Background: Systematic reviews are increasingly prevalent in environmental health due to their ability to synthesize evidence while reducing bias. Different systematic review methods have been developed by the US National Toxicology Program’s Office of Health Assessment and Translation (OHAT), the US Environmental Protection Agency’s (EPA) Integrated Risk Information System (IRIS), and by the US EPA under the Toxic Substances Control Act (TSCA), including the approach to assess risk of bias (ROB), one of the most vital steps which is used to evaluate internal validity of the studies. Our objective was to compare the performance of three tools (OHAT, IRIS, TSCA) in assessing ROB. Methods: We selected a systematic review on polybrominated diphenyl ethers and intelligence quotient and/or attention deficit hyperactivity disorder because it had been endorsed by the National Academy of Sciences. Two reviewers followed verbatim instructions from the tools and independently applied each tool to assess ROB in 15 studies previously identified. We documented the time to apply each tool and the impact the ROB ratings for each tool had on the final rating of the quality of the overall body of evidence. Results: The time to complete the ROB assessments varied widely (mean = 20, 32, and 40 min per study for the OHAT, IRIS, and TSCA tools, respectively). All studies were rated overall “low” or “uninformative” using IRIS, due to “deficient” or “critically deficient” ratings in one or two domains. Similarly, all studies were rated “unacceptable” using the TSCA tool because of one “unacceptable” rating in a metric related to statistical power. Approximately half of the studies had “low” or “probably low ROB” ratings across all domains with the OHAT and Navigation Guide tools. Conclusions: Tools that use overall ROB or study quality ratings, such as IRIS and TSCA, may reduce the available evidence to assess the harms of environmental exposures by erroneously excluding studies, which leads to inaccurate conclusions about the quality of the body of evidence. We recommend using ROB tools that circumvents these issues, such as OHAT and Navigation Guide. Systematic review registration: This review has not been registered as it is not a systematic review.

"Evidence Mapping" is an emerging tool that is increasingly being used to systematically identify, review, organize, quantify, and summarize the literature. It can be used as an effective method for identifying well-studied topic areas relevant to a broad research question along with any important literature gaps. However, because the procedure can be significantly resource-intensive, approaches that can increase the speed and reproducibility of evidence mapping are in great demand. We propose an alternative process called "rapid Evidence Mapping" (rEM) to map the scientific evidence in a time-efficient manner, while still utilizing rigorous, transparent and explicit methodological approaches. To illustrate its application, we have conducted a proof-of-concept case study on the topic of low-calorie sweeteners (LCS) with respect to human dietary exposures and health outcomes. During this process, we developed and made publicly available our study protocol, established a PECO (Participants, Exposure, Comparator, and Outcomes) statement, searched the literature, screened titles and abstracts to identify potentially relevant studies, and applied semi-automated machine learning approaches to tag and categorize the included articles. We created various visualizations including bubble plots and frequency tables to map the evidence and research gaps according to comparison type, population baseline health status, outcome group, and study sample size. We compared our results with a traditional evidence mapping of the same topic published in 2016 (Wang et al., 2016). We conducted an rEM of LCS, for which we identified 8122 records from a PubMed search (January 1, 1946-May 1, 2014) and then utilized machine learning (SWIFT-Active Screener) to prioritize relevant records. After screening 2267 (28%) of the total set of titles and abstracts to achieve 95% estimated recall, we ultimately included 297 relevant studies. Overall, our findings corroborated those of Wang et al. (2016) and identified that most studies were acute or short-term in healthy individuals, and studied the outcomes of appetite, energy sensing and body weight. We also identified a lack of studies assessing appetite and dietary intake related outcomes in people with diabetes. The rEM approach required approximately 100 person-hours conducted over 7 calendar months. Rapid Evidence Mapping is an expeditious approach based on rigorous methodology that can be used to quickly summarize the available body of evidence relevant to a research question, identify gaps in the literature to inform future research, and contextualize the design of a systematic review within the broader scientific literature, significantly reducing human effort while yielding results comparable to those from traditional methods. The potential time savings of this approach in comparison to the traditional evidence mapping process make it a potentially powerful tool for rapidly translating knowledge to inform science-based decision-making.

