v>EPA

EPA Document# EPA-740-D-24-017
December 2024

United States	Office of Chemical Safety and

Environmental Protection Agency	Pollution Prevention

Nontechnical Summary of the TSCA
Draft Risk Evaluation for 1,3-
Butadiene

^,ch2

C4H6 (CASRN: 106-99-0)

Why Is EPA Providing This Document?

EPA evaluated the risks of 1,3-butadiene to
human health and the environment under the
Toxic Substances Control Act (TSCA). This
document summarizes the results of the draft
risk evaluation.

What Is 1,3-Butadiene and How Is it Used?

1,3-Butadiene is a colorless gas produced from
fossil fuel (petroleum/petrochemical)
processing. It is primarily used as a building
block to make plastics and synthetic rubbers
like latex. Every year, billions of pounds of
1,3-butadiene are produced, imported, and used
throughout the United States.

How Might Persons Be Exposed to 1,3-
Butadiene?

Exposure to 1,3-butadiene can occur in and
near workplaces that manufacture plastic
materials and synthetic rubber products like
tires or that use it in the production of other
chemicals. 1,3-Butadiene is primarily released
into the air from manufacturing and processing
facilities. Workers can be exposed by breathing
1,3-butadiene while making plastic or rubber
products or otherwise using 1,3-butadiene in
the workplace. Once formed into plastics and
synthetic rubber, 1,3-butadiene is not released.

1 Anemia is a blood disorder that occurs when the body
does not produce enough healthy red blood cells.

Airborne 1,3-butadiene does not travel far
before quickly breaking down into smaller
chemicals, including formaldehyde. It will not
settle onto land or into water. 1,3-Butadiene is
also formed from burning tobacco, wood, and
fuel. As a result, people can be exposed to 1,3-
butadiene by breathing in air near
manufacturing and processing facilities,
automobile exhaust, fires, as well as from
smoking.

How Has EPA Assessed 1,3-Butadiene under
TSCA?

In December 2024, EPA published the Draft
Risk Evaluation for 1,3-Butadiene that
evaluated risks to the following groups:

•	workers in operations that manufacture
and process 1,3-butadiene and workers
that use products containing 1,3-
butadiene;

•	people who live near 1,3-butadiene
release sites; and

•	people who may be more susceptible to
1,3-butadiene due to age (including
young children), sex, genetic variations,
health conditions, or other factors.

The 2024 draft risk evaluation also assessed
risks to the environment, including aquatic and
terrestrial wildlife.

Is 1,3-Butadiene Harmful to People?

Based on human studies, exposure to 1,3-
butadiene can cause leukemia, a type of blood
cancer. Based on laboratory animal studies,
exposure to 1,3-butadiene might cause reduced
birthweight and anemia1 in people. Workers
and others nearby2 who breathe excess levels
of 1,3-butadiene can be at risk for harmful
blood effects and reduced birthweight
pregnancies. They can also be at risk for
cancer. Communities living near facilities that
release 1,3-butadiene to the air can also be at

2 Under TSCA, "occupational non-users" are workers in
close proximity with other workers using an industrial
product such as 1,3-butadiene.

Page 1 of 3

-------
risk for these effects. However, use of
household items containing plastic or synthetic
rubber made from 1,3-butadiene does not
present risk to human health.

Is 1,3-Butadiene Harmful to the
Environment?

1,3-Butadiene is not expected to be harmful to
the environment. Exposure is not expected via
water or soil while exposure to wildlife via air
is not expected because 1,3-butadiene quickly
breaks down. Therefore, EPA found that 1,3-
butadiene does not present an unreasonable risk
to the environment under its TSCA conditions
of use (COUs).3

What Is EPA's Draft Risk Determination
for 1,3-Butadiene under TSCA?

EPA has preliminarily determined that 1,3-
butadiene presents an unreasonable risk of
injury to human health. It does not present an
unreasonable risk of injury to the environment.

EPA considered the following factors when
determining unreasonable risk from 1,3-
butadiene:

•	the nature and severity of the health and
environmental effects;

•	the duration, amount, and frequency of
1,3-butadiene exposures;

•	the populations exposed; and

•	the Agency's confidence in the risk
estimates.

The following TSCA COUs significantly
contribute to the unreasonable risk:

•	Domestic manufacturing

•	Import

•	Processing as a reactant - intermediate

•	Processing as a reactant - monomer
used in polymerization process

•	Processing: incorporation into
formulation, mixture, or reaction

product - processing aids, not otherwise
listed

•	Processing - incorporation into
formulation, mixture, or reaction
product - other

•	Processing - incorporation into article -
polymer in - rubber and plastic product
manufacturing

•	Processing - repackaging

•	Processing - recycling

•	Commercial use - laboratory chemicals

•	Disposal.

The following TSCA COUs do not
significantly contribute to the unreasonable
risk:

•	Industrial use - adhesives and sealants;

•	Commercial use - fuels and related
products

•	Commercial uses associated with
plastic and rubber (e.g., tires, toys,
furnishings)

•	Commercial use - automotive care
products

•	Commercial use - lubricant additives,
including viscosity modifier

•	Commercial use - paints and coatings,
including aerosol spray paint

•	Commercial use - adhesives and
sealants, including epoxy resins

•	Consumer uses associated with plastic
and rubber (e.g., tires, toys, furnishings)

•	Distribution in commerce.

How Will EPA Protect Human Health from
1,3-Butadiene under TSCA?

If, after public comment and review of the draft
risk evaluation, EPA determines that 1,3-
butadiene presents an unreasonable risk of
injury to human health or the environment,
TSCA requires the Agency to address the
unreasonable risk. Regulations could include
banning or restricting 1,3-butadiene in specific
uses or labeling or recordkeeping requirements.

3 Under TSCA, COUs are the specific circumstances, "as
determined by the Administrator, under which a
chemical substance is intended, known, or reasonably

foreseen to be manufactured, processed, distributed in
commerce, used, or disposed of."

Page 2 of 3

-------
For More Technical Information, Including
Previous EPA Actions, See the Following:

•	Risk Evaluations for Existing Chemicals
under TSCA

•	EPA's 2024 Draft Risk Evaluation for
1.3 -Butadiene

•	The 2024 draft risk evaluation and
supporting materials can be found in
docket EPA-HO-QPPT-2024-0425

Page 3 of 3

-------