U.S. EPA, TSCA Inventory Representation for Polymeric Substances (1995) (ELR Order No. AD-4001)

• Author: Carolyne R. Hathaway/William K. Rawson/Ann Claassen/Julia A. Hatcher
• Pages: 317-326

TSCA Inventory Representation for Polymeric Substances Page 317

Toxic Substances Control Act

Inventory Representation for

Polymeric Substances

I. Introduction

is paper explai ns the conventions that are applied

to listings of polymeric chem ical substances for the

Chemical Substa nce Inventory t hat is maintained by

the U.S. Environmental Protection A gency (EPA)

under the Toxic Substances Control Act (TSC A).

ese conventions have been in place la rgely without

changes since t he inception of the Inventory. e

Agency’s goal in developing t his paper is to make it

easier for the users of the Inventory to inter pret list ings

for polymers and to understand how new sub stances

should be identied for Inventory inclusion.

Fundamental to the Inventory a s a whole is the prin-

ciple that entries on the Inventory are identie d as

precisely as possible for the commercia l chemical sub-

stance, as repor ted by the submitter. Substances that

are chemically i ndist inguishable, or even identical, may

be listed dierently on t he Inventory, depending on the

degree of knowledge th at the submitters possess and

report about such substance s, as well as how submit-

ters intend to represent the chemical identities to t he

Agency and to cus tomers. Alt hough t hese chemic ally

indistingu ishable substances are named di erently on

the Inventory, this is not a “nomenclature” issue, but

an issue of substance re presentation. Submitter s should

be aware that their c hoice for substa nce representat ion

plays an important role in t he Agenc y’s determination

of how the substance wil l be listed on the Inventory.

A. Polymer Def‌inition

For the purposes of the TSCA I nventory, a substance

must meet the following compositiona l requirements

in order to be considered a polymer:

1) e molecules are char acterized by a sequence

of one or more types of monomer units (where

a monomer unit is the reacted form of the

monomer in a polymer bonded to two or more

other molecules);

2) ere is a molecular weight di stribution

among the molecules present in t he chemica l

substance that is pr imarily attributable to dif-

ferences in the number of monomer units con-

tained in the molecu les.

An Inventory listin g for each poly mer describe s a cate-

gory of possible chemical s that would t that substance

name, instead of just represe nting a sing le molecula r

structure. e molecu les that fall within a given Inven-

tory listing for a polymer va ry in molecular weight;

they may also va ry in composition (i.e., in the ratios

of the startin g monomers and other reac tants used

in the polymer) so long as every monomer or other

reactant mentioned in the na me is, in fac t, part of

each polymer molecule, either as a w hole molecule or

a fragment. Polymers may also c ontain sma ll amounts

of other monomers and reactants th at are not part of

the name; the conventions applicable to th is area are

stated in section II.D.1., e Two Percent Rule, below.

e Agency’s approach to polymer nomenclature gives

manufacturer s and importers considerable exibility

to make minor chan ges in their products without the

requirement of a Premanufacture Noti cation (PMN).

B. Certain Resinous Substances are not

Polymers

Some industry segments h ave trad itional ly regarded

certain resi nous substa nces as polymers, such as the

glycerol or pentaeryt hritol esters of rosin. e Agency

believes that such re sinous substances are simple esters

of rosin (a monobasic acid), which consist of various

adducts (alcohol:acid molecular rat ios of 1:1, 1:2, 1:3,

etc.), depending on the ratio of polyhydric alcohols and

rosin used. ere are neither sequence s of monomer

units in the struc tures nor molecular weight distribu-

tions attributable to various deg rees of polymerization

of monomers and other reactants. ese t ypes of sub-

stances are u sually described for TSCA purposes w ith

non-polymer names that include the term “ester w ith ”

or “esters with... .”

II. Inventory Representation with

Examples

A. Introduction to Monomer-based versus

Structural Repeating Unit Nomenclature

Polymeric substances are represented on t he TSCA

Inventory in one of two ways. Dependin g on the ty pe

of polymer, either a monomer-based representation or

a structura l repeating unit representation (SRU) will

be used. In either cas e, the Agency generally attempts

to name chemical subs tances as specically a s possible,

based on the chemica l structure information known by

the submitter.

NOTICE: e policies set out in this doc ument are

not nal Agency a ction, but are intended solely a s

guidance. ey a re not intended, nor can they be relied

upon, to create any rights enforceable by a ny part y in

litigation with the United States. E PA ocials may

decide to follow the guidanc e provided in t his docu-

ment, or to act at variance with t his guidance, based

on an analysis of spe cic circumstances.