Control Banding Tools for Engineered Nanoparticles: What the Practitioner Needs to Know

An analysis on control banding-based methods used for occupational risk assessment of nanomaterials

Despite all benefits of nanomaterials, their unique characteristics made them an emerging hazard in workplaces, which need to be assessed for their potential risks. So, the aim of this study was to review all the studies conducted on the risk assessment of activities involving nanomaterials with CB-based methods.This study is based on a literature review on databases including Web of science, Scopus, PubMed, and SID. After reviewing and screening studies according to PRISMA, the collected data were meta-analyzed by Comprehensive Meta-Analysis Software. Also, Newcastle-Ottawa checklist was used for quality assessment of the studies. To determine similarity of methods, Cohen's Kappa was used. Sensitivity analysis was used to determine the role of each factor in the risk assessment by using the Crystal Ball tool.There are eight validated methods for risk assessment. Also, some authors used a self-deigned tool based on CB approach. The results of meta-analysis showed that the odds ratio for the risk of activities involved with nanomaterials was 0.654 (high risk). Results of simulation for Nanotool showed that the mean risk level of activities involved with nanomaterials, with a certainty of 95.07%, is moderate (RL3). Moreover, sensitivity analysis showed that the risk was depended on "Hazard band" in all methods except ISO method.The obtained results can be useful in improving existing methods and suggesting new methods. Also, there is a need to design and propose specific methods for risk assessment of incidental and natural nanomaterials.

Control Banding and the Global Rise of Qualitative Risk Assessment Strategies

PURPOSE OF REVIEW

Control banding (CB) is a risk assessment strategy that has been applied globally to a variety of occupational hazards. This article describes how this method can be applied, recent developments in the CB literature, an example of how it is utilized for a large, diverse worksite, and where the future of CB is headed.

RECENT FINDINGS

Over the past several years, the applications of CB have widened significantly and have accordingly helped bolster the public and occupational safety, health, and hygiene (OSHH) professionals' understanding of occupational exposure to various hazards. The fields of workplace chemicals, nanomaterials, and airborne pathogens (i.e., COVID-19), specifically have seen remarkable increases in the development of CB tools. Extensive CB tool validation efforts have also lent increasing credibility to this alternative approach. CB is a simplified strategy of assessing occupational exposures and providing commensurate controls and solutions to reduce workplace risks. CB can be used as a primary or tiered risk assessment and risk management approach which can be utilized by both OSHH professionals and nonexperts alike to identify solutions for reducing work-related exposures. The need for health and safety expertise will continue to grow as technological advancements, environmental changes, and economic forces increase workplace hazard complexity, and CB will continue to be a useful tool for those performing risk assessments.

Towards a surface metric to measure the dustiness of nanomaterial powders

The relevance of dustiness methods is increasingly recognized in the preliminary exposure evaluation of workers handling nanomaterials in powder form, and should also be transposed to the assessment of environmental risk in the future. The methods currently recommended in the European standards are mainly based on determining a mass-based dustiness index [mg kg^-1], whereas surface area is regularly put forward as a more appropriate determinant to assess the pulmonary toxicity of nanoparticles. In this study, we describe an operational methodology leading us to propose a surface metric to determine the dustiness index [m² kg^-1] of nanoparticulate matter. To this end, we demonstrate the equivalence between the external specific surface area of a nanopowder and that of its aerosol with five nanomaterials produced and used on an industrial scale, and covering a range of external specific surface areas from 35 to 230 m² g^-1. Compared to the conventional mass-based dustiness index, the surface-based dustiness index (1) is more discriminating, covering an additional order of magnitude, and (2) has an impact on the powder ranking with potential consequences on the preventive measures to be implemented. Finally, our proposal has the potential to be included in future revisions of European standards for workplace exposure and dustiness measurement, provided that further experimental results on surface-based dustiness indices support these preliminary data.

Characteristics and risk assessment of occupational exposure to ultrafine particles generated from cooking in the Chinese restaurant

Ultrafine particles have been increasingly linked to adverse health effects in restaurant workers. This study aimed to clarify the exposure characteristics and risks of ultrafine particles during the cooking process, and to provide a reasonable standard for protecting the workers in the Chinese restaurant. The temporal variations in particle concentrations (number concentration (NC), mass concentration (MC), surface area concentration (SAC), and personal NC), and size distributions by number were measured by real-time system. The hazard, exposure, and risk levels of ultrafine particles were analyzed using the control banding tools. The NC, MC, and SAC increased during the cooking period and decreased gradually to background levels post-operation. The concentration ratios of MC, total NC, SAC, and personal NC ranged from 3.82 to 9.35. The ultrafine particles were mainly gathered at 10.4 and 100 nm during cooking. The exposure, hazard and risk levels of the ultrafine particles were high. These findings indicated that the workers during cooking were at high risk due to exposure to high levels of ultrafine particles associated with working activity and with a bimodal size distribution. The existing control strategies, including engineering control, management control, and personal protection equipment need to be improved to reduce the risk.

Exposure characterization and risk assessment of ultrafine particles from the blast furnace process in a steelmaking plant

OBJECTIVES

This study aimed to clarify the exposure characteristics and risks of ultrafine particles from the blast furnace process and to provide a reasonable control strategy for protecting the health of workers.

METHODS

The blast furnace location of a steelmaking plant was selected as a typical investigation site. A membrane-based sampling system was used to collect ultrafine particles to analyze their morphology and elemental compositions. A real-time system was used to monitor the total number concentration (NC), total respirable mass concentration (MC), surface area concentration (SAC), and size distribution by number. The risk level of ultrafine particles was analyzed using the Stoffenmanager-Nano model.

