Strategic Vision for Adopting New Approach Methodologies - Replacement Strategies
One of EPA’s goals is to replace complex laboratory animal studies with new approach methodologies (NAMs) while maintaining the scientific defensibility of pesticide assessments. NAMs include alternative test methods and strategies, and refer to any non-animal technology, methodology, approach or combination thereof that can be used to provide information on chemical hazard and risk assessment.
EPA has already taken steps to replace in vivo animal studies through engagement with the Interagency Coordinating Committee on the Validation of Alternative Methods (ICCVAM) to draft documents and strategies moving towards eye irritation and skin sensitization testing based on in silico A general term used to mean "performed on computer or via computer simulation.", in chemico and in vitro Experiments or tests done under controlled experimental conditions outside of the body, such as in a test tube or laboratory dish. These tests tend to focus on organs, tissues, cells, cellular components, proteins, and/or biomolecules. approaches.
- NAMs in the Endocrine Disruptor Screening Program
- Retrospective Analyses of Dermal Absorption "Triple Pack" Data
Skin Sensitization Policy
EPA continues to work with the National Toxicology Program’s Interagency Center for the Evaluation of Alternative Toxicological Methods (NICEATM) (headquartered at the National Institute of Environmental Health Sciences), other Federal agencies, the European Union Joint Research Centre, and Health Canada to develop defined approaches for skin sensitization as presented and discussed in international settings such as the Organisation for Economic Co-operation and Development (OECD).
EPA released a draft interim science policy, Use of Alternative Approaches for Skin Sensitization as a Replacement for Laboratory Animal Testing, in April 2018. This draft policy document describes the science behind the non-animal alternatives that can be used (in vitro, and in chemico tests) to identify skin sensitization.
Given the substantial scientific evidence and international activities supporting the NAMs for skin sensitization testing, EPA began accepting these approaches under the conditions described in the draft policy document immediately upon its release.
Since the release of the EPA draft interim policy, the OECD has adopted defined approaches (DAs) for skin sensitization (Guideline No. 497). This internationally harmonized test guideline describes three DAs for identifying skin sensitization hazard. Two of the DAs may be used for potency categorization under the United Nations Global Harmonized System of Classification and Labeling of Chemicals (GHS). The NAMs included in the DAs are OECD test guidelines developed to provide information on 3 Key Events of the Adverse Outcome Pathway.
Mixtures Equations Pilot and Retrospective Analysis
EPA established the mixtures equations pilot program to evaluate the utility and acceptability of a mathematical tool (GHS Mixtures Equation) as an alternative to animal oral and inhalation toxicity studies for pesticide formulations. The Mixtures Equation is used in the United Nations Globally Harmonized System of Classification and Labeling of Chemicals (GHS).
Under this pilot, registrants had the option of submitting calculations (GHS Mixtures Equation data), paired with the required acute oral and inhalation acute toxicity data, to support the evaluation of pesticide toxicity. In FY 2019, OPP closed the submission period for new data and began working with NICEATM to perform the analysis.
The retrospective analysis of the concordance of the in vivo acute oral toxicity results and the calculated LD50 values using the equation was determined from 671 formulations (620 agrochemical formulations and 51 antimicrobial cleaning products) and was completed in 2021. The overall concordance across all four EPA acute oral Toxicity Categories was 55%. When less toxic mixtures were combined together (LD50>500 mg/kg), overall concordance improved to 82%. The comprehensive results of this retrospective analysis are available in the following manuscript: Hamm Jon, et al. "Performance of the GHS Mixtures Equation for Predicting Acute Oral Toxicity." Regulatory Toxicology and Pharmacology, 125 (2021):105007.
Alternative Testing Framework for Classification of Eye Irritation Potential of EPA-Regulated Pesticide Products
In May 2015, EPA released updated guidance for testing antimicrobial cleaning products for their potential to cause eye irritation. The updated guidance describes a testing framework for assessing eye irritation potential using three in vitro/ex vivo assays: Bovine Corneal Opacity and Permeability assay, EpiOcular assay, and the Cytosensor Microphysiometer assay. The same testing approach is considered on a case-by-case basis for other classes of pesticides and pesticide products.
To expand the applicability of NAMs to assess eye irritation hazard across the program, OPP collaborated with NICEATM and PETA Science Consortium to evaluate the performance of two proposed DAs. A scientific confidence framework was applied to assess the utility of the DAs to classify agrochemical formulations into EPA hazard categories for eye irritation. The DAs and the results of the retrospective testing from 29 agrochemical formulations are published in: Cutaneous and Ocular Toxicology, (2023)
New Approach Methodology (NAM) for Inhalation Risk Assessments
In December 2018, EPA presented the document Evaluation of a Proposed Approach to Refine the Inhalation Risk Assessment for Point of Contact Toxicity: A Case Study Using a New Approach Methodology (NAM) to the FIFRA Scientific Advisory Panel (SAP). The proposed approach calculates human equivalent concentrations (HECs) for inhalation risk assessment using an in vitro point of departure in conjunction with computational fluid dynamic (CFD) modeling that incorporates human relevant particle size distributions. The approach was originally developed by Syngenta for the fungicide chlorothalonil, which was presented to the SAP as a proof-of-concept for this NAM. The SAP’s report was released in April 2019.
