Control banding (CB) tools are the main practical approach for managing occupational exposure to engineered nanomaterials, which mostly lack occupational exposure limits. A 2019 comparative study (Gao et al., RSC Advances) assessed eight common CB tools on three nanomaterials in seven real factory scenarios and found divergent risk estimates for the same substance, hazard-input availability of only about 78-80%, and good but tool-dependent correlation of exposure scores with measurements; it explicitly left open whether CB tool use actually reduces workers' nanomaterial exposure to safe levels. Through August 2026 the literature shows continued tool application and method development but no outcome validation, no systematic replication across materials and sectors, and no demonstrated robustness under missing hazard information. The problem remains open.

Background

Engineered nanomaterials (materials deliberately produced with at least one dimension between roughly 1 and 100 nm, such as metal-oxide powders and carbon nanotubes) are handled in many workplaces, but quantitative risk assessment is blocked by a structural data scarcity: for most nanomaterials there are no occupational exposure limits (OELs, regulatory or authoritative concentration thresholds below which exposure is considered acceptable) and often no agreed exposure metric (mass, particle number, or surface-area concentration). Control banding (CB) is a qualitative-to-semi-quantitative risk-management strategy that bypasses this gap: it assigns a substance to a hazard band and a task to an exposure band, and their combination maps to a risk band with a corresponding control strategy (ventilation, enclosure, personal protection) following the precautionary principle. Since the mid-2000s, nanospecific CB tools have been developed, including the CB Nanotool (Paik et al. 2008), Stoffenmanager Nano (a Dutch web tool for prioritizing inhalation risk of manufactured nano-objects; van Duuren-Stuurman et al. 2012), NanoSafer, the Swiss Precautionary Matrix, the ANSES tool (French Agency for Food, Environmental and Occupational Health and Safety), the European Commission guidance, the IVAM Guidance, and the framework of the technical specification ISO/TS 12901-2:2014; the NIOSH occupational exposure banding (OEB) process (a three-tier system, from screening to expert assessment, that assigns air-concentration bands A-E when no OEL exists) extends the same idea. Reviews by Brouwer (2012), Dunn et al. (2018), and Liguori et al. (2016, who concluded the tools were not ready for regulatory use) compared tool methodologies but not their outputs against measured exposures. Zalk, Paik and Swuste (2009) had evaluated one tool (CB Nanotool) by comparing its risk levels with expert industrial-hygiene judgment, and Zalk, Paik and Chase (2019) later quantitatively validated that single tool's risk levels against exposure data - plausibility and single-tool validity, but not multi-tool validity or control effectiveness. Gao et al. (2019) performed the first systematic qualitative and quantitative comparison of eight CB tools in real exposure scenarios, using three nanomaterials (nano-Fe2_2O3_3, nano-Al2_2O3_3, nano-CaCO3_3) in seven scenarios at Chinese manufacturers. They found: the tools spread widely across nine qualitative evaluation indicators; exposure-related input fields were almost always fillable (about 99% availability from safety data sheets, literature, and site investigation) while hazard-related fields were only about 78-80% available; different tools produced different risk estimates for the same substance and scenario, which the authors attribute directly to information gaps and differing parameterization; and the exposure scores of Stoffenmanager Nano, CB Nanotool, and NanoSafer correlated well with measurement data for the seven scenarios. Crucially, the study compared tool outputs against toxicological orderings and exposure measurements; it did not, and could not, demonstrate that implementing CB-derived controls reduces exposure to safe levels. Later developments sharpen rather than close the gap: the NIOSH OEB process was extended to the graphene family (Niang et al. 2024), where Tier 1 banding was impossible (no Globally Harmonized System hazard codes exist) and Tier 2 infeasible (insufficient data), illustrating persistent nanospecific hazard-data scarcity; the EU SAbyNA project (an EU-funded project building safe- and sustainable-by-design guidance tools) found that CB tools use ordinal scoring scales on which averages and confidence intervals are statistically impermissible, leaving uncertainty evaluation underdeveloped (Nebbia et al. 2023); and 2023-2026 reviews (Halbach et al. 2023; Omari Shekaftik et al. 2023, 2026) describe widening CB application and proposed uncertainty methods (Bayesian networks, Monte Carlo simulation, fuzzy inference) but report no outcome validation.

