TOXIC SUBSTANCES CONTROL ACT

INVENTORY REPRESENTATION FOR

PRODUCTS CONTAINING TWO OR MORE SUBSTANCES:

FORMULATED AND STATUTORY MIXTURES

I. Introduction

This paper explains the conventions that are applied to

listings of certain mixtures for the Chemical Substance Inventory

that is maintained by the U.S. Environmental Protection Agency

(EPA) under the Toxic Substances Control Act (TSCA). This paper

discusses the Inventory representation of mixtures of substances

that do not react together (i.e., formulated mixtures) as well as

those combinations that are formed during certain manufacturing

activities and are designated as mixtures by the Agency (i.e.,

statutory mixtures). Complex reaction products are covered in a

separate paper. The Agency\'s goal in developing this paper is to

make it easier for the users of the Inventory to interpret

Inventory listings and to understand how new mixtures would be

identified for Inventory inclusion.

Fundamental to the Inventory as a whole is the principle

that entries on the Inventory are identified as precisely as

possible for the commercial chemical substance, as reported by

the submitter. Substances that are chemically indistinguishable,

or even identical, may be listed differently on the Inventory,

depending on the degree of knowledge that the submitters possess

and report about such substances, as well as how submitters

intend to represent the chemical identities to the Agency and to

customers. Although these chemically indistinguishable

substances are named differently on the Inventory, this is not a

\"nomenclature\" issue, but an issue of substance representation.

Submitters should be aware that their choice for substance

representation plays an important role in the Agency\'s

determination of how the substance will be listed on the

Inventory.

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NOTICE: The policies set out in this document are not final

Agency action, but are intended solely as guidance. They are not

intended, nor can they be relied upon, to create any rights

enforceable by any party in litigation with the United States.

EPA officials may decide to follow the guidance provided in this

document, or to act at variance with this guidance, based on an

analysis of specific circumstances.

II\. Definition of Terms

TSCA identifies two types of materials: (1) chemical

substances and (2) mixtures of chemical substances. The

Inventory lists only chemical substances. It does not list

mixtures; however, the individual components of mixtures are

listed separately.

\"Chemical substance\" is defined in section 3 of TSCA (and

in section 710 of the Agency\'s implementing regulations) by

chemical composition, by source or origin and by identification

of certain categories of materials that are not considered

\"chemical substances\":

\"Chemical substance\" means any organic or inorganic

substance of a particular molecular identity, including \--

\(i\) any combination of such substances occurring in

whole or in part as a result of a chemical reaction or

occurring in nature, \... .

\"Chemical substance\" does not include:

\(i\) any mixture \[710.2(q)\], \...

\"Mixture\" is defined in section 710.2(q) as:

any combination of two or more chemical substances if the

combination does not occur in nature and is not, in whole or

in part, the result of a chemical reaction; except that

\"mixture\" does include:

\(1\) Any combination which occurs, in whole or in part, as

a result of a chemical reaction if the combination could

have been manufactured for commercial purposes without a

chemical reaction at the time the chemical substances

comprising the combination were combined and if, after the

effective date of premanufacture notification requirements,

none of the chemical substances comprising the combination

is a new chemical substance, and

\(2\) Hydrates of a chemical substance or hydrated ions

formed by association of a chemical substance with water.

III\. Inventory Representations with Illustrative Examples

A. Mixtures resulting from blending substances that do not

react.

A blend of two or more substances that has been physically

combined without a chemical reaction is considered to be a

mixture. Such a blend, as a whole entity, is excluded from the

Inventory and premanufacture notification (PMN) requirements for

new chemical substances. Individual components of such a mixture

are separately reportable for the Inventory, however, and are

considered to be \"new substances\" if they are not currently

listed on the Inventory.

Note, however, that salt formation, the creation of ionic

bonds, is considered to be a chemical reaction.

1\. Combinations of materials that are physically

blended or mixed together and do not themselves result in a

chemical reaction are always considered to be mixtures.

The exclusion of these mixtures from the Inventory applies

only to the mixture itself and not to the individual chemical

substances of which the mixture is comprised. Each chemical

substance in a mixture requires a separate Inventory listing.

This approach affords considerable flexibility to processors, who

are allowed to make many different mixtures of Inventory-listed

substances without submitting PMNs.

Example 1. Consider two petroleum streams, each of which is

a complex chemical substance. The two streams are

mixed, but no reaction occurs. The Agency considers

that the combination of the two petroleum streams

themselves is a mixture; each would be listed

separately on the Inventory. A similar example from

the petroleum industry is a blended gasoline to which a

non-reactive corrosion inhibitor has been added.

