Abstract

The workshop titled “Application of evidence-based methods to construct mechanism-driven chemical assessment frameworks” was co-organized by the Evidence-based Toxicology Collaboration and the European Food Safety Authority (EFSA) and hosted by EFSA at its headquarters in Parma, Italy on October 2 and 3, 2019. The goal was to explore integration of systematic review with mechanistic evidence evaluation. Participants were invited to work on concrete products to advance the exploration of how evidence-based approaches can support the development and application of adverse outcome pathways (AOP) in chemical risk assessment. The workshop discussions were centered around three related themes: 1) assessing certainty in AOPs, 2) literature-based AOP development, and 3) integrating certainty in AOPs and non-animal evidence into decision frameworks. Several challenges, mostly related to methodology, were identified and largely determined the workshop recommendations. The workshop recommendations included the comparison and potential alignment of processes used to develop AOP and systematic review methodology, including the translation of vocabulary of evidence-based methods to AOP and vice versa, the development and improvement of evidence mapping and text mining methods and tools, as well as a call for a fundamental change in chemical risk and uncertainty assessment methodology if to be conducted based on AOPs and new approach methodologies (NAM). The usefulness of evidence-based approaches for mechanism-based chemical risk assessments was stressed, particularly the potential contribution of the rigor and transparency inherent to such approaches in building stakeholders’ trust for implementation of NAM evidence and AOPs into chemical risk assessment.

Highlights

  • The NTP’s Office of Health Assessment and Translation (OHAT) conducted a systematic review to evaluate the evidence that exposure to perfluorooctanoic acid (PFOA) or perfluorooctane sulfonate (PFOS) is associated with immune-related health effects

  • The main findings are based on the effects of PFOA on the antibody response, there is additional evidence that PFOA affects the immune system and the following sections include detailed discussions of the available evidence for effects of PFOA on all of the primary immune health outcomes considered

  • The evidence indicating that PFOA affects multiple aspects of the immune system supports the overall conclusion that PFOA alters immune function in humans

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Summary

Introduction

The NTP’s Office of Health Assessment and Translation (OHAT) conducted a systematic review to evaluate the evidence that exposure to perfluorooctanoic acid (PFOA) or perfluorooctane sulfonate (PFOS) is associated with immune-related health effects. PFOA and PFOS are extremely persistent chemicals (Figure 1) that are widely distributed in the environment as a result of extensive use over the last 50 years in commercial and industrial applications including fluoropolymer manufacturing, food packaging, lubricants, water-resistant coatings, and aqueous fire-fighting foams. They have high chemical stability and are not expected to degrade under typical environmental conditions (Lau et al 2007, EFSA 2008, ATSDR 2009, US EPA 2014b, ATSDR 2015, US EPA 2016b, a). Apparent half-lives of PFOS and PFOA are 41 and 92 years respectively. Estimated half-lives in the human body are long, ranging from 2 to 8 years (ATSDR 2009, Steenland et al 2010, US EPA 2014b)

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