Uses Of Chemicals

Polybrominated diphenyl ethers (PBDEs)

This article was researched and written by a student at Mount Holyoke College participating in the Encyclopedia of Earth's (EoE) Student Science Communication Project. The project encourages students in undergraduate and graduate programs to write about timely scientific issues under close faculty guidance. All articles have been reviewed by internal EoE editors, and by independent experts on each topic.

Introduction

 

caption The basic structure for PBDEs. (Source: Wikipedia)

 

Polybrominated diphenyl ethers or PBDEs have been used commercially as flame-retardants in electrical appliances, carpets, furniture, and in polyurethane foam since the 1970s. Since PBDEs do not bind chemically to polymers in textiles or plastics, they can leach out and be washed down sink and shower drains or become part of household or office dust, where they can be present in high concentrations. Also, PBDEs can be introduced into water and air during manufacture or combustion of household appliances. They are bioaccumulative and lipophilic. They are found in highest concentrations, therefore, in the fats of top predators worldwide. Much of the concern surrounding PBDEs exists because they are found in human breast milk. Many PBDEs have been banned in Europe and in some states in the United States (U.S.). Certain PBDEs, however, continue to be produced globally at a rate of 200,000 tons annually—the U.S. being one of the highest producers and consumers worldwide.

Types of PBDEs

There are potentially 209 congeners of PBDEs. Congeners differ by the number and location of bromine atoms. Among the PBDEs most widely used and most prevalent in animal tissues are the commercial mixtures: penta-, octa-, and deca-BDE.

  • Penta-BDEs have been used mainly in the United States in foam cushions for furniture and polyurethane foams. One congener in penta-BDE of note is BDE-47, which often accounts for the highest concentration of PBDEs in human and wildlife tissues. Penta-BDEs have not been produced in the U.S. since December 2004 and have been banned by some states in the U.S. A ban on penta-BDEs was passed in the European Union in July of 2004.
  • Octa-BDE is used mainly in the plastics of many electronics including computers and is not a major product worldwide. U.S. industries stopped producing octa-BDEs voluntarily in December of 2004, though there is no federal ban on use of existing stocks. Octa-BDEs have been banned by some states in the U.S. and have been banned in the European Union since July 2004.
  • Deca-BDE is used in wire and cable insulating plastics as well as casing for many electronics as well as the backing of heavy textiles. A ten-year scientific risk assessment of deca-BDE by the European Union concluded that there was a lack of recognized risks associated with use of deca-BDE, and that no restrictions on its use were necessary.

PBDEs and Fire

 

caption PBDEs are brominated flame retardants. (Source: Wikipedia)

 

PBDEs work as flame-retardants by releasing inert bromine gas at high temperatures. This gas coats appliances, displacing oxygen and making them harder to burn. Part of the reason why the United States uses so many PBDEs is because of fire prevention policies and regulations. In the last 25 years, fire incidence in the U.S. has dropped.

PBDE Concentrations in Humans

 

caption Trends in chemicals in breast milk in Sweden. (Reprinted with permission of NRDC, the Natural Resources Defense Council)

 

PBDEs are found in humans around the world. The concentrations and types of PBDEs in people vary depending on country, city, occupation, and diet. The main routes of exposure to PBDEs change throughout life. Infants, for example, are exposed primarily through breast milk, while toddlers are exposed through contact with household dust. In the U.S., 80% of adult exposure is accounted for by inhalation and ingestion of dust. However, in Europe, where concentrations of PBDEs in dust are much lower, diet is a more significant source.

Sweden has monitored human breast milk since the 1970s. Concentrations of measured PBDEs have increased since the start of the program up to 1997, when levels began to decline—possibly due to the decline in use of Penta-BDEs in Europe in the 1990s.

Milk from women from the U.S. and Canada contains many times the amount of PBDEs than that of women from Sweden and Japan. The last 30 years show a dramatic increase in levels of PBDEs in the breast milk of American women. Women from the U.S. generally contain 10-100 times more PBDEs in their breast milk than women from Europe.

 
 

Table 1: Varying concentrations of PBDEs in breast milk of women from different countries (Adapted from Birnbaum 2004).

