chamber air was monitored for vapors using a real-time photoionization detector (results expressed as isobutylene equivalents) to measure total volatile organic compound (TVOC) concentrations, evacuated canisters to identify specific VOCs by off-line gas chromatography-mass spectrometry (GC-MS) analysis, and liquid bubblers to identify carbonyl compounds by GC-MS. Airborne particles were collected on filters for off-line analysis using scanning electron microscopy with an energy dispersive x-ray detector to identify elemental constituents. For 3-D printing, TVOC emission rates were influenced by a printer malfunction, filament type, and to a lesser extent, by filament color; however, rates were not influenced by the number of printer nozzles used or the manufacturer's provided cover. TVOC emission rates were significantly lower for the 3-D printer (49 to 3552 microg h-1) compared to the laser printers (5782 to 7735 microg h-1). A total of 14 VOCs were identified during 3-D printing that were not present during laser printing. 3-D printed objects continued to off-gas styrene, indicating potential for continued exposure after the print job is completed. Carbonyl reaction products were likely formed from emissions of the 3-D printer, including 4-oxopentanal. Ultrafine particles generated by the 3-D printer using ABS and a laser printer contained chromium. Consideration of the factors that influenced the release of chemical contaminants (including known and suspected asthmagens such as styrene and 4-oxopentanal) from a FDM 3-D printer should be made when designing exposure assessment and control strategies. |
A new dual-collimation batch reactor for determination of ultraviolet inactivation rate constants for microorganisms in aqueous suspensions
Martin SB Jr , Schauer ES , Blum DH , Kremer PA , Bahnfleth WP , Freihaut JD . J Photochem Photobiol B 2016 162 674-680 We developed, characterized, and tested a new dual-collimation aqueous UV reactor to improve the accuracy and consistency of aqueous k-value determinations. This new system is unique because it collimates UV energy from a single lamp in two opposite directions. The design provides two distinct advantages over traditional single-collimation systems: 1) real-time UV dose (fluence) determination; and 2) simple actinometric determination of a reactor factor that relates measured irradiance levels to actual irradiance levels experienced by the microbial suspension. This reactor factor replaces three of the four typical correction factors required for single-collimation reactors. Using this dual-collimation reactor, Bacillus subtilis spores demonstrated inactivation following the classic multi-hit model with k=0.1471cm2/mJ (with 95% confidence bounds of 0.1426 to 0.1516). |
Environmental Characterization of a Coffee Processing Workplace with Obliterative Bronchiolitis in Former Workers
Duling MG , LeBouf RF , Cox-Ganser JM , Kreiss K , Martin SB Jr , Bailey RL . J Occup Environ Hyg 2016 13 (10) 770-81 INTRODUCTION: Obliterative bronchiolitis in five former coffee processing employees at a single workplace prompted an exposure study of current workers. METHODS: Exposure characterization was performed by observing processes, assessing the ventilation system and pressure relationships, analyzing headspace of flavoring samples, and collecting and analyzing personal breathing zone and area air samples for diacetyl and 2,3-pentanedione vapors and total inhalable dust by work area and job title. Mean airborne concentrations were calculated using the minimum variance unbiased estimator of the arithmetic mean. RESULTS: Workers in the grinding/packaging area for unflavored coffee had the highest mean diacetyl exposures, with personal concentrations averaging 93 parts per billion (ppb). This area was under positive pressure with respect to flavored coffee production (mean personal diacetyl levels of 80 ppb). The 2,3-pentanedione exposures were highest in the flavoring room with mean personal exposures of 122 ppb, followed by exposures in the unflavored coffee grinding/packaging area (53 ppb). Peak 15-minute airborne concentrations of 14,300 ppb diacetyl and 13,800 ppb 2,3-pentanedione were measured at a small open hatch in the lid of a hopper containing ground unflavored coffee on the mezzanine over the grinding/packaging area. Three out of the four bulk coffee flavorings tested had at least a factor of two higher 2,3-pentanedione than diacetyl headspace measurements. CONCLUSIONS: At a coffee processing facility producing both unflavored and flavored coffee, we found the grinding and packaging of unflavored coffee generate simultaneous exposures to diacetyl and 2,3-pentanedione that were well in excess of the NIOSH proposed RELs and similar in magnitude to those in the areas using a flavoring substitute for diacetyl. These findings require physicians to be alert for obliterative bronchiolitis and employers, government, and public health consultants to assess the similarities and differences across the industry to motivate preventive intervention where indicated by exposures above the proposed RELs for diacetyl and 2,3-pentanedione. |
Respiratory morbidity in a coffee processing workplace with sentinel obliterative bronchiolitis cases
