MEMORANDUM

TO: William Swietlik, U.S. EPA/EAD

FROM: Eva Knoth, ERG 

Kim Wagoner, ERG

DATE: January 23, 2015

SUBJECT: Engineered Nanomaterials in Industrial Wastewater: Literature Review and 

Implications for 304m

1. BACKGROUND 

As required by Section 304(m) of the Clean Water Act, EPA annually reviews industrial 

discharges to identify new industries requiring regulation or existing regulations that may need to 

be revised. In odd-numbered years, EPA reviews the established effluent limitations guidelines 

and standards (ELGs) used to regulate wastewater discharges from 58 point source categories. In 

even-numbered years, EPA uses additional data sources to expand its ability to identify new 

pollutants of concern or wastewater streams in industrial categories not currently regulated by 

ELGs.

As part of the 2014 Annual Review, EPA is investigating engineered nanomaterials

(ENMs), a potential emerging industrial wastewater pollutant category. ENMs are manmade 

materials composed of primary particles with sizes on the order of 1 to 100 nanometers (nm) in 

at least one dimension that exhibit properties that are not found in bulk samples of the same 

material (U.S. EPA, 2011a). Nanotechnology is a rapidly advancing field of research and 

commerce and offers potential benefits for health, consumer products, and electronics 

applications. According to the Nanotechnology Consumer Product Inventory, ENMs are 

currently used in over 800 consumer products in the U.S. (Project on Emerging 

Nanotechnologies, 2014). However, the environmental and human health risks associated with 

these materials are largely unknown.

Recent research presented at the Society of Environmental Toxicology and Chemistry 

(SETAC) North America 33rd Annual Meeting in November 2012 indicates that ENMs may 

impact human health and the environment. Although researchers have conducted little direct 

sampling and analysis of industrial wastewater discharges, they have identified industrial 

discharges as a possible route for ENMs to enter the environment (Gottschalk & Nowack, 2011; 

Hendren et al., 2011; Musee, 2011). In its Final 2010 Effluent Guidelines Program Plan, EPA 

solicited data and information for future annual reviews on the manufacture, use, and 

environmental release of silver materials, including nanosilver, due to their anti-microbial 

activity and potential to create a source of silver in associated industrial wastewater discharges

(U.S. EPA, 2011c). Several commenters indicated that EPA should investigate the impact of 

nanosilver; a few in particular indicated that EPA should investigate all nanomaterials (U.S. 

EPA, 2013d).
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January 23, 2015

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Several of EPA’s Offices are currently assessing ENMs for their potential effects on 

human health and the environment, through research into chemical safety, characterization 

techniques, and life cycle assessment and risk assessment of these ENMs in air, water, and soil 

(U.S. EPA, 2013b). Table 1 lists the types of ENMs the Agency is currently assessing and 

common applications for their use.

Source: (U.S. EPA, 2013b).

In response to the recent interest, research, and concerns raised in comments, ERG was 

tasked with reviewing and summarizing current literature about the fate and effects of ENMs on 

the environment and human health and about the presence and discharge of ENMs in industrial 

wastewater. 

This memorandum describes ERG’s literature review and presents a brief overview of

nanomaterials, production methods, and potential waste streams, as well as the status of research 

into their environmental fate and toxicity. It also describes the status and availability of 

analytical methods and tools to measure, quantify, and characterize nanomaterials in industrial 

wastewater. Lastly, it summarizes the existing data gaps and areas of research that are needed to 

fully assess the risk and impact of ENMs and inform future decisions regarding their discharge in 

industrial wastewaters.

Based on the recommendation of several leading researchers, ERG’s review of current 

research focused on the production, environmental release, fate, and toxicity of three classes of 

ENMs: silver, titanium dioxide, and carbon-based nanomaterials (Hochella, 2013; Wiesner, 

2013). These three classes of ENMs are estimated to be produced in the largest volumes and are 

commonly used in commercial and consumer products. In addition, research has more fully 

classified their impact on human health and the environment than the impacts of other types of 

ENMs (for which there is little information).

Research on the environmental health and safety of ENMs is rapidly progressing and 

many efforts are underway to advance the field. This memorandum highlights information

identified through December 2013, as described in Section 2.0.

2. LITERATURE REVIEW AND RESEARCH METHODOLOGY

To assess information available and support EPA’s evaluation of potential industrial 

wastewater discharges and associated risks of discharged ENMs, ERG’s investigation focused 

on:

Table 1. Engineered Nanomaterials Currently Being Assessed by EPA and Their 

Common Applications

Engineered 

Nanomaterial Common Applications

Carbon nanotubes Electronics, advanced materials, biomedical applications

Cerium oxide Electronics, energy, fuel additives, biomedical supplies

TiO2 Paints and coatings, cosmetics, semiconductors, water treatment and remediation

Silver Textiles, cosmetics, biomedical supplies

Iron Optics, water treatment, and remediation

Micronized copper Wood preservative
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January 23, 2015

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• Production methods and potential aqueous waste streams from manufacturing and 

processing ENMs.

• Fate, transport, and potential effects of nanomaterials on human health and the 

environment.

• Analytical techniques available to detect nanomaterials in industrial wastewater.

• Presence of nanomaterials in industrial wastewater.

• Treatment technologies to remove nanomaterials from wastewater.

SETAC’s 2012 conference proceedings included over 125 presentations and posters 

about nanomaterial-related research, which primarily focused on fate and transport, toxicity, and 

analytical techniques (SETAC, 2012). ERG reviewed this nanomaterial-related research and 

catalogued relevant abstracts as a starting point for further research.

Next, ERG identified (partly through the SETAC abstracts) principal government and 

university researchers and organizations that focus on studying the environmental impacts of 

ENMs. ERG identified additional stakeholders based on nanomaterials-related research 

conducted by several EPA offices including the Office of Pollution Prevention and Toxics

(OPPT) and the Office of Research and Development (ORD) National Exposure Research 

Laboratory (NERL). Concurrently, the EAD WAM identified and reached out to key researchers 

and stakeholders involved in nanomaterial research within the Agency.

ERG developed a list of questions (approved in advance by the EAD WAM) to discuss 

with each of the contacts. ERG and the EAD WAM used the list to direct the discussion toward 

answering EPA’s outstanding questions and to identify additional resources to further its 

understanding of the presence and potential impact of ENMs in industrial wastewater. A copy of 

the questions is provided in Appendix A for reference.

Using the contacts identified in the initial reviews, ERG corresponded with two leading 

researchers in March 2013:

• Mark Wiesner, James L. Meriam Professor, Department of Civil and 

Environmental Engineering, Duke University; Director of the Center for the 

Environmental Implications of Nanotechnology (CEINT).

• Michael Hochella Jr., University Distinguished Professor, Department of 

Geosciences, Virginia Tech; member of CEINT.

ERG also communicated by email with:

• Paul Westerhoff, Professor, School of Sustainable Engineering and the Built 

Environment, Associate Dean for Research and Graduate Affairs, Ira A. Fulton 

Schools of Engineering, Arizona State University.
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January 23, 2015

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• Suzanne Davis, Hazardous Substances Engineer, California Department of Toxic 

Substances Control.

The EAD WAM communicated with the following EPA and federal agency colleagues

between March and June 2013:

• David Meyer, Chemical Engineer, EPA ORD National Risk Management 

Research Laboratory (NRMRL), Sustainable Technologies Division.

• Thabet Tolaymat, Environmental Engineer, EPA ORD NRMRL.

• Katrina Varner, Research Chemist, EPA ORD NERL–Las Vegas/Environmental 

Sciences Division/Environmental Chemistry Branch.

• Steve Diamond, EPA National Health and Environmental Effects Research 

Laboratory Mid-Continent Ecology Division–Duluth.

• Jeff Morris, Deputy Director for Programs, EPA OPPT.

• Phil Sayre, EPA Deputy National Program Director for the Chemical Safety for 

Sustainability Research Program.

• Jim Alwood, Program Manager and Toxic Substances Control Act

Nanotechnology Coordinator, EPA OPPT, Chemical Control Division.

• Barbara Karn, Program Director, National Science Foundation; Vice President, 

Sustainable Nanotechnology Organization.

In addition to contacting the above nanomaterials researchers, ERG attended the National 

Nanotechnology Initiative (NNI) workshop on Stakeholder Perspectives on the Perception, 

Assessment, and Management of the Potential Risks of Nanotechnology in Washington, D.C., in 

September 2013.

1

To complete the literature review, ERG searched for articles written by SETAC 2012 

conference participants and additional researchers identified from previous contacts using the 

following search engines:

• American Chemical Society Publications (http://pubs.acs.org), a comprehensive 

collection of the most-cited, peer-reviewed journals in chemistry and related 

sciences.

• ScienceDirect (http://www.sciencedirect.com/), a full-text scientific database

offering over 2,500 peer-reviewed journals.

1 The NNI is a U.S. government research and development initiative involving the nanotechnology-related activities 

of 20 department and federal agency units. For more information on this NNI workshop, including the agenda and 

presentations, see http://nano.gov/node/1025.

 
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• Google Scholar (http://scholar.google.com), which provides a broad search of 

scholarly literature across disciplines, publishers, and online databases.

In addition to searching by author, ERG scanned titles and abstracts to identify relevant 

articles, using the keywords shown in Table 2 below. ERG exercised its best professional 

judgment to create multiple keyword combinations to further focus the literature search. From 

the articles identified, ERG performed additional searches to find other relevant articles from coauthors and references.

ERG created a comprehensive EndNote® reference library to store and organize 

references. Because nanotechnology is an emerging field of study, ERG strived to collect the 

most recent research, gathering material published from 2006 to December 2013. All articles are 

government publications, peer-reviewed, or conference proceedings and meet the data quality 

objectives outlined in the Environmental Engineering Support for Clean Water Regulations

Programmatic Quality Assurance Project Plan (ERG, 2013).

Table 2. Keyword Search Terms for Literature Search

Master Terms Chemical Terms General Terms

Nano

Nanomaterial

Nanoparticle

Nanoscale

Nanotechnology

Carbon

Carbon nanotubes

CNTs

Silver

Nanosilver

TiO2

Titanium dioxide

Engineered

Environmental

Environmental implication/impact

Exposure

Fate and transport

Life cycle assessment

Occurrence

Production

Release

Risk

Synthesis

Toxicity

Treatment

Wastewater

3. OVERVIEW OF NANOMATERIALS

Nanomaterials are generally defined as engineered or naturally occurring materials

composed of primary particles, with sizes on the order of 1 to 100 nm in at least one dimension,

that show physical, chemical and biological properties not found in bulk samples of the same 

material (U.S. EPA, 2011a). These primary particles, termed nanoparticles, may exhibit novel,

size-dependent characteristics such as increased strength, chemical reactivity, and conductivity 

due to their high surface area-to-volume ratio. This proportionally large surface area makes 

nanoparticles more reactive and responsive to their surroundings and influences mobility, 

aggregation, and stability in soil and water (Gavankar et al., 2012).

A growing community of researchers argue that the primary criterion in any definition of 

nanomaterials should be novel size-dependent properties, rather than particle size, because size 

alone may not reliably predict the fate, transport, and effects of exposure to nanomaterials

(Auffan et al., 2009; David, 2013; Wiesner et al., 2009).
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January 23, 2015

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Naturally occurring nanomaterials are ubiquitous in the environment, but have only 

recently been discovered due to advances in microscopy (Hochella et al., 2008). Their

background levels and mass distribution are largely unknown. In some cases, nanomaterials may 

also be incidental, meaning that they are unintentionally produced through industrial activities, 

notably through emissions from fossil fuel combustion and manufacturing (Wiesner et al., 2009). 

Engineered nanomaterials are produced to serve a particular purpose and represent a 

new or additional input to the environment. The most common ENMs are classified into two 

categories: carbon-based and inorganic or metal-containing ENMs. Table 3 lists common types 

of ENMs.