Example 2. Solid solutions are treated as mixtures; they

are found in certain alloys. For example, gold and

copper form solid solutions in which some of the copper

atoms in the lattice are replaced by gold atoms. In

general, the gold atoms are distributed at random, and

a range of gold-copper compositions is possible,

according to this mixture representation for gold and

copper.

Example 3. Consider a substance that is encapsulated in a

second substance. If the two substances do not react

together, they are considered to be a mixture under

TSCA if they do not constitute an article.

Example 4. A commercial product described as \"coating

material of linseed oil and titanium dioxide,\" formed

by the intentional mixing of two or more substances,

which produces no new substance(s) and results only in

a combination of the mixed substances, is not itself a

substance under TSCA. The component substances of such

mixtures (e.g., linseed oil and titanium dioxide),

however, are individually reportable as substances.

Example 5. Consider a multi-nutrient \"mixed fertilizer\"

that could have been prepared by physically blending

dry products such as urea, superphosphate and potash or

by chemical reaction when liquid ammonium phosphate was

granulated with potash. The Agency considers this

\"mixed fertilizer\" a mixture of urea, superphosphate

and potash regardless of the method used to make it.

Example 6. If commercially-available pine oil, a non-ionic

surfactant, and sodium soap of coconut oil acids are

mixed, without chemical reaction, a combination is

produced that is a mixture. Alternatively, if that

same combination is prepared by mixing pine oil, the

non-ionic surfactant, coconut oil acids and sodium

hydroxide, and carrying out the saponification reaction

to form the sodium soap of coconut oil acids, the

combination would be identical to that manufactured by

mixing the first set of substances without chemical

reaction. The three substances in the final

combination (i.e., pine oil, the surfactant and the

sodium salt of coconut oil) constitute a mixture and

each one is subject to Inventory reporting, regardless

of the method used to manufacture the mixture.

In some cases two substances may be physically intertwined

such that they cannot be separated without breaking bonds of one

or the other. As long as they have not reacted with each other

(i.e., there are no covalent bonds between the two types of

molecules), they are considered to be a mixture. As an extreme

example, two or more intertwined rings (i.e., concatenated

molecules) that had different chemical compositions would be

considered a mixture under TSCA if, in fact, they had no covalent

bonds connecting them.

B. Combinations that are considered to be statutory

mixtures under TSCA

1\. Certain alloys, inorganic glasses, ceramics, frits

and cements, including Portland cement are considered

to be statutory mixtures by the Agency.

Inorganic glasses, ceramics, frits and cements, including

Portland cements, are considered to be statutory mixtures under

TSCA. Manufacturers of these products are not required to report

them. When the initial Inventory was being developed, both EPA

and industry recognized that the individual substances comprising

these mixtures are complex solids and would be very difficult to

identify. Therefore, instead of requiring industry to identify

and report every such substance for the Inventory, several

special categories were created to include the various substances

formed when cement, glass, frit or ceramic are produced. These

categories were reported during the initial Inventory reporting

period and are currently listed on the TSCA Inventory. Each

category contains a definition that describes the various

components of that category in terms of the elements and the

various types of chemical substances that may be formed with

these elements. These categories of substances are:

Cement, Portland, Chemicals \[65997-15-1\* \]

Cement, Alumina, Chemicals \[65997-16-2\* \]

Glass, Oxide, Chemicals \[65997-17-3\* \]

Frits, Chemicals \[65997-18-4\* \]

Steel Manufacture, Chemicals \[65997-19-5\* \]

Ceramic Materials and Wares, Chemicals \[66402-68-4\* \]

For example, a category such as Ceramic Material and Wares,

Chemicals includes any combination of the elements listed in the

Inventory definition, as oxides, borides, carbides, etc., in

multiple oxidation states, or in more complex compounds. The

listed elements included in the definition of each of these

categories are not intended to be inclusive. EPA recognizes that

the list of elements may need to be updated from time to time as

the state of the technology changes.

Example 7. Glass, oxide, chemicals (CASRN 65997-17-3\* )

The definition of this substance is as follows:

Synonym: Chemical substances manufactured in the

production of inorganic glass

This category encompasses the various chemical

substances manufactured in the production of inorganic

glasses. For purposes of this category, \"glass\" is

defined as an amorphous, inorganic, transparent,

translucent or opaque material traditionally formed by

fusion of sources of silica with a flux, such as an

alkali-metal carbonate, boron oxide, etc. and a

stabilizer, into a mass which is cooled to a rigid

condition without crystallization in the case of

transparent or liquid-phase separated glass or with

controlled crystallization in the case of glass-

ceramics. The category consists of the various

chemical substances, other than by-products or

impurities, which are formed during the production of

various glasses and concurrently incorporated into a

glass mixture. All glasses contain one or more of

these substances, but few, if any, contain all of them.

