Derk Brouwer

Publications of Derk Brouwer

• Harmonization of measurement strategies for exposure to manufactured nano-objects; report of a workshop.

  Authors: Derk Brouwer, Markus Berges, Mohammed Abbas Virji, Wouter Fransman, Dhimiter Bello, Laura Hodson, Stefan Gabriel, Erik Tielemans

  The Annals of occupational hygiene. 12/2011; 56(1):1-9.

  The present paper summarizes the outcome of the discussions at the First International Scientific Workshop on Harmonization of Strategies to Measure and Analyze Exposure to (Manufactured)The present paper summarizes the outcome of the discussions at the First International Scientific Workshop on Harmonization of Strategies to Measure and Analyze Exposure to (Manufactured) Nano-objects in Workplace Air that was organized and hosted by the Netherlands Organization for Applied Scientific Research (TNO) and the Institute for Occupational Safety and Health of the German Social Accident Insurance (IFA) (Zeist, The Netherlands, December 2010). It reflects the discussions by 25 international participants in the area of occupational (nano) exposure assessment from Europe, USA, Japan, and Korea on nano-specific issues related to the three identified topics: (i) measurement strategies; (ii) analyzing, evaluating, and reporting of exposure data; and (iii) core information for (exposure) data storage. Preliminary recommendations were achieved with respect to (i) a multimetric approach to exposure assessment, a minimal set of data to be collected, and basic data analysis and reporting as well as (ii) a minimum set of contextual information to be collected and reported. Other issues that have been identified and are of great interest include (i) the need for guidance on statistical approaches to analyze time-series data and on electron microscopy analysis and its reporting and (ii) the need for and possible structure of a (joint) database to store and merge data. To make progress in the process of harmonization, it was concluded that achieving agreement among researchers on the preliminary recommendations of the workshop is urgent.

• Advanced REACH Tool: development and application of the substance emission potential modifying factor.

  Authors: Martie van Tongeren, Wouter Fransman, Sally Spankie, Martin Tischer, Derk Brouwer, Jody Schinkel, John W Cherrie, Erik Tielemans

  The Annals of occupational hygiene. 11/2011; 55(9):980-8.

  The Advanced REACH Tool (ART) is an exposure assessment tool that combines mechanistically modelled inhalation exposure estimates with available exposure data using a Bayesian approach. TheThe Advanced REACH Tool (ART) is an exposure assessment tool that combines mechanistically modelled inhalation exposure estimates with available exposure data using a Bayesian approach. The mechanistic model is based on nine independent principal modifying factors (MF). One of these MF is the substance emission potential, which addresses the intrinsic substance properties as determinants of the emission from a source. This paper describes the current knowledge and evidence on intrinsic characteristics of solids and liquids that determine the potential for their release into workplace air. The principal factor determining the release of aerosols from handling or processing powdered, granular, or pelletized materials is the dustiness of the material, as well as the weight fraction of the substance of interest in the powder and the moisture content. The partial vapour pressure is the main intrinsic factor determining the substance emission potential for emission of vapours. For generation of mist, the substance emission potential is determined by the viscosity of the liquid as well as the weight fraction of the substance of interest in the liquid. Within ART release of vapours is considered for substances with a partial vapour pressure at the process temperature of 10 Pa or more, while mist formation is considered for substances with a vapour pressure ≤ 10 Pa. Relative multipliers are assigned for most of the intrinsic factors, with the exception of the weight fraction and the vapour pressure, which is applied as a continuous variable in the estimation of the substance emission potential. Currently, estimation of substance emission potential is not available for fumes, fibres, and gases. The substance emission potential takes account of the latest thinking on emissions of dusts, mists, and vapours and in our view provides a good balance between theory and pragmatism. Expanding the knowledge base on substance emission potential will improve the predictive power of occupational exposure models and thereby the accuracy and precision of the exposure estimates.

• Video exposure monitoring as part of a strategy to assess exposure to nanoparticles.

  Authors: Petra A W V Beurskens-Comuth, Koen Verbist, Derk Brouwer

  The Annals of occupational hygiene. 08/2011; 55(8):937-45.

  There is a growing awareness of the potential risks for human health of exposure to ultrafine particles or nanoparticles. In that context, workplace air measurements become important, and variousThere is a growing awareness of the potential risks for human health of exposure to ultrafine particles or nanoparticles. In that context, workplace air measurements become important, and various strategies have been developed to monitor exposure. In addition, observations and time/activity registrations are part of the exposure assessment strategy in many studies. Video exposure monitoring (VEM) can be of added value in these strategies. VEM combines exposure data with simultaneous video pictures of the process. The PIMEX method (Picture Mix Exposure) was used as the VEM studied. The possibility to combine PIMEX and measurement instruments for nanoparticles was the object of this study. The starting point was a review of available instruments for workplace air measurements of nanoparticles. Publications of strategies to assess exposure to nanoparticles were also studied to review whether observations were part of these strategies. Finally, a technical review of combining PIMEX and the compatible measurement instruments was undertaken and explored as part of the strategy to assess exposure to nanoparticles. A variety of instruments are used to measure nanoparticles. One category is (near) real-time monitoring instruments, which determine numbers and particle size distribution or surface area concentration. Other instruments require sample collection in order to characterize the nanoparticles chemically and physically by microscopic analyses and/or elemental analyses. Only some of these instruments are technically compatible with PIMEX. With the PIMEX2008 version 1.02 software, it is possible to synchronize up to four different measuring instruments simultaneously with the video recording. PIMEX as a VEM method can be a useful tool as part of the strategy to assess exposure to nanoparticles. It can also be of value for other purposes like training, education, and risk communication. The possibility to synchronize more than one measuring instrument can be useful to simultaneously monitor different targets in the workplace, e.g. worker exposure in the breathing zone and background concentration.

