CBIC Control Number p. 1 

365987 

RECEIVED 

OPPT 

2O15AUS 

Chemical Substances When Manufactured or Processed as Nanoscale Materials; TSCA 

Reporting and Recordkeeping Requirements 

(Environmental Protection Agency) 

Docket # EPA-HQ-OPTT-2010-0572 

OBSERVATIONS IN DETERMINATION OF SILICA FUME AS A NANOMATERIAL UNDER THE APRIL 

6, 2015, PROPOSED RULE BY THE ENVIRONMENTAL PROTECTION AGENCY SUBMITTED BY THE 

SILICA FUME ASSOCIATION, USA 

Receive° 

SEP 0 2 2015 

EPA DOCKET CENTER 

Point of Contact: 

Mark Benedict 

Chief Operating Officer/General Counsel 

Silica Fume Association 

38860 Sierra Lane 

Lovettsville, VA 20180 

Phone: 540-822-9455 mbenedict@genesisgrouplIc.com 

Date of Submittal: August 5, 2015 
p. 2 

I. Introduction 

The following document is submitted under the April 6, 2015 proposed reporting and recordkeeping 

requirements for certain nanoscale materials, by the US Environmental Protection Agency (EPA) entitled 

"Chemical Substances When Manufactured or Processed as Nanoscale Materials; TSCA Reporting and 

Recordkeeping Requirements" (Docket # EPA-HQ-OPPT-2010-0572). 

The Silica Fume Association (SFA) was formed in 1998 to assist the producers of silica fume (CAS # 

69012-64-2; fumes, silica) in promoting its usage in concrete. SFA is a not-for-profit trade association 

with offices in Virginia, USA. The group advances the use of silica fume in the concrete infrastructure of 

North America and works to increase the awareness and understanding of silica-fume concrete in the 

private civil engineering sector; among government transportation officials; and in the academic 

community. The Association's goals are two-fold: 1) To provide a legacy of durable concrete structures, 

saving public and private dollars spent on early repair and reconstruction; and 2) to decrease silica fume 

volume in the national waste stream. 

In the late 1990s there was over 112,000 tons of silica fume landfilled annually. That added up to a 

tremendous amount of money and even more land use contributing to the national solid waste steam. 

At that time the domestic silica fume industry began working with EPA to qualify the substance as a 

recycled material under the CPG. EPA placed silica fume on the listing stating the material as having 100 

percent recyclable content. As a result, despite increasing levels of silica fume being produced each year 

no longer is any of the material landfilled, but rather it is being used for multiple applications benefiting 

US society. 

In commenting upon the proposed reporting and recordkeeping requirements pursuant to TSCA section 

8(a) it is the general position of the SFA that silica fume is not a "reportable chemical substance" under 

the proposed rule and should not be subject to its scope of action. 

II. Background 

SFA has had extensive working relationships with the public sector since its inception. In 1999, the 

group was awarded a cooperative agreement (DTFH61-99-X-00063) by the US Federal Highway 

Administration to evaluate and promote the use of silica fume high performance concrete in the 

nation's infrastructure. This was followed by two additional awards over the next 3 years totaling $1.5 

million. In 2002, SFA worked with the US Environmental Protection Agency (EPA) for inclusion of silica 

fume high performance concrete on the Comprehensive Procurement Guideline (CPG) for Products 

Containing Recovered Materials, resulting in its statutory inclusion in April of 2004. In 2012 the US 

Department of Transportation asked SFA to partner with the Federal Railroad Administration (DTFR53- 

12-C-00010) to develop silica fume high performance concrete mixes for use in rail ties to prevent train 

derailments resulting from deterioration of the rail seat. Phase I of that project was completed in 2014 

and is to be followed with final qualification of the materials in concrete rail tie prototypes later this 

year. As evidenced by SFA's active participation in multiple public contracts and regulatory rulemakings, 

over the past two decades, the association is well positioned to respond to the proposed rule by EPA as 

it applies to silica fume and nanoscale materials. 

One of the primary uses of silica fume is as a key ingredient in high performance concrete mixtures that 

can be used for multiple infrastructure applications ranging from marine bridges to concrete rail ties. 

The following is a short review of that application as a case example that can be helpful in understanding 

the unique characteristics of the material, as well as suggesting appropriate guidelines for its treatment 

under EPA's proposed rule. 
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Figure 1. Origin and Production of Amorphous Silica Polymorphs , Including Silica Fume 

Silica fume (CAS # 69012-64-2) is an amorphous (non-crystalline) polymorph of silicon dioxide. Silica 

fume is collected as a by-product of the silicon and ferrosilicon alloy production and consists of spherical 

particles with an average particle diameter of 150 nm. The main field of application is as pozzolanic 

material for high performance concrete because of its fine particles, large surface area, and the high 

Si02 content. The individual particles are extremely small, approximately 1/100th the size of an average 

cement particle. The bulk density of silica fume depends on the degree of densification and varies from 

130 (undensified) to 600 kern 3 . The specific gravity of silica fume is generally in the range of 2.2 to 2.3. 