Table 3. Common Types of Engineered Nanomaterials

Category Engineered Nanomaterial

Carbon-based ENMs

Carbon nanotubes

Fullerenes

Graphene

Inorganic or metal-containing ENMs

Silver

Titanium dioxide

Quantum Dots

Cerium Oxide

Zinc Oxide

Iron

Copper

Silicon

Gold

Bi- and tri-metallic alloys

Source: (SETAC, 2012) and (U.S. EPA, 2013a).

Some ENMs, such as cadmium selenide quantum dots and some complex carbon-based 

nanomaterials, are completely novel and do not occur in nature. Any of these materials detected 

in the environment can be assumed to be anthropogenic (ERG, 2008; Hochella, 2013). However, 

many types of nanomaterials that can be engineered also occur naturally in the environment, 

particularly silver and metal oxides. Silver ENMs are used extensively an anti-microbial agents

in consumer products, but silver particles on the nanoscale are also found in nature. In addition, 

titanium dioxide (TiO2) nanoparticles that are identical to engineered nanoparticles have been 

found in rivers that do not receive wastewater discharges and are remote from industrial 

activities (Hochella, 2013).

Typical concentrations of naturally occurring and incidental nanomaterials far exceed the 

total release of ENMs into the environment (Hochella, 2013; Wiesner et al., 2009). However, 

there is concern that the increased release of ENMs to the environment at large, above and 

beyond what occurs naturally, may have unintended consequences, especially to ecosystems that 

have not been exposed to or developed adaptation mechanisms for specific types of ENMs. The 

remainder of this memorandum focuses on ENMs.

Based on a conversation with CEINT Director Mark Wiesner, and available literature 

sources, ERG focused the literature review, research, and subsequent discussion presented in this 

memorandum on the ENMs with the largest production quantities and potential for discharge to 
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January 23, 2015

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the environment from industrial wastewater: silver, nano-TiO2, and carbon nanotubes (CNTs)

(Wiesner, 2013).

Quantum dots are a distinctive category of metal-containing ENMs that do not occur in 

nature. These nano-sized semiconductors are being investigated for use as biomarkers for 

biomedical research and for optoelectronic applications, such as solar cells and light emitting 

diodes, but are just beginning to be translated into commercial products (Bullis, 2013). Quantum 

dots have different optical properties depending on their size (Lowry et al., 2012b), and can be 

synthesized from a variety of metals in solution, most commonly cadmium selenide (Mahendra 

et al., 2008; Woo, 2013). Although their manufacture could potentially generate an aqueous 

waste stream, ERG’s literature review indicated that most production is lab scale and information 

pertaining to the environmental impact, release, or exposure of quantum dots is limited (Musee, 

2011; Yong et al., 2013); therefore, ERG does not further focus on quantum dots in this 

memorandum.

4. ENGINEERED NANOMATERIAL PRODUCTION METHODS, VOLUMES AND POTENTIAL 

SOURCES OF INDUSTRIAL DISCHARGE

To assess the potential sources and magnitude of industrial wastewater discharges, ERG 

gathered available information on ENM manufacturing and ENM processing into nano-enabled

products (products containing nanomaterials). Manufacturing is the synthesis of ENMs; 

processing (or formulating) includes any industrial transformation or processing of ENMs into a 

form that could be used to make nano-enabled products, as well as the production of nanoenabled products. ERG also collected information about the generation and handling of aqueous 

waste streams produced during manufacturing and processing. Information about waste 

generation and management for manufacturing and processing is scarce, but is needed to 

determine if and where ENMs may be discharged to the environment due to industrial activities.

Commercial and consumer end use of nano-enabled products and their waste 

management are outside the scope of the Effluent Guidelines Program. However, significant 

discharges of ENMs to the environment may occur from release and degradation during product 

use (Gottschalk & Nowack, 2011; Rezić, 2011; Windler et al., 2012). Mueller and Nowack 

(2008) estimated that up to 95 percent of silver and TiO2 nanoparticles could to be transported to 

wastewater treatment plants due to release from products during their commercial and consumer 

use (e.g., from application of coatings, rinsing of cosmetics or weathering due to abrasion).

Current global production quantities of ENMs are largely unknown and growth rates are 

uncertain, but both the rates and types of materials produced are expected to rapidly increase. For 

example, growth rates from 2006 to 2008 for nano-enabled products ranged from 10 percent for 

electronics up to 41 percent for appliances, and future growth is expected to far outpace these 

rates (Musee, 2011).

In the absence of wastewater discharge data, information about the inputs (including raw 

and ancillary materials) and emissions from manufacturing and/or processing is needed to 

estimate potential ENM discharges. For purposes of the Effluent Guidelines planning process, 

production quantities in themselves do not provide suitable information on potential wastewater 

discharges without knowledge of the processes used to manufacture or process ENMs. The 

identification of aqueous waste streams generated from manufacturing and processing is the first 
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January 23, 2015

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ENM Production and Waste Streams 

Data Gaps:

• Unknown universe of facilities 

manufacturing and processing ENMs

• No current data quantifying 

wastewater discharges of ENMs from 

manufacturing or processing

• Little publicly available data 

quantifying ENM production volumes 

from manufacturing or processing

• Unknown generation of aqueous 

waste streams from manufacturing 

and processing of ENMs

• Unclear understanding of current 

ENM waste handling/management 

practices

step in determining whether industrial wastewater could be a source of environmental releases of

ENMs.

The following sections describe the production methods and various routes by which

ENMs could enter the environment from their manufacturing and processing into nano-enabled 

products. It is important to stress that these are potential routes of release. Very little is known

about the actual release of ENMs to the environment, and there are currently no standardized 

techniques to monitor emissions and environmental concentrations (Gottschalk & Nowack, 

2011). If a particular process generates an aqueous waste, the next step is to identify how the 

waste is handled and in particular, if the waste is discharged to surface waters or POTWs. From 

its review of current literature and research, ERG did not identify any information documenting 

the release or measurement of ENMs in industrial wastewater from manufacturing or processing 

activities.

4.1 ENM Production and Waste Streams

Very little publicly available information exists to 

characterize the waste streams from ENM manufacturing 

and processing or describe how the aqueous wastes are 

managed and disposed. Several papers, especially those 

on the topic of life cycle assessment, discuss the need to 

quantify both production and release of ENMs and 

analyze or model possible waste stream pathways

(Gavankar et al., 2012; Gottschalk et al., 2009; Musee, 

2011). The literature also suggests that the processes

associated with the manufacturing and processing of 

ENMs may create aqueous waste streams (Eckelman et 

al., 2012; Musee, 2011).

Commercial ENM manufacturing methods and volumes are often proprietary and are not 

shared publicly. The EPA Nanoscale Materials Stewardship Program solicited voluntary reports 

from U.S. companies producing ENMs in 2008 (U.S. EPA, 2013c). The program estimated that 

about 600 companies manufactured, processed, or used nanotechnology in 2005; although the 

program expected reports from 240 entities, it received only 31. Of the companies that 

responded, only two publicly reported any production data. These two reported manufacturing 

capacity but not the actual quantities of ENMs manufactured (Hendren et al., 2011). In a separate 

effort, Duke University researchers, using data from patents, company websites, and requests, 

identified 30 companies producing silver, nano-TiO2, or CNTs (provided in Appendix B)

(Hendren et al., 2011). ERG has not contacted any U.S. companies for information regarding 

manufacturing and processing methods or production quantities.

4.1.1 Manufacturing of ENMs

From its review of the literature, ERG identified the following manufacturing methods as 

well as research and development (R&D) laboratory methods used to synthesize ENMs.

Depending on the post-processing steps, the resulting ENM may be in the form of powders, 

sprays, or solutions. The manufacturing methods ERG identified are published in peer-review 

literature and do not necessarily characterize a process from a particular company or laboratory.
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January 23, 2015

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Silver nanomaterials can be synthesized using several physical and chemical methods.

They are often produced in dilute aqueous solutions by chemical reduction. Silver salts are

reduced by sodium borohydride, citrate, ascorbate, or another reducing agent (Fabrega et al., 

2011; Mulfinger et al., 2007). In addition, researchers are investigating biosynthesis processes 

(e.g., using fungi) to generate silver nanoparticles (Fabrega et al., 2011).

Single-walled carbon nanotubes are manufactured by three gas-phase processes: 

chemical vapor deposition, arc ablation, and high-pressure carbon monoxide (Eckelman et al., 

2012; Healy et al., 2008). Multi-walled CNTs are often manufactured using chemical vapor 

deposition (Plata et al., 2009). These synthesis processes do not generate an aqueous waste 

stream, but they are followed by an aqueous purification step. Purification may involve several 

rinses with one or several of the following solutions: deionized water, nitric acid, sodium 

hydroxide, and ethanol (Healy et al., 2008). The use of an aqueous purification rinsing scheme 

suggests that CNT manufacturing could generate an aqueous waste stream, but ERG did not 

identify any information related to the onsite treatment and/or subsequent disposal of the waste 

stream.

EPA’s OPPT recently promulgated Significant New Use Rules (SNURs) for CNTs under 

the authority of the Toxic Substances Control Act, which became effective in August and 

October 2013 (U.S. EPA, 2013a, 2013e). These SNURs require entities that intend to 

manufacture, process, or use certain CNTs to notify EPA at least 90 days before engaging in a 

significant new use. Any Significant New Use notices made under these SNURs will give EPA 

the opportunity to evaluate the intended new uses of the CNTs and, if necessary, to limit or 

prohibit activity to mitigate any unreasonable risks to human health and the environment. 

Titanium dioxide nanomaterials are manufactured by gas- and wet-phase synthesis 

methods. About 60 percent of the world’s manufactured nano-TiO2 is synthesized through a gasphase chloride process (Liu et al., 2013); however, ERG did not find information on how much

of the nano-TiO2 produced in the U.S. is manufactured through this process. Nano-TiO2 is also 

synthesized by wet-phase methods, including sulfate, sol-gel, and hydrothermal methods (Liu et 

al., 2013; Robichaud et al., 2009).

Both gas- and wet-phase nano-TiO2 synthesis methods potentially produce aqueous waste 

streams. Early methods of synthesis generally occurred in solution, but combustion (gas-phase) 

processes have evolved to allow greater control, efficiency, and output of products (Healy et al., 

2008). The use of gas-phase synthesis methods may significantly reduce potential wastewater 

discharges; however, steps common to both gas- and wet-phase synthesis may generate aqueous 

waste, for example, during purification and washing of the nanomaterial. From its review of 

literature and current research, however, ERG did not find information describing how the nanoTiO2 aqueous wastes from industrial manufacturing processes are managed.

Although not much is known about waste handling, unused reagents and chemical wastes

from manufacturing are strictly managed and likely to be handled as hazardous waste, and not 

released in wastewater (Eckelman et al., 2012). In addition, researchers suggest that laboratorygenerated waste streams are probably recovered or reused due to the high cost of producing 

ENMs (Wiesner, 2013). However, cleaning or washing of laboratory equipment may be a 

potential source of wastewater. Equipment, such as glassware, is typically cleaned first with 
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January 23, 2015

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solvents before being washed with detergents and water in a sink. The solvents are disposed of as 

hazardous waste, while detergents, water, and any residuals may be discharged as wastewater.

4.1.2 Processing/Formulating

After manufacturing, ENMs are often further processed and incorporated into nanoenabled products. Nano-enabled products are used across many industrial sectors. They are used 

extensively for biomedical and electronics applications, and incorporated into industrial and 

domestic products, chemicals, and construction materials. TiO2 ENMs are used as catalysts and 

are included in paints, coatings, plastics, paper, and cosmetics. Silver ENMs are widely used in 

consumer products, such as cosmetics and kitchen products, for their antimicrobial properties. 

CNTs are used in the electronics and polymer industries, with ongoing research into their 

applications for the energy and consumer goods sectors (Mueller & Nowack, 2008).

