ATSDR TOXZINE

Phosphate Ester 

Flame Retardants

CONTENTS

1 . . . . . . . . . . Phosphate Ester Flame Retardants 

 Overview

2 . . . . . . . . . . Phosphate Ester Flame Retardants

 and the Environment

3 . . . . . . . . . . . . . . . Exposure to Phosphate Ester 

 Flame Retardants

4 . . . . . . . . . . Phosphate Ester Flame Retardants 

 and the Body

6 . . . . . . . . . . . . . . . . . Health Effects of Exposure

9 . . . . . . . . . . Phosphate Ester Flame Retardants 

 and Children

10 . . . . . . . . . . . . . . . . . Reducing Risk of Exposure

11 . . . . . . . . . . . . . . . . . . . . . . . . . . Exposure Testing

12 . . . . . . . . . . Governmental Recommendations

13 . . . . . . . . . . . . . . . . . . . . Additional Information

1

PHOSPHATE ESTER FLAME 

RETARDANTS OVERVIEW 

Phosphate ester flame retardants are human-made chemicals 

added to consumer and industrial products for the purpose of 

reducing flammability. 

Phosphate ester flame retardants are composed of a group of chemicals with similar 

properties but slightly different structures. Phosphate esters are typically liquids at 

room temperature; however, some are solids.

Phosphate esters have a multitude of uses including flame retardants, plasticizers, 

hydraulic fluids, solvents, extraction agents, antifoam agents, and coatings for 

electronic devices.◆
PHOSPHATE ESTER FLAME 

RETARDANTS AND THE 

ENVIRONMENT 

Phosphate ester flame retardants are released to the 

environment from industrial sources and disposal of consumer 

products containing flame retardants.

Phosphate ester flame retardants can change chemical composition in the 

environment. There is no specific information available for these phosphate ester 

flame retardants; however, in general, these compounds are degraded by chemical 

reactions in the air. If they attach themselves to particles, they can settle out onto 

the ground. Generally, most phosphate esters are poorly soluble in water and 

adsorb strongly to soils. These compounds are commonly detected in water due 

to their widespread use in commercial products. Phosphate esters are subject to 

biodegradation in aquatic and terrestrial environments. ◆

2

These compounds 

are commonly 

detected in water 

due to their 

widespread use 

in commercial 

products.
3

EXPOSURE TO PHOSPHATE ESTER 

FLAME RETARDANTS

Humans can be exposed by a combination of oral, inhalation, 

and dermal routes.

Ingesting food contaminated with phosphate esters is the primary source of 

exposure. Most foods have been found to contain trace amounts of phosphate ester 

flame retardants due to their wide use in plastics and presence in the environment.

Breathing in contaminated air, both outdoor and indoor, is a potential route of 

exposure. Hydraulic fluid is the primary source of phosphate esters in outdoor 

air. Indoor air can contain phosphate ester flame retardants from certain plastics, 

adhesives, foams, or electronics.

Drinking water contaminated with phosphate esters due to leaching from plastics or 

industrial waste water discharge is another potential exposure route. Additionally, 

you may be exposed if your skin comes into contact with contaminated soil. 

Hydraulic fluid spills or industrial waste water used for agriculture can result in the 

presence of phosphate esters in soil.

Young children may be at a higher risk of exposure since they are more likely to put 

phosphate ester flame retardant treated materials in their mouths. ◆

Breathing in 

contaminated air, 

both outdoor 

and indoor, 

is a potential 

route of exposure.
4

PHOSPHATE ESTER FLAME 

RETARDANTS AND THE BODY 

Currently, we do not know much about phosphate ester flame 

retardants and the body. 

There is virtually no information about the entrance of these substances into the 

body. However, tris (1,3-dichloro-2-propyl) phosphate (TDCP) had been found in 

human tissues and body fluids, so we know that this substance can enter the body 

possibly by inhaling aerosols or dusts or ingesting contaminated food or water.