Tobacco smoking continues to cause considerable premature mortality and morbidity worldwide. Most of the approximately six trillion cigarettes sold globally each year are discarded improperly as toxic environmental waste. Tobacco product waste, including cigarette butts, is the most commonly collected waste item worldwide. Of particular concern is the cellulose acetate filter, a poorly degradable plastic additive attached to most commercially manufactured cigarettes. This filter was introduced by the tobacco industry to reduce smokers’ perception of harm and risk but it has no health benefit. To inform health policy and practice and improve public health outcomes, governments and society can benefit from cost estimates of preventing, properly disposing of and/or cleaning up tobacco product waste. Estimating the costs of tobacco product waste to communities and responsible authorities could encourage the development of health, environmental and fiscal policy interventions and shift accountability for the costs of tobacco product waste onto the global tobacco industry. To support health and environmental policy-making, we therefore propose an empirical approach to estimate the economic costs of tobacco product waste based on its negative environmental externalities. We first present general estimates for six representative countries and then identify data gaps that need to be addressed to develop global estimates. Interventions against tobacco product waste may be new channels to regulate tobacco products across sectors – for example, health, environment and finance – and consequently reduce overall tobacco use.

Synthesizing environmental health science is crucial to taking action to protect public health. Procedures for evidence evaluation and integration are transitioning from "expert-based narrative" to "systematic" review methods. However, little is known about the methodology being utilized for either type of review. To appraise the methodological strengths and weaknesses of a sample of "expert-based narrative" and "systematic" reviews in environmental health. We conducted a comprehensive search of multiple databases and identified relevant reviews using pre-specified eligibility criteria. We applied a modified version of the Literature Review Appraisal Toolkit (LRAT) to three environmental health topics that assessed the utility, validity and transparency of reviews. We identified 29 reviews published between 2003 and 2019, of which 13 (45%) were self-identified as systematic reviews. Across every LRAT domain, systematic reviews received a higher percentage of "satisfactory" ratings compared to non-systematic reviews. In eight of these domains, there was a statistically significant difference observed between the two types of reviews and "satisfactory" ratings. Non-systematic reviews performed poorly with the majority receiving an "unsatisfactory" or "unclear" rating in 11 of the 12 domains. Systematic reviews performed poorly in six of the 12 domains; 10 (77%) did not state the reviews objectives or develop a protocol; eight (62%) did not state the roles and contribution of the authors, or evaluate the internal validity of the included evidence consistently using a valid method; and only seven (54%) stated a pre-defined definition of the evidence bar on which their conclusions were based, or had an author disclosure of interest statement. Systematic reviews produced more useful, valid, and transparent conclusions compared to non-systematic reviews, but poorly conducted systematic reviews were prevalent. Ongoing development and implementation of empirically based systematic review methods are required in environmental health to ensure transparent and timely decision making to protect the public's health.

Multiple lines of evidence suggest that exposure to per- and polyfluoroalkyl substances (PFAS) may alter glucose homeostasis, particularly during pregnancy, and may affect risk for developing gestational diabetes mellitus (GDM). While previous systematic reviews have been conducted on this topic, they did not assess internal validity of the included studies and their search strategies were narrowly focused. The objective of this study is to assess the effect of higher PFAS exposure (defined by individual compounds or mixtures measured before or during pregnancy) on GDM and subclinical measures of impaired glucose homeostasis (measured during pregnancy) compared to lower PFAS exposure in pregnant. We developed our systematic review protocol in accordance with the Navigation Guide. Peer-reviewed journal and grey literature searches were piloted in to identify relevant studies and refine our search terms and strategy. We also piloted the study screening criteria and data extraction form in DistillerSR, and refined our protocol accordingly. The risk of bias assessment protocol was adapted from Navigation Guide guidance and will be piloted and performed in DistillerSR. Pending the identification of comparable studies, quantitative meta-analyses will be performed where possible. Study results that cannot be quantitatively synthesized will be included in a narrative synthesis. The quality and strength of the body of evidence will be evaluated using Navigation Guide methodology, which is informed by guidance from the Cochrane Collaboration and Grading of Recommendations Assessment, Development and Evaluation (GRADE). We also made refinements to the quality of evidence considerations based on guidance from the National Institute of Environmental Health Sciences (NIEHS) Office of Health Assessment and Translation (OHAT). This work was supported by the Systematizing Data on Per- and Polyfluoroalkyl Substances and Health Northeastern University TIER 1 Award.