Systematic Evidence Map of Inorganic Mercury Salts
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Systematic evidence mapping (SEM) approaches are increasingly being used to aid in scoping and problem formulation for chemical assessments. In brief, SEMs use systematic review methods to identify the relevant literature and characterize the amount and type of evidence available for an assessment. Through this process, key data gaps and areas of scientific complexity are also identified. The IRIS Program has begun to routinely conduct SEMs as part of its problem formulation activities to promote transparency in the early stages of assessment development. The use of specialized software applications makes production time for SEMs relatively rapid, weeks to several months for most chemicals.
This methodology was used to identify relevant literature on the three inorganic mercury salts (mercuric chloride, mercuric sulfide and mercurous chloride) currently under development as IRIS assessments. First, Populations, Exposures, Comparators, and Outcomes (PECO) criteria were developed to outline the evidence considered applicable to address the specific aims of the assessment. Following the literature search from three different databases (PubMed, Toxline, and Web of Science), studies were sorted in SWIFT Review, a text mining work bench tool, using a predetermined list of health outcomes (cancer, cardiovascular, developmental, endocrine, gastrointestinal, etc.) and evidence streams (human, animal, in vitro).
In addition to screening title and abstract and full-text against the PECO criteria, studies containing supplemental material that may be potentially relevant to the assessment were tracked in DistillerSR. Following full-text review, study designs and results were summarized in a structured format and visualized in Tableau software. The SEM approach identified several oral subchronic and chronic animal studies for both mercuric chloride and mercuric sulfide for further study quality evaluation. No oral studies on mercurous chloride were found. A pool of mechanistic studies, tagged as supplemental, were informative for hazard characterization and linking biomarkers to apical effects.
In conclusion, these results will be helpful for consideration of alternative approaches, such as bioavailability and read-across, for use in the derivation of reference values for other data-poor mercury salts.
This methodology was used to identify relevant literature on the three inorganic mercury salts (mercuric chloride, mercuric sulfide and mercurous chloride) currently under development as IRIS assessments. First, Populations, Exposures, Comparators, and Outcomes (PECO) criteria were developed to outline the evidence considered applicable to address the specific aims of the assessment. Following the literature search from three different databases (PubMed, Toxline, and Web of Science), studies were sorted in SWIFT Review, a text mining work bench tool, using a predetermined list of health outcomes (cancer, cardiovascular, developmental, endocrine, gastrointestinal, etc.) and evidence streams (human, animal, in vitro).
In addition to screening title and abstract and full-text against the PECO criteria, studies containing supplemental material that may be potentially relevant to the assessment were tracked in DistillerSR. Following full-text review, study designs and results were summarized in a structured format and visualized in Tableau software. The SEM approach identified several oral subchronic and chronic animal studies for both mercuric chloride and mercuric sulfide for further study quality evaluation. No oral studies on mercurous chloride were found. A pool of mechanistic studies, tagged as supplemental, were informative for hazard characterization and linking biomarkers to apical effects.
In conclusion, these results will be helpful for consideration of alternative approaches, such as bioavailability and read-across, for use in the derivation of reference values for other data-poor mercury salts.