TECHNICAL REPORT

Occupational Exposure Sampling 

for Engineered Nanomaterials

Centers for Disease Control

and Prevention

National Institute for Occupational 

Safety and Health
Front cover image: A worker cleaning a nano metal oxide reactor. 

Photo by NIOSH.
TECHNICAL REPORT

Occupational Exposure Sampling for 

Engineered Nanomaterials

DEPARTMENT OF HEALTH AND HUMAN SERVICES 

Centers for Disease Control and Prevention

National Institute for Occupational Safety and Health
 ii | Occupational Exposure Sampling for Engineered Nanomaterials 

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Suggested Citation

NIOSH [2022]. Occupational exposure sampling for engineered nanomaterials. Technical report. By Hodson L, Eastlake A. Cincinnati, OH: U.S. Department of Health and 

Human Services, Centers for Disease Control and Prevention, National Institute for 

Occupational Safety and Health, DHHS (NIOSH) Publication No. 2022-153.

DOI: https://doi.org/10.26616/NIOSHPUB2022153

DHHS (NIOSH) Publication No. 2022-153

July 2022
Occupational Exposure Sampling for Engineered Nanomaterials | iii

Foreword

Increased engineered nanomaterial production, combined with widespread formulation 

and incorporation into nanomaterial enabled products, has increased the likelihood of 

occupational exposure. A key component in managing the occupational risk is exposure 

assessment. The National Institute for Occupational Safety and Health (NIOSH) developed guidance for workplace sampling for three engineered nanomaterials: carbon 

nanotubes and nanofibers, silver, and titanium dioxide, each of which have an elemental 

mass-based NIOSH Recommended Exposure Limit (REL). In addition, NIOSH developed a practical approach to exposure sampling for other engineered nanomaterials 

that do not have exposure limits. Occupational health and safety professionals have 

expressed a need for one document that explains all of the available nanomaterial 

sampling techniques, and this document provides a summary of the different sampling 

techniques. These techniques can be used to identify and assess potential occupational 

exposures to nanomaterials and to evaluate process emissions and engineering controls.

John Howard, M.D.

Director, National Institute for Occupational

 Safety and Health

Centers for Disease Control and Prevention 
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Occupational Exposure Sampling for Engineered Nanomaterials | v

Contents

Foreword . .

Abbreviations . 

Acknowledgements . .

Background .

Health Effects .

Recommendations .

Exposure Monitoring Program .

Carbon Nanotubes and Nanofibers (CNTs and CNFs) .

Silver .

Titanium Dioxide .

Other ENMs: Use of the Nanomaterial Exposure Assessment Technique .

Optional Sampling Methods . 

Conclusions . 

References . 
 vi | Occupational Exposure Sampling for Engineered Nanomaterials 

Abbreviations

Ag silver

CIB current intelligence bulletin

CNF carbon nanofiber

CNT carbon nanotube

DRI direct reading instrument

ENM engineered nanomaterial

HVAC heating, ventilation, and air conditioning

ICP-AES inductively coupled plasma atomic emission spectroscopy

NEAT 2.0 nanomaterial exposure assessment technique 2.0

MCE mixed cellulose ester

nm nanometer

NMAM NIOSH Manual of Analytical Methods

NRD nanoparticle respiratory deposition 

PBZ personal breathing zone

PENS personal nanoparticle sampler

PPE personal protective equipment

PVC polyvinyl chloride

REL recommended exposure limit

TEM transmission electron microscope

TiO2 titanium dioxide

TWA time-weighted average 
Occupational Exposure Sampling for Engineered Nanomaterials | vii

Acknowledgements

The authors gratefully acknowledge the contributions of the following NIOSH personnel 

who assisted with the technical content and review of the document, including Matt 

Dahm PhD, Kevin L. Dunn MS, Kevin H. Dunn ScD, Charles Geraci PhD (retired), Eric 

Glassford MS, Eileen Kuempel PhD, Jenny Roberts PhD, Aleksandr Stefaniak PhD, Jay 

Vietas PhD, and Chen Wang PhD. External reviewers included David Abrams MSPH, ARS 

Environmental Health Inc.; John Baker MS, MBA, BSI EHS Services and Solutions 

(retired); Peter Raynor PhD, University of Minnesota; Keith Rickabaugh BS, MBA, R.J. 