Throughout FY 2019, OPP continued to work with Syngenta Crop Protection on science activities to address the SAP’s recommendations, such as evaluation of in vitro repeat dosing, determination of appropriate particle size distributions for dosimetry modeling, and updates to human equivalent concentration calculations.
In May 2021, OPP published its draft risk assessments (DRAs) for chlorothalonil and additional supporting documents in the Federal Register docket number EPA-HQ-OPP-2011-0840 at www.regulations.gov. The chlorothalonil human health DRA was the first application of this NAM to calculate HEC's for conventional and antimicrobial uses of a pesticide. More information on the application of the NAM approach for inhalation risk assessment can be found in the document titled "Chlorothalonil: Revised Human Health Draft Risk Assessment for Registration Review".
Development of NAMs to Evaluate Developmental Neurotoxicity Data for Human Health Risk Assessments
EPA’s Office of Research and Development (ORD) has been developing in vitro assays to evaluate key neurodevelopmental processes for inclusion in a NAM battery for evaluating developmental neurotoxicity (DNT). In September 2020, a FIFRA Scientific Advisory Panel (SAP) Peer Review meeting was held on "The Use of NAMs to Derive Extrapolation Factors and Evaluate Developmental Neurotoxicity (DNT) for Human Health Risk Assessments". At this meeting, technical presentations were given by members of OPP and ORD on the assay development and regulatory use of the available DNT NAM battery along with a case study demonstrating its potential application. Overall, the SAP agreed that the current DNT NAM battery reflects, if not models directly, critical processes for neurodevelopment and that data from the battery can be used as part of a weight of evidence (WOE) evaluation. All meeting materials, the SAP report, and EPA’s response to the SAP report are available in the SAP Federal Register docket number EPA-HQ-OPP-2020-0263 at www.regulations.gov.
OPP has collaborated with scientists in ORD to utilize data from in vitro DNT testing in WOE analyses to evaluate the need for additional DNT data for L-glufosinate isomers and DCNA. OPP has also continued to work with ORD to analyze data from the DNT NAM battery for use in chemical-specific WOE analyses to evaluate the DNT potential of organophosphate (OP) pesticides with the WOE evaluation for acephate released recently as part of Registration Review.
In 2023, the OECD Working Group of the National Coordinators for the Test Guidelines Programme (WNT) also approved a guidance document that describes the use of the DNT NAM battery as part of an integrated approach for testing and assessment (IATA) for DNT. This document includes several case studies for application of the battery to DNT decision-making. Additionally, it contains appendices with "ToxTemp" forms for each assay with information regarding the biological/human relevance, technical performance, appropriate assay positive controls, and domains of applicability.
As part of this work, EPA also released data evaluation records (DERs) for DNT studies along with support memos that provide additional information on the results of those reviews that have been generated by OPP. These DERs will also contribute to EPA's ongoing collaboration with European Food Safety Authority (EFSA) and other international partnerships to further evaluate the DNT NAM battery. The DERs and support memos are publicly available in docket EPA-HQ-OPP-2016-0093 at www.regulations.gov.
Collaborative Acute Toxicity Modelling Suite (CATMoS)
EPA continues to collaborate with NICEATM and the Humane Society on the use of the CATMoS computational model for predicting rat acute oral toxicity. OPP primarily uses data from in vivo acute oral toxicity studies to inform pesticide product label precautionary statements and environmental risk assessment. This effort involves a comparative analysis of measured and predicted LD50 values, and has the potential to identify pesticides for which acute oral toxicity testing might be waived.
CompTox Chemicals Dashboard
EPA’s Office of Research and Development (ORD)’s CompTox Chemicals Dashboard is a tool that provides risk assessors access to in vivo toxicity and in vitro bioassay data for thousands of substances searchable by chemical structures.
NAMs in the Endocrine Disruptor Screening Program
The draft document "Availability of New Approach Methodologies (NAMs) in the Endocrine Disruptor Screening Program (EDSP)" describes the high-throughput in vitro assays and in silico models the agency determined may be used as an alternative to certain EDSP Tier 1 screening assays. The Estrogen Receptor pathway model and the Androgen Receptor pathway model have been validated and data from these NAMs will be considered for specific chemicals. The draft guidance also describes other NAMs that may be used for priority setting and as other scientifically relevant information in weight of evidence evaluations.
Additional information on the USEPA Endocrine Disruptor Screening Program is found here.
Retrospective Analyses of Dermal Absorption "Triple Pack" Data
The "triple pack" approach for dermal absorption combines data from in vivo and in vitro studies to calculate an estimated human dermal absorption factor (DAF). The triple pack typically consists of a rat in vivo study and in vitro studies using rat and human skin. OPP collaborated with NICEATM to perform retrospective analyses of the dermal triple pack data in order to evaluate whether in vivo dermal absorption studies are needed to estimate dermal absorption or if in vitro studies alone could be used to derive DAFs. In July 2021, the results of these analyses were published and demonstrated that the in vitro studies alone provide similar or more protective estimates of dermal absorption, with only limited exceptions. The analyses are available in the following manuscript: Allen et al. (2021). Retrospective Analysis of Dermal Absorption Triple Pack Data. Alternatives to Animal Experimentation.