Transforming manufactured ENMs into nano-enabled products may require one or 

several intermediate handling and processing steps. These intermediate processing steps may 

occur at the primary manufacturing facility or a separate facility before the ENM is formulated 

into a nano-enabled product. The extent of processing is likely proprietary and could be highly 

variable, depending on the intended use. As a result, ERG could not identify adequate 

information to describe the nature of and variability of intermediate processing.

The extent and number of ENM processing and formulating facilities is unknown, but

literature and current research suggests that they likely far outnumber facilities that solely 

manufacture ENMs. The EPA Nanoscale Materials Stewardship Program estimated that about 

600 companies manufactured or applied nanotechnology in 2005 (U.S. EPA, 2013c), but the 

number of companies has most likely significantly increased since then. Further, some 

processors may use ENMs or nano-enabled devices to manufacture products that do not contain 

nanomaterials.

Researchers indicate that processing and production of nano-enabled products may be 

more likely to produce an aqueous waste stream than manufacturing ENMs because many of the 

nano-enabled products may be formulated with the ENMs in solution (Wiesner, 2013). A variety 

of aqueous waste streams may be generated during processing, depending on the product and 

industry. However, information is not currently sufficient to characterize and quantify the waste 

streams generated from ENM processing or describe how the waste streams are handled and 

ultimately disposed.

4.2 Environmental Concentrations of Nanomaterials

Researchers do not currently have a good understanding of the concentrations of 

engineered or naturally occurring nanomaterials in the environment (Hochella, 2013; Wiesner et 

al., 2011). Information on background environmental concentrations of nanomaterials could be 

used to identify releases of ENMs based on areas with unnaturally high concentrations and to 

evaluate the inputs from potential future emissions from industrial wastewater and other sources.

Knowledge of environmental concentrations is also important for conducting relevant toxicity, 

risk assessment, and life cycle assessment studies.
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Environmental Concentrations 

Data Gaps:

• Incomplete data characterizing 

concentrations of engineered and 

naturally occurring nanomaterials 

in the environment

• Little research into the relative 

contribution of manufacturing, 

processing, and end use to the 

quantities of ENMs in the 

environment

To estimate potential exposure and risk to aquatic 

organisms, researchers have developed models that predict 

the ENM concentrations in the environment. Researchers 

at the Swiss Federal Laboratories for Materials Testing and 

Research (Empa) calculated predicted environmental 

concentrations (PECs) of several ENMs in wastewater 

treatment plant (WWTP) effluent (from a combination of 

industrial and domestic sources) and surface waters in the 

U.S. based on probabilistic material flow analysis of 

current production volumes (Gottschalk et al., 2009). As 

shown in Table 4, the PECs of ENMs in WWTP effluent are orders of magnitude larger than 

what is predicted for surface waters. The researchers then compared the PECs to predicted no

effect concentrations (PNEC) from ecotoxicological studies and concluded that silver and TiO2

ENMs in WWTP effluent may pose a risk to aquatic organisms based on their risk quotients 

(Table 4). A risk quotient greater than one indicates a need to further evaluate the risks posed to 

aquatic organisms.

Table 4. Calculated Model Values for Predicted Environmental Concentrations of 

Engineered Nanomaterials in the U.S.

Engineered 

Nanomaterial

Predicted Environmental Concentration 

(PEC) (ng/L)

WWTP Effluent Risk Quotient 

(PEC/PNEC)

WWTP Effluent Surface Water WWTP Effluent Surface Water

Silver 21.0 0.116 30.1 0.17

TiO2 1,750 2.0 1.8 0.002

CNTs 8.6 0.001 <0.0005 <0.0005

Fullerenes 4.6 0.003 0.023 <0.0005

Source: (Gottschalk et al., 2009)

Risk quotients greater than one are indicated in bold.

Quantifying production and waste volumes for specific industries and commercial 

applications is critical for developing life cycle assessment models needed to accurately assess 

risk associated with environmental releases. The Empa model was based upon estimated 

worldwide production volumes, which are incomplete and uncertain. Therefore, the significance 

of the Empa study’s results to the U.S. is uncertain. The results do suggest that aquatic 

ecosystems may be at risk from exposure to silver and TiO2 ENMs released into the 

environment, though they do not clearly distinguish between potential inputs from releases to 

wastewater from manufacturing, processing, and end use.

5. ENVIRONMENTAL FATE, TOXICITY, AND EXPOSURE

ENMs are likely to be transformed and exist in different forms in the environment than 

the original form in which they were created. ENMs undergo complex and dynamic 

transformations in aqueous media, the extent of which are not fully understood (Lowry et al., 

2012b). The different forms in which a nanomaterial can exist will influence fate, reactivity, and 

toxicity in the environment. For example, silver can exist as discrete nanoparticles, aggregated 

nanoparticles, or dissolved ions and can form complexes with other molecules. The following 

sections describe the physical properties, general fate in the environment and WWTPs, and 

known toxicity impacts of silver, TiO2, and CNT ENMs.
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Fate and Environmental 

Transformations Data Gaps:

• Incomplete understanding of how 

different types of ENMs will 

interact and transform in aqueous 

environments

• No studies of ENM fate and 

transformations in industrial 

wastewaters

5.1 Fate and Environmental Transformations

Once released into the environment, ENMs 

undergo complex and dynamic interactions, transforming 

and aggregating in aqueous media (Lowry et al., 2012b; 

Wiesner et al., 2011). Several properties of nanomaterials 

may contribute to their fate, transport and ecotoxicity. 

Particle size and surface area influence the degree of 

interaction with substances and organisms in the 

environment. A larger surface area (smaller particle) 

allows for greater reaction rates (Healy et al., 2008). Surface coatings that are either engineered 

onto the nanomaterial or attached through transformations can strongly influence the solubility 

and reactivity of an ENM. The behavior of nanoparticles in the environment is relatively more 

responsive (compared to bulk materials) to the specific conditions of the environment to which 

the particle is emitted (Gavankar et al., 2012).

Nanoparticles may be transformed in water through any of the following mechanisms:

• Nanoparticle aggregation

• Formation of complexes with other molecules in water, soil, or biological systems

• Sorption processes

• Degradation

• Dissolution of coatings or the core particle

The interactions and transformations that occur are dependent on the chemistry of the 

environment, which will affect the mobility and bioavailability of the nanomaterial. In addition, 

most nanomaterials in the environment tend to aggregate and do not exist as single, dispersed 

nanoparticles in water (Zhang et al., 2008). The fate and common interactions of silver, CNTs,

and TiO2 ENMs with the aqueous environment are discussed below.

Silver ENMs are spherical particles with high electrical and thermal conductivity; 

however, they are best known for their broad antimicrobial properties. Their size and stability are 

strongly influenced by the conditions under which they are manufactured (Fabrega et al., 2011).

Silver nanoparticles are commonly coated with various polymers that affect the type, rate, and 

extent of transformations that may occur in aqueous media (Lowry et al., 2012b). The solubility 

of silver nanoparticles is highly dependent on surface coating. For example, citrate-coated silver 

nanoparticles tend to stay in the water phase, while polyvinylpyrrolidone (PVP)-coated silver 

nanoparticles more readily partition to solid phases (Unrine et al., 2012).

Silver nanoparticles readily form complexes with sulfur in various aqueous media, which 

can transform the nanoparticle into many different forms. The nanoparticle can be oxidized into

silver ions or remain as nanoparticle and form complexes with other chemicals in the 

environment, such as sulfur (Dale et al., 2013). These transformations are illustrated in Figure 1. 

Silver nanoparticle sulfidation has been demonstrated in many environmental media, notably 

during activated sludge treatment in WWTPs (Doolette et al., 2013; Kim et al., 2010), in the 

laboratory (Levard et al., 2011), and in the natural environment (Levard et al., 2012; Lowry et 

al., 2012a). Researchers at CEINT constructed wetland mesocosms to study the long-term 
Memorandum

January 23, 2015

Page 13

behavior of silver nanoparticles. A study of PVP-coated silver nanoparticles indicated that a 

majority of the silver nanoparticles were transformed to silver-sulfide compounds and primarily 

partitioned to soils and sediments (70 percent by weight) (Lowry et al., 2012a). Researchers at 

Carnegie Mellon University reported that silver nanoparticles are transformed to similar 

chemical forms as bulk silver in a pilot WWTP (Ma et al., 2013).

Adapted from Dale et al., 2013.

Figure 1. Representation of Chemical Transformations of Silver Nanoparticles with Sulfur 

in Aqueous Environments

Titanium dioxide ENMs are crystalline and can be as small as a few nanometers in 

diameter. This small size and large surface area provides an excellent catalytic surface. Their

effectiveness at absorbing UV light makes them useful in sunscreens, other cosmetics, and 

coatings (Hendren et al., 2011; Robichaud et al., 2009).

TiO2 nanoparticles are highly reactive with sunlight, and can act as catalysts. This 

behavior can vary depending on the form and surface coatings of nano-TiO2, which has certain 

implications for toxicity (discussed in Section 5.3) (U.S. EPA, 2010b). Nano-TiO2 is fairly 

soluble in water and solubility increases when organic material is present. Studies on 

environmental transformations of nano-TiO2 are limited (Liu et al., 2013). The nanoparticles

have a strong tendency to form aggregates at neutral pH, but aggregation strongly depends on the 

chemistry of the medium (Liu et al., 2013).

Carbon nanotubes can be described as one-atom-thick sheets of carbon rolled into a 

tubular shape. Single-walled CNTs have a diameter of approximately 1 nm, a length of several 

microns, and a tendency to curve. Multi-walled CNTs contain at least two layers, with diameters 

typically ranging from 3 to 50 nm (Petersen et al., 2011). The bonding structure of CNTs gives 

rise to unique properties, such as metallic conduction, semi-conduction, and tensile strength 

approximately 50 times that of steel (Healy et al., 2008).

CNTs have a high affinity to partition to solid media. However, CNTs may stay 

suspended in water in aqueous environments with high concentrations of dissolved organic 
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January 23, 2015

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Wastewater Treatment Data Gaps:

• No data quantifying industrial 

wastewater treatment removal 

performance of ENMs 

• No data characterizing and

quantifying ENMs in biosolids 

produced from industrial wastewater 

treatment, or their associated risks for 

land application

matter. The environmental transformations CNTs undergo are not well understood, and may vary 

depending on the structure of the CNTs (Petersen et al., 2011). The chemistry of the environment 

can also change the physiochemical properties of CNTs, which can affect their behavior. For 

example, high-salinity environments increase CNT aggregation (Eckelman et al., 2012).

5.2 Fate in Wastewater Treatment Plants

Presence and fate of nanomaterials has been 

studied in municipal wastewater, in part to determine how 

well current municipal treatment systems remove ENMs

from wastewater. In general, municipal WWTPs with 

post-secondary treatment should remove the majority of 

nanoparticles from the wastewater by transfer from the 

wastewater to the sewage sludge (biosolids generated as a 

byproduct of wastewater treatment). Research on the 

performance of several treatment processes to remove nanomaterials is discussed below. 

However, the applicability of municipal wastewater research to industrial wastewater is 

unknown. Nanomaterial reactions and transformations may vary depending on the aqueous

environment, and industrial wastewater tends to have higher concentrations and varieties of 

constituents than either municipal wastewater or the ambient environment.

Researchers have studied nanomaterial fate in suspended growth biological wastewater 

treatment and filtration processes. Silver, CNTs, and TiO2 nanoparticles readily attach to 

biomass, resulting in partitioning to the sewage sludge (Wiesner, 2013). More than 90 percent of 

nanomaterials may leave wastewater via this sorption mechanism and subsequent filtration 

during wastewater treatment, but removal efficiency strongly depends on the size of the 

nanomaterials. Smaller nanoparticles, e.g., 30 nm or less, have been detected in WWTP effluent

(Westerhoff et al., 2011).