The specific surface area of silica fume ranges from 15 to 30 m 2/g. In the carbothermic manufacturing 

process of silicon metal/ferrosilicon, quartz mineral is reduced to silicon by carbonaceous material. 

During this reaction, silicon monoxide gas (SiO) is formed as an intermediate. This, in contact with 

oxygen, oxidizes to silicon dioxide (Si02) which condenses forming ultra-fine spherical particles referred 

to as silica fume. The purity of commercial silica fume is typically > 80% , and will contain small amounts 

of impurities, mainly carbon, silicon carbide, diiron trioxide, calcium oxide, magnesium oxide and sodium 

oxide (up to 5%). Silica fume may also contain traces of crystalline silicon dioxide in the form of quartz 

or cristobalite. These impurities originate mainly from carry-over of the off-gas from the production 

process. The concentration of quartz in silica fume is usually below 1.5 wt%, and < 0.1wt% in its 

respirable form. During collection, cooling and bagging, the primary particles tend to form larger 

agglomerates. The solubility of silicon dioxide in water is low. 

III. Observations 

1. It is suggested that guidelines being proposed by the EPA to exclude nonclays and zinc oxide from 

the reporting requirement are also applicable to silica fume. When silica fume is viewed individually 

from other silica types the material has been "well characterized" and "presents nominal exposure 

potential". Silica fume meets both of these guidelines as applied by EPA. Information collected on 

the material through the reporting requirement would be redundant and of limited value.--The US 

silica fume industry supports the exclusion of nanoclays, zinc oxide, and other chemical substances from 

the reporting requirements of the proposed rule because they have been "well characterized" and/or 

"present little exposure potential". Application of these guidelines to other chemical substances will 

ensure the scope of the reporting requirement provides EPA with helpful information and avoids placing 

an undue burden on US companies - especially small manufacturers to report data of little value. 

P. 3 
p. 4 

Silica fume has been under intense scrutiny concerning its nanoscale properties and exposure potential 

resulting in an vast accumulation of laboratory and field findings that are available to EPA, business, and 

the general public. Much of this data has already been provided and reviewed by the government, as 

well as the broader business and academic sectors. In 2003 EPA added cement and concrete containing 

silica fume to the recycled materials listing under the auspices of the Resource Conservation and 

Recovery Act (RCRA) accepting silica fume as a recycled waste product. This began a detailed sharing of 

information by industry with federal agencies concerning the properties of silica fume, subsequently 

funded in multiple federal research contracts. To report on the material under the proposed rule for 

TSCA Section 8(a) would be redundant and of little value to the federal government. 

a) Separate Consideration of Amorphous Versus Crystalline Silicas: Silica fume should be viewed 

separately from other silica types in the determination of whether it is an excludable chemical 

substance not needing to be reported under the TSCA Section 8(a) rule, or other future rulemaking on 

nanomaterials. EPA states that the parameters used in the rule to identify reportable chemical 

substances are not to be a definition of what is a nanoscale material. But, once finalized, these 

parameters will form a basis for what will be considered as key elements in defining nanoscale materials 

in possible future broader rulemaking. SFA shares the government's belief that it is important to 

establish a foundation of knowledge to support scientifically and technically informed decision making 

to advance the proposed TSCA section 8(a) reporting rule, as well as future nanomaterial regulations. 

As noted, silica fume is an amorphous (non-crystalline) polymorph of silicon dioxide. Amorphous silicas 

share little in common with crystalline silicas. Unlike crystalline silicas, which have long been recognized 

as a cause of occupational disease, amorphous silicas are not associated with any permanent or 

debilitating lung or other disorders. For more than 30 years, silica exposure levels and their health 

effects have been intensively studied. As a result, crystalline silicas have become heavily regulated by 

OSHA, ACGIH, NIOSH, and many other organizations. In 2006, the ACGIH withdrew the threshold limit 

values (TLV) of respirable silica, (Amorphous silica fume, Chemical Abstracts Service Registry Number 

69012-64-2); thereby supporting the industry practice of following the prescribed cautions in the MSDS 

for silica fume and treating silica fume as a "nuisance dust" in relation to worker safety. It is considered 

to pose minimal risk of pulmonary fibrosis (sillicosis). Animal inhalation studies with intentionally 

manufactured synthetic amorphous silica showed at least partially reversible inflammation, granuloma 

formation and emphysema, but no progressive fibrosis of the lungs. Epidemiological studies do not 

support the hypothesis that amorphous silicas have any relevant potential to induce fibrosis in workers 

with high occupational exposure to these substances. 