 

 

Country

 

Concentration (ppb Lipid)

Sweden

3.2

Japan

1.4

Canada

25

United States

41

 

In some Asian and countries, which tend to have low labor costs and lax environmental regulation, recycling of electronic goods by villagers presents health risks, in part because of chemicals like PBDEs. Brominated dioxins and furans can form when plastics containing PDBEs burn at low temperatures. When people “bake” plastics at dumps to recover metals, the release of contaminants presents health risks and raises issues of environmental justice. Recent studies show high levels of various PBDEs in people working at municipal waste disposal sites in Managua, Nicaragua.

 

Studies Regarding the Effects of PBDEs

 

 

There has been much concern regarding increasing levels of PBDE in humans because studies show that there are health effects in animals fed PBDEs. Early studies showed that very high doses of deca-BDEs caused neoplastic nodules in the livers of male and female rats, low incidence of thyroid tumors, and delay in reproductive development of male rats.

More recent studies using lower doses showed neurobehavioral alterations and thyroid dysfunction in male and female mice. This may be due to the similarity in structure of PBDEs to thyroxine, the main hormone produced by the thyroid gland. This similarity could result in disruption of thyroid hormone metabolism and transport. Since the thyroid controls growth, development and reproduction, interference with thyroid hormone balance is of great concern.

PBDEs in the Environment

Concentrations of PBDEs in sediments and sewage sludge, fish, marine mammals, and humans are shown in Table 2. Although concentrations of PBDEs are increasing in humans, concentrations are even greater in some marine mammals and in such terrestrial birds of prey as peregrine falcons.

 
 

Table 2: Concentrations of PBDEs in parts per billion for different organisms. (Adapted from the Washington state PBDE Chemical Action Plan

Subject

Location

PBDEs (ppb)

 

Source

 

Sediments

Major river basins of Portugal

0.000 03- 0.1 dry weight

Lacorte 2003

Sewage sludge

United States.

33,000

Hale et al. 2002

Breastmilk

Women from Texas

6.2 – 419 lipid, mean of 73.9 lipid

Schecter et al 2003

Farmed fish

Southern Chile

1.46 wet weight

12-20 lipid weight

Montory 2006

Dungeness crab

West coast, Canada; 1993-1995

4.2-480 lipid

Ikonomou et al. 2002

Bald eagle egg

Lower Columbia River, Washington and Oregon, 1994-1995

446-1,206 wet weight

Buck et al. 1999

Average for fish

California Coast, 2000

302.17 lipid

Brown et al. 2006

Speckled sanddab

Eureka/Arcata, California Coast, 2000

13.25 lipid

Brown et al. 2006

Shiner surf perch

San Francisco Waterfront, CA, 2000

314.45 lipid

Brown et al. 2006

Shiner surf perch

Mission Bay/Crown Point, California Coast, 2000

1023.75 lipid

Brown et al. 2006

Canary rockfish

Santa Cruz, CA, 2000

281.98 lipid

Brown et al. 2006

Harbor Seal Fat

Puget Sound, WA 2000.

1,064 lipid

www.epa.gov

Harbor Seal Fat

Vancouver, British Columbia

497 lipid

www.epa.gov

Harbor seals

Dutch Coast, Atlantic Ocean

1,000 lipid

de Boer et al. 1998

Whitebeaked dolphin,

Dutch Coast, Atlantic Ocean

7,000 lipid

de Boer et al. 1998

Orca blubber

Northeaster Pacific Ocean, 1993-1996

87-1,629 lipid

Rayne et al. 2004

Beluga whale blubber

Canadian Arctic

17.2-160 lipid

Alaee et al. 1999

Beluga whale blubber

St. Lawrence Estuary, Canada 1988-1999

17.2-935 lipid

Lebeuf et al. 2004

Sperm whale blubber

Dutch Coast, Atlantic Ocean

100 lipid

de Boer et al. 1998

 

The Future of PBDEs

 

caption Marine mammals like orcas contain some of the highest concentrations of PBDEs. (Source: Wikipedia)

 

According to the Washington State Department of Health's PBDE Chemical Action Plan there are alternatives to producing products containing PDBEs. One option is to use the least toxic or least persistent flame-retardants available. One issue with this approach is that many “alternative chemicals” have yet to be tested (for example, under the U.S. Toxic Substances Control Act) for human and environmental health effects, their impacts, therefore, are largely unknown. Another option is to design products in a way that makes them less flammable without the use of flame-retardants.

References

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Further Reading

Glossary

Citation

Guerra, C. (2013). Polybrominated diphenyl ethers (PBDEs). Retrieved from http://www.eoearth.org/view/article/51cbeea67896bb431f6995d2