The MCRA toolbox of models and data to support chemical mixture risk assessment

A model and data toolbox is presented to assess risks from combined exposure to multiple chemicals using probabilistic methods. The Monte Carlo Risk Assessment (MCRA) toolbox, also known as the EuroMix toolbox, has more than 40 modules addressing all areas of risk assessment, and includes a data repository with data collected in the EuroMix project. This paper gives an introduction to the toolbox and illustrates its use with examples from the EuroMix project. The toolbox can be used for hazard identification, hazard characterisation, exposure assessment and risk characterisation. Examples for hazard identification are selection of substances relevant for a specific adverse outcome based on adverse outcome pathways and QSAR models. Examples for hazard characterisation are calculation of benchmark doses and relative potency factors with uncertainty from dose response data, and use of kinetic models to perform in vitro to in vivo extrapolation. Examples for exposure assessment are assessing cumulative exposure at external or internal level, where the latter option is needed when dietary and non-dietary routes have to be aggregated. Finally, risk characterisation is illustrated by calculation and display of the margin of exposure for single substances and for the cumulation, including uncertainties derived from exposure and hazard characterisation estimates.</p

Annexes to the EFSA external scientific report on the standard regulatory action for retrospective cumulative risk assessment of pesticides in MCRA

&lt;p&gt;Annexes to the EFSA external scientific report on the standard regulatory action for retrospective cumulative risk assessment of pesticides in MCRA.&lt;/p&gt; &lt;p&gt;Harmonized methodology for retrospective dietary cumulative risk assessment (CRA) of pesticides was established by the European Commission (EC) and the European Food Safety Authority (EFSA) in 2018, in close collaboration with the Dutch National Institute for Public Health and the Environment (RIVM). An update of this regulatory methodology (RM) was proposed and adopted by EFSA in 2022 in a CRA on craniofacial alterations. This updated RM was implemented in version 10 of the MCRA software and validated as part of the first action defined in the third framework partnership agreements between EFSA and RIVM. This report describes the implementation of this updated methodology in the MCRA software for risk assessment. This is done from a proposed framework of standard regulatory actions (SRAs). SRAs offer a user-friendly and simple to use option for regulators to perform retrospective and prospective CRAs in MCRA according to agreed-upon RMs. In particular, this report provides guidance on the use of an SRA for a retrospective dietary CRA for craniofacial alterations according to the updated RM in MCRA version 10.&lt;/p&gt; &lt;p&gt;Detailed results of the comparison between&nbsp;reported by MCRA and EFSA&rsquo;s SAS&reg; software and MCRA formatted input files for the catalogues and secondary data are presented in the following annexes:&lt;/p&gt; &lt;ul&gt; &lt;li&gt;Annex A &ndash; Comparison of the MOET at different percentiles reported by MCRA and EFSA&rsquo;s SAS&reg; software for retrospective dietary CRA of craniofacial alterations.&nbsp;&lt;/li&gt; &lt;li&gt; &lt;p&gt;Annex B &ndash; Comparison of risk-driver contributions reported by MCRA and EFSA&rsquo;s SAS&reg; software for retrospective dietary CRA of craniofacial alterations.&nbsp;&lt;/p&gt; &lt;/li&gt; &lt;/ul&gt; &lt;ul&gt; &lt;li&gt; &lt;p&gt;Annex C &ndash; MCRA formatted input data file containing the primary entity catalogues for the SRA on retrospective dietary CRA of craniofacial alterations.&nbsp;&lt;/p&gt; &lt;/li&gt; &lt;li&gt; &lt;p&gt;Annex D &ndash; MCRA formatted input data file containing the secondary data for the SRA on retrospective dietary CRA of craniofacial alterations.&nbsp;&lt;/p&gt; &lt;/li&gt; &lt;li&gt; &lt;p&gt;Annex E &ndash; MCRA formatted input data file containing the unit- variability factors for the Tier II calculations of the SRA on retrospective dietary CRA of craniofacial alterations.&nbsp;&lt;/p&gt; &lt;/li&gt; &lt;li&gt; &lt;p&gt;Annex F &ndash; MCRA formatted input data file containing the unit- variability factors for the Tier I calculations of the SRA on retrospective dietary CRA of craniofacial alterations.&nbsp;&lt;/p&gt; &lt;/li&gt; &lt;/ul&gt; &lt;p&gt;&nbsp;&lt;/p&gt;EU; xlsx; [email protected]

