Nanotechnology · evidence and evaluation

What an exposure or safety study does and does not settle

A toxicology or exposure result applies to the material, the dose, the route and the model it used. Extending it to a different particle, coating, medium or exposure route is a new claim.

How it works

The evidence here has moved, and the direction it moved in is the lesson. In 2009 NIOSH wrote that no specific US exposure limits then existed for airborne engineered nanomaterials, reasoning that limits set for larger particles of the same chemistry may not be protective at the nanoscale — its example being that the OSHA permissible exposure limit for graphite may not be a safe limit for carbon nanotubes. It has since set limits of its own. Current Intelligence Bulletin 63 (2011) recommends 2.4 mg/m³ for fine titanium dioxide and 0.3 mg/m³ for ultrafine, including engineered nanoscale, titanium dioxide, as time-weighted averages for up to 10 hours a day in a 40-hour week — two different numbers for one chemical, separated only by size — and classifies the ultrafine fraction as a potential occupational carcinogen while finding insufficient data to classify the fine fraction. Current Intelligence Bulletin 65 (2013) recommends 1 µg/m³ of elemental carbon as a respirable-mass 8-hour average for carbon nanotubes and nanofibres. Two things about those numbers matter more than the numbers. They are recommendations, not enforceable standards. And NIOSH says residual risk remains at the carbon-nanotube limit, with chronic effects still uncertain, so the figure is a control target rather than a demonstrated safe level. EPA separately treats many nanoscale materials as chemical substances under TSCA, with reporting and premanufacture review that gather information rather than pronounce safety. Maha’s role here is to separate what a study measured from what a product description implies, not to assess any material.

A concrete case

An inhalation study on an uncoated powder reports a no-observed-adverse-effect level. A supplier cites it for a polymer-embedded version of the same chemistry. The embedded form may never become airborne in use — which is a reason to expect lower exposure, and not evidence about the hazard of the particles themselves if they are released during sanding or disposal.

What this establishes

That recommended occupational limits now exist for two specific nanomaterials and did not in 2009, that a single chemical can carry two different limits and two different carcinogenicity findings purely on size, and that a recommended limit is a control target rather than a demonstrated safe level.

What it does not

Nothing here is a hazard assessment, a control-banding recommendation or medical advice, and Maha runs no toxicology and certifies nothing. The two recommended limits quoted are NIOSH recommendations for two named materials, not enforceable standards and not transferable to any other material. A limit is also not a safety finding: NIOSH records residual risk at the carbon-nanotube figure and continuing uncertainty about chronic effects. Nothing here states what any enforceable standard requires.

Questions worth asking

  • Ask which exact material, including coating and aggregation state, was tested, and how it compares with the one in use.
  • Ask which exposure route was studied and whether it matches the realistic route in the workplace or product.
  • Ask whether release during use, maintenance, abrasion or disposal was measured, not only the intact product.
  • Check the date on any statement that no limit exists — the 2009 position was overtaken in 2011 and 2013, and a claim about the regulatory landscape ages faster than one about physics.
  • Separate a recommended limit from an enforceable one, and both from evidence that a material is safe at that level.

Sources

  • NIOSH — Approaches to Safe Nanotechnology: Managing the Health and Safety Concerns Associated with Engineered Nanomaterials (DHHS/NIOSH 2009-125) ↗

    NIOSH reports the ISO/TS 27687:2008 definition of a nano-object as material with one, two or three external dimensions in the range of approximately 1–100 nm, with nanoplate, nanofibre (nanotube hollow, nanorod solid) and nanoparticle as the subcategories by how many dimensions are nanoscale; it distinguishes engineered nanoparticles from incidental ultrafine particles while noting it is unclear whether that source-based distinction is justified for safety purposes; and it states that limits set for larger particles of similar chemical composition may not be health-protective at the nanoscale — its example being that the OSHA permissible exposure limit for graphite may not be a safe limit for carbon nanotubes — and that nanoparticles may be more biologically reactive than larger particles of similar composition.