Adverse health effects seen in humans after exposure to tri-o-cresyl phosphate 

(TCP) indicate that this substance can enter the body and pass into the bloodstream.

Studies found that TDCP, tris(2-chloroethyl) phosphate (TCEP), TCP, and tri-n-butyl 

phosphate (TnBP) can easily pass from the stomach and intestines into the blood 

stream after oral exposure to these chemicals. Studies on dermal exposure found 

that less amounts entered the body through the skin of rats and only very small 

amounts through the skin of pigs.

Neither phosphate 

ester flame retardants 

nor their breakdown 

products seemed 

to accumulate 

in the body based on 

studies in animals.
5

There is no information on how these chemicals leave your body, but based on 

studies in animals, phosphate ester flame retardants may be broken down in the 

body and the breakdown product may be eliminated in the urine. However, there are 

no studies in humans to prove that this actually happens. Neither phosphate ester 

flame retardants nor their breakdown products seemed to accumulate in the body 

based on studies in animals. Most breakdown products were eliminated in the urine 

in 2–3 days. ◆
6

HEALTH EFFECTS

OF EXPOSURE 

Few studies have looked at the health effects of exposure to 

phosphate ester flame retardants.

Almost no information is available regarding these effects in members of the general 

population. However, accidental ingestion of a component of TCP has caused adverse 

effects on the nervous system. There have been a few cases of allergic reactions to 

consumer products that contain triphenyl phosphate (TPP), but a study that examined 

several hundred people exposed to plastics and glues that contained TPP or TCP did 

not find any allergic reactions.

Studies of occupational exposure to phosphate ester flame retardants found that 

long-term exposure of workers to TDCP, TCP, or TPP was not associated with adverse 

health effects. No information was available regarding occupational exposure to other 

phosphate ester flame retardants.
7

One way to learn about the effects of phosphate ester flame retardants is to see 

how they affect test animals. Almost all studies in animals have administered these 

substances orally and generally at levels much higher than what can be expected 

from environmental exposures. TCEP, given to rats for 16 weeks or longer, caused 

brain lesions. When given for 2 years, it also caused lesions in the kidneys. TCEP also 

decreased the fertility of mice that were exposed for 18 weeks before mating. TnBP 

induced lesions in the urinary bladder of rats when given for 10 weeks or longer.

Tris(2-butoxyethyl) phosphate (TBEP) caused liver lesions in rats after the rats ate food 

that contained TBEP for 18 weeks. A study showed that rats that ate food containing 

TCP for 2 years developed lesions in the ovary and adrenal gland and male mice 

developed liver lesions. TCP also decreased fertility in rats and mice. Rats that ate food 

containing TDCP for 2 years developed lesions in the kidneys and liver. The few studies 

that examined the effects of TPP, tri-iso-butyl phosphate (TiBP), and tris(1-chloro-2-

propyl) phosphate (TCPP) in animals did not report significant adverse health effects.
8

There is not enough information available to determine with certainty whether or 

not phosphate ester flame retardants produce cancer in humans. Studies of workers 

employed in the manufacture of TDCP and TCP did not find significant associations 

between exposure and cancer. No information was available regarding the 

carcinogenic potential of the other phosphate esters to humans. Rats that received 

oral doses of TCEP for 2 years developed kidney tumors. Feeding mice a diet that 

contained TCEP for 18 months induced tumors in the kidney, liver, and stomach, and 

also induced leukemia. Long-term administration of TnBP to rats and mice induced 

tumors in the urinary bladder and the liver, respectively. Feeding rats with a diet that 

contained TDCP for 2 years produced tumors in the liver, kidneys, testes, and adrenal 

gland. Neither the EPA nor the Department of Health and Human Services (DHHS) has 

classified the carcinogenic potential of the phosphate esters discussed in this profile.