In addition, nanomaterials tend to aggregate in water, so conventional sedimentation 

processes can be effective in removing them from wastewater. Conventional coagulation and 

sedimentation can remove 20 to 60 percent of total nanoparticles, as measured by mass (Zhang et 

al., 2008). However, typical sedimentation processes cannot remove discrete and stable 

nanoparticles with sizes less than 0.1 micrometers (Westerhoff et al., 2013).

After conventional treatment, tertiary filtration processes can further remove

nanomaterials from the water. For example, WWTPs using microfiltration removed TiO2

nanoparticles more effectively than those using conventional settling methods (Westerhoff et al., 

2011). TiO2 nanoparticles can be removed from wastewater through granular media filtration, 

but removal efficiency is strongly dependent on the filtration media and water chemistry. 

Diatomaceous earth granular filtration was effective in capturing and retaining TiO2

nanoparticles at a concentration of 50 mg/L (Rottman et al., 2013). ERG did not identify research

on nanomaterial removal performance in industrial WWTPs or discrete treatment processes other 

than filtration and sedimentation.

Biosolids generated from wastewater treatment are often used as fertilizers and land 

application of biosolids is considered a potential major source of environmental exposure to 

ENMs (Lowry et al., 2012b; Westerhoff et al., 2013). Researchers have identified and 
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January 23, 2015

Page 15

Toxicity and Exposure Data Gaps:

• Limited toxicity studies on the 

relevant forms and concentrations 

of nanomaterials that may be 

present in complex media, such as 

industrial wastewater

• Limited measurements and hazard 

assessments of ENMs in complex, 

natural systems

• Incomplete understanding of 

environmental and human health 

impacts

characterized silver and TiO2 nanoparticles in U.S. municipal wastewater sludge samples, which 

raises concerns about this potential exposure pathway (Kim et al., 2010; Kim et al., 2012).

5.3 Toxicity and Exposure

Numerous toxicity studies have reported hazards to 

microbial and aquatic organisms; however, research has 

focused on toxicity in controlled laboratory environments 

using ENMs in the forms in which they were created. These 

results are difficult to extrapolate to ecosystems, where 

exposures will likely be at lower concentrations and where 

a diversity of organisms is present (Colman et al., 2013).

Some researchers recommend that fate and toxicity 

measurements should be made in complex, natural systems 

in order to accurately assess hazards (Lowry et al., 2012b; 

Wiesner et al., 2009). It is also important to take environmental transformations into 

consideration, and investigate toxicity in the forms that ENMs exist in an ecosystem (Gottschalk 

& Nowack, 2011; Lowry et al., 2012b).

The primary toxicity mechanism for silver nanomaterials is their dissolution into silver 

ions (Arnaout & Gunsch, 2012; Nowack et al., 2011). Toxic effects from silver nanomaterials in 

humans are only observed at very high concentrations (Nowack et al., 2011), but silver ions 

cause oxidative stress in microorganisms and aquatic organisms (Yang et al., 2012). Because of 

their tendency to dissolve in aqueous media, silver ENMs are often coated to stabilize the 

particles.

Though many toxicity studies to date were conducted using untransformed nanoparticles 

in laboratory environments, toxicity studies that were conducted in simulated natural 

environments (mesocosms) and natural environments have reported fewer toxic effects. This 

suggests that the impacts of ENMs are affected and potentially dampened by environmental

transformations, microbial activity, and the physical and chemical properties of the environment

(Colman et al., 2012; Unrine et al., 2012). Researchers at CEINT have shown that the short-term 

impacts of silver nanoparticles on microbes are attenuated by stream water and sediment

(Colman et al., 2012). However, even low doses of silver nanoparticles may have appreciable 

effects on an environment. For example, a dose of 0.14 mg/kg soil of PVP-coated silver 

nanoparticles applied to wetland mesocosms reduced the microbial and plant biomass each by 35

percent and significantly shifted the wetland microorganism population (Colman et al., 2013).

Silver has been used for over 100 years as an anti-microbial agent. However, it is unclear 

whether silver nanoparticles exhibit novel toxicity mechanisms, outside of generating silver ions.

Therefore, the observed toxicity effects in silver nanoparticles may not differ from those of bulk 

or colloidal silver (Nowack et al., 2011).

There is also concern that nanomaterials may affect biological processes in WWTPs.

Researchers at the University of Adelaide in Australia added silver nanoparticles to aerobic and 

anaerobic wastewater treatment batch reactors to test their effect on microbial populations. They 

found that addition of silver nanoparticles had no effect on nitrification rates and methane 

production, but shifted niche microbial populations in both reactors (Doolette et al., 2013).
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January 23, 2015

Page 16

Titanium dioxide ENMs may exhibit ecotoxicity impacts because of their catalytic 

surface (Hochella, 2013). Nano-TiO2 can be activated by photons (sunlight) to produce reactive 

oxygen species, which cause cellular damage. Nano-TiO2 has been shown to suppress the growth 

of freshwater green algae, which is a concern for freshwater habitats (Cardinale et al., 2012). 

Nano- Researchers have observed photo-dependent mortality effects in model organisms 

exposed to nano-TiO2 in the part per billion range (Alloy & Roberts, 2012; Heideman et al., 

2012). This implies that exposure to sunlight in ecosystems with nano-TiO2 may threaten

organisms in shallow surface waters and soils. However, more research is needed to determine 

nano-TiO2 impacts on aquatic ecosystems and microorganisms in particular.

The toxicity of carbon nanotubes is strongly affected by their structure. An important 

mechanism of CNT toxicity is the production of reactive oxygen species, as the ability to 

generate reactive oxygen species may increase as the size of the nanotubes decrease (Chae et al., 

2011). Various studies have shown that exposure to CNTs can cause growth inhibition, hatching 

delays, and mortality in some aquatic organisms (Petersen et al., 2011).

Currently, human health effects of exposure to ENMs in any environmental medium are 

not fully understood, but risks are presumed to be rather low. However, there have been recent 

efforts to minimize airborne exposure to ENMs in the workplace, due to concern for inhalation 

hazards. In 2013, the National Institute for Occupational Safety and Health (NIOSH) published 

guidelines to minimize workplace exposure to ENMs (NIOSH, 2013). In addition, the 

Occupational Safety and Health Administration (OSHA) published recommended best practices 

and exposure limits for airborne CNTs and TiO2 ENMs (2013). There is concern that multiwalled CNTs generate asbestos-like toxicity, however, this effect can be mitigated by decreasing 

the effective length of the nanotubes (Ali-Boucetta et al., 2013). While airborne exposure is not a 

direct concern for the Effluent Guidelines Program, concerns about airborne ENM 

concentrations may increase future use of wet scrubbers for air pollution control, with possible 

generation of an ENM-containing wastewater.

Humans are exposed to TiO2 and silver nanoparticles outside the workplace because of 

their use in personal care products (e.g., cosmetics and sunscreens), textiles, and other consumer 

goods. Current information indicates that human health risks are low, but there is ongoing 

research into the physiological responses and human health outcomes from exposure to these and 

other types of ENMs.

6. ANALYTICAL METHODS

Methods for detecting, quantifying, and characterizing nanomaterials in any aqueous 

media—let alone a complex, high-strength medium such as industrial wastewater—are not fully 

developed. EPA has not approved standardized methods for sampling, detecting, monitoring, 

quantifying, or characterizing nanomaterials in aqueous media. This is a critical area of research

because the ability to detect and characterize nanomaterials is essential to understanding the 

implications of their release into the environment (U.S. EPA, 2010a). EPA approved methods are 

also needed to support any future potential regulatory structure for industrial discharges of 

ENMs.
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January 23, 2015

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Analytical Methods Data Gaps:

• No EPA standard methods to detect, 

monitor, characterize, and quantify 

nanomaterials in complex 

environmental media

• No current standard sampling 

protocols

• For some ENMs, inability to 

distinguish between naturally

occurring, incidental, and engineered 

forms

6.1 Method Development

Many U.S. and international organizations are 

working to develop guidance and standards for ENM 

characterization. These organizations include, but are 

not limited to standard-setting groups, such as the 

International Standardization Organization (ISO), 

ASTM International, and the American National 

Standards Institute (ANSI); U.S. federal research led by 

the National Institute of Standards and Technology 

(NIST) is also relevant (NNI, 2013b). The Organisation 

for Economic Co-operation and Development (OECD) 

has published guidance for safety testing and characterization of toxicological properties of 

ENMs. It is recognized as a living document, subject to refinement as research into the 

development of nanomaterial test methods progresses (OECD, 2012).

Spectroscopy and spectrometry methods are commonly used and being further developed 

to detect and characterize nanomaterials in the laboratory. Direct visualization and determination 

of nanoparticle size and shape is often accomplished through electron microscopy. Transmission 

electron microscopy (TEM) can produce images with spatial resolutions greater than 0.1 nm, 

while scanning electron microscopy (SEM) can achieve resolutions between 1 nm and 1 μm.

Electron microscopy is often coupled with other measurement techniques, such as energydispersive x-ray spectroscopy (EDS) to determine structure and chemical composition. However, 

most of these methods are not appropriate for analyzing nanomaterials in complex media, such 

as industrial wastewater, typically because they require a simple matrix to accurately measure

samples.

Researchers are developing new tools to characterize nanomaterials in complex media, 

which could then be applied to industrial wastewaters. For example, hyperspectral imagery with 

enhanced darkfield microscopy has been used to detect, characterize, and analyze silver 

nanoparticles in complex waters (Badireddy et al., 2012). EPA’s ORD is using single-particle 

inductively coupled plasma mass spectrometry (SP-ICPMS) to measure concentration and metal 

mass of inorganic nanoparticles in complex aqueous media (U.S. EPA, 2010a, 2011b). Mobile 

application of laser-induced breakdown detection (LIBD) is another promising method for

detecting particle size and number density for nanoparticles in aqueous suspensions (Latkoczy et 

al., 2010). ERG’s literature search identified a larger body of research developing methods to 

characterize metal-containing nanomaterials in complex media as compared to carbon-based 

nanomaterials. Table 5 outlines these and other analytical methods ERG identified. For a 

comprehensive review of analytical methods, see Sampling and Analysis of Nanomaterials in the 

Environment: A State-of-the Science Review (ERG, 2008) and Characterizing Concentrations 

and Size Distributions of Metal-Containing Nanoparticles in Waste Water (U.S. EPA, 2010a).
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Table 5. Common Measurement Methods and Characterization Metrics for ENMs

Measurement Methods

Characterization Metric

Average 

Surface 

Area

Chemical 

Composition

Geometry 

and Shape

Size 

Distribution 

by Diameter

Size 

Distribution 

by Mass

Atomic absorption spectrometry 

(AAS) ✔

Atomic/optical emission 

spectrometry (AES) ✔

Atomic force microscopy (AFM) ✔ 2 ✔ ✔

Brunauer-Emmett-Teller method 

(BET) ✔

Capillary electrophoresis (CE) ✔

Dynamic light scattering (DLS) ✔ 1 ✔

Energy-dispersive x-ray 

spectroscopy (EDX/EDS) ✔

Electron energy loss spectroscopy 

(EELS) ✔

Field-flow fractionation (FFF) ✔ 1 ✔

Surface area sedimentation fieldflow fractionation (Sed-FFF) ✔ ✔

Hydrodynamic chromatography 

(HDC) ✔

Hyperspectral imagery with 

enhanced darkfield microscopy (HI)

Silver 

nanoparticles

only

Silver 

nanoparticles 

only 

Single particle-inductively coupled 

plasma mass spectrometry (SPICPMS)

✔ ✔

Laser-induced breakdown detection 

(LIBD) ✔

Nanoparticle tracking analysis 

(NTA) ✔

Scanning electron microscopy 

(SEM) ✔ ✔

Synchronous luminescence 

spectroscopy (SLS) ✔ 1 ✔

Scanning probe microscopy (SPM) ✔ ✔

Transmission electron microscopy 

(TEM) ✔ 2 ✔ ✔

Sources:(Badireddy et al., 2012); (ERG, 2008); (Latkoczy et al., 2010); (Madden et al., 2006); (U.S. EPA, 2010a, 

2011b). 1 SLS used with DLS or FFF (U.S. EPA, 2010a). 2 Surface area calculated using measurements from TEM and AFM (Madden et al., 2006).