The elements listed below are principally present as

components of oxide systems but some may also be

present as halides or chalcogenides, in multiple

oxidation states, or in more complex compounds. Trace

amounts of other oxides or chemical compounds may be

present. Oxides of the first seven elements listed\*

comprise more than 95 percent, by weight, of the glass

produced.

Aluminum\* Lanthanum

Boron\* Lead

Calcium\* Lithium

Magnesium\* Manganese

Potassium\* Molybdenum

Silicon\* Neodymium

Sodium\* Nickel

Antimony Niobium

Arsenic Nitrogen

Barium Phosphorus

Bismuth Praseodymium

Cadmium Rudibium

Carbon Selenium

Cerium Silver

Cesium Strontium

Chromium Sulfur

Cobalt Tellurium

Copper Tin

Germanium Titanium

Gold Tungsten

Holmium Uranium

Iron Vanadium

Zinc

Definitions such as this may be subject to revision to

reflect changes in the underlying technology.

Alloys that are solid or liquid mixtures of two or more

metals or of one or more metals with certain nonmetallic elements

(e.g., certain carbon steels), are considered mixtures and are

not reportable. However, intermetallic compounds of well-defined

stoichiometry are not considered alloys and should be reported.

2\. Certain combinations of metals, inorganic metal

compounds and inert supports, which are frequently used

for commercial purposes, including for use as solid

phase heterogeneous catalysts, are also considered to

be mixtures for the purposes of the TSCA Inventory.

Example 8. Consider the following supported catalysts:

Pt supported on SiO2, Al2O3 or C

Pd supported on SiO2, Al2O3 or C

Rh supported on SiO2, Al2O3 or C

Ni supported on SiO2, Al2O3 or C

In supported catalysts, the catalytic ingredient is

dispersed in the internal porosity of such supports as

silica gel, alumina or charcoals. Tiny crystallites of

such metals as platinum, palladium, rhodium and nickel

can be formed in the pore structure. Supported

catalysts have much larger surface area of the

catalytic ingredient and are much more resistant to

coalescence of the catalytic ingredient than are

powders. For example, the supported catalyst Pt/C was

prepared by the reduction of PtCl2 adsorbed on

charcoal. Although a reaction was involved in the

preparation, the resultant catalyst is represented in

terms of the products formed and is viewed under TSCA

as a mixture of the two substances, platinum and

carbon.

Example 9. Zeolites are considered for TSCA purposes to be

mixtures of the substances used to manufacture them.

The individual reactant materials used to produce

zeolites are required to be listed separately on the

Inventory. The application of EPA\'s guidance is not

affected by the chemical composition of the zeolite

under consideration.

EPA recognizes zeolites as a family of aluminosilicates

manufactured from a number of commercial processes and techniques

that utilize different proportions of alumina, silica and a

variety of sources of different inorganic and organic cations.

The final zeolites are characterized by covalently linked AlO4

and SiO4 tetrahedra. Zeolites as a class of substances are

considered mixtures under TSCA regardless of the commercial

manufacturing processes and reactants utilized to achieve the

desired chemical composition of the final zeolite structure.

Example 10. Consider a cobalt oxide-aluminum oxide

catalyst. A mixed hydroxide precipitate formed by the

reaction of sodium hydroxide and an aqueous solution of

cobalt (II) nitrate and aluminum nitrate is heated in

air to produce a mixed oxide catalyst. Some of the

cobalt is known to be oxidized to Co(III) in the

process. In this case, cobalt (II) oxide, cobalt (III)

oxide and aluminum oxide would each be reported for the

Inventory. More complex compounds of cobalt and/or

aluminum which may be formed incidentally in the

manufacture of the catalyst mixture are not reported.

C. Hydrates of a chemical substance or hydrated ions formed

by association of a chemical substance with water are

considered to be mixtures of the anhydrous form of the

chemical substance and water.

Hydrated forms of chemical substances are exempt from the

Inventory as mixtures; the anhydrous chemical substances,

however, are reportable for the Inventory. Thus the manufacturer

of hydrated copper sulfate, CuSO4.(H2O)x, would use the anhydrous

form, CuSO4, for Inventory purposes.

Example 11. Na2CO3.10H2O is a mixture of Na2CO3 and H2O;

CuSO4.5H2O is a mixture of CuSO4 and H2O. The anhydrous

forms, Na2CO3 and CuSO4, are subject to reporting under

TSCA.

This provision does not apply to the product of discrete

chemical reactions in which either water or a solvent is a

reactant. For example, hydrates are not formed when water reacts

with an ester to form an acid and an alcohol; likewise,

substances with Chemical Abstracts (CA) names containing the term

\"hydrolyzed\" are not hydrates. Similarly, metal hydroxides

formed by the reactions of metal oxides with water are not

considered to be hydrates for TSCA Inventory purposes.