MCRA Core

The Monte Carlo Risk Assessment (MCRA) software contains models for human health risk assessment for combined exposure to multiple chemicals via food intake, inhalation and dermal contact. Models are available to address all major areas of risk assessment, including hazard identification, hazard characterisation, (dietary and non-dietary) exposure assessment and risk assessment. The software supports risk assessments for any group of substances, health effect and population. MCRA also contains models following the guidelines and regulatory methodologies of the European Commission and the European Food Safety Authority (EFSA). The MCRA Core library contains the model implementations of the MCRA software that are used in the MCRA Web platform.The tool is implemented in C# (C Sharp). EU; en; .zip; [email protected]

Calcium Imaging of GPCR Activation Using Arrays of Reverse Transfected HEK293 Cells in a Microfluidic System

Reverse-transfected cell arrays in microfluidic systems have great potential to perform large-scale parallel screening of G protein-coupled receptor (GPCR) activation. Here, we report the preparation of a novel platform using reverse transfection of HEK293 cells, imaging by stereo-fluorescence microscopy in a flowcell format, real-time monitoring of cytosolic calcium ion fluctuations using the fluorescent protein Cameleon and analysis of GPCR responses to sequential sample exposures. To determine the relationship between DNA concentration and gene expression, we analyzed cell arrays made with variable concentrations of plasmid DNA encoding fluorescent proteins and the Neurokinin 1 (NK1) receptor. We observed pronounced effects on gene expression of both the specific and total DNA concentration. Reverse transfected spots with NK1 plasmid DNA at 1% of total DNA still resulted in detectable NK1 activation when exposed to its ligand. By varying the GPCR DNA concentration in reverse transfection, the sensitivity and robustness of the receptor response for sequential sample exposures was optimized. An injection series is shown for an array containing the NK1 receptor, bitter receptor TAS2R8 and controls. Both receptors were exposed 14 times to alternating samples of two ligands. Specific responses remained reproducible. This platform introduces new opportunities for high throughput screening of GPCR libraries

Calcium imaging of GPCR activation using arrays of reverse transfected HEK293 cells in a microfluidic system

Reverse-transfected cell arrays in microfluidic systems have great potential to perform large-scale parallel screening of G protein-coupled receptor (GPCR) activation. Here, we report the preparation of a novel platform using reverse transfection of HEK293 cells, imaging by stereo-fluorescence microscopy in a flowcell format, real-time monitoring of cytosolic calcium ion fluctuations using the fluorescent protein Cameleon and analysis of GPCR responses to sequential sample exposures. To determine the relationship between DNA concentration and gene expression, we analyzed cell arrays made with variable concentrations of plasmid DNA encoding fluorescent proteins and the Neurokinin 1 (NK1) receptor. We observed pronounced effects on gene expression of both the specific and total DNA concentration. Reverse transfected spots with NK1 plasmid DNA at 1% of total DNA still resulted in detectable NK1 activation when exposed to its ligand. By varying the GPCR DNA concentration in reverse transfection, the sensitivity and robustness of the receptor response for sequential sample exposures was optimized. An injection series is shown for an array containing the NK1 receptor, bitter receptor TAS2R8 and controls. Both receptors were exposed 14 times to alternating samples of two ligands. Specific responses remained reproducible. This platform introduces new opportunities for high throughput screening of GPCR libraries

The MCRA toolbox of models and data to support chemical mixture risk assessment

International audienceA model and data toolbox is presented to assess risks from combined exposure to multiple chemicals using probabilistic methods. The Monte Carlo Risk Assessment (MCRA) toolbox, also known as the EuroMix toolbox, has more than 40 modules addressing all areas of risk assessment, and includes a data repository with data collected in the EuroMix project. This paper gives an introduction to the toolbox and illustrates its use with examples from the EuroMix project. The toolbox can be used for hazard identification, hazard characterisation, exposure assessment and risk characterisation. Examples for hazard identification are selection of substances relevant for a specific adverse outcome based on adverse outcome pathways and QSAR models. Examples for hazard characterisation are calculation of benchmark doses and relative potency factors with uncertainty from dose response data, and use of kinetic models to perform in vitro to in vivo extrapolation. Examples for exposure assessment are assessing cumulative exposure at external or internal level, where the latter option is needed when dietary and non-dietary routes have to be aggregated. Finally, risk characterisation is illustrated by calculation and display of the margin of exposure for single substances and for the cumulation, including uncertainties derived from exposure and hazard characterisation estimates