Two current projects to develop field sampling or rapid screening nanoparticle detection 

methods were discussed at SETAC 2012. Researchers at State University of New York at 

Binghamton (SUNY-Binghamton) are developing a novel membrane for application as a sensor 

to isolate, detect, and quantify ENMs in complex environmental matrices (Sadik et al., 2012).

Researchers at Trent University are developing three types of passive sampling devices to detect 

silver nanoparticles in natural waters (Fischer et al., 2012).
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6.2 Sampling Protocols

There are no standard protocols for collecting aqueous samples for nanomaterial analysis. 

Due to their low environmental concentrations, extra consideration should be taken to minimize 

the risk of contamination (ERG, 2008). Nanoparticles are constantly changing various states of 

aggregation and dispersion in aqueous media (Wiesner, 2013), so sample preservation and 

holding times may affect nanomaterial structure and hence the results of subsequent 

measurements. Nanoparticle stability in water is dependent on water chemistry, especially pH, 

which may necessitate development of nanomaterial-specific and water-quality-specific 

sampling protocols.

6.3 Challenges for Monitoring in Complex Environmental Media

Standard methods to monitor and quantify nanomaterials in complex environmental 

media, like industrial wastewater, are not yet developed. Many of the analytical methods 

developed to date characterize nanomaterials in simple media. With additional research, some of 

these methods may be refined and adapted to characterize ENMs in complex environmental 

media. Once standardized detection methods are developed to measure ENM discharges to, and 

concentrations in, the environment, strategies will be needed to distinguish between engineered 

and naturally occurring nanomaterials to fully inform monitoring. Engineered and naturally 

occurring nanoparticles are often indistinguishable under a microscope (Hochella, 2013; Wiesner 

et al., 2011). For example, TiO2 nanoparticles that are identical to manufactured nanoparticles 

have been found in rivers that do not receive wastewater discharges and are remote from 

industrial activities (Hochella, 2013). Therefore, it may be important to assess present

environmental concentrations as a strategy to distinguish the sources of nanomaterials in the 

environment (Gottschalk et al., 2009).

7. NATIONAL NANOTECHNOLOGY INITIATIVE

The NNI is a collaborative, interagency U.S. government research and development 

initiative. The NNI provides a framework for individual and cooperative nanotechnology-related 

activities for 20 federal department and agency units, including EPA, with a range of research 

and regulatory roles and responsibilities. The NNI expedites the discovery, development, and 

deployment of nanoscale science and technology to serve the public good; this is accomplished

through a program of coordinated research and development aligned with the missions of the 

participating agencies (NNI, 2013c). NNI agencies and academic research centers coordinate 

research that may facilitate EPA’s understanding of the potential for wastewater discharges from 

ENM manufacture and processing and potential impacts on the environment.

The 2014 NNI Strategic Plan describes the high-level goals, priorities and specific 

objectives, for at least the next three years, related to nanotechnology research but does not 

provide performance measures or timeframes for meeting the objectives (NSET, 2014). The NNI 

Strategic Plan describes several areas of research focused on the environmental, health, and 

safety implications of nanotechnology (NSET, 2014). A subset of these research areas, listed 

below, may inform EPA’s assessment of the presence and impact of ENMs in industrial 

wastewater discharge:

• Nanomaterial measurement infrastructure
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January 23, 2015

Page 20

• Predictive modeling and informatics

• Human exposure and health

• Environmental health

• Risk assessment and risk management

The NNI Strategic Plan also establishes Nanotechnology Signature Initiatives to spotlight 

topical areas that exhibit particular promise, existing effort, and significant opportunity, and to

accelerate their development (NSET, 2014). One initiative in particular applies to the needs of 

the Effluent Guidelines Program: Nanotechnology for Sensors and Sensors for Nanotechnology. 

This initiative aims, in part, to support research and development methods and devices to detect 

and identify ENMs across their life cycles; this will allow researchers to assess the potential 

human health and environmental impacts of ENMs.

NNI member agencies also fund, in part, much of the ongoing research discussed in this 

section (e.g., research by the National Science Foundation, NIST, NIOSH, OSHA, and others).

In particular, EPA supports research on environmental exposure, impacts, risk assessment, and 

analytical method development through the National Center for Environmental Research and 

extramural grant, fellowship, and research contract programs (NNI, 2013a).

8. SUMMARY OF RESEARCH AND DATA GAPS

Nanotechnology is a rapidly progressing field, expected to continue to grow as the 

number of products and technological applications increases. Some manufacturing and 

processing methods likely generate wastewater, potentially for each of the ENMs of interest 

(silver, nano-TiO2, and CNTs), but the quantity generated and waste management practices are 

not documented. As the number of ENMs and nano-enabled products increases, so will their 

potential to be released into the environment through industrial wastewater and other emissions.

This growth in ENM manufacturing has been accompanied by some research into ENMs’ 

presence and fate in wastewater. Methods for detecting and characterizing nanomaterials in 

complex media, including industrial wastewater, are under development. Research has also 

shown that common treatment technologies used in municipal WWTPs are effective at removing 

nanomaterials from the wastewater, and some nanomaterials (i.e., silver, TiO2) have been 

detected in U.S. WWTP biosolids.

Despite the body of current research, ENMs present a challenge for environmental 

monitoring, risk assessment, and regulation due to their small size, unique properties, and 

complexity. EPA has not approved any standardized methods for sampling, detection, or 

quantification of nanomaterials in aqueous media. New methods and means of quantification 

need to be developed to assess the environmental implications of ENMs and inform future 

regulatory decisions. While some exposure hazards have been demonstrated, the environmental 

and human health risks associated with these materials are largely unknown. Fate and toxicity 

assessments for ENMs, in the forms and relevant concentrations to which organisms will be 

exposed, are needed to accurately determine risk. Industrial wastewater releases of ENMs to the 

environment have not been studied in detail.

The data gaps listed below identify research necessary to assess the hazards and 

implications of the environmental release of ENMs via industrial wastewater discharge. ERG has 

also identified prominent academic, EPA, and international organizations that are currently 
Memorandum

January 23, 2015

Page 21

conducting research in these areas. This information is a summary based on sources reviewed as 

of December 2013, described in Section 2.0.

1. Standard methods and sampling techniques to detect and characterize nanomaterials in 

industrial wastewater

Standard methods to detect and characterize nanomaterials have not been fully 

developed, but are critical for determining the extent of nanomaterials in industrial wastewater

and to support any potential future regulation of their discharge. Development of standard

methods will also support research into the environmental implications of nanomaterials and 

especially aid in research regarding fate and transport needed for more accurate exposure and 

risk assessments.

Many of the analytical methods developed to date characterize nanomaterials in simple

media. With additional research, these methods may be refined and adapted to characterize 

ENMs in complex environmental media, including industrial wastewater. The following 

organizations (among others) are currently researching and developing analytical methods to 

characterize ENMs in simple and complex media.

Table 6. Prominent Organizations Developing Analytical Methods for ENMs

Organization Analytical Method Nanomaterial

EPA Office of Research and Development, 

National Exposure Research Laboratory,

Environmental Sciences Division 

(EPA ORD/NERL/ESD)

Screening and characterization methods Metal-containing 

nanomaterials

Swiss Federal Institute of Aquatic Science 

and Technology (Eawag)

Electron microscopy (SEM, ESEM, 

TEM, EDX); mobile LIBD

Not specified

Center for the Environmental Implications 

of Nanotechnology (CEINT)

Testing protocols; hyperspectral 

imagery with enhanced darkfield 

microscopy

Silver, TiO2, and other 

metal oxides

University of California Center for 

Environmental Implications of 

Nanotechnology (UC-CEIN)

Testing protocols; microscopic and 

spectroscopic methods

Metal oxides, CNTs 

and others not specified

Arizona State University (ASU) Detection and characterization of ENMs 

during water treatment

Silver, TiO2

Like analytical methods, research into real-time monitoring techniques to quantify 

nanomaterials in complex media, like wastewater, is in its infancy. The NNI identified 

development of devices to detect and identify ENMs across their life cycles as a priority, and 

aims to accelerate research through its initiatives. In addition, EPA has supported analytical 

method research through the National Center for Environmental Research and grant programs, 

which fund, in part, some of the ongoing research discussed in this memorandum (NNI, 2013a).

ERG identified the following organizations researching real-time monitoring and field sensing 

methods for complex media:

• ASU (detection of CNTs in complex media).

• Trent University (detection of silver ENMs).

• SUNY-Binghamton (membrane sensor to detect and quantify ENMs).
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Because of their low environmental concentration and tendency to transform in the 

environment, nanomaterial-specific sampling techniques may be needed to ensure that sample

collection does not compromise the quality and reliability of measurement methods and results.

2. Studies on toxicity and exposure to ENMs in complex media, including industrial 

wastewater

Existing laboratory studies of the ENMs of interest have shown toxicity impacts on 

aquatic organisms and the environment. The primary mechanism of toxicity for silver 

nanomaterials is their dissolution into silver ions, which cause oxidative stress in organisms.

However, that ecotoxicity may be attenuated in natural environments. TiO2 nanomaterials and 

CNTs can form reactive oxygen species that cause cellular damage.

Currently, human health effects of nanomaterials in any environmental medium are not 

fully understood, but risks are presumed to be rather low. However, there have been recent 

efforts by OSHA to minimize airborne exposure to nanomaterials in the workplace.

Though numerous laboratory toxicity studies have been conducted, research has focused 

on toxicity in controlled laboratory environments using ENMs in the forms in which they were 

created. ERG did not identify any studies on toxicity from exposures to ENMs in industrial 

wastewater to date. Toxicity studies to date largely have not considered relevant forms and 

concentrations of nanomaterials that may be present in complex media, such as industrial 

wastewater. In addition, few toxicity studies have been conducted within complex media and 

ecosystems, where exposures will likely be at lower concentrations and where a diversity of 

organisms are present (Colman et al., 2013). The complex interactions and interdependencies 

within an ecosystem, especially at the microbial level, will influence the hazard effects of ENMs.

The following organizations are conducting toxicity assessments in complex media 

and/or environments:

• EPA Mid-Continent Ecology Division (assessing toxicity of ENMs to aquatic 

species, particularly nano-TiO2).

• CEINT (silver, zinc, and cerium oxide exposure and toxicity in simulated wetland 

mesocosms).

• Trent University (silver nanoparticles in lake mesocosms—the LENS Project).

3. Universe of facilities, production volumes, and waste generated from ENM 

manufacturing and processing

A major data gap is the lack of information on the facilities manufacturing and processing 

ENMs, as well as production quantities and waste volumes generated. Data collection efforts 

from EPA’s Nanoscale Materials Stewardship Program in 2008 suggest that the number of 

facilities manufacturing or processing ENMs may be on the order of hundreds to several 

thousand facilities. Further, the Nanotechnology Consumer Product Inventory (Project on 

Emerging Nanotechnologies, 2014) identified over 800 consumer products containing 

nanomaterials in the U.S. These data sources indicate that nanomaterials processing spans
Memorandum

January 23, 2015

Page 23

multiple industrial categories, however, little progress has been made to date to quantify 

production volumes.

Although available literature suggests that aqueous waste streams are likely generated 

through manufacturing and processing of CNTs, silver, nano-TiO2, and other ENMs, it is unclear 

how these waste streams are managed and ultimately disposed. Further, ERG did not identify any

studies on the presence or quantity of ENMs discharged in industrial wastewater.

To inform future potential actions and decisions for the Effluent Guidelines Program 

related to nanomaterials, information on ENM production and waste generation and management 

is needed. This information will help EPA accurately assess life cycle and exposure pathways, 

which in turn will better inform hazard and risk assessments (Gavankar et al., 2012; Gottschalk 

et al., 2009).

