Replacing Animals for Acute Systemic Toxicity Testing
ICCVAM, with support from NICEATM, published a U.S. strategy and roadmap including an implementation plan to use alternative approaches for required acute systemic toxicity testing. Development and implementation of these approaches will involve four key steps:
- Defining testing needs.
- Identifying available alternatives.
- Developing integrated approaches to testing and assessment.
- Addressing both scientific and non-scientific challenges.
The ICCVAM Acute Toxicity Workgroup began to address these goals by first compiling agency needs and decision contexts, and identifying existing alternatives and deciding what activities were needed to promote their use. They then used this information to develop an implementation plan for addressing the roadmap goals in the area of acute systemic toxicity testing. Ongoing activities supporting this effort include:
- Compiling an outline of the current requirements and testing needs for U.S. (Strickland et al. 2018) and international (manuscript in preparation) government agencies.
- Evaluating in vitro and in silico methods of predicting acute systemic toxicity that use high-throughput screening data and quantitative structure-activity relationship models.
The workgroup organized a global project to develop in silico models of acute oral systemic toxicity that predict five specific endpoints needed by regulatory agencies. Other NICEATM and ICCVAM activities related to this effort are described below and throughout this website.
Retrospective Analysis of Triple Pack Studies for Dermal Absorption
Acute systemic toxicity can occur through absorption of toxic chemicals through the skin. To provide an estimate of dermal absorption, EPA combines data from in vivo rat, in vitro rat, and in vitro human dermal absorption studies, commonly referred to as the “triple pack”, to calculate a chemical-specific dermal absorption factor. The dermal absorption factor estimates how much chemical will cross the skin barrier and end up in the bloodstream.
The EPA Office of Pesticide Programs and NICEATM conducted an analysis (Allen et al. 2021) to assess the feasibility of using in vitro data alone to estimate the dermal absorption factor. For most chemicals examined, estimates of absorption were higher for in vitro data than for in vivo data, indicating that hazard classifications based on in vitro data could be more protective than those based on in vivo data. Absorption values from in vitro rat studies were also compared to in vitro human studies, and indicated that the dermal absorption in rat skin is greater than in human skin.
Additivity Approaches to Predicting Toxicity of Formulations
The EPA Office of Pesticide Programs has been accepting submissions of oral and inhalation toxicity data for agrochemical formulations paired with toxicity calculations done in accordance with the GHS additivity equation based on the individual components of the formulation. NICEATM evaluated the extent to which acute toxicity results predicted using the additivity equation compare to the in vivo results for the formulation (Hamm et al. 2021).
NICEATM Evaluation of the Use of Acute Oral Hazard Classification to Predict EPA Acute Dermal Hazard Classification
Acute oral and dermal systemic toxicity test data are used to determine hazard label and protective equipment requirements for pesticide users, workers, and handlers.
NICEATM conducted a retrospective data analysis that was used to support EPA guidance on waiving acute dermal toxicity tests for pesticide formulations. This guidance is expected to greatly reduce laboratory animal use. This analysis used acute oral and dermal toxicity data provided by EPA for active ingredients and similar information for pesticide formulations. NICEATM ensured only high-quality data was used in its evaluation.
Workshops on Alternatives for Acute Toxicity Testing
Four NICEATM workshops assessed the state of the science for replacements for animal use in acute systemic toxicity testing:
- Attendees at a 2015 workshop on Alternative Approaches for Identifying Acute Systemic Toxicity: Moving from Research to Regulatory Testing (summarized in Hamm et al. 2017) developed strategies to advance alternative methods for product safety testing that meet the needs of regulatory agencies (workshop organized by NICEATM, PETA-ISC, and PCRM).
- A 2016 workshop and webinar series (summarized in Clippinger et al. 2018) focused on needs to replace animals for acute inhalation toxicity testing (workshop and webinars organized by NICEATM and PETA-ISC).
- A 2018 workshop on Predictive Models for Acute Oral Systemic Toxicity (summarized in Kleinstreuer et al. 2018) focused on in silico models submitted to address regulatory needs. Workshop participants discussed developing a consensus model (described in Mansouri et al. 2021) that integrates the submitted models to predict acute oral toxicity, as well as next steps needed to encourage appropriate use of these models in regulatory contexts.
- A 2019 workshop (summarized in Sullivan et al. 2021) considered predictive non-animal approaches available to assess acute lethality associated with chemicals and chemical mixtures. Follow-up actions include an analysis of variability in the in vivo test to establish confidence in toxicity predictions, a comprehensive assessment of an additivity equation for predicting mixtures toxicity, and exploring the addition of biological and mechanistic information to complement in silico predictions (workshop organized by NICEATM and PCRM).
Request for Data and Information on Technologies Used to Identify Substances with the Potential to Cause Acute Systemic Toxicity
In a July 2016 Federal Register notice, NICEATM requested available data and information on approaches and/or technologies currently used to identify substances with the potential to cause acute systemic toxicity. Submitted information would be used to assess the state of the science and determine technical needs for non-animal test methods.
Acute systemic toxicity tests are conducted to determine whether a single or short-term dose of a substance can cause illness or death when inhaled (inhalation toxicity testing), swallowed (oral toxicity testing), or absorbed through the skin (dermal toxicity testing). These tests are required by multiple regulatory agencies and can use large numbers of animals. NICEATM supports efforts to develop, validate, and implement alternative approaches for acute systemic toxicity testing that replace, reduce, or refine animal use.
While the Federal Register notice asked that data be submitted by September 2016, NICEATM continues to accept submissions of relevant data. Respondents should provide information on any activities relevant to the development or validation of alternatives to in vivo tests currently required by regulatory agencies that assess acute oral, dermal, or inhalation toxicity. Of specific interest are chemical-specific data from non-animal tests for acute systemic toxicity hazard, as well as available data on the same chemicals from in vivo acute systemic toxicity tests, such as human or animal studies or accidental human exposures.
Respondents should include their name, affiliation (if applicable), mailing address, telephone, email, and sponsoring organization (if any) with their communications.
Responses to this request may be made public, so no proprietary, classified, confidential, or sensitive information should be included in responses.
- Guidelines for Submission of Acute Toxicity Data
- NTP Guidelines for Public Comments
- Federal Register notice announcing data request – July 18, 2016
Responses to Federal Register Notice
- Yves Alarie, Ph.D., Professor Emeritus, University of Pittsburgh: QSARs to Replace RD50 for Inhalation of Volatile Organic Chemicals (received August 19, 2016)
- Relevant references are available on the SOT Eminent Toxicologist Lecture Series page.