• Exposure to manufactured nanoparticles in different workplaces.

  Authors: Derk Brouwer, Tno Quality Of Life, Zeist, The Netherlands

  Toxicology. 11/2009;

  In potential nano objects can be release into the workplace air during production, during the handling of nano powders and during the treatment of end-products that contain manufactured nanoIn potential nano objects can be release into the workplace air during production, during the handling of nano powders and during the treatment of end-products that contain manufactured nano materials. Experimental studies that could mimic the exposure processes revealed the formation of larger agglomerates after release. Studies conducted in workplaces confirmed this assumption, however, the data are still very scarce and not easily to compare due to differences in the format of reporting the data. Number-, mass-, and surface area concentrations are reported, however, currently an estimate of the potential for worker exposure is not possible. It is recommended that future workplace exposure studies will be conducted according to a more harmonized approach for analyzing and reporting of the results.

• Quantitative self-assessment of exposure to solvents among shoe repair men.

  Authors: Selma Hertsenberg, Derk Brouwer, Marc Lurvink, Carina Rubingh, Esther Rijnders, Erik Tielemans

  The Annals of occupational hygiene. 02/2007; 51(1):45-51.

  Self-assessment of exposure (SAE) refers to any exposure assessment methodology wherein the worker takes an active role in establishing his or her exposure status. The objective of this study was toSelf-assessment of exposure (SAE) refers to any exposure assessment methodology wherein the worker takes an active role in establishing his or her exposure status. The objective of this study was to investigate the reliability and feasibility of SAE approaches among shoe repair workers collecting exposure data over a 3 month period. This study was conducted in 26 Dutch shoe repair shops, which were divided into two groups of SAE with different levels of expert supervision. Participants in group 1 received only written instructions on sampling methods, whereas workers in group 2 were also instructed face-to-face by an occupational hygienist. Participants were asked to do 20 (group 1) or 14 (group 2) measurements by themselves. In group 2, an additional 6 measurements in each company were conducted under supervision of an expert. Organic solvents were measured by passive samplers (3M badges) and a sum score for volatile organic compounds (VOC score) was used in data analysis. Mixed effect models and principal component analysis were used to compare concentration levels and exposure variability between group 1 and group 2. Finally, 473 out of the 520 distributed samplers (91%) were available for analysis. Measurements in group 1 were not evenly spread over the 3 month period, whereas dispersal of measurements was much better if experts were more closely involved (group 2). No significant differences in average VOC scores were found between group 1 and group 2. The exposure variability in group 1 appeared to be significantly larger than that in group 2. However, analysis within group 2 showed that no differences exist in geometric means and exposure variability between 'expert' and 'self-assessment' measurements. Thus, the study results are ambiguous with respect to the reliability of SAE, and more research is needed to corroborate and refine the present results. This new methodology can, if proven reliable, be seen as a cost-effective way of collecting exposure data.

• Gloves and dermal exposure to chemicals: proposals for evaluating workplace effectiveness.

  Authors: John W Cherrie, Sean Semple, Derk Brouwer

  The Annals of occupational hygiene. 11/2004; 48(7):607-15.

  There are standardized laboratory tests for chemical protective gloves that provide estimates of breakthrough time and steady-state permeation flux. However, there is evidence to suggest that theseThere are standardized laboratory tests for chemical protective gloves that provide estimates of breakthrough time and steady-state permeation flux. However, there is evidence to suggest that these tests may not be completely relevant to glove usage in the workplace. There is no consensus about how glove workplace effectiveness should be assessed, although a few studies have attempted to measure the effectiveness of chemical protective gloves. We have used a conceptual model of dermal exposure to help analyse how workers' skin may become exposed while wearing gloves, and propose a new glove workplace protection factor (PFgloves), which is based on the ratio of the estimated uptake of chemicals through the hands without gloves to the uptake through the hands while wearing protective gloves. Mathematical simulations demonstrate that glove protection factor is unlikely to be constant for a glove type, but will be strongly influenced by the work situation and the duration of the exposure. This has important consequences for the selection of protective gloves.

• A structured observational method to assess dermal exposure to manufactured nanoparticles DREAM as an initial assessment tool.

  Authors: Birgit Van Duuren-Stuurman, Johannes Pelzer, Carsten Moehlmann, Markus Berges, Delphine Bard, Derrick Wake, Dave Mark, Elzbieta Jankowska, Derk Brouwer

  International journal of occupational and environmental health. 16(4):399-405.

  Preliminary results of inventories of exposure scenarios for nanomaterials have indicated possible dermal exposure. Within the NANOSH project focused on occupational safety and health aspects ofPreliminary results of inventories of exposure scenarios for nanomaterials have indicated possible dermal exposure. Within the NANOSH project focused on occupational safety and health aspects of nanotechnology a shortened version of the observational DeRmal Exposure AssessMent (DREAM) method was used as an initial method to assess dermal exposure. A total of 45 tasks (such as bagging, dumping, and cleaning) involving different manufactured nanoparticles (MNPs) such as carbon nanotubes, fumed silica, and cerium oxide, were observed in industrial and research facilities. In 39 tasks potential dermal exposure (that is, exposure of the skin and clothing) was likely to occur. Exposure resulted from different routes, including direct contact with MNPs as well as the deposition or transfer of MNPs. The survey showed it is both feasible and useful to assess the potential dermal exposure using shortened DREAM questionnaires.