REACH TNO | Knowledge for businesss
Erik Tielemans1*, Nick Warren2, Thomas Schneider3, Martie van Tongeren4, Martin Tischer5, Peter Ritchie4, Wouter Fransman1, Hans Kromhout6, Jody Schinkel1, Joop van Hemmen1, John Cherrie4
1 TNO Quality of Life, P.O. Box 360, 3700 AJ Zeist, The Netherlands 2 HSL, United Kingdom 3 NRCWE, Denmark 4 IOM, United Kingdom 5 BAuA, Germany 6 IRAS, Utrecht University, The Netherlands * P +31 30 694 49 90 F +31 30 694 40 70
[email protected]
Development of an advanced exposure assessment tool for REACH The REACH process requires a Tiered exposure assessment to effectively cope with the broad range of Exposure Scenarios. Currently, a higher Tier model generating realistic exposure estimates is missing. A new advanced exposure assessment tool is under development. Outline of project The new framework incorporates both a mechanistic model and an empirical part with information from an exposure database. Both parts are to be combined using a Bayesian process in order to produce realistic exposure estimates (Figure). The approach facilitates the inclusion of any new exposure data that become available in the future or during the risk assessment process. The proposal consists of five strongly interrelated Work Packages: 1) Development of mechanistic model 2) Bayesian framework 3) Database development 4) Software development 5) Testing and validation The advanced tool will be completed by 2010 and will be made freely available to stakeholders, probably as a web-based tool. Exposure database, with contextual information
Similarity module to select data for risk assessment
Deterministic model, incl. Monte Carlo module
Bayesian process to combine data and model output
Exposure estimates for risk assessment
Figure. Proposed structure of exposure model (from Creely et al., 2005).
Mechanistic model The mechanistic model for inhalation exposure is based on a stepwise process following the transfer of a contaminant from the source to the receptor, i.e. the worker. The conceptual model is constructed using three components: 1) source; 2) several transmission compartments; and 3) receptor. A list of nine mutually independent principal modifying factors (MF) is used to describe the transfer (Table). Table. Nine mutually independent modifying factors. Model component
Modifying factor
Source
Activity emission potential Substance emission potential
KvL-Z.08-04.631 Ep Version 2
Transmission
Localized control Separation Segregation Mixing Dilution Surface contamination
Receptor
Respiratory protection
We will identify further categories within these nine modifying factors and subsequently estimate their effect on emission, transmission and exposure. For example, we will need to identify a limited number of categories of local control measures and quantify their effectiveness. An evidence database is built that collates information from the literature on efficacy of various Risk Management Measures in order to underpin this process (ECEL: Exposure Control Efficacy Library). The mechanistic model will need to be calibrated using a broad range of exposure data and we are currently collating existing exposure data from various sources in Europe.
Current status The current development focuses on inhalation exposure. Dermal exposure will follow soon. The project is currently part-funded by the Dutch Government, HSE, AFSSET and CEFIC LRI. With the current funding we will develop the mechanistic model (WP 1) and demonstrate the proof of concept using the Bayesian update (WP 2). The proof of principle will be demonstrated during a stakeholder meeting to be held in September 2009. To ensure that the tool incorporates the state-of-the art knowledge we are keen to receive input from a number of experts across Europe.
Key references • Creely KS, Tickner J, Soutar AJ, Hughson GW, Pryde DE, Warren ND, Rae R, Money C, Phillips A, Cherrie JW. (2005) Evaluation and further development of EASE model 2.0 Ann Occup Hyg; 49:135-46. • Cherrie JW, Schneider T. (1999) Validation of a new method for structured subjective assessment of past concentrations. Ann Occup Hyg; 43: 235-45. • Tielemans E, Warren N, Schneider T, Tischer M, Ritchie P, Goede H, Kromhout H, van Hemmen J, Cherrie J. (2007) Tools for regulatory assessment of occupational exposure: development and challenges. J Exp Anal Environ Epidemiol; 17: S72-S80. • Tielemans E, Schneider T, Goede H, Tischer M, Warren N, Kromhout H, van Tongeren M, van Hemmen JJ, Cherrie J. (2008) Conceptual model for inhalation exposure: defining modifying factors. Submitted for publication.