The following organizations (among others) are conducting research on production

volumes, risk, and life cycle assessments:

• EPA NRMRL (life cycle assessment and impact assessment models).

• EPA OPPT (SNURs for CNTs).

• UC-CEIN (environmental risk management and regulation; risk perception).

• CEINT (estimation of production volumes of metal oxide and carbon ENMs).

• Center for Nanotechnology in Society at ASU (risk perception and public policy).

• Risk Assessment for Manufactured Nanoparticles Used in Consumer Products, or 

RAMNUC (an EPA grant assessing risk associated with zinc oxide, silver, and 

cerium oxide nanoparticles in consumer products).

• Empa (life cycle assessment; release and exposure modeling).

4. Evaluation and characterization of the fate, transformation, and treatment of ENMs in 

industrial wastewaters

The transformation, fate, and treatment of nanomaterials in industrial wastewaters have 

not been studied. However, researchers have studied nanomaterial fate and treatment 

performance to some extent in municipal WWTPs in the U.S. and Switzerland. Common 

treatment technologies employed in WWTPs, such as activated sludge, settling, and filtration, are 

effective at removing nanomaterials from the wastewater, although the nanomaterials likely 

partition to the biosolids and may impact its beneficial use. However, the applicability of the

research on municipal wastewater to industrial wastewater is unknown. Nanomaterial reactions

and transformations may vary depending on the aqueous environment, and industrial wastewater 

tends to have higher concentrations and varieties of constituents than either municipal 

wastewater or the ambient environment. In addition, industrial wastewater quality varies greatly 

between point source categories and industrial processes. 
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January 23, 2015

Page 24

ERG did not identify any organizations currently investigating ENMs in industrial 

wastewater; however, the following organizations are investigating nanomaterials in municipal 

WWTPs:

• ASU (occurrence and removal of TiO2 in full-scale WWTP; silver and fullerenes

in simulated wastewater treatment processes).

• Eawag (silver and gold ENM transformation and removal in activated sludge 

processes).

5. Methods to distinguish between naturally occurring and engineered nanomaterials in 

aqueous media

Once detection methods are established, distinguishing between engineered and naturally

occurring nanomaterials will be critical for monitoring activities, because concentrations of 

naturally occurring and incidental nanomaterials generally far exceed potential releases of ENMs 

into the environment (Hochella, 2013; Wiesner et al., 2009). The ability to distinguish 

engineered and natural nanomaterials will allow for identifying and targeting potential releases 

of ENMs and quantifying the associated risks and hazards. In addition, background levels of 

naturally occurring nanomaterials and nanomaterials that are incidentally generated during 

manufacturing as a result of chemical transformations may need to be considered as part of any 

future potential regulatory structure for industrial discharges of ENMs.

9. REFERENCES

1. Ali-Boucetta, H., Nunes, A., Sainz, R., Herrero, M. A., Tian, B., Prato, M., Bianco, A., & 

Kostarelos, K. 2013. Asbestos-like pathogenicity of long carbon nanotubes alleviated by 

chemical functionalization. Angewandte Chemie International Edition. 52 (8): 2274-

2278. (February 18). www.dx.doi.org/10.1002/anie.201207664. 

2. Alloy, M. & Roberts, A. 2012. Photo-enhanced toxicity of nano-titanium dioxide 

(anatase) on freshwater zooplankton. Presented at the Society of Environmental 

Toxicology and Chemistry North America (SETAC) 33rd Annual Meeting, Long Beach, 

California. Available online at: http://longbeach.setac.org/sites/default/files/SETACabstract-book-2012.pdf. 

3. Arnaout, C. L. & Gunsch, C. K. 2012. Impacts of silver nanoparticle coating on the 

nitrification potential of nitrosomonas europaea. Environmental Science & Technology. 

46 (10): 5387-5395. (May 15). www.dx.doi.org/10.1021/es204540z. 

4. Auffan, M., Rose, J., Bottero, J.-Y., Lowry, G. V., Jolivet, J.-P., & Wiesner, M. R. 2009. 

Towards a definition of inorganic nanoparticles from an environmental, health and safety 

perspective. Nature Nanotechnology. 4: 634-641. 

www.dx.doi.org/10.1038/nnano.2009.242. 

5. Badireddy, A. R., Wiesner, M. R., & Liu, J. 2012. Detection, characterization, and 

abundance of engineered nanoparticles in complex waters by hyperspectral imagery with 

enhanced darkfield microscopy. Environmental Science & Technology. 46 (18): 10081-

10088. (2012/09/18). www.dx.doi.org/10.1021/es204140s. 
Memorandum

January 23, 2015

Page 25

6. Bullis, K. 2013. Quantum Dots Get Commercial Debut in More Colorful Sony TVs. MIT 

Technology Review. Available online at: 

http://www.technologyreview.com/news/509801/quantum-dots-get-commercial-debut-inmore-colorful-sony-tvs/. 

7. Cardinale, B. J., Bier, R., & Kwan, C. 2012. Effects of TiO2 nanoparticles on the growth 

and metabolism of three species of freshwater algae. Journal of Nanoparticle Research. 

14 (8): 1-8. (July 14). www.dx.doi.org/10.1007/s11051-012-0913-6. 

8. Chae, S. R., Therezien, M., Budarz, J. F., Wessel, L., Lin, S. H., Xiao, Y., & Wiesner, M. 

R. 2011. Comparison of the photosensitivity and bacterial toxicity of spherical and 

tubular fullerenes of variable aggregate size. Journal of Nanoparticle Research. 13 (10): 

5121-5127. (July 15). www.dx.doi.org/10.1007/s11051-011-0492-y. 

9. Colman, B. P., Wang, S.-Y., Auffan, M., Wiesner, M. R., & Bernhardt, E. S. 2012. 

Antimicrobial effects of commercial silver nanoparticles are attenuated in natural 

streamwater and sediment. Ecotoxicology. 21 (7): 1867-1877. (October). 

www.dx.doi.org/10.1007/s10646-012-0920-5. 

10. Colman, B. P., Arnaout, C. L., Anciaux, S., Gunsch, C. K., Hochella, M. F., Kim, B., 

Lowry, G. V., McGill, B. M., Reinsch, B. C., Richardson, C. J., Unrine, J. M., Wright, J. 

P., Yin, L., & Bernhardt, E. S. 2013. Low concentrations of silver nanoparticles in 

biosolids cause adverse ecosystem responses under realistic field scenario. PLoS ONE. 8 

(2): e57189. (February 27). www.dx.doi.org/10.1371/journal.pone.0057189. 

11. Dale, A. L., Lowry, G. V., & Casman, E. A. 2013. Modeling nanosilver transformations 

in freshwater sediments. Environmental Science & Technology. 47 (22): 12920-12928. 

(November 19). www.dx.doi.org/10.1021/es402341t. 

12. David, R. M. 2013. Measuring engineered nanomaterials in the environment: A 

consortium view of how to address the problem. Environmental Engineering Science. 30 

(3): 97-100. www.dx.doi.org/10.1089/ees.2012.0327. 

13. Doolette, C. L., McLaughlin, M. J., Kirby, J. K., Batstone, D. J., Harris, H. H., Ge, H., &

Cornelis, G. 2013. Transformation of PVP coated silver nanoparticles in a simulated 

wastewater treatment process and the effect on microbial communities. Chemistry 

Central Journal. 7 (1): 46. (March 4). www.dx.doi.org/10.1186/1752-153X-7-46. 

14. Eckelman, M. J., Mauter, M. S., Isaacs, J. A., & Elimelech, M. 2012. New perspectives 

on nanomaterial aquatic ecotoxicity: Production impacts exceed direct exposure impacts 

for carbon nanotoubes. Environmental Science & Technology. 46 (5): 2902-2910. 

(2012/03/06). www.dx.doi.org/10.1021/es203409a. 

15. ERG. 2008. Eastern Research Group, Inc. Sampling and Analysis of Nanomaterials in the 

Environment: A State-of-the-Science Review [Final Report]. Chantilly, VA. (August 29). 

16. ERG. 2013. Eastern Research Group, Inc. Environmental Engineering Support for Clean 

Water Regulations Programmatic Quality Assurance Project Plan (PQAPP, Rev. 1, 

Approved October 20, 2013). Chantilly, VA. 
Memorandum

January 23, 2015

Page 26

17. Fabrega, J., Luoma, S. N., Tyler, C. R., Galloway, T. S., & Lead, J. R. 2011. Silver 

nanoparticles: Behaviour and effects in the aquatic environment. Environment 

International. 37 (2): 517-531. (February). 

www.dx.doi.org/10.1016/j.envint.2010.10.012. 

18. Fischer, J., Hoque, E., Metcalfe, C. D., & Hintelmann, H. 2012. A comparison of passive 

sampling devices for dissolved and nanoform silver in the aquatic environment. Presented 

at the Society of Environmental Toxicology and Chemistry North America (SETAC) 

33rd Annual Meeting, Long Beach, California. Available online at: 

http://longbeach.setac.org/sites/default/files/SETAC-abstract-book-2012.pdf. 

19. Gavankar, S., Suh, S., & Keller, A. 2012. Life cycle assessment at nanoscale: Review and 

recommendations. The International Journal of Life Cycle Assessment. 17 (3): 295-303. 

(March 1). www.dx.doi.org/10.1007/s11367-011-0368-5. 

20. Gottschalk, F., Sonderer, T., Scholz, R. W., & Nowack, B. 2009. Modeled environmental 

concentrations of engineered nanomaterials (TiO2, ZnO, Ag, CNT, fullerenes) for 

different regions. Environmental Science & Technology. 43 (24): 9216-9222. (December 

15). www.dx.doi.org/10.1021/es9015553. 

21. Gottschalk, F. & Nowack, B. 2011. The release of engineered nanomaterials to the 

environment. Journal of Environmental Monitoring. 13 (5): 1145-1155. 

www.dx.doi.org/10.1039/C0EM00547A. 

22. Healy, M. L., Dahlben, L. J., & Isaacs, J. A. 2008. Environmental assessment of singlewalled carbon nanotube processes. Journal of Industrial Ecology. 12 (3): 376-393. 

www.dx.doi.org/10.1111/j.1530-9290.2008.00058.x. 

23. Heideman, W., Bar-Ilan, O., Peterson, R., Pedersen, J., & Robert, H. 2012. TiO2

nanoparticle exposure and illumination during zebrafish development: Mortality at parts 

per billion concentrations. Presented at the Society of Environmental Toxicology and

Chemistry North America (SETAC) 33rd Annual Meeting, Long Beach, California. 

Available online at: http://longbeach.setac.org/sites/default/files/SETAC-abstract-book2012.pdf. 

24. Hendren, C. O., Mesnard, X., Droge, J., & Wiesner, M. R. 2011. Estimating production 

data for five engineered nanomaterials as a basis for exposure assessment. Environmental 

Science & Technology. 45 (7): 2562-2569. (April 1). 

www.dx.doi.org/10.1021/es103300g. 

25. Hochella, M. F., Lower, S. K., Maurice, P. A., Penn, R. L., Sahai, N., Sparks, D. L., & 

Twining, B. S. 2008. Nanominerals, mineral nanoparticles, and earth systems. Science.

319 (5870): 1631-1635. (March 21). www.dx.doi.org/10.1126/science.1141134. 

26. Hochella, M. F. 2013. Telephone Communication between Michael Hochella, Virginia 

Tech, and Eva Knoth and Kim Wagoner, Eastern Research Group, Inc., Re: Request for 

Information on Nanomaterials Research. (March 15). 
Memorandum

January 23, 2015

Page 27

27. Kim, B., Park, C.-S., Murayama, M., & Hochella, M. F. 2010. Discovery and 

characterization of silver sulfide nanoparticles in final sewage sludge products. 

Environmental Science & Technology. 44 (19): 7509–7514. (September 14). 

www.dx.doi.org/10.1021/es101565j. 

