Review of DOD's Approach to Deriving an Occupational Exposure Level for Trichloroethylene (2019) / Chapter Skim
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3 Scoping and Problem Formulation
3 Scoping and Problem Formulation
Pages 19-27
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From page 19... ...
Scoping and problem formulation help to define the purpose of the assessment, to identify what health outcomes to evaluate, and to determine the type of evaluation to be performed. These steps play an important role in all risk assessments that rely on literature searching and data gathering methods, whether they are narrative or systematic reviews, because they established the parameters and techniques for the subsequent analyses.
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From page 20... ...
, and conducted its own literature searches to identify newer studies. The committee agrees that this was a practical approach, but it was difficult to understand from the presentation of the evidence how DOD concluded that TCE "could produce toxic effects on the nervous system, liver, kidney, immune system, reproductive system and the developing fetus" (Sussan et al.
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From page 21... ...
Developing explicit review questions will strengthen the TCE hazard assessment, improve transparency, and increase process efficiency. DOD should avoid developing overly broad research questions, which can result in retrieving heterogeneous studies that complicate the analysis and may prevent the effective integration of the evidence needed to reach a conclusion (NASEM 2017)
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From page 22... ...
Animal: Nonhuman mammalian species that have been exposed either prenatally/lactationally or as adults. Postnatal adolescent exposures and in vitro study designs may only be included as supporting information.
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From page 23... ...
The following guidance on problem formulation should be considered by DOD for identifying outcomes to focus on and developing the review questions: Work with an information specialist (i.e., specially trained librarian) to design and conduct a broad literature search for scoping to identify possible outcomes associated with the chemical under investigation.
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From page 24... ...
DOD's problem formulation does not clearly indicate how in vitro and in vivo laboratory studies at the cellular, biochemical, and molecular levels and other mechanistic data might be used in the assessment. Mechanistic information often provides support for the biological plausibility of in vivo observations in animal or human studies.
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From page 25... ...
. TABLE 3-1 Advantages and Disadvantages of Narrative Review and Systematic Review Methods Approach Advantages Disadvantages Narrative Evidence based Limited transparency review Provides a synthesis or description Variable rigor of the literature No standardized guidelines for Can be less time- and labor- conduct intensive compared with Lack quantitative synthesis systematic review High potential for low May be broader in scope methodological quality and bias Increased flexibility Rarely employ peer-reviewed methods Typically lacks pre-defined review criteria Systematic Evidence based Can be time and labor intensive, review Guidelines for conduct are especially with well-studied available chemicals Hypothesis driven Often requires larger review teams Protocol based with expertise in systematic review Pre-defined review criteria More narrow scope Often includes duplicate curation Can be difficult to combine the of evidence findings of different studies that use May provide quantitative data different animal models, end points, synthesis, such as meta-analysis assessment methods, etc.
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From page 26... ...
The review questions and their associated PECO statements should be clearly linked to improve transparency. Clarify how mechanistic data might be identified and used in the hazard assessment.
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From page 27... ...
U.S. Army Public Health Center, Aberdeen Proving Ground, MD.
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