Commonly used as flame retardants, polybrominated diphenyl ethers (PBDEs) are routinely detected in the environment, animals, and humans. Although these persistent organic pollutants are increasingly recognized as having serious health implications, particularly for children, this is the first study, to our knowledge, to investigate an intervention for human elimination of bioaccumulated PBDEs.
Used since the early 1960s as flame retardants, polybrominated diphenyl ethers (PBDEs) were first identified as global contaminants in 1987 [
Although researchers have brought attention to the ubiquitous presence of and human health risks from PBDES, research into the elimination of bioaccumulated PBDEs has been limited to animal studies and to depuration occurring during human breastfeeding. This investigation reports the results of a study examining the concentration of five common PBDE congeners (28, 47, 99, 100, and 153) in the blood serum, urine, and perspiration of 20 study participants. The objectives of the study are to determine the efficacy of these body fluids as PBDE biomonitoring mediums, to assess the excretion of the identified congeners in urine and perspiration, and to explore the potential of induced perspiration as a means of decreasing bioaccumulated PBDEs. Data for this investigation are derived from the Blood, Urine, and Sweat (BUS) study. Other findings from this study have been published elsewhere [
Because of their toxicity, resistance to degradation, and potential for bioaccumulation, regulatory agencies have begun to place limitations on the production and use of PBDEs. For example, two common commercial mixtures of PBDEs (PentaBDE and OctaBDE) have been banned for over 10 years in the European Union [
Primary PBDE exposure routes for humans have been identified as indoor air and dust, diet, and breast milk and in utero transmission.
Toddlers and young children are at particular risk for PBDE accumulation because of exposure to and ingestion of indoor dust [
The exposure of developing neonates and infants to PBDEs is particularly concerning in light of rapidly accumulating empirical evidence for the adverse and persisting impact of these pollutants [
A comprehensive discussion of the mechanisms of harm from PBDE congeners or their metabolites is outside the scope and goals of this investigation. It is valuable, however, to briefly highlight three of the mechanisms of harm suggested in the research literature: hormone dysregulation, cellular disruption, and neurotoxicity.
Studies indicate that PBDEs are “endocrine active” [
There is substantial evidence indicating that PBDEs and/or their metabolites interfere with physiological processes at a cellular level. In a systematic review, Costa et al. [
In addition, increasing evidence demonstrates that neurotoxicity is a mechanism of harm from PBDEs [
Other pathophysiological mechanisms include epigenetic dysregulation [
Investigation of BPDE elimination has been largely restricted to in vitro and in vivo studies of rodents. Overall, studies indicate that rates of PBDE absorption, distribution, metabolism, and excretion are influenced by congener, gender, and species [
In the relative absence of studies exploring PBDE elimination in humans, animal investigations are an important means for advancing scientific investigation of these contaminants. It is important to note that congener elimination characteristics differ in animals and humans [
Nine males and 11 females with mean ages 44.5 ± 14.4 years and 45.6 ± 10.3 years, respectively, were recruited to participate in the study. Ethical approval was received from the Health Research Ethics Board of the University of Alberta. Ten participants were patients with diagnosed, chronic health conditions and 10 were healthy adults (Table
Participant characteristics.
Participant | Sex | Age | Clinical diagnosis |
---|---|---|---|
1 | M | 61 | Diabetes, obesity, hypertension |
2 | F | 40 | Rheumatoid arthritis |
3 | M | 38 | Addiction disorder |
4 | F | 25 | Bipolar disorder |
5 | F | 47 | Lymphoma |
6 | F | 43 | Fibromyalgia |
7 | F | 48 | Depression |
8 | F | 40 | Chronic fatigue |
9 | F | 68 | Diabetes, fatigue, obesity |
10 | M | 49 | Chronic pain, cognitive decline |
11 | M | 53 | Healthy |
12 | M | 23 | Healthy |
13 | M | 21 | Healthy |
14 | F | 47 | Healthy |
15 | M | 53 | Healthy |
16 | F | 43 | Healthy |
17 | F | 51 | Healthy |
18 | M | 46 | Healthy |
19 | M | 57 | Healthy |
20 | F | 50 | Healthy |
All blood samples were collected at one DynaLIFE Dx laboratory site in western Canada with vacutainer blood collection equipment (BD Vacutainer, Franklin Lakes, NJ 07417, USA) using 21-gauge stainless steel needles which were screwed into the “BD Vacutainer One-Use Holder” (REF 364815). The 10 mL glass vacutainer was directly inserted into the holder and into the back end of the needle. This process and the use of glass blood collection tubes were used to prevent contamination. Blood was collected directly into plain 10 mL glass vacutainer tubes, was allowed to clot, and after 30 minutes was centrifuged for 10 minutes at 2,000 revolutions per minute (RPM). After the serum was separated, samples were picked up by ALS Laboratories (about 3 kilometres from the blood collection site) for storage pending analysis. After being received at the ALS, serum samples were transferred to 4 mL glass vials and stored in a freezer at −20°C, pending transfer to the ALS analytical laboratory.
For urine collection, participants were instructed to collect a first morning midstream urine sample directly into a provided 500 mL glass jar container with Teflon-lined lid on the same day that blood samples were collected. Urine samples were delivered by the participants directly to ALS Laboratories. Samples were transferred by laboratory staff to 4 mL glass vials and stored in a freezer at −20°C, pending transfer.