Lee Group; Kevin Sheffield PhD, Phillips 66; and Candace Tsai PhD, University of 

California at Los Angeles.
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Occupational Exposure Sampling for Engineered Nanomaterials | 1

Background

Engineered nanomaterial (ENM) is a classification for a diverse group of materials that 

have at least one dimension in the size range of 100 nanometer (nm) or less. Increased 

ENM production, combined with widespread formulation and incorporation into 

ENM-enabled products, has increased the likelihood of occupational exposure. Considering that some ENMs have enhanced toxicological concerns relative to their larger 

microscale material forms, there is a clear need to develop, implement, and apply a suitable strategy for occupational risk assessment and management [NIOSH 2011, 2013, 

2021]. A key component of this strategy is exposure assessment. Unfortunately, a single 

instrument or analytical technique cannot always assess occupational exposure due to 

the variety of ENMs. Therefore, NIOSH recommends using a combination of measurement techniques and instruments to collect data to characterize process emissions and 

potential occupational exposures.

Health Effects

Studies in animals and cell systems show that some ENMs are more toxic than the 

microscale form of the same substance at equivalent mass doses. Based on high volume 

use and available toxicological information of three types of ENMs, NIOSH has developed recommended exposure limits (RELs) for airborne carbon nanotubes and nanofibers (CNTs and CNFs) [NIOSH 2013], silver (Ag) [NIOSH 2021], and titanium dioxide 

(TiO2) [NIOSH 2011]. Studies in rats and mice show that CNTs and CNFs can pose a 

respiratory hazard due to pulmonary inflammation and rapidly developing, persistent 

fibrosis [NIOSH 2013; Wang et al. 2016]. Occupational exposure to CNTs and CNFs is 

associated with biomarkers of early effect for fibrosis, inflammation, oxidative stress, 

and cardiovascular responses in workers [Beard et al. 2018]. Silver nanoparticle inhalation exposure in rats for 90 days caused decreased lung function, inflamed lung tissue, 

and histopathological (microscopic tissue) changes in the liver and kidney [NIOSH 

2021]. Studies of TiO2

 nanomaterials in rats found lung cancer after long-term inhalation exposures and non-cancerous effects (pulmonary inflammation, oxidative stress) 

after shorter exposures [Baranowska-Wójcik et al. 2020; NIOSH 2011]. 

Recommendations

Exposure Monitoring Program*

Safety and health professionals should incorporate ENMs into the existing exposure 

monitoring program with appropriate adjustments to ensure that worker exposures to 

ENMs are maintained below the RELs and to minimize exposures for ENMs without a 

*

NIOSH recognizes contact through the skin, eating, or drinking as relevant pathways. This document focuses on exposure from breathing the material in because this is the only pathway for which RELs are available.
2 | Occupational Exposure Sampling for Engineered Nanomaterials

REL [NIOSH 2011, 2013, 2021]. Aspects of the program should include the following:

1. Identify sources of potential ENM exposures

2. Establish similar exposure groups by area or job tasks where workers may be 

exposed 

3. Characterize exposures of all potentially exposed workers, and

4. Assess the effectiveness of engineering controls, work practices, personal protective equipment (PPE), training, and other factors used to reduce or eliminate 

potential exposures.

Exposure monitoring should include these elements:

 Develop an exposure assessment strategy. The details of the strategy will depend 

on several factors, including the number of workers potentially exposed to ENMs 

and the day-to-day and worker-to-worker variability in airborne concentrations. 