Bailey RL , Cox-Ganser JM , Duling MG , LeBouf RF , Martin SB Jr , Bledsoe TA , Green BJ , Kreiss K . Am J Ind Med 2015 58 (12) 1235-45 RATIONALE: Obliterative bronchiolitis in former coffee workers prompted a cross-sectional study of current workers. Diacetyl and 2,3-pentanedione levels were highest in areas for flavoring and grinding/packaging unflavored coffee. METHODS: We interviewed 75 (88%) workers, measured lung function, and created exposure groups based on work history. We calculated standardized morbidity ratios (SMRs) for symptoms and spirometric abnormalities. We examined health outcomes by exposure groups. RESULTS: SMRs were elevated 1.6-fold for dyspnea and 2.7-fold for obstruction. The exposure group working in both coffee flavoring and grinding/packaging of unflavored coffee areas had significantly lower mean ratio of forced expiratory volume in 1 s to forced vital capacity and percent predicted mid-expiratory flow than workers without such exposure. CONCLUSION: Current workers have occupational lung morbidity associated with high diacetyl and 2,3-pentanedione exposures, which were not limited to flavoring areas. |
Effects of ultraviolet germicidal irradiation (UVGI) on N95 respirator filtration performance and structural integrity
Lindsley WG , Martin SB Jr , Thewlis RE , Sarkisian K , Nwoko JO , Mead KR , Noti JD . J Occup Environ Hyg 2015 12 (8) 509-17 The ability to disinfect and reuse disposable N95 filtering facepiece respirators (FFRs) may be needed during a pandemic of an infectious respiratory disease such as influenza. Ultraviolet germicidal irradiation (UVGI) is one possible method for respirator disinfection. However, UV radiation degrades polymers, which presents the possibility that UVGI exposure could degrade the ability of a disposable respirator to protect the worker. To study this, we exposed both sides of material coupons and respirator straps from four models of N95 FFRs to UVGI doses from 120 to 950 J/cm2. We then tested the particle penetration, flow resistance and the bursting strengths of the individual respirator coupon layers, and the breaking strength of the respirator straps. We found that UVGI exposure led to a small increase in particle penetration (up to 1.25%) and had little effect on the flow resistance. UVGI exposure had a more pronounced effect on the strengths of the respirator materials. At the higher UVGI doses, the strength of the layers of respirator material was substantially reduced (in some cases, by >90%). The changes in the strengths of the respirator materials varied considerably among the different models of respirators. UVGI had less of an effect on the respirator straps; a dose of 2360 J/cm2 reduced the breaking strength of the straps by 20% to 51%. Our results suggest that UVGI could be used to effectively disinfect disposable respirators for reuse, but the maximum number of disinfection cycles will be limited by the respirator model and the UVGI dose required to inactivate the pathogen. |
Exposure to influenza virus aerosols in the hospital setting: is routine patient care an aerosol generating procedure?
Cummings KJ , Martin SB Jr , Lindsley WG , Othumpangat S , Blachere FM , Noti JD , Beezhold DH , Roidad N , Parker JE , Weissman DN . J Infect Dis 2014 210 (3) 504-5 We read with interest the article by Bischoff et al, in which they describe detection of influenza virus in aerosols around hospitalized patients with influenza virus infection who were receiving routine care [1]. As the authors note, current World Health Organization and Centers for Disease Control and Prevention guidelines for protection of healthcare professionals from influenza virus infection rely on the supposition that, under routine conditions, most transmission occurs via large droplets, rather than via small-particle aerosols [2, 3]. Under these guidelines, aerosol transmission is presumed to be limited to certain aerosol-generating procedures (AGPs), for which higher-level respiratory protection is recommended. The designation of AGPs has been made in large part by extrapolation from epidemiologic studies of outbreaks of other respiratory infections, such as tuberculosis and SARS coronavirus infection [4]. Whether such procedures are uniquely associated with generation of potentially infectious aerosols has not been established. | As part of a pilot study, we recently enrolled patients with and those without respiratory infections who were undergoing potential AGPs at a tertiary-care hospital. All patients provided written informed consent. We included patients with documented influenza virus infection during periods when they were undergoing mechanical ventilation and/or during periods when they were breathing on their own. We sampled air within 0.91 m (3 feet) and 1.83 m (6 feet) of the patient and outside the room for 3.25 hours, using National Institute for Occupational Safety and Health 2-stage aerosol samplers [5]. Aerosol sampling was also performed for 1 to several minutes near the patient's mouth, using closed-faced filter cassettes during extubation, suctioning, and use of an incentive spirometer. Influenza virus RNA copy number was determined by polymerase chain reaction (PCR), and the mean value of 2 replicates was used in analysis. |
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