Flame Retardants

Overview

Flame retardants are various chemicals applied to materials to prevent ignition or slow the spread of fire. The term applies to the function of these chemicals, not a specific composition. The most common classes are brominated flame retardants (BFRs) and organophosphate flame retardants (OPFRs).

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 foam, and polyurethane insulation such as spray foams

These chemicals can remain in the environment and in a person’s body for years. Although flame retardants may offer benefits when added to certain products, they are often not chemically bound, resulting in considerable leaching. Increasing scientific evidence shows some may be hazardous to people and animals. These negative health effects may include endocrine and thyroid disruption, immunotoxicity, reproductive toxicity, cancer, and altered neurodevelopment.

Related Health Effects

Learning how these chemicals, and in what amounts, may cause human health effects is an area of active research. This research includes the development and use of cell-based assays and other alternatives to traditional animal models.

Neurodevelopment

Chronic exposure to flame retardants in the general population, as well as evidence of neurotoxicity from animal studies, raises concern for neurodevelopmental effects in people. Some flame retardants are associated with impaired cognitive and behavioral development in children. Neurodevelopmental disorders — such as symptoms of attention deficit hyperactivity disorder (ADHD), problems with fine motor coordination, and lower cognition — were found in children exposed to high levels of flame retardants called polybrominated diphenyl ethers (PBDEs). While many PBDEs are being phased out, research is revealing that replacements also have neurodevelopmental toxicity and endocrine-disrupting activity at exposure levels relevant to humans.

Metabolic Disorders

Several researchers funded by NIH are looking at the role that newly introduced flame-retardant mixtures may play in metabolic disorders such as obesity and high blood pressure.

Reproductive Health

Researchers are also looking at how maternal and paternal exposure to flame retardants might affect reproduction and genes critical to proper human development.

Endocrine Disruption

Some flame retardants may also act as endocrine disruptors — chemicals that may mimic, block, or interfere with the body’s hormones. Even low doses of endocrine-disrupting chemicals may be unsafe. The body’s normal endocrine functioning involves very small changes in hormone levels. So small changes can cause significant developmental and biological effects. Endocrine disruption can lead to reproductive, metabolic, and developmental health effects.

Key Types of Flame Retardants and Their Health Effects

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. The following are key types of flame retardants and what research has found about their health effects:

Brominated Flame Retardants (BFRs) contain bromine and are used in many electronics, furniture, and building materials. They have been linked to endocrine disruption. Older compounds including PBDEs have been replaced by new versions that also show toxic endocrine effects.

Chlorinated Tris (TDCPP) is an organophosphate flame retardant once added to children’s pajamas but banned in 1977 after the Consumer Product Safety Commission found it to be toxic and carcinogenic. It has also been linked to lower sperm counts and endocrine disruption. While banned in pajamas, chlorinated tris remains widely used in furniture, insulation, and other building materials as well as in automobiles and electronics.

Hexabromocyclododecane (HBCD) is a brominated flame-retardant additive used primarily in polystyrene foam building materials. These chemicals enter the environment during the production process and by leaching from consumer products. 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 PBDEs and other types of flame retardants. Studies suggest these chemicals could pose risks to human 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 this phaseout, PBDEs are stable in the environment and products containing them remain in use, suggesting exposure will continue for some time. 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.

Risk Factors

How People Come in Contact with Flame Retardants

People can encounter 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, disposal, or application.
• 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.

Why Children Face Higher Risk

Children are more vulnerable to the toxic effects of flame retardants because their brains and other organs are still developing. Several studies demonstrate that exposure is higher in children than adults. Specific reasons children face greater risk include:

• Children eat, drink, and breathe more relative to their size than adults do.
• Children frequently put objects in their mouths and play on the floor and ground.
• Protective bodily systems, such as the blood-brain barrier and systems that filter pollutants from inhaled air and process chemicals in the body, are not yet fully developed.
• During periods of rapid growth and development, normal biological processes may be disrupted by environmental chemicals.

Prevention Guidance

Endocrine-disrupting chemicals, including some flame retardants, cannot be completely avoided or removed. However, people can make informed choices to reduce exposure and the risk of potential health effects.

• Use flame-retardant-free furniture and other household items that are still fire-safe, when possible. Flame resistance can be achieved by ways other than adding chemical flame retardants, including via the use of fire-resistant textiles.
• Dust and vacuum with a HEPA filter regularly to reduce contaminated dust levels in the home.
• Choose items made from natural materials such as wool or cotton or those that specifically state they do not contain chemical flame retardants.
• Use tight-fitting clothing for children to meet the fire safety standard for pajamas.

NIH researchers reported that when pregnant women improved their nutrition and reduced exposure to hazardous chemicals, they were more likely to have healthy babies, and their children were better able to cope with environmental stressors later in life.

Find Clinical Trials

Clinical trials uncover better ways to prevent, diagnose, treat, and understand diseases and conditions. To ensure results apply to everyone, volunteers of all ages, sexes, and backgrounds, including both healthy individuals and those with specific medical conditions, are needed. Find clinical trials on flame retardants.

Research Information

The National Institutes of Health (NIH) is the largest public funder of biomedical research in the world. NIH invests most of its budget in medical research seeking to enhance life and to reduce illness and disability. NIH-funded research has led to breakthroughs and new treatments helping people live longer, healthier lives, and building the research foundation that drives discovery.

Research on flame retardants is ongoing. 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.

Current and recent research areas supported by NIH include:

• The role that newly introduced flame-retardant mixtures may play in metabolic disorders such as obesity and hypertension
• How maternal and paternal exposure to flame retardants might affect reproduction, neurodevelopment, and genes critical to proper human development
• The health effects of newer flame-retardant alternatives including OPFRs
• Different ways to dispose of products that contain flame retardants
• Supporting research that will help companies develop safer alternatives to current flame retardants

NIH-funded researchers are also studying how exposure to chemical mixtures, including flame retardants, affects human health. Real-world exposures occur in complex mixtures, so researchers are developing new methods to study these combined exposures.

Find NIH-funded research projects using NIH RePORTER, a searchable database of current and past research projects supported by NIH and other federal agencies.