NORA Manufacturing Sector Strategic Goals
927ZJLVa - Factors Affecting Exposure to Engineered Nanomaterials (NTRC)Start Date: 10/1/2009
End Date: 9/30/2013
Principal Investigator (PI)Name: Mohammed Abbas Virji
Funded By: NIOSH
Primary Goal Addressed9.0
Secondary Goal Addressed
Attributed to Manufacturing
A critical need exists to understand factors that impact exposures in the workplace. Such data are extremely useful in providing opportunities to identify and prioritize control measures; predict current exposures for unsampled workers or historical exposures of individuals; or to assess time trends in exposures. A major barrier to understanding exposure factors is the paucity of contextual information on job and work environment characteristics. The objectives of this study are to understand the: 1) inter-relationships among EN exposure characteristics (mass, number, surface area, surface chemistry); and 2) workplace-, process-, environmental-, and individual-factors as well as material characteristics that affect exposure levels during production of EN. Understanding the impact of these exposure factors on exposure levels will enable the identification development and implementation of evidence-based prioritization of control measures and will improve future exposure assessment studies.
The overall objective of this study is to understand and better characterize factors that impact EN exposures in the workplace. Such data are necessary for: identifying and prioritizing control measures and for predicting worker exposures or future work scenarios for use in epidemiologic studies or to support risk assessments respectively. A major barrier to understanding exposure factors is the paucity of contextual information on job and work environment characteristics. We plan to achieve our objectives through four specific aims conducted in two phases. The focus of phase one will be to refine the theoretical model of inhalation exposure, and using existing datasets identify the key exposure determinants achieved through specific aims 1 and 2. Depending on the findings of phase one, exposure monitoring will be conducted at two facilities, information on the relevant exposure determinants will be gathered and exposure models will be developed in the second phase of the study. Specifically, in specific aim 1, we will adapt and modify an existing model to estimate inhalation exposures to assess EN exposures. In specific aim 2, we will identify, evaluate and pool existing data on EN exposures, develop a determinants of exposure matrix based on existing information as well as information that can be obtained retrospectively, and run statistical models to identify the determinants of exposure levels or exceedance of certain thresholds. In specific aim 3, we will conduct exposure assessment at a TiO2 manufacturing facility, and a facility manufacturing carbon nanotubes identified by the field team. The exposure data developed from this study can be used to support a range of objectives, and assess the determinants of a range of EN exposure metrics (including mass, number and surface area). Finally in aim 4, we will attempt to conduct video exposure monitoring in conjunction with direct reading exposure monitoring to identify more specific determinants of exposure and potential control measures. The results of this study will enhance and support the development and use of modern and robust exposure assessment methods being currently considered by NIOSH.
It will be possible to substantiate the outcome by evaluating the use of the approach by the field team; the number of NIOSH publications using results from this study; and number of publications generated from this study.
Engineered nanomaterials (EN) are materials designed and produced with at least one dimension =100 nm. EN materials can be classified into a number of categories including pure metals, oxides, carbon based nano particles, quantum dots, macro molecules and self-assembled molecules (ICON, 2008). EN particles are heterogeneous and can be present in a combination of size, shape, composition, charge, crystallinity, solubility, functional groups and impurities, leading to different toxicological effects (Schulte et al., 2009). Limited evidence suggests that exposure to some EN materials can lead to adverse health effects (Schulte et al., 2009). EN materials are increasingly used in a wide range of manufacturing processes (computer chip polishing, etc.) and products (paints, etc.); over 600 consumer and commercial products may contain EN material (Schulte et al., 2009). Increasing number of workers are exposed to EN materials and it is expected that nearly 2 million workers may be employed in nanotechnology industries by about 2020, with many workplaces employing only a handful of workers (Schulte et al., 2008).
There are few published studies of EN exposures, and even fewer that provide detailed information on factors affecting EN exposures. The potential factors affecting EN exposure occur at three levels: the macro level (which examines differences in exposure across industry sectors or product types); the mid-level (which examines differences in exposure among workplaces); and the micro level (which examines differences in exposure among operations or tasks). Information on macro level exposure determinants are very limited and mostly describe the stage of EN manufacturing (R&D or manufacturing), the size of the business, years of experience and type of EN material used (pure metals, oxides, carbon nano-tubes etc.) (ICON, 2006). There are no data that link these macro-level determinants to EN exposures. Similarly, there is a lack of data linking the potential midlevel EN exposure determinants such as the type of product, company demographics, descriptors of the physical worksite, rating of worksite health and safety programs, or geographic location to EN exposures. To date only one study has compared the particle number concentrations for two operations (reactor and pelletizer) at three carbon black plants (Kuhlbusch et al., 2004, 2006). Only a few studies have examined EN exposures associated with tasks, jobs, ventilation systems and other micro-level exposure determinants related to process factors, environmental factors or personal factors.
This study will help understand factors that impact exposures. A major barrier to understanding exposure factors is the paucity of contextual information on job and work environment characteristics. The importance of understanding the work environment is especially critical for EN because factors influencing exposures in the workplace are poorly understood and currently not evaluated in industrial hygiene (IH) field studies in general.
Through this project, a conceptual model for inhalation exposure to EN material will be developed and potential exposure factors and determinants will be proposed. The existing EN exposure data sets (e.g. for CNTs and TiO2) will be analyzed and summarized to support development of recommended exposure levels (RELs) and other guidance documents. Finally, understanding determinants of exposure to EN material will help identify and prioritize control measures and for predicting worker exposure or future work scenarios for use in epidemiologic studies or to support risk assessments respectively. Also this study will support the development and use of modern and robust exposure assessment methods being currently considered by NIOSH.
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