28. Kim, B., Murayama, M., Colman, B. P., & Hochella, M. F. 2012. Characterization and 

environmental implications of nano- and larger TiO2 particles in sewage sludge, and soils 

amended with sewage sludge. Journal of Environmental Monitoring. 14 (4): 1128-1136. 

www.dx.doi.org/10.1039/C2EM10809G. 

29. Latkoczy, C., Kagi, R., Fierz, M., Ritzmann, M., Gunther, D., & Boller, M. 2010. 

Development of a mobile fast-screening laser-induced breakdown detection (LIBD) 

system for field-based measurements of nanometre sized particles in aqueous solutions. 

Journal of Environmental Monitoring. 12 (7): 1422-1429. 

www.dx.doi.org/10.1039/C002020F. 

30. Levard, C., Reinsch, B. C., Michel, F. M., Oumahi, C., Lowry, G. V., & Brown, G. E. 

2011. Sulfidation processes of PVP-coated silver nanoparticles in aqueous solution: 

Impact on dissolution rate. Environmental Science & Technology. 45 (12): 5260-5266. 

(June 15). www.dx.doi.org/10.1021/es2007758. 

31. Levard, C., Hotze, E. M., Lowry, G. V., & Brown, G. E. 2012. Environmental 

transformations of silver nanoparticles: Impact on stability and toxicity. Environmental 

Science & Technology. (February). www.dx.doi.org/10.1021/es2037405. 

32. Liu, X., Chen, G., Keller, A. A., & Su, C. 2013. Effects of dominant material properties 

on the stability and transport of TiO2 nanoparticles and carbon nanotubes in aquatic 

environments: from synthesis to fate. Environmental Science: Processes & Impacts. 15 

(1): 169-189. www.dx.doi.org/10.1039/C2EM30625E. 

33. Lowry, G. V., Espinasse, B. P., Badireddy, A. R., Richardson, C. J., Reinsch, B. C., 

Bryant, L. D., Bone, A. J., Deonarine, A., Chae, S., Therezien, M., Colman, B. P., HsuKim, H., Bernhardt, E. S., Matson, C. W., & Wiesner, M. R. 2012a. Long-term 

transformation and fate of manufactured Ag nanoparticles in a simulated large scale 

freshwater emergent wetland. Environmental Science & Technology. 46 (13): 7027-7036. 

(April). www.dx.doi.org/10.1021/es204608d. 

34. Lowry, G. V., Gregory, K. B., Apte, S. C., & Lead, J. R. 2012b. Transformations of 

nanomaterials in the environment. Environmental Science & Technology. 46 (13): 6893-

6899. (July). www.dx.doi.org/10.1021/es300839e. 

35. Ma, R., Levard, C., Judy, J. D., Unrine, J. M., Durenkamp, M., Martin, B., Jefferson, B., 

& Lowry, G. V. 2013. Fate of zinc oxide and silver nanoparticles in a pilot wastewater 

treatment plant and in processed biosolids. Environmental Science & Technology. 48 (1): 

104–112. (November 22). www.dx.doi.org/10.1021/es403646x. 

36. Madden, A. S., Hochella, M. F., & Luxton, T. P. 2006. Insights for size-dependent 

reactivity of hematite nanomineral surfaces through Cu2+ sorption. Geochimica et 
Memorandum

January 23, 2015

Page 28

Cosmochimica Acta. 70 4095-4104. (August 15). 

www.dx.doi.org/10.1016/j.gca.2006.06.1366. 

37. Mahendra, S., Zhu, H., Colvin, V. L., & Alvarez, P. J. 2008. Quantum Dot Weathering 

Results in Microbial Toxicity. Environmental Science & Technology. 42 (24): 9424-

9430. (2008/12/15). www.dx.doi.org/10.1021/es8023385. 

38. Mueller, N. C. & Nowack, B. 2008. Exposure modeling of engineered nanoparticles in 

the environment. Environmental Science & Technology. 42 (12): 4447-4453. (June 1). 

www.dx.doi.org/10.1021/es7029637. 

39. Mulfinger, L., Solomon, S. D., Bahadory, M., Jeyarajasingam, A. V., Rutkowsky, S. A., 

& Boritz, C. 2007. Synthesis and study of silver nanoparticles. Journal of Chemical 

Education. 84 (2): 322. (February). Available online at: 

http://www.qi.fcen.uba.ar/materias/cqi/2011/infosuplementaria/practicas/practica2/Ag%2

0npartics%20Solomon%202007.pdf. 

40. Musee, N. 2011. Nanowastes and the environment: Potential new waste management 

paradigm. Environment International. 37 (1): 112-128. (January). 

www.dx.doi.org/10.1016/j.envint.2010.08.005. 

41. NIOSH. 2013. U.S. Department of Health and Human Services National Institute for 

Occupational Safety and Health DHHS (NIOSH). Current strategies for engineering 

controls in nanomaterial production and downstream handling processes. Cincinnati, 

OH. (November). DHHS (NIOSH) Publication No. 2014–102. 

42. NNI. 2013a. NSI: Nanotechnology for sensors and sensors for nanotechnology: 

Improving and protecting health, safety, and the environment. Available online at: 

http://www.nano.gov/NSISensors. Accessed: December 12, 2013. 

43. NNI. 2013b. National Nanotechnology Initiative. Standards for nanotechnology. 

Available online at: http://nano.gov/you/standards. Accessed: December 12, 2013. 

44. NNI. 2013c. National Nanotechnology Initiative. About the NNI. Available online at: 

http://nano.gov/about-nni. Accessed: December 12, 2013. 

45. Nowack, B., Krug, H. F., & Height, M. 2011. 120 years of nanosilver history: 

Implications for policy makers. Environmental Science & Technology. 45 (4): 1177-

1183. (February 15). www.dx.doi.org/10.1021/es103316q. 

46. NSET. 2014. National Nanotechnology Initiative Strategic Plan. (February). Available 

online at: 

http://www.nano.gov/sites/default/files/pub_resource/2014_nni_strategic_plan.pdf. 

47. OECD. 2012. Organisation for Economic Co-operation and Development. Guidance on 

Sample Preparation and Dosimetry for the Safety Testing of Manufactured 

Nanomaterials. Series on the Safety of Manufactured Nanomaterials. (December 18). 

Available online at: 
Memorandum

January 23, 2015

Page 29

http://search.oecd.org/officialdocuments/displaydocumentpdf/?cote=env/jm/mono(2012)

40&doclanguage=en. 

48. OSHA. 2013. U.S. Department of Labor Occupational Saftey and Health Administration. 

OSHA fact sheet: Working safely with nanomaterials. (April). Available online at: 

https://www.osha.gov/Publications/OSHA_FS-3634.pdf. 

49. Petersen, E. J., Zhang, L., Mattison, N. T., O’Carroll, D. M., Whelton, A. J., Uddin, N., 

Nguyen, T., Huang, Q., Henry, T. B., Holbrook, R. D., & Chen, K. L. 2011. Potential 

release pathways, environmental fate, and ecological risks of carbon nanotubes. 

Environmental Science & Technology. 45 (23): 9837-9856. (December 1). 

www.dx.doi.org/10.1021/es201579y. 

50. Plata, D. L., Hart, A. J., Reddy, C. M., & Gschwend, P. M. 2009. Early evaluation of 

potential environmental impacts of carbon nanotube synthesis by chemical vapor 

deposition. Environmental Science & Technology. 43 (21): 8367-8373. (November 1). 

www.dx.doi.org/10.1021/es901626p. 

51. Project on Emerging Nanotechnologies. 2014. Consumer Products Inventory. Available 

online at: http://www.nanotechproject.org/cpi. Accessed: June 2, 2014. 

52. Rezić, I. 2011. Determination of engineered nanoparticles on textiles and in textile 

wastewaters. TrAC Trends in Analytical Chemistry. 30 (7): 1159-1167. 

www.dx.doi.org/10.1016/j.trac.2011.02.017. 

53. Robichaud, C. O., Uyar, A. E., Darby, M. R., Zucker, L. G., & Wiesner, M. R. 2009. 

Estimates of upper bounds and trends in nano-TiO2 production as a basis for exposure 

assessment. Environmental Science & Technology. 43 (12): 4227-4233. (May 15). 

www.dx.doi.org/10.1021/es8032549. 

54. Rottman, J., Platt, L. C., Sierra-Alvarez, R., & Shadman, F. 2013. Removal of TiO2 

nanoparticles by porous media: Effect of filtration media and water chemistry. Chemical 

Engineering Journal. 217 (1): 212-220. (February). 

www.dx.doi.org/10.1016/j.cej.2012.11.117. 

55. Sadik, W., Du, N., & Okello, V. 2012. Flexible poly(amic) acid membrane captures, 

isolates & simultaneously detects engineered nanoparticles. Presented at the Society of 

Environmental Toxicology and Chemistry North America (SETAC) 33rd Annual 

Meeting, Long Beach, California. Available online at: 

http://longbeach.setac.org/sites/default/files/SETAC-abstract-book-2012.pdf. 

56. SETAC. 2012. Society of Environmental Toxicology and Chemistry. SETAC North 

America 33rd Annual Meeting Abstract Book. Long Beach, California. Available online 

at: http://longbeach.setac.org/sites/default/files/SETAC-abstract-book-2012.pdf. 

57. U.S. EPA. 2010a. Characterizing Concentrations and Size Distributions of MetalContaining Nanoparticles in Waste Water. Washington, D.C. EPA/600/R-10/117. 
Memorandum

January 23, 2015

Page 30

58. U.S. EPA. 2010b. Nanomaterial Case Studies: Nanoscale Titanium Dioxide in Water 

Treatment and in Topical Sunscreen. Washington, D.C. EPA/600/R-09/057F. 

59. U.S. EPA. 2011a. Nanotechnology basic information. Available online at: 

http://epa.gov/ncer/nano/questions/. Accessed: May 24, 2013. 

60. U.S. EPA. 2011b. Screening methods for metal-containing nanoparticles in water. 

Washington, DC. EPA/600/R-11/096. 

61. U.S. EPA. 2011c. Final 2010 Effluent Guidelines Program Plan. Washington, D.C. EPAHQ-OW-2008-0517-0575. 

62. U.S. EPA. 2013a. Significant New Use Rules on Certain Chemical Substances.

Washington, D.C. (June 26). EPA-HQ-OPPT-2010-0279-0134. 

63. U.S. EPA. 2013b. Nanomaterials EPA is assessing. Available online at: 

http://www.epa.gov/nanoscience/quickfinder/nanomaterials.htm#carnan. Accessed: 

December 11, 2013. 

64. U.S. EPA. 2013c. Nanoscale Materials Stewardship Program. Available online at: 

http://epa.gov/oppt/nano/stewardship.htm. Accessed: May 20, 2013. 

65. U.S. EPA. 2013d. Response to Comments for the Final 2010 Effluent Guidelines 

Program Plan. Washington, D.C. EPA-HQ-OW-2010-0824-0196. 

66. U.S. EPA. 2013e. Significant New Use Rules on Certain Chemical Substances. 

Washington, D.C. (August 7). EPA-HQ-OPPT-2013-0399-0001. 

67. Unrine, J. M., Bertsch, P., Tsyusko, O., Shoults-Wilson, W. A., Lowry, G. V., Colman, 

B. P., & Bernhardt, E. S. 2012. Fate and effects of silver nanoparticles in terrestrial 

environments. Presented at the Society of Environmental Toxicology and Chemistry 

North America (SETAC) 33rd Annual Meeting, Long Beach, California. Available 

online at: http://longbeach.setac.org/sites/default/files/SETAC-abstract-book-2012.pdf. 

68. Westerhoff, P., Song, G., Hristovski, K., & Kiser, M. A. 2011. Occurrence and removal 

of titanium at full scale wastewater treatment plants: implications for TiO2 nanomaterials. 

Journal of Environmental Monitoring. 13 (5): 1195-1203. (May). 

www.dx.doi.org/10.1039/c1em10017c. 