Because there is no ‘’best” exposure measurement strategy that can be applied 

to all workplaces, multi-shift random sampling of workers (or all workers, if the 

exposed workforce is small) may be necessary to have an accurate assessment of 

worker airborne exposure concentration [NIOSH 2013].

 Identify areas and tasks that are more likely to emit ENMs, such as handling dry 

powders, or sonication of liquids [Dahm et al. 2018; Johnson et al. 2010]. The use 

of direct reading instruments may assist with identifying these work areas.

 Collect personal breathing zone (PBZ) samples for the worker’s full shift to determine adherence to the applicable REL. Collect two paired side-by-side filter-based 

samples—one for elemental mass-based analysis, and one for ENM identification 

using electron microscopy. PBZ samples are also collected for samples without a 

REL to identify exposure potentials. Note that an ENM mass-based sample analysis may be below the detection limit of the method, and electron microscopy may 

be necessary to identify if there are ENMs.

 Collect area samples using filter-based samples at indoor locations both in near 

proximity and removed from the use of the ENM of interest to determine product migration and the extent of any cross contamination (from production to 

non-production work areas) from work practices or improperly designed HVAC or 

other ventilation systems.

 Use task-specific short-term PBZ and area sampling to identify those tasks that 

are more likely to emit ENMs.

 Consult with the analytical laboratory to evaluate detection limits and sample 

time/volumes to achieve a sensitive enough measurement.

 Submit media blanks, field blanks, and bulk materials, in addition to the samples 

collected, as required by the analytical laboratory.

Carbon Nanotubes and Nanofibers (CNTs and CNFs)

NIOSH derived a REL of 1 microgram per cubic meter (μg/m3) for CNTs/CNFs (with two 

dimensions < 100 nm) as measured by elemental carbon as a respirable mass 8-hour 
Occupational Exposure Sampling for Engineered Nanomaterials | 3

time-weighted average (TWA) concentration [NIOSH 2013]. Personal exposure concentrations to elemental carbon as a proxy for CNT and CNF, can be determined by NIOSH 

Method 5040 [NIOSH 2003, 2004, 2013].

Use the following approach for paired filter-based sampling (Figure 1) [NIOSH 2013]:

 Sample collection:

о Collect paired filter air samples in the worker’s PBZ near process locations 

with at least one at a background location as described below. Each sampling 

pair should include one air sampling cassette that contains a quartz fiber filter 

attached to a respirable cyclone, and one cassette containing a mixed cellulose 

ester or polycarbonate filter, with each cassette connected to a separate sampling pump. Consider additional sampling for the inhalable fraction of elemental carbon using a quartz fiber filter in the PBZ and background as some CNT/

CNF materials may agglomerate to particle sizes beyond the respirable size 

fraction [Dahm et al. 2018].

 Elemental mass-based analysis—carbon:

о Analyze the quartz fiber filter for elemental carbon using NIOSH Method 5040. 

 Nanomaterial identification—electron microscopy:

о Use elemental microscopy techniques such as transmission electron microscopy, high resolution scanning electron microscopy, or scanning transmission 

electron microscopy analysis for CNT and CNF identification. If possible, 

elemental microscopy analysis should also be performed on bulk samples to 

characterize the characteristics of the ENM to apply to air samples.

о Consider analyzing the mixed cellulose ester filters as described in Chapter 

CN of the NIOSH Manual of Analytical Methods (NMAM), 5th edition [NIOSH 

2016]. Elemental microscopy visualization can also identify whether there 

are particles, agglomerates, or whether the CNT or CNF is embedded within a 

matrix. 

о Determine the elemental composition of particles and morphological features 

(e.g., size, shape, and agglomeration state) consistent with CNT and CNF by 

using an energy dispersive X-ray spectrometry system attached to the transmission electron microscope.