Problem Statement

Provide validation evidence, benchmarked against occupational exposure measurements, on whether the use of control banding tools for engineered nanomaterials adequately reduces workers' exposure to safe levels. Concretely, this comprises three jointly posed questions left open by Gao et al. 2019: (1) outcome validity - when workplaces implement the control strategies recommended by CB tools for nanomaterial handling tasks, is exposure actually reduced to levels consistent with defensible safe-level benchmarks (authoritative occupational exposure bands or best-available surrogate limits), relative to comparable uncontrolled or differently controlled tasks? (2) generalization - do the observed inter-tool agreement and divergence patterns and tool-versus-measurement correlations, established for nano-Fe2_2O3_3, nano-Al2_2O3_3, and nano-CaCO3_3 in seven factory scenarios, persist across a materially broader set of nanomaterials, industrial sectors, and real exposure scenarios (all three coverage dimensions are required), or was the observed performance pattern an artifact of a narrow material and setting base? (3) robustness under missing hazard information - since hazard-input availability was only about 78-80% and information gaps demonstrably drive divergent risk estimates for the same substance and scenario, do different tools, or repeated use under incomplete data, produce conflicting estimates and control recommendations, and on what grounds can such conflict be resolved? Support for or refutation of the tools' exposure-control effectiveness is bounded by the tools, materials, sectors, exposure metrics, and safe-level benchmarks concerned; the conclusion may be negative or conditional if the data so indicate.

