Charles L. Geraci

Nanoparticle Emission Assessment Technique (NEAT) for the Identification and Measurement of Potential Inhalation Exposure to Engineered Nanomaterials—Part B: Results from 12 Field Studies

The National Institute for Occupational Safety and Health (NIOSH) conducted field studies at 12 sites using the Nanoparticle Emission Assessment Technique (NEAT) to characterize emissions during processes where engineered nanomaterials were produced or used. A description of the NEAT appears in Part A of this issue. Field studies were conducted in research and development laboratories, pilot plants, and manufacturing facilities handling carbon nanotubes (single-walled and multi-walled), carbon nanofibers, fullerenes, carbon nanopearls, metal oxides, electrospun nylon, and quantum dots. The results demonstrated that the NEAT was useful in evaluating emissions and that readily available engineering controls can be applied to minimize nanomaterial emissions.

Occupational Risk Management of Engineered Nanoparticles

The earliest and most extensive societal exposures to engineered nanoparticles are likely to occur in the workplace. Until toxicologic and health effects research moves forward to characterize more broadly the potential hazards of nanoparticles and to provide a scientific basis for appropriate control of nanomaterials in the workplace, current and future workers may be at risk from occupational exposures. This article reviews a conceptual framework for occupational risk management as applied to engineered nanomaterials and describes an associated approach for controlling exposures in the presence of uncertainty. The framework takes into account the potential routes of exposure and factors that may influence biological activity and potential toxicity of nanomaterials; incorporates primary approaches based on the traditional industrial hygiene hierarchy of controls involving elimination or substitution, engineering controls, administrative controls, and use of personal protective equipment; and includes valuable secondary approaches involving health surveillance and medical monitoring.

Nanoparticle Emission Assessment Technique (NEAT) for the Identification and Measurement of Potential Inhalation Exposure to Engineered Nanomaterials—Part A

There are currently no exposure limits specific to engineered nanomaterial nor any national or international consensus standards on measurement techniques for nanomaterials in the workplace. However, facilities engaged in the production and use of engineered nanomaterials have expressed an interest in learning whether the potential for worker exposure exists. To assist with answering this question, the National Institute for Occupational Safety and Health established a nanotechnology field research team whose primary goal was to visit facilities and evaluate the potential for release of nanomaterials and worker exposure. The team identified numerous techniques to measure airborne nanomaterials with respect to particle size, mass, surface area, number concentration, and composition. However, some of these techniques lack specificity and field portability and are difficult to use and expensive when applied to routine exposure assessment. This article describes the nanoparticle emission assessment technique (NEAT) that uses a combination of measurement techniques and instruments to assess potential inhalation exposures in facilities that handle or produce engineered nanomaterials. The NEAT utilizes portable direct-reading instrumentation supplemented by a pair of filter-based air samples (source-specific and personal breathing zone). The use of the filter-based samples are crucial for identification purposes because particle counters are generally insensitive to particle source or composition and make it difficult to differentiate between incidental and process-related nanomaterials using number concentration alone. Results from using the NEAT at 12 facilities are presented in the companion article (Part B) in this issue.

A Strategy for Assessing Workplace Exposures to Nanomaterials

This article describes a highly tailorable exposure assessment strategy for nanomaterials that enables effective and efficient exposure management (i.e., a strategy that can identify jobs or tasks that have clearly unacceptable exposures), while simultaneously requiring only a modest level of resources to conduct. The strategy is based on strategy general framework from AIHA® that is adapted for nanomaterials and seeks to ensure that the risks to workers handling nanomaterials are being managed properly. The strategy relies on a general framework as the basic foundation while building and elaborating on elements essential to an effective and efficient strategy to arrive at decisions based on collecting and interpreting available information. This article provides useful guidance on conducting workplace characterization; understanding exposure potential to nanomaterials; accounting methods for background aerosols; constructing SEGs; and selecting appropriate instrumentation for monitoring, providing appropriate choice of exposure limits, and describing criteria by which exposure management decisions should be made. The article is intended to be a practical guide for industrial hygienists for managing engineered nanomaterial risks in their workplaces.

Issues in the development of epidemiologic studies of workers exposed to engineered nanoparticles.

Objective: Capitalizing on phenomena at the nanoscale may present great benefits to society. Nevertheless, until the hazards and risks of engineered nanoparticles are determined, the technological products and advances of nanotechnology may be impeded by the societal concerns. Although animal data provide the necessary first step in hazard and risk assessment, ultimately epidemiological studies will be required, especially studies of workers exposed to engineered nanoparticles. It may be too soon to conduct informative epidemiological studies but it is now appropriate to identify issues that will be pertinent and prepare strategies to address them. Methods: The published scientific literature on incidental and engineered nanoparticles and air pollution were reviewed to identify issues in the conduct of epidemiological studies of workers exposed to engineered nanoparticles. Results: Twelve important issues were identified—the most critical pertaining to particle heterogeneity, temporal factors, exposure characterization, disease endpoints, and identification of the study population. Conclusion: Consideration of these issues provides the foundation for initiating epidemiologic research on workers exposed to engineered nanoparticles.

