Next Generation Risk Assessment for Occupational Chemical Safety – a Real World Example with Sodium-2-hydroxyethane sulfonate

Next Generation Risk Assessment (NGRA) is an exposure-led approach to safety assessment that uses New Approach Methodologies (NAMs). Application of NGRA has been largely restricted to assessments of consumer use of cosmetics and is not currently implemented in occupational safety assessments, e.g. under EU REACH. By contrast, a large proportion of regulatory worker safety assessments are underpinned by toxicological studies using experimental animals. Consequently, occupational safety assessment represents an area that would benefit from increasing application of NGRA to safety decision making. Here, a workflow for conducting NGRA under an occupational safety context was developed, which is illustrated with a case study chemical; sodium 2-hydroxyethane sulphonate (sodium isethionate or SI). Exposures were estimated using a standard occupational exposure model following a comprehensive life cycle assessment of SI and considering factory-specific data. Outputs of this model were then used to estimate internal exposures using a Physiologically Based Kinetic (PBK) model, which was constructed with SI specific Absorption, Distribution, Metabolism and Excretion (ADME) data. PBK modelling indicated a worst-case plasma maximum concentration (Cmax) of 0.8μM across the SI life cycle. SI bioactivity was assessed in a battery of NAMs relevant to systemic, reproductive, and developmental toxicity; a cell stress panel, high throughput transcriptomics in three cell lines (HepG2, HepaRG and MCF-7 cells), pharmacological profiling and specific assays relating to developmental toxicity (Reprotracker and devTOX quickPredict). Points of Departure (PoDs) for SI ranged from 104-5044µM. Cmax values obtained from PBK modelling of occupational exposures to SI were compared with PoDs from the bioactivity assays to derive Bioactivity Exposure Ratios (BERs) which demonstrated the safety for workers exposed to SI under current levels of factory specific risk management. In summary, the tiered and iterative workflow developed here represents an opportunity for integrating non animal approaches for a large subset of substances for which systemic worker safety assessment is required. Such an approach could be followed to ensure that animal testing is only conducted as a "last resort" e.g. under EU REACH.

3.) Opportunities and a strategy for integrating NGRA into worker safety assessment.
4.) Case study chemical: Sodium-2hydroxyethane sulfonate (SI) • Workers can be exposed to substances that could be detrimental to health if not assessed and managed adequately.
• Typically, assessment of risks from occupational exposures come from comparisons of exposures with occupational limit values, e.g., occupational exposure limits (OELs) or Derived No-effect levels (DNELs).
• A large proportion of OELs/DNELs are based on outputs of toxicological studies performed using experimental animals.
Current worker safety assessment approach The need for non-animal safety assessments Human Relevance Societal Attitudes/Consumer Preference Regulatory Change (e.g.EU Cosmetic regulation)

Resource/time constraints
What is next generation risk assessment (NGRA)?
"An exposure-led, hypothesis driven risk assessment approach that incorporates one or more NAMs to ensure that chemical exposures do not cause harm to consumers" Introduction to NGRA • Toolbox not protective for 3/46 of the high-risk exposure scenarios  Useful for Tier 2/bespoke safety assessment when differentiation between bioactivity & adversity is needed but assessment based on bioactivity is the feasible, current approach.
• Often simultaneous exposure over multiple routes (dermal and inhalation) and limited biomonitoring data to calibrate PBK models.
• Different exposure estimation models.
• Large number of scenarios to consider professional, cleaning etc).
• Complex supply chains and ways of working under worker safety regulations (lead registrant/confidential information).
Application of NGRA to occupational safety assessment -challenges vs cosmetic sector

Complexity Resource Uncertainty Confidence
Perceived industry challenges for uptake of occupational NGRA