In June 2015 the European Commission's Scientific Committee on Consumer Safety (SCCS) published an 

opinion on the use of 4 categories of synthetic amorphous silica (SAS - Silica, Hydrated 3 Silica, Silica 

Sylilate and Silica Dimethyl Silylate) in cosmetics stating insufficient evidence is available to decide if the 

use of silica nanomaterials in cosmetics is safe. SCCS concluded that the evidence, from both 

submissions and existing scientific literature, is technically inadequate to determine the safety of the 

materials in its application as a cosmetic ingredient. Importantly, the decision states that, within a SAS 

category, the materials have significant differences in the experimental values for certain physicochemical properties. SCCS could not use data from one material for another stating that a case-by-case 

approach must be used instead, leading to several data gaps. Under this proposed rule it is critical that 

evaluation of possible nanomaterials is completed in a fashion which fully recognizes these technical 

differences between categories of silica. EPA has expressed this concern in the proposed rule, stating 

the technical review "of multiple nanoscale forms of the same chemical substance would, in some cases, 

need to report separately for each discrete form of the reportable chemical" and that the government's 
intent for the reporting requirements under the proposed rule "is to focus reporting on intentionally 

manufactured chemical substances at the nanoscale". This focus on "intentionally manufactured" 

substances is especially important to consideration of silica fume which is an unintended byproduct 

from the production of metallurgical silicon metal and ferrosilicon. Silica fume is not intentionally 

manufactured like other forms of silica and that distinction alone, justifies, an individual review. 

b) Characterization of Amorphous Silica Fume: Information on silica fume has been well characterized 

since its widespread use in products, such as high performance concrete, began 3 decades ago. Noncrystalline (amorphous) silica particles - including silica fume - are generally regarded to be safe, with no 

chronic effects. Beyond the concrete applications for silica fume, other types of amorphous noncrystalline silica particles are increasingly used for numerous applications including construction work, 

medical diagnosis, cancer therapy and drug delivery. They are being added to cosmetics and food. 

However, differences do exist, both technically and under the proposed review criteria of this 

consultation, that separates silica fume from other silica nanomaterials. After nearly 30 years of use a 

large body of scholarly research exists demonstrating the significant differences between silica fume and 

other silica nanomaterials. For example, please refer to the recent OECD publications about silica 

nanomaterials (Safety of manufactured NM, Dossier on silicon dioxide (NM 200), Part 1-6, June 2015). 

Under this review 6 different forms of manufactured SAS-NM were investigated by the international 

sponsors and did not result in any hazard classification. 

Silica fume does not meet the classification criteria as physical, environmental or health hazard in 

accordance with the Globally harmlonized System (GHS). Silica fume does not meet the criteria for 

classification in any hazard class according to REACH and to Regulation (EC) N01272/2008 (CLP). Silica 

fume is generally considered a nuisance dust of low toxicity, and consequently it is considered to pose 

minimal risk of pulmonary fibrosis (silicosis). Silica fume is an inorganic substance which is not 

biodegradable. The material is not regarded as a hazardous or bioaccumulative contaminant. 

c) Potential For Exposure: Silica fume presents little exposure potential to consumers, in the work place, 

or in an environmental release. As noted earlier, it is a key ingredient of high strength concrete, and as 

such can be found in hardware stores, which is available to consumers in very limited quanities. It is 

important to understand that silica fume as a pozzolanic material is consumed during the concrete 

reaction. It is therefore an intermediate. Furthermore, there is no residual silica fume in end-products 

manufactured using the substance. There is no release of nanoparticles because silica fume has 

chemically reacted to calcium silicate hydrates, and even surplus unreacted silica fume is incorporated in 

the solid concrete matrix. A release is not expected even after end-of-life and demolition. Worker 

exposure is also nominal at manufacturing sites and/or laboratories (including academic settings). Silica 

fume is not acutely toxic via the oral, inhalation or dermal route. Silica fume is not a skin or eye irritant, 

and for the respiratory system. Like any other dust, the dust from silica fume may cause non-specific 

mechanical irritation to the eyes and respiratory tract. Finally, there is little exposure potential for 

environmental releases. Manufacturing occurs under controlled conditions, with only very small 

releases to air and waste water. Environmental exposure is severely limited by applying air and waste 

water abatement technologies to remove dust, unreacted substance and reaction products. 