 Background correction of elemental carbon:

о Collect background respirable and, if determined necessary, inhalable samples for 

elemental carbon determination. Use a quartz fiber filter in a sampling cassette 

attached to a respirable cyclone and sampling pump at indoor locations where 

exposure to CNT or CNF is unlikely. For example, a location removed from the 

use of CNTs or CNFs and in an area with a different ventilation system. Also 

consider collecting an outdoor background sample as some areas, like those near 

major public roads, may have higher outdoor contributors to elemental carbon 

than indoor background samples. This collection strategy considers the potential 

for incidental elemental carbon contributions, such as from internal combustion 

engines or wildfires.
4 | Occupational Exposure Sampling for Engineered Nanomaterials

о Subtract the elemental carbon concentrations determined from background 

samples from the PBZ sample results to determine whether worker exposures 

exceed the REL. Initially, more samples may be required to characterize the 

workplace thoroughly. This initial assessment will help refine the sampling 

approach and determine whether elemental carbon interference is an issue. 

Careful consideration of environmental background is essential. For example, 

outdoor elemental carbon may sometimes be higher or lower than indoor background depending on the facility’s air handling system. 

 If the PBZ sample results are above the REL, consider following methods outlined in the hierarchy of controls (elimination, substitution, engineering controls, 

administrative controls and personal protective equipment), until exposures are 

controlled below the REL.

 Once the exposure is well characterized and controlled below the REL, use quartz 

fiber filter samples collected with the chosen size-selective sampler and analyzed 

with NIOSH Method 5040 to periodically monitor elemental carbon exposure. 

Reassess exposures if the production increases or the process changes.

Figure 1. Exposure measurement strategy for CNT and CNF [NIOSH 2013].
Occupational Exposure Sampling for Engineered Nanomaterials | 5

Silver

NIOSH derived a REL for silver nanoparticles (all three primary particle size dimensions < 100 nm) of 0.9 μg/m3

 as a respirable 8-hour TWA concentration [NIOSH 2021]. 

NIOSH continues to recommend a REL of 10 μg/m3

 as an 8-hour TWA for total silver 

(metal dust, fume, and soluble compounds).

Use the following approach for paired filter-based sampling (Figure 2) [NIOSH 2021]:

 Sample collection:

о Collect a set of two filter air samples in the worker’s PBZ and a set in at least 

one location outside of the production area. Use 37-millimeter (mm) diameter 

mixed cellulose ester filters in sampling cassettes attached to respirable cyclones with each connected to a sample pump calibrated at the cyclone specified 

flow rate. A polycarbonate filter could also be used instead of a mixed cellulose 

ester filter for a sample collected for elemental microscopy analysis if scanning 

electron microscopy analysis techniques are used.

 Elemental mass-based analysis—silver:

о Analyze one of the mixed cellulose ester PBZ filters from the set by NIOSH 

Method 7300 utilizing Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES) to determine the mass of silver present, accounting for wall 

deposits as described by NIOSH Method 7306 and Chapter 0 [NIOSH 1994, 

2016]. Results below 0.9 μg/m3

 will affirm that exposures are below the REL for 

silver nanoparticles.

 Nanomaterial identification—electron microscopy:

о If the mass-based result is at or above 0.9 μg/m3

, further characterize the duplicate sample with electron microscopy equipped with X-ray energy dispersive 

spectroscopy. Determine the silver particle size since there are different RELs 

depending upon the particle size (0.9 μg/m3

 for ultrafine < 100 nm and 10 μg/m3

for total silver). This analysis can identify particles and agglomerates of primary particles of 100 nm or less, so the mass fraction that the silver nanomaterial REL applies to can be determined. For example, if the mass-based result 

is 9 μg/m3

, and the percent of < 100 nm silver particles determined by electron 

microscopy is only 5%, the exposure to silver ENM would be 0.45 μg/m3

 and 

the REL would not be exceeded.

 Collect area air samples for silver at indoor locations removed from the use of 

silver to determine whether the source is controlled or the extent of any cross 

contamination from the work practices. These area samples are not considered 

“background” samples; they should not be subtracted from the silver PBZ sample 

results to determine whether worker exposures exceeded the REL.