RESULTS

The total NC, total MC, and SAC increased significantly relative to background concentrations after slag releasing started and decreased gradually after the activity stopped. The three highest total concentrations during slag releasing were 3-10 times higher than those of the background or non-activity period. The ultrafine particles were mainly gathered at 10.4 or 40 nm, and presented as lump-like agglomerates. The metal elements (Al and Pt) in the ultrafine particles originated from slag and iron ore. The risk level of the ultrafine particles was high, indicating the existing control measures were insufficient.

CONCLUSIONS

The blast furnace workers are at high risk due to exposure to high levels of ultrafine particles associated with working activity and with a bimodal size distribution. The existing control strategies, including engineering control, management control, and personal protection equipment need to be improved.

Identification of nanomaterials by the volume specific surface area (VSSA) criterion: application to powder mixes

We demonstrate the relevance of the Volume Specific Surface Area (VSSA) parameter to identify the nanoparticulate character of powder mixes based on either spherical constituent particles with bimodal size distributions (TiO₂), or fiber-like constituent particles with unimodal size distributions (sepiolite and sepiolite-based pigments). These new results indicate that VSSA could reasonably be proposed as an optional criterion in the future for the definition of nanomaterials based on the European Commission recommendation, provided certain requirements are fulfilled.

A Quantitative Validation of the Control Banding Nanotool

Eleven years (by publication) years after the development and application of the control banding (CB) Nanotool for the qualitative assessment and control of engineered nanoparticles (ENP), there remains no quantitative gold standard to serve as an alternative to the qualitative assessment. Many CB models have been developed during the years subsequent to the initial development of the CB Nanotool and the literature continues to blossom with comparisons and applications of these various tools; however, these developments have hitherto been made in the absence of validating and verifying their effectiveness using existing, albeit limited, quantitative methods. This paper reviews the existing literature on the CB Nanotool to evaluate its effectiveness in a variety of settings and presents a summary of qualitative and quantitative information from its application in a broad range of ENP handling activities performed in two different research institutions. A total of 28 ENP activities were assessed using the CB Nanotool (Version 2.0). Due to the lack of guidance on a single exposure assessment methodology, a combination of real-time monitoring, filter analysis, and microscopic analysis was used to assess various quantitative metrics, including mass concentration, particle number concentration, and particle speciation. All the results indicated that the control outcomes from the CB Nanotool qualitative assessment were sufficient to prevent workers from being exposed to ENP at levels beyond established exposure limits or background levels. These data represent an independent quantitative validation of CB Nanotool risk level outcomes and give further credence to the use of the CB Nanotool to effectively control worker exposures in the absence of quantitative air monitoring results.

Toward an operational methodology to identify industrial-scaled nanomaterial powders with the volume specific surface area criterion

Nanoparticulate powders are increasingly found in the workplace. Inhalation exposure to airborne nanoparticles (NPs) is possible throughout the life-cycle of the powders. As the toxicity of NPs has never been demonstrated, it remains essential to evaluate the risks associated with NPs in order to propose preventative measures. The first step of a risk assessment strategy consists in the identification of the 'nano' nature of a material, which suffers from a lack of an operational methodology. Here, we present a simplified and operational strategy relying on the volume specific surface area (VSSA) for nanomaterial identification, based on the recommendation stemming from the European Commission and previous work on this topic from the European Project Nanodefine. The proposed strategy was tested on a set of 15 representative industrial powders (TiO₂, SiO₂, CuO, and ZnO), covering a wide range of properties, and previous published data. The VSSA classification was validated via a comparison with the particle size obtained by transmission electron microscopy (TEM). It was evidenced that the VSSA is in accordance with particle size for nanomaterial powder classification. The proposed methodology involves relatively accessible methods such as thermogravimetric analysis, nitrogen adsorption and helium pycnometry and limits the detection of false negatives. Moreover, it does not imply systematic confirmation of the results with the reference particle size criterion. Our results suggest that the VSSA is a promising parameter to be used for risk assessment and should be further investigated on powder mixings to confirm its relevancy to define nanomaterial powders.

Qualitative and quantitative differences between common control banding tools for nanomaterials in workplaces

A number of control banding (CB) tools have been developed specifically for managing the risk of exposure to engineered nanomaterials. However, data on the methodological differences between common CB tools for nanomaterials in workplaces are rare. A comparative study with different CB tools, such as Nanosafer, Stoffenmanager-Nano, Nanotool, Precautionary Matrix, ECguidance, IVAM Guidance, ISO, and ANSES, was performed to investigate their qualitative and quantitative differences in real exposure scenarios. These tools were developed for different purposes, with different application domains, methodological principles, and criteria. Multi-criteria analysis showed that there was a diverse distribution of these eight CB tools across different evaluation indicators. The total evaluation scores for Nanotool, Stoffenmanager-Nano, and Nanosafer were higher than the other tools. Quantitative comparisons demonstrated that ANSES, ECguidance, and IVAM Guidance tools were better in terms of information availability. Nanotool, Stoffenmanager-Nano, and ECguidance were better in terms of the sensitivity of outputs to changes in exposure parameters. The Nanotool, ANSES, and ECguidance tools were better in terms of accuracy of hazard outcomes evaluated with toxicological data. The Stoffenmanager-Nano, Nanotool, and Nanosafer tools' exposure scores for seven scenarios had a good correlation with measurement data. The Nanotool and Stoffenmanager-Nano tools had much higher comprehensive advantages based on quantitative and qualitative assessment. More comparative studies evaluating different tools are required, using more types of nanomaterials in real exposure scenarios.

A number of control banding (CB) tools have been developed specifically for managing the risk of exposure to engineered nanomaterials.