References

  1. Gao X, Zou H, Zhou Z, Yuan W, Quan C, Zhang M, Tang S (2019). Qualitative and quantitative differences between common control banding tools for nanomaterials in workplaces. RSC Advances 9(59):34512-34528. doi:10.1039/c9ra06823f, https://doi.org/10.1039/c9ra06823f
  2. Paik SY, Zalk DM, Swuste P (2008). Application of a pilot control banding tool for risk level assessment and control of nanoparticle exposures. Annals of Occupational Hygiene 52(5):419-428. doi:10.1093/annhyg/men041, https://doi.org/10.1093/annhyg/men041
  3. Zalk DM, Paik SY, Swuste P (2009). Evaluating the Control Banding Nanotool: a qualitative risk assessment method for controlling nanoparticle exposures. Journal of Nanoparticle Research 11(7):1685-1704. doi:10.1007/s11051-009-9678-y, https://doi.org/10.1007/s11051-009-9678-y
  4. van Duuren-Stuurman B, Vink SR, Verbist KJH, Heussen HGB, Brouwer DH, Kroese DE, van Niftrik MF, Tielemans E, Fransman W (2012). Stoffenmanager Nano Version 1.0: a web-based tool for risk prioritization of airborne manufactured nano objects. Annals of Occupational Hygiene 56(5):525-541. doi:10.1093/annhyg/mer113, https://doi.org/10.1093/annhyg/mer113
  5. Brouwer DH (2012). Control banding approaches for nanomaterials. Annals of Occupational Hygiene 56(5):506-514. doi:10.1093/annhyg/mes039, https://doi.org/10.1093/annhyg/mes039
  6. Liguori B, Hansen SF, Baun A, Jensen KA (2016). Control banding tools for occupational exposure assessment of nanomaterials - Ready for use in a regulatory context? NanoImpact 2:1-17. doi:10.1016/j.impact.2016.04.002, https://doi.org/10.1016/j.impact.2016.04.002
  7. Dunn KH, Eastlake AC, Story M, Kuempel ED (2018). Control Banding Tools for Engineered Nanoparticles: What the Practitioner Needs to Know. Annals of Work Exposures and Health 62(3):362-388. doi:10.1093/annweh/wxy002, https://doi.org/10.1093/annweh/wxy002
  8. National Institute for Occupational Safety and Health (2019). Technical report: the NIOSH occupational exposure banding process for chemical risk management (DHHS/NIOSH Publication No. 2019-132). doi:10.26616/nioshpub2019132, https://doi.org/10.26616/nioshpub2019132
  9. Isigonis P, Hristozov D, Benighaus C, Giubilato E, Grieger K, Pizzol L, Semenzin E, Linkov I, Zabeo A, Marcomini A (2019). Risk Governance of Nanomaterials: Review of Criteria and Tools for Risk Communication, Evaluation, and Mitigation. Nanomaterials 9(5):696. doi:10.3390/nano9050696, https://doi.org/10.3390/nano9050696
  10. Zalk DM, Paik SY, Chase WD (2019). A Quantitative Validation of the Control Banding Nanotool. Annals of Work Exposures and Health 63(8):898-917. doi:10.1093/annweh/wxz057, https://doi.org/10.1093/annweh/wxz057
  11. Halbach JH, Cala JM, Paik SY, Zalk DM (2023). Control Banding and the Global Rise of Qualitative Risk Assessment Strategies. Current Environmental Health Reports 10(4):410-416. doi:10.1007/s40572-023-00416-5, https://doi.org/10.1007/s40572-023-00416-5
  12. Niang M, Barcellos N, Edmondson M, Chen L, McCormick S, Dahm MM (2024). Application of the Tier 3 NIOSH occupational exposure banding process for the graphene family of nanomaterials: A case study. Journal of Occupational and Environmental Hygiene 22(1):62-77. doi:10.1080/15459624.2024.2420998, https://doi.org/10.1080/15459624.2024.2420998
  13. Omari Shekaftik S, Nasirzadeh N, Mohammadiyan M, Mohammadpour S (2023). An analysis on control banding-based methods used for occupational risk assessment of nanomaterials. Nanotoxicology 17(10):628-650. doi:10.1080/17435390.2023.2293141, https://doi.org/10.1080/17435390.2023.2293141
  14. Omari Shekaftik S, Moghadasi N, Nasirzadeh N (2023). National (Iranian) and global use of control banding-based methods for assessing the risks of activities involved with nanomaterials: a comparative review. Journal of Nanoparticle Research 25. doi:10.1007/s11051-023-05800-8, https://doi.org/10.1007/s11051-023-05800-8
  15. Nebbia R, Hanlon J, Boyles M, Genta G, Galetto M, Bergamaschi E, Tran L (2023). 120 An Evaluation of Uncertainty Within Control Banding Tools used for Occupational Exposure Assessment of Nanoforms and Nano-Enabled Products (conference abstract). Annals of Work Exposures and Health 67(Supplement_1):i98. doi:10.1093/annweh/wxac087.240, https://doi.org/10.1093/annweh/wxac087.240
  16. Omari Shekaftik S, Sheikhtaheri A, Farhang Dehghan S, Mehrparvar N, Golbabaei F (2026). Managing uncertainties in risk assessment of activities involving nanomaterials: the case of control banding-based methodologies. Nanotoxicology 20(3):168-175. doi:10.1080/17435390.2026.2632280, https://doi.org/10.1080/17435390.2026.2632280
  17. Cazzagon V, Vanhauten R, Hanlon J, Sanchez Jimenez A, Harrison S, Auffan M, Braakhuis H, Boyles M, Candalija A, Katsumiti A, Rodriguez-Llopis I, Catalan J, Cross RK, Lahive E, Morel E, Simeone F, Delpivo C, Clavaguera S, Seddon R, Salmatonidis A, Barruetabena L, Traas L, Lotti D, Mays C, Vazquez-Campos S (2025). The SAbyNA platform: a guidance tool to support industry in the implementation of safe- and sustainable-by-design concepts for nanomaterials, processes and nano-enabled products. Environmental Science: Nano 12(8):4008-4025. doi:10.1039/d5en00312a, https://doi.org/10.1039/d5en00312a
  18. Floeder A, Jones RM, Arnold SF (2025). Risk assessment methods in occupational health and hygiene: a scoping review. Annals of Work Exposures and Health 69(2):120-131. doi:10.1093/annweh/wxae095, https://doi.org/10.1093/annweh/wxae095
  19. Di Cristo L, Balusamy B, Romaldini A, Tombolini F, Ferrante R, Cavallo D, Ursini CL, Leoncino L, Del Rio Castillo AE, Bonaccorso F, Iavicoli S, Boccuni F, Sabella S (2025). From exposure to risk prevention: an integrated, data driven approach to testing and assessing occupational hazards of inhaled nanomaterials. NanoImpact 40:100598. doi:10.1016/j.impact.2025.100598, https://doi.org/10.1016/j.impact.2025.100598