 If PBZ sample results are above the REL, consider following methods outlined in 

the hierarchy of controls until exposures are controlled below the REL.

 Once the exposure is well characterized and controlled below the REL, periodically 

monitor exposure. Use mixed cellulose ester filter samples collected with the 

respirable cyclone and analyzed with NIOSH Method 7300. Reassess exposures if 

the production increases or the process changes.
6 | Occupational Exposure Sampling for Engineered Nanomaterials

Figure 2. Exposure measurement strategy for silver nanoparticles [NIOSH 2021].
Occupational Exposure Sampling for Engineered Nanomaterials | 7

Titanium Dioxide

NIOSH derived RELs of 2.4 milligrams per cubic meter (mg/m3) for fine TiO2 (> 100 nm) 

and 0.3 mg/m3 for ultrafine (all three primary particle size dimensions < 100 nm) TiO2, 

as TWA concentrations for up to 10 hours per day during a 40-hour work week [NIOSH 

2011].

Use the following approach for paired filter-based sampling (Figure 3) [NIOSH 2011]:

 Sample collection:

о Collect a set of two filter-based air samples in the worker’s PBZ and a set of filter 

samples in an area location using a 37-mm cassette containing a hydrophobic 

polyvinyl chloride filter in one cassette and a mixed cellulose ester filter in the 

second cassette. Sets of samples in both locations should be attached to respirable cyclones and sample pumps calibrated at the cyclone specified flow rate.

 Mass-based analysis—TiO2:

о Analyze the polyvinyl chloride filter for respirable mass. If the air concentration 

result is less than 0.3 mg/m3

, no further action is required. Sampler wall losses 

can be addressed following NMAM Chapter O [NIOSH 2016].

о If the total mass is ≥ 0.3 mg/m3

, analyze the same polyvinyl chloride filter for 

elemental titanium by NIOSH Method 7300 [NIOSH 1994].

Figure 3. Exposure measurement strategy for titanium dioxide (TiO2) [NIOSH 2011].
8 | Occupational Exposure Sampling for Engineered Nanomaterials

Nanomaterial identification—electron microscopy:

о If the exposure concentration of elemental titanium by mass ≥ 0.3 mg/m3

 using 

NIOSH Method 7300, characterize the mixed cellulose ester filter using electron 

microscopy. This is necessary to determine the particle size since there are 

different RELs depending upon the particle size. When feasible, determine the 

percentage of fine (> 0.1 micrometer [μm]) and ultrafine (< 0.1 μm) TiO2

 based 

on the measurement of “primary” particles (including agglomerates comprised 

of primary particles).

о The primary particle size of the bulk powder can also be used as a starting point 

to determine whether to apply the REL for fine or ultrafine TiO2

.

 Collect area air samples for TiO2 at indoor locations removed from the use of TiO2

to determine whether the source is controlled or the extent of any cross contamination from the work practices. These area samples are not considered “background” 

samples; they should not be subtracted from the PBZ sample results to determine 

whether worker exposures exceeded the REL.

 If PBZ sample results are above the REL, consider following methods outlined in 

the hierarchy of controls until exposures are controlled below the REL.

 Once the exposure is well characterized and controlled below the REL, use polyvinyl 

chloride filter samples collected with the respirable cyclone and analyzed with 

NIOSH Method 7300 to periodically monitor exposure. Reassess exposures if the 

production increases or the process changes.

Other ENMs: Use of the Nanomaterial Exposure

Assessment Technique

When there is no available REL with described sampling techniques, the Nanomaterial 

Exposure Assessment Technique (NEAT 2.0) can help to quantify exposures to the ENM 

of interest [Eastlake et al. 2016]. NEAT 2.0 includes paired filter-based sampling in concert with real-time direct reading instruments (DRIs), including particle counters with 

data logging capabilities.