    Boundary: Guidance for managing workplace risk, not a toxicological finding about any specific material and not a regulation, and reading it does not substitute for qualified occupational-health practice. Critically, it is a 2009 document: its statement that no specific US exposure limits then existed for airborne engineered nanomaterials describes 2009 and has since been overtaken by NIOSH’s own recommended exposure limits for titanium dioxide (2011) and carbon nanotubes and nanofibres (2013). This section cites it only for the definitions and the size-versus-composition reasoning, never for the current state of exposure limits.

    Locator, anchor and reuse basis

    Read at: §4.1 Nano-objects and §4.2 Ultrafine Particles, p. 8; §8.3.5 Respirators, pp. 43–44. Inspected 2026-09-20. Public-domain federal document; paraphrased with short attributed wording and linked, not reproduced.

    Verify by searching the source for: one, two, or three external dimensions in the size range from approximately 1–100 nm. If that phrase is not there, or does not carry the meaning stated above, this citation is wrong and we want to know.

  • NIOSH Current Intelligence Bulletin 63 — Occupational Exposure to Titanium Dioxide (DHHS/NIOSH 2011-160) ↗

    NIOSH recommends exposure limits of 2.4 mg/m³ for fine titanium dioxide and 0.3 mg/m³ for ultrafine, including engineered nanoscale, titanium dioxide, as time-weighted average concentrations for up to 10 hours per day during a 40-hour work week. It determined that ultrafine titanium dioxide is a potential occupational carcinogen while there were insufficient data to classify fine titanium dioxide as one, and set separate limits for the two size fractions of the same chemical.

    Boundary: A recommended limit, not an enforceable standard, and it addresses occupational inhalation exposure only — NIOSH states its conclusions should not be inferred to pertain to non-occupational exposures. It concerns titanium dioxide and no other material.

    Locator, anchor and reuse basis

    Read at: Executive summary, p. iii. Inspected 2026-09-20. Public-domain federal document; paraphrased with short attributed wording and linked, not reproduced.

    Verify by searching the source for: 2.4 mg/m3 for fine TiO2 and 0.3 mg/m3 for ultrafine. If that phrase is not there, or does not carry the meaning stated above, this citation is wrong and we want to know.

  • NIOSH Current Intelligence Bulletin 65 — Occupational Exposure to Carbon Nanotubes and Nanofibers (DHHS/NIOSH 2013-145) ↗

    NIOSH recommends an exposure limit of 1 µg/m³ of elemental carbon as a respirable mass 8-hour time-weighted average concentration for carbon nanotubes and nanofibres, published in 2013.

    Boundary: A recommended limit, not an enforceable standard. NIOSH notes residual risk remains at the limit and that uncertainty persists about chronic effects, including whether some types of carbon nanotube may be carcinogenic, so the figure is a control target rather than a demonstrated safe level.

    Locator, anchor and reuse basis

    Read at: Publication summary — recommended exposure limit. Inspected 2026-09-20. Public-domain federal document; paraphrased with short attributed wording and linked, not reproduced.

    Verify by searching the source for: 1 µg/m3 elemental carbon as a respirable mass. If that phrase is not there, or does not carry the meaning stated above, this citation is wrong and we want to know.

  • EPA — Control of Nanoscale Materials under the Toxic Substances Control Act ↗

    EPA treats many nanoscale materials as chemical substances under TSCA, notes that the same substance at the nanoscale may behave differently, and describes a regulatory approach that includes an information-gathering reporting rule and premanufacture notification for new nanoscale materials.

    Boundary: Reporting or review under TSCA is a regulatory process, not a finding that a material is safe, effective or approved for a use.

    Locator, anchor and reuse basis

    Read at: Nanoscale Materials; Regulatory Approach; Information gathering rule; Reporting under the rule. Inspected 2026-09-19. Original paraphrase and link only.

    Verify by searching the source for: regarded as “chemical substances” under the Toxic Substances Control Act. If that phrase is not there, or does not carry the meaning stated above, this citation is wrong and we want to know.

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Maha Strategies publishes explanation and evaluation method. We make no nanomaterials, run no characterisation, certify nothing, and give no medical or legal advice.