What are flame retardants?
Flame retardants are various chemicals applied to materials to prevent burning or slow the spread of fire. The term applies to the function, not a specific composition, of these chemicals.
Flame retardants are studied because of their abundance in the environment and concerns about their potential health effects.
Where are flame retardants used?
Since the 1970s, flame-retardant chemicals have been added to many types of products:
- Furnishings such as seating foam and coverings (including transport vehicles), mattresses, and carpets.
- Electronics and electrical devices such as computers, phones, televisions, and household appliances.
- Building and construction materials such as coatings for electrical wires and cables, polystyrene foams, and polyurethane insulation such as spray foams.
Because these chemicals do not easily break down, they can remain in the environment and in a body for years. Studies show that some may be hazardous to people and animals.
How are people exposed to flame retardants?
People can come in contact with flame retardants in a variety of ways.
- Chemicals can leach from products into the air and then attach to dust, food, and water, which can be ingested.
- Chemicals seep into the air, water, and soil during manufacturing or application.
- Similarly, the burning or dismantling of electrical and electronic equipment (e-waste), can contaminate the environment with these chemicals, particularly in low- and middle-income countries.
What are some of the potential health effects associated with flame retardants?
Learning how these chemicals, and in what amounts, may cause human health effects is an area of active research. Although flame retardants can offer benefits when added to certain products, increasing scientific evidence shows that many of these chemicals may harm animals and humans.
Adverse health effects may include endocrine and thyroid disruption, immunotoxicity, reproductive toxicity, cancer, and adverse effects on fetal and child development and neurobehavioral function.
Who is most vulnerable?
Children are more vulnerable to toxic effects because their brains and other organs are still developing. Hand-to-mouth behavior and play that is close to the floor increases the potential of children to come in contact with harmful chemicals. Several studies demonstrate that exposure is higher in children than adults.
Chronic exposure to flame retardants in the general population, as well as evidence of neurotoxicity from animal studies, raises concern for neurodevelopmental effects in all people.
What is known about different types of flame retardants?
The hundreds of different flame retardants are often grouped according to chemical structure and properties. In general, such groups may be based on whether the flame retardant contains bromine, chlorine, phosphorus, nitrogen, metals, or boron. A few types are described here.
Brominated flame retardants (BFRs) contain bromine and are used in many electronics, furniture, and building materials. BFRs have been linked to endocrine disruption and thyroid disfunction. Older compounds have been replaced by new versions that also show toxic endocrine effects.
Hexabromocyclododecane (HBCD) is a brominated flame-retardant additive used primarily in polystyrene foam building materials. HBCD enters the environment during its production and by leaching from consumer products. It has been found to enter the food supply. Health concerns include alterations in immune and reproductive systems, neurotoxic effects, and endocrine disruption.
Organophosphate flame retardants (OPFRs) are widely used in textiles, electronics, and industrial materials and as replacements for other types of flame retardants. Studies suggest these chemicals could pose a risk to bone and brain health.
Polybrominated diphenyl ethers (PBDEs) do not chemically bind with the products to which they are added, such as furniture, and are easily released into air and dust. Production was phased out beginning in 2004. Despite phaseout, this compound is stabile in the environment and products containing PBDEs remain in use, suggesting exposure will continue for some time. A major effort has been devoted to evaluating potential health risks. Evidence links human exposure to neurodevelopmental disorders.
Tetrabromobisphenol A (TBBPA) is used in plastic paints, synthetic textiles, and electronic devices, and as an additive in other flame retardants. This compound was found to cause cancer in rats and mice.
What is NIEHS Doing?
Research on flame retardants is ongoing. Within NIEHS, several programs study flame retardants. The types chosen for study tend to be those most used and thought to be most hazardous, along with some newer compounds. Scientists use a variety of approaches and seek to assess potential hazards across classes of flame retardants, instead of testing one chemical at a time.
In addition, several NIEHS-funded researchers are looking at the role that newly introduced flame-retardant mixtures may play in metabolic disorders such as obesity and hypertension. Others are looking at how maternal and paternal exposure to flame retardants might affect reproduction and genes critical to proper human development.
Pregnant women exposed to flame-retardant chemicals could face an increased risk of premature birth, according to NIH-funded research. The researchers quantified flame retardant biomarkers in the urine of a large cohort of pregnant women who were geographically and socio-demographically diverse. The study found that greater prenatal exposure to certain flame-retardant chemicals was linked to higher risks of preterm birth and shorter gestational age, especially among female newborns.
Stories from the Environmental Factor (NIEHS Newsletter)
- Flame Retardants Decrease Immune Response in Children With Autism (February 2024)
- Eight Substances Added to 15th Report on Carcinogens (January 2022)
- Canine Companions Shed Light on Chemicals and Disease (July 2020)
- Assessing Risks from Flame Retardants – U.S. Environmental Protection Agency
- Flame Retardants – Consumer Product Safety Commission
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