This strategy requires the collection of a pair of full-shift, filter-based air samples from the 

worker’s PBZ. If there is interest in identifying task-specific exposure information, collect 

additional samples in the worker’s PBZ for the duration of that specific task. Evaluate area 

airborne particle measurements using DRIs such as a condensation particle counter, an 

optical particle counter, or a photometer to identify potential emission sources.

 Sample collection:

о Collect filter-based samples at the desired aerosol size fraction using a size 

selective cyclone that meets the volume and loading requirements specified by 

the analysis method, in the worker’s PBZ and in area locations close to process 

areas and in areas removed from the process. The type of filter media used for 

the elemental analysis will depend on the chemical composition of the ENM 

of interest (for example, mixed cellulose ester for metals and either mixed 

cellulose ester or polycarbonate for electron microscopy) as specified in the 
Occupational Exposure Sampling for Engineered Nanomaterials | 9

NMAM [NIOSH 2016]. Consult with an analytical lab before collecting samples to determine if an appropriate analysis method exists. Flow rates and the 

use of size selective samplers will depend on methodological needs. In some 

cases, an additional filter-based sample can be collected at a different particle 

size fraction, such as one sample collected at the inhalable fraction and one 

sample collected at the respirable fraction. This paired sampling approach enables better understanding of the contribution of particle agglomeration and 

exposure to larger particles in the analysis of worker exposures.

 Elemental mass-based analysis:

о Conduct elemental analysis of the ENM of interest on one of the filters from 

each sampling set. Since occupational exposure criteria do not exist for most 

ENMs, it is not possible to compare the PBZ measurements with corresponding occupational exposure criteria for the parent compound. Comparisons to 

the parent compound are inappropriate because many of the ENMs studied to 

date have more significant toxicological concerns than the larger forms of the 

element(s) from which they are derived [NIOSH 2011, 2013, 2021].

 Nanomaterial identification—electron microscopy:

о Analyze the second filter sample from the set by electron microscopy for 

visualization of size and determination of elemental composition of particles 

to confirm the presence or absence of the ENM of interest. The use of electron 

microscopy-based methods also enables the examination of various particle attributes (such as physical size, morphology, and composition) that helps distinguish the ENM of interest from incidental nanomaterials [Peters et al. 2008]. 

In addition, electron microscopy methods can identify the presence of an ENM 

of interest even when its mass concentration is below the level of detection of 

the elemental analysis. Consult with your microscopist to determine the best 

filter type and analytical technique for the ENM of interest. If possible, provide 

a sample of the bulk ENM to the analytical laboratory.

о Consideration should be given to use of nanoparticle sampling methods that 

deposit particles directly onto microscopy grids in addition to collection on a 

filter. See the section on Optional Sampling Methods below.

 Collect area filter-based air samples at indoor locations both in near proximity and 

removed from the use of the ENM to determine whether the source is controlled 

or the extent of any cross contamination from the work practices. These samples 

can also be used to identify low level/trace contamination in nonoperational areas. 

These area samples are not considered “background” samples; they should not be 

subtracted from the PBZ sample results to determine worker exposures.

 If the worker is expected to wear multiple pumps (such as two for a task-based set 

and two for a full-shift sampling set), consider using a sampling vest to hold the 

sampling equipment. This will disturb the worker less and distribute the weight of 

the pumps more evenly (Figure 4). 
10 | Occupational Exposure Sampling for Engineered Nanomaterials

Figure 4. Exposure measurement sampling for ENMs using NEAT 2.0. This 

worker has two filter-based personal breathing zone samples in addition to a 

thermophoretic sampler, which was being evaluated (Photo by NIOSH).

 Direct reading instruments:

о Use DRIs for area air sampling to help find the tasks with the greatest emission 

and exposure potential to identify workers who should be monitored with PBZ 

filter-based sampling. The DRIs can also supplement the time-integrated filter 

samples (including those collected to determine compliance to nano RELs), by 

logging changes in particle counts or mass over time and correlating to events. 