Example 12. A stable, hydrated complex of two substances

and water is considered to be a mixture of the three

chemicals. In this case, the only chemical interaction

between the three entities is hydrogen bonding, which

EPA does not recognize as bonding for purposes of

chemical identification under TSCA.

Hydrogen bonding does not result in the formation of a new

chemical substance for the purposes of TSCA, even though it has

significant effects on physical properties. For example, the

hydrogen of the chloroform molecule, Cl3CH, forms hydrogen bonds

with an electron pair of the oxygen of the acetone molecule,

Cl3CH O=C(CH3)2, and chloroform-acetone mixtures have higher

boiling points than either pure component. This type of

interaction between two molecules is caused by the

electronegative atoms (such as fluorine, nitrogen or oxygen) in

one molecule and hydrogen atoms bound to electronegative atoms in

another molecule. The hydrogen-bonded materials are considered

to be mixtures for the purposes of TSCA.

Example 13. Consider the reaction of calcium oxide (CaO)

(CASRN 1305-78-8) with water (CASRN 7732-18-5) to form

calcium hydroxide (Ca(OH)2) (CASRN 1305-62-0). The

calcium hydroxide is not a hydrate with water and thus

would require its own Inventory listing.

CaO + H2O Ca(OH)2

Example 14. Consider the reaction of acetyl chloride

(CASRN 75-36-5) with water (CASRN 7732-18-5) to form

acetic acid (CASRN 64-19-7) and hydrochloric acid

(CASRN 7647-01-0). Both products of this reaction

would require Inventory listing.

CH3-COCl + H2O CH3-COOH + HCl

D. Surface Treatment

With this term the Agency generally means the process of

chemically treating the surface of a substance, the substrate,

with another substance so as to enhance some physical property of

the surface of the substrate or to impart chemical reactivity to

the surface (i.e., to functionalize the surface chemically). The

surface-treating substance adheres to the surface by van der

Waal\'s forces, ionic bonds or covalent bonds. If the substance

only alters a physical characteristic, the combination of the

surface treatment substance and the substrate is considered to be

a mixture of two substances, each requiring its own Inventory

listing. If, however, the surface treatment is intended to

impart chemical reactivity, the reaction product is required to

be on the Inventory.

Example 15. Consider the following reaction:

º º Me

º º

º-OH º-O-SiC10H21

silica º + ClSiMe2C10H21 \-\-\--\> silica º

º-OH º Me

silica surface hydrophobic silica

In this example, the silica surface was modified by a

chemical reaction to introduce a material onto the

outermost layer of the silica, contributing the

property of hydrophobicity to the silica without

changing the bulk properties of the silica. This type

of reaction is usually not stoichiometric and would not

be reportable under TSCA.

Example 16. On the other hand, if the surface of the

substrate is functionalized, the reaction product

formed upon reaction of the substrate and surface

treating substance is considered to be a reportable

substance, as illustrated below:

º º

º-OH º-O-Si(CH2)3NH2

glass º + (EtO)3Si(CH2)3NH2 \-\-\--\> glass º

º-OH º

glass surface silane coupling agent

chemically bonded to

surface, providing

amine functionality

The glass filler (particles, spheres, flakes and

fibers) is coated with an organofunctional silane.

Chemical modification of the filler through treatment

with the silane is necessary to promote interfacial

adhesion between the filler and a polymer in making

polymer blends, which allows for uniform dispersion of

the filler in the polymer blend. Such functionalized

glasses, which are formed by chemical reactions, are

reportable substances and not considered mixtures under

TSCA. Generally, when the surface of glass or silica

is modified to incorporate certain functional group(s)

intended to react with other chemical substance(s), the

Agency considers the surface modified glass or silica

to be a chemical substance.

Example 17. If a functionalized glass sphere is coated with

a polymer having reactive sites capable of reaction

with the functionalized glass, the functionalized

glass-polymer reaction product is not reportable. This

type of substance is generally a combination of two or

more materials present as separate phases and combined

to form desired structures that take advantage of

certain desirable mechanical/physical properties of

each component. Chemical reactions merely take place

over the interface region of the polymeric matrix and

the dispersed particulate (filler) phases. The Agency

considers such combinations comprising separate phases

in the polymer blend to be, for purposes of TSCA, the

same as a physical suspension of the functionalized

filler in the polymer. Consequently, this type of

material is considered to be a mixture of the

suspending filler(s) and polymer(s), even though a

reaction was involved.

º º

º-O-Si(CH2)3NH2 º-O-Si(CH2)3NHCO/\\/\\/

glass º \-\--\> glass º

º + HO2C/\\/\\/\\ º

º-O º

Functionalized Polyester The linking moiety at

Glass molecule with the interface between

its acid end polyester and glass

group