69. Westerhoff, P. K., Kiser, M. A., & Hristovski, K. 2013. Nanomaterial removal and 

transformation during biological wastewater treatment. Environmental Engineering 

Science. 30 (3): 109-117. www.dx.doi.org/10.1089/ees.2012.0340. 

70. Wiesner, M. R., Lowry, G. V., Jones, K. L., Hochella, M. F., Di Giulio, R. T., Casman, 

E., & Bernhardt, E. S. 2009. Decreasing uncertainties in assessing environmental 

exposure, risk, and ecological implications of nanomaterials. Environmental Science & 

Technology. 43 (17): 6458-6462. (September 1). www.dx.doi.org/10.1021/es803621k. 
Memorandum

January 23, 2015

Page 31

71. Wiesner, M. R., Lowry, G. V., Casman, E., Bertsch, P. M., Matson, C. W., Di Giulio, R. 

T., Liu, J., & Hochella, M. F. 2011. Meditations on the ubiquity and mutability of nanosized materials in the environment. ACS Nano. 5 (11): 8466-8470. (November 22). 

www.dx.doi.org/10.1021/nn204118p. 

72. Wiesner, M. R. 2013. Telephone Communication Between Mark Wiesner, Duke 

University, and Eva Knoth and Kim Wagoner, Eastern Research Group, Inc., Re: Request 

for Information on Nanomaterials Research. (March 13). 

73. Windler, L., Lorenz, C., von Goetz, N., Hungerbuhler, K., Amberg, M., Heuberger, M., 

& Nowack, B. 2012. Release of titanium dioxide from textiles during washing. 

Environmental Science & Technology. 46 (15): 8181-8188. (August 7). 

www.dx.doi.org/10.1021/es301633b. 

74. Woo, M. 2013. A quantum dot shows its true colors. American Physical Society. 

Available online at: http://link.aps.org/doi/10.1103/Physics.6.73. 

75. Yang, X., Gondikas, A. P., Marinakos, S. M., Auffan, M., Liu, J., Hsu-Kim, H., & 

Meyer, J. N. 2012. Mechanism of silver nanoparticle toxicity is dependent on dissolved 

silver and surface coating in Caenorhabditis elegans. Environmental Science & 

Technology. 46 (2): 1119-1127. (January 17). www.dx.doi.org/10.1021/es202417t. 

76. Yong, K.-T., Law, W.-C., Hu, R., Ye, L., Liu, L., Swihart, M. T., & Prasad, P. N. 2013. 

Nanotoxicity assessment of quantum dots: from cellular to primate studies. Chemical 

Society Reviews. 42 (3): 1236-1250. www.dx.doi.org/10.1039/C2CS35392J. 

77. Zhang, Y., Chen, Y., Westerhoff, P., Hristovski, K., & Crittenden, J. C. 2008. Stability of 

commercial metal oxide nanoparticles in water. Water Research. 42 (8-9): 2204-2212. 

www.dx.doi.org/10.1016/j.watres.2007.11.036. 
Memorandum

January 23, 2015

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APPENDIX A

KEY QUESTIONS FOR DISCUSSIONS WITH RESEARCHERS

1. Are there analytical techniques/methods available to detect nanomaterials in industrial 

wastewater?

a. Are there methods sensitive enough to detect the nanomaterials at typical levels 

present?

2. Are nanomaterials toxic to human health or aquatic ecosystems?

a. Any studies from demonstrated exposure to nanomaterials in industrial 

wastewater?

b. Are studies demonstrating toxicity in vivo or in vitro, any observing effects in the 

natural environment?

3. Have there been any studies on the presence of nanomaterials in industrial wastewater?

a. Where should we focus our efforts, primary manufacturers or the industries that 

use nanomaterials in development of secondary products? Which would have the 

greatest wastewater discharge impact?

b. Are there certain industries or types of nanomaterials that would typically have a 

wastewater discharge release?

Are there technologies that can treat nanomaterials in wastewater discharge? Are any 

conventional technologies effective at treating nanomaterials?
Memorandum

January 23, 2015

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APPENDIX B2

U.S. COMPANY INFORMATION FOR PRIMARY PRODUCERS OF ENGINEERED NANOMATERIALS

Adapted from (Hendren et al., 2011) Supplemental Information.

Table B-1. Nano-TiO2 Company Information

Company Product Website Other Sources

Altair Nano Nano-TiO2 http://www.altairnano.com U.S. Patent Number 6974566,

http://www.edgar-online.com

DuPont Several TiO2 products 

including Dupont TS-6200, 

fine powders that may include 

nano-TiO2

http://www2.dupont.com/Titanium_Tech

nologies/en_US/index.html

http://www.sec.gov/Archives/edgar/data/30554/000104746910

000945/a2196441z10-k.htm,

http://money.cnn.com/magazines/fortune/global500/2006/snap

shots/451.html

NanoAmor Nano-TiO2 http://www.nanoamor.com http://www.139001.net/company.asp?id-535458

NanoGram Nano-TiO2 — http://www.linkedin.com/companies/nanogram-corporation

Sigma Aldrich 8 nano-TiO2 products: 6 

nanopowders, 1 dispersion, 

and 1 paste

http://www.sigmaaldrich.com/materialsscience/material-scienceproducts.html?TablePage=16376794Email techserv@sial.com

Sky Spring 

Nanomaterials

4 nano-TiO2 powders http://www.ssnano.com/inc/sdetail/316 http://www.globalspec.com/supplier/proficle/SkySpring_Nano

materials

2 The tables in this appendix, adapted from the cited literature source, provide a snapshot of U.S. manufacturers of nanomaterials as identified through patents, 

company websites, and requests for information. ERG has not confirmed whether the companies listed continue to manufacture ENMs.

 
Memorandum

January 23, 2015

Page 34

Table B-2. Nanosilver Company Information

Company Product Website Other Sources

American BioTech Labs Nanosilver solutions—wound 

care, supplements, etc.

http://www.americanbiotechlabs.co

m/

Blue Nano Inc. Nanosilver particles 100 nm http://www.bluenanoinc.com http://www.linkedin.com/companies/bluenano?trk=co_search_results&goback=.cps_1271784864897_1

NanoAmor Polymer-coated nanopowder http://www.nanoamor.com http://www.139001.net/company.asp?id=535458

NanoHorizons Inc. SmartSilverTM http://www.nanohorizons.com http://www.linkedin.com/profile?viewProfile=&key=6385716

3&authToken=ZvLv&authType=OUT_OF_NETWORK&loca

le=en_US&srchindex=38pvs=ps&goback=.fps_*1_*1_*1_*1_

*1_*1_NanoHorizons_C_Y_*1_*1_*1_false_1_R_true_N%2

CG%2CI%2CED%2CFG%2CL%2CDR%2CCC%2CPC_*2_*

2_*2_*2_*2_*2_*2_*2_*2_*2_*2_*2_*2_*2_*2_*2_*2_*2_

*2

NanoMas Technologies, 

Inc.

NanoSilverTM http://www.nanomastech.com/index.

html

http://www.linkedin.com/companies/363757

Quantum Sphere QSI-Nano silver nanopowder http://www.qsinano.com/about.php http://www.qsinano.com/products.php

Sigma Aldrich 2 silver nanopowders http://www.sigmaaldrich.com http://www.sigmaaldrich.com/catalog/Lookup.do?N5=All&N3

=mode+matchpartialmax&N4=silver+nano&D7=0&D10=silve

r+nano&N1=S_ID&ST=RS&N25=0&F=PR

Silver Nanotechnologies, 

Inc.

NanoSilver Solutions — http://snti.en.ec21.com/
Memorandum

January 23, 2015

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Table B-3. CNT Company Information

Company Product Website Other Info Sources

Alfa Aesar 11 types of nanotubes http://www.alfa.com/en/GP140W.p

gm

http://www.manta.com/c/mtkhc1b/alfa-aesar

American Elements 4 types of CNTs, some single, 

some double, and some multiwalled

http://www.americanelements.com/

nanotech.htm

http://www.manta.com/c/mmcmm64/american-elementscorporation

Carbon Solutions, Inc. 7 SWCNT products at various 

purities and solubilities

http://carbonsolution.com/ http://www.manta.com/c/mm2jknd/carbon-solutions-inc

Catalytic Materials LLC 1 grade of MWCNTs http://www.catalyticmaterials.com/ http://www.azonano.com/Suppliers.asp?SupplierID=674

http://www.catalyticmaterials.com/patentportfolio.html

Cnano Technology Single, double, and multi-walled 

CNTs

http://www.cnanotechnology.com/e

n/pro.html

http://www.pangaeaventures.com/news/41-cnanotechnology-commissions-worlds-largest-carbon-nanotubemanufacturing-plant-with-a-capacity-of-500-tons-per-year

Helix Material Solutions 2 types of SWCNTs, 1 DWCNT, 

and 3 types of MWCNTs

http://www.helixmaterial.com/prod

uct.html

—

Hyperion Catalysis Hyperion FIBRIL MWCNTs http://www.hyperioncatalysis.com/

emerging2.htm

http://www.manta.com/c/mm3ht3h/hyperion-catalysis-intl

http://investing.businessweek.com/research/stocks/private/s

napshop.asp?privcapId=29658

Mer Corporation Various single, double, and multiwalled CNTshttp://www.mercorp.com/products2

.htm

http://www.linkedin.com/companies/mer-corporation

MicroTech Nano Various single, double, and multiwalled CNTshttp://www.microtechnano.com/ —

Nano-C SWCNTS in 2 purity grades http://nano-c.com/nanoprod.html http://www.spoke.com/info/c5ZZAgi/Nano-CInc

Nanocs, Inc. SWCNTs and MWCNTs with a 

variety of diameters

http://www.nanocs.com/nanotube.h

tm

http://dnb.powerprofiles.com/profile/931146919/NANOCS

+INTERNATIONAL,+INC-MALDEN-MA

NanoLab, Inc. 6 varieties of single, double, and 

multi-walled CNTs

http://www.nano-lab.com/swnt-apja.htmlhttp://www.manta.com/c/mmgjlkw/nanolab-inc

Nanostructured & 

Amorphous Materials, Inc.

Over 70 varieties of CNTs http://www.nanoamor.com/inc/pdet

ail?v=1&pid=602

http://www.139001.net/company.asp?id=535458

NanoTechLabs MWCNTs with a variety of 

diameters

http://www.nanotechlabs.com/page

s/products/nanotubes.html

http://www.manta.com/c/mtbzf4y/nanotechlabs-inc

SES Research 8 types of MWCNTs, 2 types of 

SWCNTs, and 1 type of DWCNT

http://sesres.com/Nanotubes.asp http://www.manta.com/c/mm6h4zs/ses-research

Skyspring Nanomaterials 8 types of single and multi-walled 

CNTs and many functionalized 

CNTs

http://www.ssnano.com/inc/sdetail/

869

http://www.globalspec.com/supplier/profile/SkySpringNan

omaterials
Memorandum

January 23, 2015

Page 36

Table B-3. CNT Company Information

Company Product Website Other Info Sources

SouthWest Nanotechnologies 4 types of SWCNT products and 

1 specialty MWCNT product

http://www.swentnano.com/ http://www.crunchbase.com/company/southwestnanotechnologies

http://www.linkedin.com/companies/southwestnanotechnologies-inc

Unidym, now merged with 

CNI

3 purity grades of SWCNTs http://www.unidym.com/products/

materials.html

http://www.hoovers.com/company/Unidym_Inc/rfjfyci1.html

Xintek, Inc., or “Applied 

Nanotechnologies”

“Few-wall” CNTs, DWCNTs,

and MWCNTs

http://www.xintek.com/products/m

aterials/index.htm

http://www.manta.com/c/mm8z7g0/appliednanotechnologies-inc

DWCNT: double-walled carbon nanotube

MWCNT: multi-walled carbon nanotube

SWCNT: single-walled carbon nanotube