DRIs such as condensation and optical particle counters, and photometers can 

determine variations in number concentration, mass concentration, and/or 

approximate size range of particles. NEAT 2.0 recommends the use of a suite of 

DRIs together at the same locations where filter-based area samples are collected 

because not all instruments can determine the presence of all size ranges. These 

instruments should be used in data-log mode. If accurate field notes are taken 

detailing worker processes and the timing of tasks throughout the day, the data 

obtained from the stationary DRIs can provide insight into specific worker activities or tasks that contribute to an increase or decrease in particle concentrations 

or counts. Ensure that the data/time settings of each of the DRIs intended to be 

used are simultaneously synchronized to ease the data comparison task.

о While NIOSH often uses an array of different DRIs to collect information on 

particles of different size ranges and agglomeration states, this may not always 

be necessary. For instance, one type of DRI could be used to conduct control 

technology evaluations, like a condensation particle counter that counts particles in the size range of nominally 10−1,000 nm. NIOSH includes additional 

DRIs to fully understand whether the nanomaterial of interest is also present in 

the larger particle sizes or agglomerates. NIOSH recommends the use of DRIs 

primarily to verify that engineering controls are functioning properly and to 

qualitatively identify tasks or areas of potential exposure. DRIs lack the specificity required for a quantitative exposure assessment but can help identify and 

evaluate particle concentration trends.
Occupational Exposure Sampling for Engineered Nanomaterials | 11

 Use all three sampling methods (elemental mass-based analysis, electron microscopy identification, and direct-reading instruments) for a complete exposure 

assessment (Figure 5).

Figure 5. Area sampling shown in the figure includes three real-time data 

logging particle counters (one condensation particle counter and two optical 

particle counters), two 25-mm open-face filter cassettes, and two thermophoretic 

samplers (Photo by NIOSH).

Optional Sampling Methods

Personal samplers for ENMs are continually being developed, and several are listed in 

Table 1. In general, these instruments consist of a particle size-selective inlet, a sampling substrate like a filter cassette/net/grid, and a sampling pump [Eastlake et al. 2020; 

Iavicoli et al. 2018; Tsai et al. 2018]. Substrates from personal sampling devices can be 

removed and characterized using sophisticated analytical techniques, such as inductively coupled plasma mass spectrometry (ICP-MS); electron microscopic with chemical 

detectors, or Raman spectroscopy analyses, to obtain information (e.g., mass, chemical 

composition, size, and shape). These techniques can also be used for area sampling and 

provide a wealth of information about the ENM of interest. Nanoparticle sampling 

methods that deposit particles directly onto electron microscopy grids show great promise [Asbach et al. 2017; Iavicoli et al. 2018; NanoIndEx Project 2016; Tsai et al. 2018]. 

These personal samplers could also be used for area sampling.
12 | Occupational Exposure Sampling for Engineered Nanomaterials

Table 1. Personal measurement methods and brief descriptions

Measurement Method Manufacturer Description

Electrostatic Precipitator

[Miller et al. 2010]

ESPNano; Spokane, WA Eliminates the use of filterbased sampling by collecting 

directly onto an electron 

microscopy grid using a 

charge differential. Analyzed 

in a laboratory using 

electron microscopy.

Identifier C1 (carbon 

nanotubes & graphene),

S1 (silica), or 

N1 (nanocellulose)

[Bieri and Cattaneo 2016]

StatPeel; Switzerland A product composed of 

several individual employee 

badge sensors and an 

integrated bench-top optical 

reader. The badges are 

used to monitor and record 

exposure to nanomaterials. 

Analysis is performed on site 

by Raman spectroscopy in 

the integrated optical reader 

or can be submitted for 

laboratory analysis.

MPS Mini-Particle Sampler

[R’mili et al. 2013]

Ecomesure; Janvry, France Uses a transmission electron 

microscopy grid as a filter 

to collect particles with 

subsequent identification 

and chemical analysis. 