The International Agency for Research on Cancer (IARC) determined that TCEP is not 

classifiable as to its carcinogenicity to humans. ◆
9

PHOSPHATE ESTER FLAME 

RETARDANTS AND CHILDREN 

Children may be exposed to phosphate ester flame retardants 

in similar ways as adults. 

There are no studies that examined the health effects in children of phosphate ester 

flame retardants. Furthermore, there are no studies that examined the health effects 

of the phosphate ester flame retardants on pregnant women or on their embryo or 

fetus. There is no information regarding transfer of phosphate ester flame retardants to 

the fetus across the placenta in pregnant women. Additionally, no studies have been 

conducted to determine whether phosphate ester flame retardants can be detected in 

human breast milk from women exposed at work or from the general population.

There have been some studies done in laboratory animals on the effects of phosphate 

ester flame retardants in utero. In general, exposure of rodents during gestation to 

TCEP, TnBP, TBEP, TDCP, TPP, or TCPP did not result in adverse effects to the fetuses or 

newborn animals. However, continuous exposure of two generations of mice to TCEP 

reduced the number of male pups born alive in the third generation. A similar study 

with TnBP in rats found that pups born to exposed rats had lower body weight during 

the first weeks of life than pups born to untreated rats. Studies in rats and mice also 

found that exposure to TCP before and during pregnancy can increase the number of 

pups born dead. ◆
10

REDUCING RISK 

OF EXPOSURE 

If you believe that you have been exposed to high levels of 

phosphate ester flame retardants, you should contact your 

doctor or local health department.

In order to reduce the risk of exposure to phosphate ester flame retardants, avoid 

food that is generally high in phosphate ester content as indicated by the current 

market basket for the U.S. Total Diet study.

Additionally, avoid installation or use of materials that are known to contain 

phosphate ester-based flame retardants in indoor environments to minimize 

exposure to them via air and particulate matter. ◆
11

EXPOSURE 

TESTING 

Phosphate ester flame retardants can be measured in blood 

and urine.

This is not a routine test that can be performed in a doctor’s office. You should, 

however, see a physician if you believe that you have been exposed to high levels of 

these substances. No studies have been conducted to measure these chemicals in 

blood samples from groups of people representative of the U.S. general population.

The presence of phosphate ester flame retardants in your blood may indicate 

that you have been exposed to these substances and some amount entered your 

bloodstream. However, the presence of phosphate ester flame retardants in your 

blood does not necessarily indicate that adverse health effects will occur. Additional 

studies are needed to help to determine the health effects associated with exposure 

to these substances. ◆

The presence of 

phosphate ester 

flame retardants 

in your blood does not 

necessarily indicate 

that adverse health effects 

will occur.
12

GOVERNMENTAL 

RECOMMENDATIONS 

Recommendations and regulations are updated periodically 

as more information becomes available. 

For the most current information, check with the federal agency or organization that 

issued the regulation or recommendation.

Some regulations and recommendations for phosphate ester flame retardants 

include the following: 

FEDERAL 

ORGANIZATION

REGULATION OR 

RECOMMENDATION

Occupational Safety and 

Health Administration 

(OSHA)

OSHA set a legal limit of 3 and 5 mg/m3 for 

TPP and TnBP, respectively, in air averaged 

over an 8-hour work day.

U.S. Environmental 

Protection Agency (EPA) 

The EPA has permitted TnBP, TBEP, and TPP 

for use in nonfood pesticide products.
13

ADDITIONAL 

INFORMATION 

If you have any more questions or concerns, please contact 

your community or state health or environmental quality 

department or contact ATSDR at the address and phone 

number below. 

Agency for Toxic Substances and Disease Registry

Division of Toxicology and Human Health Sciences

1600 Clifton Road NE, Mailstop F-57

Atlanta, GA 30329-4027

Toll-free information and technical assistance:

1-800-CDCINFO (1-800-232-4636)
something like: A publication from the Centers for 

Disease Control and Prevention

ATSDR TOXZINE A publication of CDC/ATSDR

CS252399-A