# Fiber sampling technique and counting protocol development for carbon nanotubes

> **NIH ALLCDC R21** · UNIVERSITY OF CALIFORNIA LOS ANGELES · 2024 · $181,583

## Abstract

PROJECT ABSTRACT
The goal of this project is to develop a new method for fiber sampling. The method currently used for airborne
sampling of carbon nanotubes (CNTs) is adapted from micrometer-scale asbestos sampling. To achieve our
goal, we will study surface properties of different CNTs and sampling filters contributing to efficiency, develop a
novel image analysis protocol with our algorithms, use a newly developed nanoparticle (NP) isokinetic diffusion
sampler, simulate and elucidate the particle behavior, and produce a new method suitable to CNTs sampling.
Burden: Exposure to airborne CNTs has been of highest concern following their designation as a potential
human carcinogen. The potential health effects of CNTs have shown some similarity to those of asbestos fibers
in animal models. CNTs global market is projected to reach $103.2 billion by 2030 with 16.3% annual growth.
The fiber sampling method used for asbestos has been a recommended method for sampling CNT fibers. CNTs
contain individual fibers with diameters that are one tenth to one hundredth that of asbestos fibers. The NIOSH
Methods 7402 was found to be very challenging and time consuming for identifying a few very fine CNT fibers
on a grid sample under electron microscopy. Questions raised by this challenge include whether the number and
size of CNT fibers collected by 7402 method are representative of those in the air, whether these sizes are
affected by the sampling and extensive processing required by the method, and how the exposure to fine fibers
can be quantified properly to evaluate associated health effects when this method is not yet validated for CNT.
Need: A new method and technique for sampling fine fibers to 1) collect fibers efficiently in the sampled air
without loss, 2) directly analyze the collected fibers with minimal processing of the sample, and 3) easily count
the fibers to obtain the concentration and size, which will resolve the lack of accuracy of exposure measurements
and the significant time requirement of sample analysis. When used for CNTs, the collection efficiency and
performance of sampling and analysis must be evaluated. It is critical to design a new sampling substrate
because the currently used mixed cellulose ester (MCE) filter for collecting asbestos may not be suitable for
collecting CNTs. The fibers collected on the MCE filter need to be processed for transfer to a grid for analysis,
small fibers can be agglomerated or lost. A new sampling method and substrate that can effectively collect fibers
to be analyzed directly will prevent the loss or change of collected fibers through the transfer process.
Impact: The wide range of applications that use fiber materials such as CNTs, asbestos and fiberglass and other
NPs can employ the developed protocol and method to effectively quantify the exposure level in terms of
fiber/particle concentration. This information may change the current measurement metric for CNTs from mass
concentration to fiber/parti...

## Key facts

- **NIH application ID:** 10914635
- **Project number:** 5R21OH012397-02
- **Recipient organization:** UNIVERSITY OF CALIFORNIA LOS ANGELES
- **Principal Investigator:** Candace SuJung Tsai
- **Activity code:** R21 (R01, R21, SBIR, etc.)
- **Funding institute:** ALLCDC
- **Fiscal year:** 2024
- **Award amount:** $181,583
- **Award type:** 5
- **Project period:** 2023-09-01 → 2025-08-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10914635

## Citation

> US National Institutes of Health, RePORTER application 10914635, Fiber sampling technique and counting protocol development for carbon nanotubes (5R21OH012397-02). Retrieved via AI Analytics 2026-05-26 from https://api.ai-analytics.org/grant/nih/10914635. Licensed CC0.

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