Analyzed in a laboratory 

using electron microscopy. 

Nanobadge

[Iavicoli et al. 2018]

Nano Inspect, Alcen Group; 

Paris, France and French 

Alternative Energies and 

Atomic Energy Commission 

CEA, Grenoble, France

Product collects particles 

directly onto a polycarbonate 

track-etched membrane 

or quartz filter. Analyzed 

in a laboratory using X-ray 

fluorescence spectroscopy 

or scanning electron 

microscopy.

Nanoparticle Respiratory 

Deposition Sampler (NRD)

[Cena et al. 2011]

Zefon International; 

Ocala, FL

Sampler designed to 

mimic the deposition of 

nanoparticles (of less than 

300 nanometers) in the 

human respiratory system. 

Analyzed in a laboratory 

using specialized NRD 

protocol.
Occupational Exposure Sampling for Engineered Nanomaterials | 13

Measurement Method Manufacturer Description

Partector TEM

[Fierz et al. 2015]

Naneos Particle Solutions 

GmbH; Windisch, Switzerland

Eliminates the use of filterbased sampling by collecting 

directly onto an electron 

microscopy grid. Analyzed in 

a laboratory using electron 

microscopy.

PENS Personal 

Nanoparticle Sampler 

Electrostatic Precipitator

[Tsai et al. 2012]

Institute of Environmental 

Engineering, National Chiao 

Tung University; Taiwan

The PENS consists of a 

respirable cyclone, a microorifice impactor and a 

rotating, silicone oil-coated 

Teflon filter substrate. 

Analyzed in a laboratory for 

mass. 

Personal Sampling System, 

Personengetragenes 

GefahrstoffProbenahmesystem (PGP)

[Asbach et al. 2015]

GSA Messgerätebau GmbH; 

Ratingen, Germany

Product collects particles 

directly onto a gold-coated 

etch membrane filter. 

Analyzed in a laboratory 

using scanning electron 

microscopy.

TDS-Diffusion sampler 

[Tsai and Theisen 2018]

Tsai Lab at University of 

California; Los Angeles, CA

A 3D-print sampling cassette 

connecting to personal 

sampling pump, collects 

size-selective nanoparticles 

and respirable particles 

onto a transmission 

electron microscopy 

grid and polycarbonate 

membrane filter. Analyzed in 

a laboratory using electron 

microscopy.

Thermophoretic Sampler 

[Leith et al. 2014]

RJ Lee Group; 

Monroeville, PA

Eliminates the use of filterbased sampling by collecting 

directly onto an electron 

microscopy grid using a 

temperature differential. 

Analyzed in a laboratory 

using electron microscopy.

Incorporating surface wipe or bulk dust sampling can also be useful to identify ENM 

migration throughout production areas or contamination of nonproduction work areas 

of the facility. Although there are no surface contamination standards for ENMs, some 

workplaces have developed internal standards for surface contamination. For example, 

Brookhaven National Laboratory developed guidance for surface contamination of some 

non-nano elements [BNL 2017]. Periodic surface sampling can identify if there is material transfer out of working or production areas, and helps to ensure that risk management practices operate effectively by keeping ENMs from spreading within production 

areas or into surrounding nonproduction areas.
14 | Occupational Exposure Sampling for Engineered Nanomaterials

Conclusions

A comprehensive exposure assessment evaluation for ENMs collects information that can 

be used to (1) identify sources of potential ENM exposures, (2) establish similar exposure 

groups by area or job tasks, (3) characterize exposures of all potentially exposed workers, 

and (4) assess the effectiveness of engineering controls, work practices, PPE, training, and 

other factors used in reducing exposures. Using a combination of the techniques described 

above can provide an in-depth characterization of potential occupational exposure to 

ENMs. This information is then available for incorporation into risk management strategies to minimize worker exposure to ENMs and confirm ongoing control of risk.

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