Why is exposure to BFR relevant to health?
Several classes of flame retardants are used in consumer products. The most commonly studied have been a class of brominated based compounds. Brominated flame retardants (BFR) are added to a wide variety of products, including plastics, polyurethane foam, textiles, furniture, and electronics, to reduce their flammability and to meet flammability standards.
Polybrominated diphenyl ethers (PBDE) were once the most widely used BFR in the U.S., until they were phased out between 2004 and 2013. However, many products that contain PBDEs are still in use, allowing PBDE to escape from these products into the environment. Humans of all ages are exposed to PBDE through diet, contact with flame-retardant products, and contaminated house dust. Young children tend to have higher exposures to PBDE compared to adults due to frequent contact with floors and other surfaces where dust gathers, as well as frequent hand-to-mouth activity. In addition, children may be particularly vulnerable to the effects of PBDE exposure because they tend to have higher exposures (per kilogram of body weight) than adults and may be exposed during critical periods of development.
Exposure to PBDE has been associated with disruption of the endocrine system, particularly thyroid hormone regulation, and with effects on the liver and brain development. Pregnant women may be especially vulnerable to these effects as thyroid hormones play a key role in healthy pregnancies and fetal development. Reproductive hormones may also be affected, as some studies suggest that PBDE exposure may be linked to decreased fertility in women and changes in male reproductive development. Exposure to PBDE during in utero and early development has been linked to altered cognitive function and behavior in childhood.
In newly manufactured products, PBDE have been replaced by a range of “replacement” or “alternative” flame retardants. These include other BFR such as hexabromocyclododecane (HBCD), decabromodiphenyl ethane (DBDPE), tetrabromobisphenol-A (TBBPA), and Firemaster 550, as well as several types of organophosphate ester (OPE) flame retardants. Although exposure to some of these replacement flame retardants may be widespread, potential health effects related to these exposures are not well understood.
What types of questions can be answered?
Exposure to BFR can be estimated by measuring the parent chemicals or metabolites in plasma, serum or urine (depending on the chemical type), as well as measurement of parent chemicals in hand wipes, household dust, and wristbands.
With respect to PBDE, each congener has a distinct elimination profile, which can vary between individuals. In general, PBDE levels in blood reflect exposure over the past several months or years. However, BDE209 (“Deca-BDE”) has a half-life of only 15 days, so multiple samples or studies to indicate within-person stability over time may be necessary. Many published data exist with which to compare PBDE exposures including general U.S. population data published in CDC’s National Report on Human Exposure to Environmental Chemicals.
How can exposure to BFR be measured?
- Analytes: Exposure to PBDE and other BFR can be measured by quantifying the parent chemicals or their metabolites in plasma, serum or urine, or in environmental samples, such as house dust or wristbands.
- Methods: Most BFR analysis methods use gas chromatography coupled with mass spectrometry. Some replacement BFR are measured using HPLC-MS/MS.
- Types of biospecimens: Plasma and serum are the most commonly used biological matrices for BFR, although other matrices such as urine have been used.
- Types of environmental samples: Dust is the most common medium analyzed, but air, silicone wristbands, and other media have been used. Most halogenated persistent organic pollutants (POP) are lipophilic. Additional sample volumes are required for lipid measurements.
How does HHEAR ensure the quality of its analyses?
If possible, the inclusion of field “blanks” in a study can help identify any contamination from collection/storage sources. All assays are well validated with respect to accuracy and precision. All assays have embedded positive and negative controls. The positive controls are used to check assay accuracy within each set of samples. The negative controls are generally blanks that are included to assess the possibility of any cross contamination in the assay procedure. Laboratories participate in proficiency testing programs to validate assays.
What sample quality and quantity are necessary?
This is highly dependent on the assay to be run and the sample type, but in general a few milliliters of serum or plasma or urine or 500 mg of dust are required. Less volume/mass usually translates to lower frequency of detection. Multiple freeze-thaw cycles should not be a significant problem for the analysis of these substances.
References
Centers for Disease Control and Prevention. National Biomonitoring Program Factsheet: Polybrominated Diphenyl Ethers (PBDE) and Polybrominated Biphenyls (PBB).
Fromme H, Becher G, Hilger B, et al. Brominated flame retardants. Exposure and risk assessment for the general population. International Journal of Hygiene and Environmental Health. 2016;219(1):1-23.
Linares V, Bellés M, Domingo JL. Human exposure to PBDE and critical evaluation of health hazards. Archives of Toxicology. 2015;89(3):335-356.
U.S. Environmental Protection Agency. Biomonitoring: Polybrominated Diphenyl Ethers. America’s Children and the Environment. 2013.