Material Flow Analysis and Occupational Exposure Assessment in Additive Manufacturing End-of-Life Material Management.

Additive manufacturing (AM) offers a variety of material manufacturing techniques for a wide range of applications across many industries. Most efforts at process optimization and exposure assessment for AM are centered around the manufacturing process. However, identifying the material allocation and potentially harmful exposures in end-of-life (EoL) management is equally crucial to mitigating environmental releases and occupational health impacts within the AM supply chain. This research tracks the allocation and potential releases of AM EoL materials within the US through a material flow analysis. Of the generated AM EoL materials, 58% are incinerated, 33% are landfilled, and 9% are recycled by weight. The generated data set was then used to examine the theoretical occupational hazards during AM EoL material management practices through generic exposure scenario assessment, highlighting the importance of ventilation and personal protective equipment at all stages of AM material management. This research identifies pollution sources, offering policymakers and stakeholders insights to shape pollution prevention and worker safety strategies within the US AM EoL management pathways.

Review of generic scenario environmental release and occupational exposure models used in chemical risk assessment.

Under the Toxic Substances Control Act (TSCA), the United States Environmental Protection Agency (USEPA) is required to determine whether a new chemical substance poses an unreasonable risk to human health or the environment before the chemical is manufactured in or imported into the United States. This manuscript provides a review of the process used to evaluate the risk associated with a chemical based on the scenarios and models used in the evaluation. Specifically, the Generic Scenarios and Emission Scenario Documents developed by the USEPA were reviewed, along with background documentation prepared by USEPA to identify the core elements of the environmental release and occupational exposure scenarios used to assess the risk of the chemical being evaluated. Additionally, this contribution provides an overview of methods used to model occupational exposures and environmental releases as part of the chemical evaluation process used in other jurisdictions, along with work being performed to improve these models. Finally, the alternative methods to evaluate occupational exposures and environmental releases that may be used as part of the decision-making process regarding a chemical are identified. The contribution provides a path forward for reducing the time required and improving the chemical evaluation of the unreasonable risk determination regarding the manufacture or import of a chemical.

Confidence limit variation for a single IMRT system following the TG119 protocol.

PURPOSE: To evaluate the robustness of TG119-based quality assurance metrics for an IMRT system. METHODS: Four planners constructed treatment plans for the five IMRT test cases described in TG119. All plans were delivered to a 30 cm x 30 cm x 15 cm solid water phantom in one treatment session in order to minimize session-dependent variation from phantom setup, film quality, machine performance, etc. Composite measurements utilized film and an ionization chamber. Per-field measurements were collected using a diode array device at an effective depth of 5 cm. All data collected were analyzed using the TG119 specifications to determine the confidence limit values for each planner separately and then compared. RESULTS: The mean variance of ion chamber measurements for each planner was within 1.7% of the planned dose. The resulting confidence limits were 3.13%, 1.98%, 3.65%, and 4.39%. Confidence limit values determined by composite film analysis were 8.06%, 13.4%, 9.30%, and 16.5%. Confidence limits from per-field measurements were 1.55%, 0.00%, 0.00%, and 2.89%. CONCLUSIONS: For a single IMRT system, the accuracy assessment provided by TG119-based quality assurance metrics showed significant variations in the confidence limits between planners across all composite and per-field evaluations. This observed variation is likely due to the different levels of modulation between each planner's set of plans. Performing the TG119 evaluation using plans produced by a single planner may not provide an adequate estimation of IMRT system accuracy.

Treatment of osteochondral lesions of the talus with cryopreserved talar allograft and ankle distraction with external fixation.

This article presents the results of a retrospective review of six osteochondral lesions on six patients (five men and one woman) treated with transplantation of cryopreserved talar allograft and ankle joint distraction. All patients complained of ankle pain existing for a long time secondary to a traumatic episode confirmed through MRI. Lesions ranged in measurement from 0.8 cm x 0.8 cm to 3.2 cm x 1.8 cm with an average size of 2.1 cm x 1.5 cm. Each patient underwent talar dome transplantation using fresh frozen talar allograft followed by ankle distraction. Distraction was obtained using a three-ring multiplanar external fixation device. All surgeries were performed between 2002 and 2004. All external fixators were removed at 8 weeks and patients remained partial-weight bearing in a removable cast boot for an additional 8 weeks. Serial postoperative radiographs showed complete consolidation of the allograft within 16 weeks. The average follow up time was 24 months, and all patients related a subjective decrease in symptoms and increase in activity levels. Patients were also evaluated utilizing the Maryland Foot Score both pre- and postoperatively. Preoperatively, four patients were graded as fair and two were graded as poor. Postoperatively, two patients related excellent results, three patients related good results, and one patient related fair results. Several patients experienced minor complications such as pin site irritation (five patients), painful talar wire (one patient), and periostitis (one patient). No patients experienced any major complications and none have required additional surgery. We feel that these initial results warrant further investigation of this treatment.