Development of risk-based nanomaterial groups for occupational exposure control.

Given the almost limitless variety of nanomaterials, it will be virtually impossible to assess the possible occupational health hazard of each nanomaterial individually. The development of science-based hazard and risk categories for nanomaterials is needed for decision-making about exposure control practices in the workplace. A possible strategy would be to select representative (benchmark) materials from various mode of action (MOA) classes, evaluate the hazard and develop risk estimates, and then apply a systematic comparison of new nanomaterials with the benchmark materials in the same MOA class. Poorly soluble particles are used here as an example to illustrate quantitative risk assessment methods for possible benchmark particles and occupational exposure control groups, given mode of action and relative toxicity. Linking such benchmark particles to specific exposure control bands would facilitate the translation of health hazard and quantitative risk information to the development of effective exposure control practices in the workplace. A key challenge is obtaining sufficient dose–response data, based on standard testing, to systematically evaluate the nanomaterials’ physical–chemical factors influencing their biological activity. Categorization processes involve both science-based analyses and default assumptions in the absence of substance-specific information. Utilizing data and information from related materials may facilitate initial determinations of exposure control systems for nanomaterials.

Focused actions to protect carbon nanotube workers

There is still uncertainty about the potential health hazards of carbon nanotubes (CNTs) particularly involving carcinogenicity. However, the evidence is growing that some types of CNTs and nanofibers may have carcinogenic properties. The critical question is that while the carcinogenic potential of CNTs is being further investigated, what steps should be taken to protect workers who face exposure to CNTs, current and future, if CNTs are ultimately found to be carcinogenic? This paper addresses five areas to help focus action to protect workers: (i) review of the current evidence on the carcinogenic potential of CNTs; (ii) role of physical and chemical properties related to cancer development; (iii) CNT doses associated with genotoxicity in vitro and in vivo; (iv) workplace exposures to CNT; and (v) specific risk management actions needed to protect workers.

Options for occupational health surveillance of workers potentially exposed to engineered nanoparticles: state of the science.

Objective: Health authorities, employers, and worker representatives are increasingly faced with making decisions about occupational health surveillance of workers potentially exposed to engineered nanoparticles. This article was developed to identify options that can be considered. Methods: The published scientific literature on health effects from engineered and incidental nanoparticles and the principles of occupational health surveillance were reviewed to describe possible options and the evidence base for them. Results: Various options for occupational health surveillance were identified. The options ranged from no action targeted to nanotechnology workers to an approach that includes documentation of the presence of engineered nanoparticles, identification of potentially exposed workers, and general and targeted medical testing. Conclusions: Although the first priority should be to implement appropriate primary preventive measures, additional efforts to monitor employee health may be warranted. Continued research is needed, and the collection of such information for exposure registries may be useful for future epidemiologic studies.

Solid sorbent tube sampling and ion chromatographic analysis of formaldehyde

A new method for the collection and analysis of atmospheric formaldehyde is described. Known concentrations of formaldehyde were generated and collected on solid sorbent tubes containing impregnated charcoal which converted formaldehyde to formate. After desorption with dilute hydrogen peroxide, the formate was analyzed by ion chromatography. The sample generation system, collection on impregnated charcoal, desorption, ion chromatographic analysis, and recoveries are presented. The overall recovery of laboratory generated samples was 100% with 11% relative standard deviation. These samples were collected at 50 cc/min and 200 cc/min.

Occupational safety and health, green chemistry, and sustainability: a review of areas of convergence

With increasing numbers and quantities of chemicals in commerce and use, scientific attention continues to focus on the environmental and public health consequences of chemical production processes and exposures. Concerns about environmental stewardship have been gaining broader traction through emphases on sustainability and “green chemistry” principles. Occupational safety and health has not been fully promoted as a component of environmental sustainability. However, there is a natural convergence of green chemistry/sustainability and occupational safety and health efforts. Addressing both together can have a synergistic effect. Failure to promote this convergence could lead to increasing worker hazards and lack of support for sustainability efforts. The National Institute for Occupational Safety and Health has made a concerted effort involving multiple stakeholders to anticipate and identify potential hazards associated with sustainable practices and green jobs for workers. Examples of potential hazards are presented in case studies with suggested solutions such as implementing the hierarchy of controls and prevention through design principles in green chemistry and green building practices. Practical considerations and strategies for green chemistry, and environmental stewardship could benefit from the incorporation of occupational safety and health concepts which in turn protect affected workers.