Joop Van Hemmen

Publications of Joop Van Hemmen

• The Accuracy of DERM may be a Self-fulfilling DREAM.

  Authors: Hans Kromhout, Berna van Wendel de Joode, Joop Van Hemmen

  The Annals of occupational hygiene. 11/2008;

• Conceptual Model for Assessment of Inhalation Exposure: Defining Modifying Factors.

  Authors: Erik Tielemans, Thomas Schneider, Henk Goede, Martin Tischer, Nick Warren, Hans Kromhout, Martie van Tongeren, Joop Van Hemmen, John W Cherrie

  The Annals of occupational hygiene. 10/2008;

  The present paper proposes a source-receptor model to schematically describe inhalation exposure to help understand the complex processes leading to inhalation of hazardous substances. The modelThe present paper proposes a source-receptor model to schematically describe inhalation exposure to help understand the complex processes leading to inhalation of hazardous substances. The model considers a stepwise transfer of a contaminant from the source to the receptor. The conceptual model is constructed using three components, i.e. (i) the source, (ii) various transmission compartments and (iii) the receptor, and describes the contaminant's emission and its pattern of transport. Based on this conceptual model, a list of nine mutually independent principal modifying factors (MFs) is proposed: activity emission potential, substance emission potential, localized control, separation, segregation, dilution, worker behavior, surface contamination and respiratory protection. These MFs describe the exposure process at a high level of abstraction so that the model can be generically applicable. A list of exposure determinants underlying each of these principal MFs is proposed to describe the exposure process at a more detailed level. The presented conceptual model is developed in conjunction with an activity taxonomy as described in a separate paper. The proposed conceptual model and MFs should be seen as 'building blocks' for development of higher tier exposure models.

• Development and Evaluation of an Exposure Control Efficacy Library (ECEL).

  Authors: Wouter Fransman, Jody Schinkel, Tim Meijster, Joop Van Hemmen, Erik Tielemans, Henk Goede

  The Annals of occupational hygiene. 09/2008;

  OBJECTIVES: This paper describes the development and evaluation of an evidence database on the effectiveness of risk management measures (RMMs) to control inhalation exposure. This database isOBJECTIVES: This paper describes the development and evaluation of an evidence database on the effectiveness of risk management measures (RMMs) to control inhalation exposure. This database is referred to as Exposure Control Efficacy Library (ECEL). METHODS: A comprehensive review of scientific journals in the occupational hygiene field was undertaken. Efficacy values for RMMs in conjunction with contextual information on study design, sampling strategy and measurement type (among other parameters) were stored in an MS Access database. In total, 433 efficacy values for six RMM groups (i.e. enclosure, local exhaust ventilation, specialized ventilation, general ventilation, suppression techniques and separation of the worker) were collected from 90 peer-reviewed publications. These RMM categories were subdivided into more specific categories. RESULTS: Estimated average efficacy values ranged from 87% for specialized ventilation to 43% for general ventilation. Substantial variation in efficacy values was observed within RMM categories based on differences in selected covariables within each study (i.e. study design, sampling strategy, measurement type and others). More contrast in efficacy values was observed when evaluating more detailed subcategories. CONCLUSIONS: It is envisaged that ECEL will contribute to exposure modelling, but should be supplemented with expert opinion, preferably in a formal expert elicitation procedure. The work presented here should be considered as a first attempt to collate and analyse RMM efficacy values and inclusion of additional (unpublished) exposure data is highly warranted.

• Tools for regulatory assessment of occupational exposure: development and challenges.

  Authors: Erik Tielemans, Nick Warren, Thomas Schneider, Martin Tischer, Peter Ritchie, Henk Goede, Hans Kromhout, Joop Van Hemmen, John W Cherrie

  Journal of exposure science & environmental epidemiology. 01/2008; 17 Suppl 1:S72-80.

  REACH (Registration, Evaluation and Authorization of CHemicals) requires improved exposure models that can be incorporated into screening tools and refined assessment tools. These are referred to asREACH (Registration, Evaluation and Authorization of CHemicals) requires improved exposure models that can be incorporated into screening tools and refined assessment tools. These are referred to as tier 1 and 2 models, respectively. There are a number of candidate in tier 1 models that could be used with REACH. Tier 2 models, producing robust and realistic exposure assessments, are currently not available. A research programme is proposed in this paper that will result in a new, advanced exposure assessment tool for REACH. In addition, issues related to variability and uncertainty are discussed briefly, and some examples of tier 1 screening tools are presented. The proposed framework for the tier 2 tool is based on a Bayesian approach, and makes full use of mechanistically modelled estimates and any relevant measurements of exposure. The new approach will preclude the necessity to conduct of case-by-case exposure measurements for each chemical and scenario, since the system will allow for the use of analogous exposure data from relatively comparable scenarios. The development of the new approach requires substantial effort in the area of mechanistic modelling, database development and Bayesian statistical techniques. In this paper, the data gaps and areas for future research are identified to help realise and further improve this type of approach within REACH. A structured data collection and storage system is a central element of the research programme and the availability of this type of tool may also facilitate the sharing of exposure data down and up the supply chain. In addition, new data that are stored according to the proposed structure could enable the validation of any exposure model and thus this programme enhances the exposure assessment field as a whole.

• Inhalation exposure to isocyanates of car body repair shop workers and industrial spray painters.

  Authors: Anjoeka Pronk, Erik Tielemans, Gunnar Skarping, Ivana Bobeldijk, Joop Van Hemmen, Dick Heederik, Liesbeth Preller

  The Annals of occupational hygiene. 02/2006; 50(1):1-14.