In the use of silica fume, the potential for human exposure depends on the way the substance is being 

used and is likely to be greater in situations of free handling in powder form in the workplace where it 

may potentially become airborne, than when the substance is embedded in a structure or product such 

as concrete. To control exposure to any nanoscale chemical substance the most effective approach is to 

contain the processes involving the sources of the materials. Techniques for measuring and protecting 

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against exposure to nanoscale silica fume in working environments and general public exposure to 

embedded products are being optimized, for example through numerous European Commission-funded 

projects, and partnership projects between the US government and US silica fume industry. The result is 

that the potential for human or environmental exposure is very limited. 

Silica fume does not release airborne nanomaterials upon handling in accordance with EN 15051 

dustiness tests. Furthermore, focusing on occupational exposure where the primary route of exposure 

is by inhalation, 11 longitudinal and cross-sectional studies from the Norwegian smelting industry did 

not show any specific impact of silica fume exposure. Based on the intrinsic physico-chemical properties 

of SF, ecotox-test, epidemiological studies, and the non-wide spread use, human exposure to silica fume 

is adequately controlled and silica fume should not be prioritized for further action. 

This is supported by measurement of nanoscaled dustiness, through criteria defined by the test 

institute IGF (Institut NI. Gefahrsstoffforschung, Bochum, Germany): "Only dustiness numbers above a 

particle number concentration ~ 1500 particles/cm' (NOT blank corrected) and at least a blank corrected 

number concentration two times as high as the respective background concentration is regarded as 

significant." Under this review, both, the silica fume high grade and low grade sample revealed particle 

number concentrations well below this threshold, and can be declared as "does not release 

nanoparticles". When the experiments would be performed in real aerosol background concentrations 

the product-generated nanoparticles would not be detectable. 

Figure 2. Release of airborne nanoparticles when applying the continuous drop method according to the 

European dustiness standard EN 15051. 
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These results are in line with previous dustiness tests of the same material, showing that despite the 

small primary particle size . the dustiness in the respirable size fraction is rather low leading to the 

conclusion that silica fume is not a hazardous material 

P. 7 

Figure 3. Dustiness tests on undensified and densified silica fume according to the European dustiness 

standard EN 15051. Rotating drum method. 

2. It is suggested, that chemical substances that only have trace amounts of primary particles, 

aggregates, or agglomerates in the size range of 1 - 100 nm, and do not exhibit unique characterstics 

or properties because of particle size, should not be defined as a nanomaterial for purposes of this 

rule. In making that clarification a threshhold value should be established for trace amounts to 

explain how much nanomaterials are required present in a bulk material to bring the chemical 

substance under the namomaterials definition .-- 

For purposes of the pending EPA proposed rule on nanomaterials reporting, nanomaterials are generally 

described as chemical substances containing primary particles, aggregates, or agglomerates in the size 

range of 1 - 100 nm in at least one dimension. The description requires further clarification. Parameters 

are needed to determine how much nanomaterial is required to bring a bulk material under the 

consultation document's definition, and thereby subject to its scope of actions. There is no 

harmonized test method defined in the proposed rule. 

The Proposed Rule says that it will not apply to chemical substances that contain 'trace amounts of 

primary particles, aggregates, or agglomerates in the size range of 1-100 nm'. EPA has not defined what 

'trace amount' means. The proposed rule does not define a threshold where a given material is 

classified as a nanomaterial. Without defining a specific threshold, it will be difficult to segregate a 

majority of bulk materials that contains a small fraction of particles below 100nm. It is not clear under 

the EPA proposed rule whether particle size distribution is based on volume or number. It is necessary 

to know the standards being used by the agency to exclude certain substances from the reporting 

requirements so that a uniform criterion is used in reviewing other substances. 

3. In the proposed rule EPA suggests that a company who intends to manufacture a discrete form of a 

reportable chemical substance would report at least 135 days before commencement of manufacture 

or processing. We believe that the 135 day reporting period is non-competitive and not workable 

with the practices of many small manufacturers.--Reference by EPA to the Pre-manufacture Notice 

(PMN) process as justification for the 135 day period fails to recognize the difference between PMN, 

which is a notification process, versus the proposed rule which is a reporting requirement. Much less 

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time is required for the latter. Further, the scope of this proposed rule will potentially affect many small 

manufacturers. It should be structured to accommodate the short and quick turnaround times typical of 

these small companies for them to remain competitive. At present, PMNs are submitted at least 90 

days before commencing manufacture. Within this context it would be appropriate to use a 30 - 60 day 

period for the TSCA Section 8(a) proposed rule. 

If silica fume is not included under the exemption listing that EPA is considering for materials such as 

nanoclays and zinc oxidexe respectfully ask for clarification on the rationale for that decision. SFA 

appreciates the opportunity provided by EPA to comment upon the TSCA Section 8(a) proposed rule. 

We hope these observations will be useful to your deliberation. Thank you.