Regulatory acceptance
Case studies needed to improve confidence of chemical sector with NGRA and to address worker safety specific challenges that make its uptake more challenging from a (non) technical perspective.
"there is a fear, or assumption, that nonanimal methods will be rejected by regulators, borne out of experience that they must provide information directly equivalent to that of animal tests." Service Life of fabrics  -Life cycle assessment performed to identify relevant scenarios of use (process categories/PROCs).
-From these PROCs, exposures are typically estimated using variety of modelling software packages (e.g., ECETOC TRA, ART etc).
-Although worker exposure to SI occurs from a limited number of scenarios, approach can still be followed for more complex supply chains.
-External exposure estimates serve as inputs to SI specific PBK model.
External exposure assessment: • Worst-case exposures were selected by consultant using simple procedure.
• Procedure converts inhalation and dermal exposures into an intravenous infusion.
• Probabilistic models included ranges for uncertain parameters (e.g., fraction unbound) and variable population parameters (e.g., blood flows).In Vitro Biological Activity Characterisation Limited bioactivity demonstrated across 5 NAM assays: • SI showed limited bioactivity across all assays.
• Lowest PoD came from the high throughput transcriptomics assay (MCF-7 cell line), based on a single probe significantly more sensitive than others.
• Some deviation from nominal concentration was observed in dose-confirmation assays due to a dosing error.
• Final PoD taken forward for risk characterisation = 104 µM.• Framework developed here includes multiple options for refinement and is applicable to large subset of substances to which worker exposure occurs.
• Simple procedure to convert external inhalation/dermal exposures to infusion dose can be used by consultants to manage feasibility of PBK modelling and NGRA under REACH WoW.
• NGRA frameworks such as this can be implemented to address shortcomings of tonnage driven testing requirements.
For SI: • Limited bioactivity across a broad range of bioactivity assays.Consistent with in silico profiling results and existing knowledge on the substance.
• Current occupational exposures (and any RMM already in place) is sufficient for protection of workers.
• Performance of additional animal testing would not provide any human health benefit.

Wrap up
NGRA (especially this one) is a multidisciplinary exercise requiring the involvement of a multitude of individuals across a broad range of expertise areas.
Contents of talk today form the basis of a paper titled "Next Generation Risk Assessment for Occupational Chemical Safety -a Real World Example with Sodium-2-hydroxyethane sulfonate" submitted last week -watch this space!
Overview e.g. 90 Day Repeat Dose Study 1.) How are worker/occupational safety assessments performed currently.

ICCR
Baltazar et al., (2020) Tox Sci Volume 176, Issue 1, 236-252 Testing the principles with case studies 0.1% COUMARIN IN FACE CREAM AND BODY LOTION (NEW FRAGRANCE) Also known as in vitro pharmacological profiling (IPP) What about a larger subset of chemicals?(Part 1): Middleton AM et al (2022).Are Non-animal Systemic Safety Assessments Protective?A Toolbox and Workflow.Toxicological Sciences, 189:124-147.Selection of chemicals and exposure scenario • Chemicals with well-defined human exposures • Traditional safety assessment available • High certainty in the risk classification for each chemical-exposure scenario • Risk class is relative to consumer health BER=lowest POD/Plasma Cmax Blue: low risk chemical-exposure scenario Yellow: high risk chemical-exposure scenario Blue shaded region BER> 11 10 chemicals -25 exposure scenarios See oral presentation by Sophie Cable for further details NAM Systemic toolbox remains protective (>90%) when 38 additional chemicals and 70 exposure scenarios were tested (Part 2): NGRA framework with additional NAMs relevant for DART endpoints Rajagopal et al.Frontiers in Toxicology, Volume 4, March 2022, See oral presentation by Katy Wilson and poster presentation by Kathryn Wolton for current evaluation of DART NGRA framework Integrating DART Safety Assessment into Existing NGRA Framework: Safety, Environmental & Regulatory Science (SERS) | Unilever Points of Departure (PODs) from NAMs can be protective even if not predictive al., 2020.Toxicol.Sci 173, 202-225 '… understanding how construction of NAM-based POD estimates may offer equivalent levels of public health protection as the PODs produced by animal methods …' Paul Friedman et al, 2023, Computational Toxicology, 28assays need to be performed if multiple AOPs are identified

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(O)(=O)= O)OC(C(O)C1O)C(Oof any concerns.Problem formulation, in silico predictions and literature data Safety, Environmental & Regulatory Science (SERS) | Unilever Exposure assessment -external: Confidential business information (CBI) seen as blocker to perform exposure led approach Solution -independent consultant 1) To collect CBI (manufacturing process, volume…) and convert them to PROCs, ECS etc 2) To identify the worst case scenario(s) and refine them further with additional CBI 3) To provide the worst case exposure values (mg/kg/d) within the entire life cycle to the consortium for modelling.
on achieved concentrations to increase confidence in QIVIVE.Safety, Environmental & Regulatory Science (SERS) | Unilever Bioactivity Exposure Ratio Determination and Safety Decision • Current lack of published examples of application of NGRA to worker safety.

preparation Risk Assessment Conclusion Exposure Estimation Consumer Habits and Practices Applied Dose Use Scenario Molecular Structure In silico Predictions Collation of Existing Information
• Chemical-Exposure scenarios not protective for: o Warfarin therapeutic oral dose o Trimellitic anhydride inhalation exposure • On a case-by-case basis (e.g., depending on wider literature), deviation may be possible.Cable et al (2024) -in
Internal exposure assessment -PBK