  As part of a large-scale epidemiological study, occupational isocyanate exposure was assessed in spray-painting environments. The aim was to assess which compounds contribute to isocyanate exposureAs part of a large-scale epidemiological study, occupational isocyanate exposure was assessed in spray-painting environments. The aim was to assess which compounds contribute to isocyanate exposure in car body repair shops and industrial painting companies, and to identify tasks with high risk of isocyanate exposure. Mainly personal task-based samples (n = 566) were collected from 24 car body repair shops and five industrial painting companies using impingers with DBA in toluene. Samples were analysed by LC-MS for isocyanate monomers, oligomers and products of thermal degradation. From the 23 analysed compounds, 20 were detected. Exploratory factor analysis resulted in a HDI, TDI and MDI factor with the thermal degradation products divided over the TDI and MDI factors. The HDI factor mainly consisted of HDI oligomers and was dominant in frequency and exposure levels in both industries. Spray painting of PU lacquers resulted in the highest exposures for the HDI factor (<LOD-2643 microg/m(3) NCO), with no significant difference between the industries. Exposure variability during PU spray painting was large with a variability over time of (ww)S(2) = 9.1 compared with between-worker variability of (bw)S(2) = 1.6. Lower level exposure to the HDI factor was found during other painting-related tasks and even tasks without direct exposure to paint. Exposure to the TDI factor was found more regularly in car body repair shops than in industrial painting companies. Exposure levels were low (<LOD-5 microg/m(3) NCO) compared with the HDI factor and no clear contrast in levels between the tasks was observed. Exposure to the MDI factor was found incidentally during spraying and welding in car body repair shops (<LOD-0.5 microg/m(3) NCO). The results indicate that paint is the most important source and major contributor of isocyanate exposure in both industries with highest exposures during PU spraying. However, since respiratory protection is less extensively used during other tasks, lower level exposure during these other tasks may significantly contribute to the internal dose.

• Effectiveness of personal protective equipment: relevance of dermal and inhalation exposure to chlorpyrifos among pest control operators.

  Authors: Katinka van der Jagt, Erik Tielemans, Ingrid Links, Dick Brouwer, Joop Van Hemmen

  Journal of occupational and environmental hygiene. 07/2004; 1(6):355-62.

  This study assessed the effectiveness of a custom fit personal protective equipment (PPE) program aimed at reducing occupational exposure to pesticides. The intervention study was carried out on 15This study assessed the effectiveness of a custom fit personal protective equipment (PPE) program aimed at reducing occupational exposure to pesticides. The intervention study was carried out on 15 pest control operators (PCOs) during mixing/loading and application of chlorpyrifos. Each worker was measured twice; first while the worker used PPE as normal (baseline measurement), and second after making some adjustments to the PPE (postintervention measurement). The applied intervention consisted of a tight-fitting, full-face respirator, fit-testing, long gloves, chemical-proof boots, a Tyvek hood, and an instruction video that was shown prior to putting on the PPE. A comprehensive evaluation program was used for the within-subject comparisons, including assessment of potential dermal exposure, actual dermal exposure, inhalation exposure, and internal dose as measured by the urinary metabolite 3,5,6-trichloro-2-pyridinol (TCP). The PPE program resulted in a significant increase in fit factors from a mean of 670 to 132,000. Actual dermal exposure levels decreased on average by fourfold after implementation of the PPE program (baseline AM = 132.1 microg; postintervention AM = 32.6 microg). The TCP levels in urine collected 24-32 hours after spray activities were lower in the postintervention data set (AM = 21.2 microg TCP/g creatinine vs. AM = 13.9 microg TCP/g creatinine). However, it is impossible to attribute these differences totally to the PPE program since workers had significant and varying urinary TCP levels before onset of spraying activities. Linear regression models showed that dermal exposure was only a predictive parameter for TCP levels in urine in the baseline data set. Although the results should be interpreted cautiously this study suggests a protective effect of the evaluated PPE program.

• Excluding exposure data of very poor quality is a core principle for regulatory risk assessment.

  Authors: Erik Tielemans, Yvette Christopher, Hans Marquart, Monique Groenewold, Joop Van Hemmen

  The Annals of occupational hygiene. 09/2002; 46(6):559-60; author reply 560.

• A proposal for evaluation of exposure data.

  Authors: Erik Tielemans, Hans Marquart, Johan De Cock, Monique Groenewold, Joop Van Hemmen

  The Annals of occupational hygiene. 05/2002; 46(3):287-97.

  There is a growing need for transparency concerning ways in which existing exposure data are weighted for their relative value and quality. Currently, this evaluation is largely subjective and isThere is a growing need for transparency concerning ways in which existing exposure data are weighted for their relative value and quality. Currently, this evaluation is largely subjective and is dependent on the quality of the judgement of the individual assessor or expert group. In this paper some general guidelines are presented for a quality assessment procedure. Such a predetermined procedure potentially enhances the consistency among different assessors and assessments and facilitates harmonization of assessment procedures. The guidelines are presented in the context of a decision tree with four decision rules for data quality, i.e. 'availability of occupational hygiene information', 'variability and precision issues', 'internal validity' and 'external validity'. These methodological issues are considered to be the most important aspects of data quality and will be discussed in this paper. The decision tree eventually results in three quality classes, i.e. exposure data providing sufficient information, supplementary information and data which should be excluded from the exposure assessment process. The guidelines should not be used in a rigid manner but have to be interpreted in the light of the particular circumstances and purposes of the assessment.