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1. REACH and modelling

1. REACH and modelling



The fist lecture on modelling exposure for a course held in Norway 2011. Some of these slides are based on material presented by Andy Gillies - used with his permission (Thanks Andy).

The fist lecture on modelling exposure for a course held in Norway 2011. Some of these slides are based on material presented by Andy Gillies - used with his permission (Thanks Andy).



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  • The first puzzle is created by the DNELs. They will usually be derived from animal experiments and the assessment will have to allow for uncertainties in both the data and the extrapolation to humans. This will be done by including in the calculation a series of Assessment Factors to take into account interspecies differences, intraspecies difference, differences in duration of exposure, issues related to dose-response, and the quality of the whole database. Default values are prescribed and reduce as further information becomes available. For chemicals with only basic testing information available, the safety margin incorporated could be a factor of 10-100 times, and therefore it is likely that DNELs will in general be much lower than traditional OELs.The situation is even more difficult for substances such as genotoxic carcinogens where no safe threshold can be defined. For these materials the manufacturer is expected to set a Derived Minimum-Effect Level, that corresponds to a “low, possibly theoretical, risk” (ECHA, 2008a). It is not clear how that will be defined – will it equate to the so-called Threshold of Toxicological Concern ie. a risk of one death in a million which equates to around 1 microgram per cubic metre? Will it use a linear extrapolation or a Margin of Error calculation? In such cases, the default Assessment Factor could be as high as 10,000.
  • Consider sub-populations of people who may be susceptible or who have particularly high exposure
  • One of the keys to simplification is the use of generic exposure scenarios. Generic scenarios group together substances with similar properties and scenarios with similar exposures so that there are fewer unique situations to deal with.

1. REACH and modelling 1. REACH and modelling Presentation Transcript

  • REACH and the use of occupational exposure modelling
    John Cherrie
  • Summary…
    The role of regulatory risk assessments and REACH
    Substances of Very High Concern (SVHC)
    The supply chain and its role
    Chemical Safety Assessments (CSA) and Chemical Safety Reports (CSR)
    Exposure Scenarios (ES) and Process Categories (PROC)
    Exposure routes
    Risk characterisation – DNELs and DMELs
    Risk Management Measures (RMM)
  • REACH…
    Single system to replace 40 existing sets of regulations
    Applies to new and existing chemicals
    Covers worker, environmental, and consumer risks
    Burden of proof on industry
    Manufacturer/importer responsible for:
    testing and assessment
    safe downstream use and disposal
    Authorisation and Restriction of
  • The role of regulatory risk assessment…
    A workplace
    Chemical Agents Directive
    Requirement to assess risks in that wokplace to ensure safe work
    Responsibility on employer
    All workplaces
    Requirement to assess safety of products on the market
    Responsibility of “society” as a whole (for REACH with industry providing leadership)
  • SVHC…
    SVHC subject to Authorisation (Article 57 and Annex XIV)
    Class 1 and 2 CMR substances (Directive 67/548)
    PBT and vPvB substances (Annex XIII criteria)
    equivalent level of concern
    First Authorisation List published by EChA in 2009
    Priority given to PBT, vPvB, large quantities, or wide dispersive applications
    Aim is to progressively replace SVHC by less harmful substances or technologies
  • The supply chain…
    Manufacturer – production or extraction of substances in the natural state
    Importer – physical introduction into the customs territory of the Community
    Downstream User – use of a substance, either on its own or in a preparation
    Where USE means any processing, formulation, consumption, storage, keeping, treatment, filling into containers, transfer from one container to another, mixing, production of an article or any other utilisation
  • Example of a complex supply chain…
    Marquart (2006) Exposure scenarios for REACH – why should the user care? NvVA Conference Presentation
  • The CSA and CSRs
    For chemicals > 10 tonnes/year manufacturers/importers:
    Must predict the exposures in manufacture and use(s)
    Identify the conditions that will ensure control of risks
    Prepare a corresponding Exposure Scenario (ES) to be communicated to the users in an extended-Safety Data Sheet (e-SDS)
    Document the assessment in a Chemical Safety Report (CSR)
    Exposure Scenarios
    Exposure estimates
    Risk characterisation
    Risk Management Measures
  • DNELs and DMELs
    DNELs, derived no effect levels, or DMELs, derived minimal effect levels (for substances without threshold)
    Acute/Chronic, route specific
    Tension between DNELs and Occupational Exposure Limits
  • Comparison DNELs and OELs
    OELs and possible chronic inhalation DNEL in mg/m3
    Roy et al, “The Use of Health-Based Occupational Exposure Limits As REACH Derived No Effect Levels.” Poster presented at SOT Meeting, Seattle Wa 2008
  • Risk characterisation…
    For worker exposure, determine residual risk to workers (after RMM implemented) by comparing exposure with the relevant DNEL or DMEL
    If ratio >1, additional RMMs required
    Perform similar calculation for:
    all routes of exposure (especially air and skin)
    other groups of people at risk
    environmental risks
  • Exposure scenarios…
    An ES describes:
    processes and tasks
    frequency and duration
    operational conditions
    measured exposure data or modelling data
    risk management measures required
    Covers manufacture and intended uses throughout substance life cycle, including disposal/recycling
    For each population exposed (as workers, consumers, via the environment, or a combination)
  • The role of an ES…
    Exposure scenarios have multiple functions in the REACH system
    document manufacturer’s own exposures
    provide information to be fed into exposure assessment tools (to enable comparisons with DNELs)
    form part of Chemical Safety Report to be submitted with the Registration package to the authorities
    Included as an appendix to extended Safety Data Sheet
    guidance on how to safely use the substance, for formulators, trade and industrial end users
    Development of ES envisaged as an iterative process of communications between manufacturer and downstream user
  • PROCs…
    Process category
    Application techniques or process types defined from the occupational perspective
    29 codes describing most uses
    Described in ECHA Guidance on information requirements and chemical safety assessment Chapter R.12: Use descriptor system.
    Basis for the ECETOC TRA tool
  • Generic ESs…
  • Risk Management Measures…
    Must cover workers, consumers, and general public
    For workers, consider…
    Hierarchy of control
    General principles of good control practice
    All routes of exposure (inhalation, dermal, accidental ingestion)
    Must be able to determine the residual risk after RMM implemented
  • CEFIC RMM Library
  • RMM effectiveness…
    Default and “max. achievable” values for RMM efficiencies in RMM Library
    Evidence base is poor for worker, environment and consumer control measures
    CEFIC RMM task force working with national associations to produce consensus
    Separate initiatives from industry, academia, professions (e.g. ECEL database)
  • ECEL…
    Fransman et al. Development and Evaluation of an Exposure Control Efficacy Library (ECEL). Annals of Occupational Hygiene (2008) vol. 52 (7) pp. 567-575
  • Conclusions concerning modelling…
    REACH has the potential to stimulate continuous development of modelling and modelling tools
    The need to a cost-effective way of evaluating exposure is clear
    It is a problem that the systems for risk assessment – toxicology and exposure assessment - are being developed independently