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Table 3 Central considerations to be addressed for deriving a defined “mixture allocation factor” to take account for unintentional environmental co-occurrences of chemicals

From: Options for an environmental risk assessment of intentional and unintentional chemical mixtures under REACH: the status and ways forward

Open question Options Needs and challenges
Process and responsible actor? MAF set by authorities to be implemented in legal text, supported by ECHA GD. Applicable during Chemical safety assessment of registrants and/or Downstream user assessments The premise is that chemicals are not reaching environmental compartments alone but co-occur and may produce joint effects and risks—which is currently not addressed during the single substance’s CSA nor DU assessments
Takes account for limited information and resources of REG and DU and follows the legal setup of REACH that safe use ensured during CSA
Location for implementation in legal text? In Annex I on CSA factor could be introduced on: PNEC (reflects intrinsic properties and includes AFs for 1 substance)
PEC (reflects exposure for compartment/use)
RCR (reflects predicted risk for use and compartment)
Msafe (reflects safe use amounts)
Communication along supply chain to be ensured
Confusion with existing uncertainty factors to be avoided
Clear wording, definitions and references in legal text and guidances
Uniform or specific factors? Either the same or specific factors for:
different environmental compartments
different uses and product categories
different tonnages
One uniform MAF more pragmatic, assumed to affect substances close to RCR of 1, easier to communicate
Implications, evidences and benefits would need to be justified for possible differentiated factors
Definition of the appropriate order of magnitude? The order of magnitude or “size” of a MAF can be based on: Evidence on averaged environmental co-occurrences and predicted risks
Knowledge on predicted exposures or emissions from substances/mixtures
Analysis of current chemical safety assessments and potential impact of a factor on the reduction of safe use amounts, predicted emissions or risks
Review and analyses of available scientific studies on environmental co-occurrence and possible risks of chemicals. Use of modelling approaches to estimate EU level co-exposures and current risk underestimations
Analyses of current CSAs
Refinements or exemptions? Refinements may justifiable: in certain situations (no exposure due to close system) if sufficient and reliable data are available to conduct specific assessment Conceivable that a generic default factor may be refined via specific assessments in cases where data available or exposures can be excluded
Chemicals and types of mixtures covered? It needs to be defined whether a MAF should cover possible risks due to exposures of chemicals regulated under REACH
co-occurring other substances, such as pesticides, biocides or pharmaceuticals
The coverage needs to be clearly defined
Covering substances not falling within REACH is legally challenging
Possibilities for a later review? The magnitude or specification of a MAF could be readjusted
After a fixed time span
In case of new scientific evidence
A re-assessment could be in accordance with the REACH Review and could imply a surveillance of chemicals exposures and predicted risks