Community-based wheelchair caster failures call for improvements in quality and increased frequency of preventative maintenance.

STUDY DESIGN: Secondary data analysis of wheelchair failures and service repair logs from a network of wheelchair suppliers. OBJECTIVE: To determine the frequency of wheelchair caster failures and service repairs across wheelchair manufacturers and models and investigate the relationships between them. SETTING: Wheelchair caster failures and service repairs occurred in the community. METHODS: Reported caster failure types were classified based on the risk they pose for user injuries and wheelchair damage. Caster failures experienced by users of tilt-in-space and ultralightweight manual wheelchair models and Group 2, 3 and 4 power wheelchair models between January 2017 and October 2019 were analyzed using Chi-Square tests for independence. Correlational analysis of failures and service repairs was performed. RESULTS: A total of 6470 failures and 151 service repairs reported across four manufacturers and five models were analyzed. Failure types were significantly associated with manufacturers and models, respectively. Users of tilt-in-space wheelchairs, who require greater seating support, experienced twice the proportion of high-risk caster failures than the ultralightweight manual wheelchair users. Similarly, Group 3 and 4 power wheelchair users, who have complex rehabilitation needs, experienced 15-36% more high-risk failures than Group 2 users. Service repairs negatively correlated with high-risk manual wheelchair caster failures. CONCLUSIONS: Wheelchair users who have greater seating and complex rehabilitation needs are at a higher risk for sustaining injuries and secondary health complications due to frequent caster failures. The study findings call for significant reforms in product quality and preventative maintenance practices that can reduce wheelchair failures and user consequences.

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.

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.

Rolling resistance of casters increases significantly after two years of simulated use.

INTRODUCTION: Manual wheelchair propulsion is associated with upper limb pain and injury, and clinical guidelines recommend minimizing propulsive force to lower health risks. One of the strategies to reduce propulsive force is by minimizing rolling resistance (RR). Product testing studies suggest that RR of casters is affected by wear and tear which could have implications on the health risk of wheelchair users. The study will investigate the relationship between caster RR and environmental exposure using standard testing protocols. METHODS: RR of ten casters representing a range of diameters for different models of wheelchairs were measured before and after environmental exposure that includes corrosion, shock and abrasion simulating two years of community use. RESULTS: Four casters exhibited failures during durability testing, one catastrophically. Increases to RR after corrosion, shock and abrasion exposure were statistically significant using mixed-effects modeling, and four casters had increased RR greater than 20%. CONCLUSIONS: Many of the casters evaluated exhibited increased RR forces and failure after environmental exposure. Improved caster design and use of corrosion resistant materials may reduce these failures. In addition, modification of the provision process could include replacement casters to reduce failures and avoid breakdowns that leave manual wheelchair users stranded or injured.

Use of 3-Dimensional Printers in Educational Settings: The Need for Awareness of the Effects of Printer Temperature and Filament Type on Contaminant Releases.

Material extrusion-type fused filament fabrication (FFF) 3-D printing is a valuable tool for education. During FFF 3-D printing, thermal degradation of the polymer releases small particles and chemicals, many of which are hazardous to human health. In this study, particle and chemical emissions from 10 different filaments made from virgin (never printed) and recycled polymers were used to print the same object at the polymer manufacturer's recommended nozzle temperature ("normal") and at a temperature higher than recommended ("hot") to simulate the real-world scenarios of a person intentionally or unknowingly printing on a machine with a changed setting. Emissions were evaluated in a college teaching laboratory using standard sampling and analytical methods. From mobility sizer measurements, particle number-based emission rates were 81 times higher; the proportion of ultrafine particles (diameter <100 nm) were 4% higher, and median particle sizes were a factor of 2 smaller for hot-temperature prints compared with normal-temperature prints (all p-values <0.05). There was no difference in emission characteristics between recycled and virgin acrylonitrile butadiene styrene and polylactic acid polymer filaments. Reducing contaminant release from FFF 3-D printers in educational settings can be achieved using the hierarchy of controls: (1) elimination/substitution (e.g., training students on principles of prevention-through-design, limiting the use of higher emitting polymer when possible); (2) engineering controls (e.g., using local exhaust ventilation to directly remove contaminants at the printer or isolating the printer from students); (3) administrative controls such as password protecting printer settings and establishing and enforcing adherence to a standard operating procedure based on a proper risk assessment for the setup and use (e.g., limiting the use of temperatures higher than those specified for the filaments used); and (4) maintenance of printers.