Participants were instructed to collect perspiration from any site on their body directly into the provided 500 mL glass jar container with Teflon-lined lid. Participants washed with soap and water and rinsed their skin thoroughly before collecting perspiration. Collection was accomplished by placing the jar against their prewashed area when actively sweating or by using a stainless steel spatula against their skin to transfer perspiration directly into the glass jar. Stainless steel, a compound primarily composed of iron, chromium, and nickel, was chosen as it is the same material as the needles used in standard blood collections and does not off-gas or leach at room or body temperature. An excess of 100 mL of sweat was provided in all but one case. Each of the glass bottles used for sampling in this study was provided by ALS Laboratories and had undergone extensive cleaning and rinsing to ensure negligible risk of contamination: laboratory-grade phosphate-free detergent wash, acid rinse, hot and cold deionized water rinses, oven drying, and capping and packing in quality-controlled conditions. Sweat was collected within one week (either before or after) of collecting the blood and urine samples. Collection of perspiration occurred at any point during sweating episodes. Ten participants collected samples inside a dry infrared sauna; 7 collected samples inside a steam sauna; and 3 collected samples during and immediately after exercise. The type of exercise and location were determined by participants. Following collection, perspiration samples were delivered by the participants directly to ALS Laboratories. Samples were transferred by laboratory staff to 4 mL glass vials and stored in a freezer at −20°C, pending analysis. No preservatives were used in the jars provided for sweat and urine collection, nor in the serum storage vials.
Because of congener toxicokinetic differences, we investigated elimination of five common PBDE congeners (28, 47, 99, 100, and 153) in three body fluids: blood, urine, and perspiration. For each body fluid, an isotope dilution method was used to determine levels of each congener. In accordance with standard practice, the lipid fraction of serum was analyzed and reported. Urine and perspiration were tested in their entirety. It is recognized that perspiration contains both a water component from sweat glands and a lipid component originating from sebum (sebaceous glands in hair follicles). Unlike blood testing, testing of perspiration does not fractionate into components enabling isolated lipid testing.
The blood was then weighed in an Erlenmeyer flask and spiked with an extraction standard solution containing 13C12-labeled PBDEs 28, 47, 99, 100, and 153. A solution of 5 g ammonium sulphate in 20 mL of distilled water and 50 mL of methanol were added to the sample. 40 mL of hexane/diethyl ether (2/1) was added to the sample. After 10 minutes of sonication, the mixture was shaken for 10 minutes. A hexane layer was transferred into another flask. The extraction with fresh portion of hexane/diethylether was repeated. Combined hexane extracts were dried by shaking with anhydrous Na2SO4. Dried separated hexane extract was concentrated using a Kuderna-Danish apparatus to a volume of about 1 mL. Residual solvent was evaporated in an oven at 102 ± 5°C until a constant weight of the fat was achieved. Fat content was determined gravimetrically.
For clean-up, the fat was again diluted in 5 mL of hexane and transferred into a separator funnel. This is combined with the same volume of dimethyl sulfoxide. The mixture was shaken intensively for about 0.5 minutes. The DMSO layer was removed and transferred into an Erlenmeyer flask. The extraction was repeated with fresh DMSO three times. Combined DMSO portions were diluted with at least the same volume of distilled water while being cooled with running water. Reverse extraction procedures with 3 × 5 mL of n-hexane were then carried out. Combined hexane extracts were concentrated in a Kuderna-Danish apparatus to a volume of ca. 1 mL. The final extract was spiked with injection standard containing 13C12-labeled PBDE 138. Finally, 2–4
For clean-up, the extract was precleaned by shaking with 5 mL of concentrated sulphuric acid at laboratory temperature. The precleaned extract was transferred on the top of a multilayer silicagel column and eluted with hexane. The extract was concentrated with the modified Kuderna-Danish concentrator up to 0.5–1 mL. The final extract was spiked with injection standard containing 13C12-labeled PBDE 138. Finally, 2–4
Twenty participants provided samples of blood, urine, and perspiration for PBDE testing. Relevant participant characteristics are provided in Table
PBDE congeners detected in body
BDE28 | BDE47 | BDE99 | BDE100 | BDE153 | |
---|---|---|---|---|---|
Detected in body fluids ( |
16 | 20 | 19 | 18 | 18 |
Detected in blood ( |
11 | 20 | 12 | 15 | 17 |
Detected in perspiration ( |
16 | 17 | 17 | 17 | 17 |
Detected in urine ( |
0 | 0 | 0 | 0 | 0 |
Although average serum levels of all PBDEs other than PBDE 100 were higher in patients diagnosed with chronic illness (Table
Health status of participants and mean PBDE levels.
Health status | BDE 28 | BDE 47 | BDE 99 | BDE 100 | BDE 153 | |||||
---|---|---|---|---|---|---|---|---|---|---|
Bl1 |
|
Bl |
|
Bl |
|
Bl |
|
Bl |
| |
Healthy | 0.31 | 0.017 | 13.26 | 0.6 | 1.61 | 0.55 | 6.7 | 0.012 | 4.06 | 0.072 |
Chronically ill | 1.43 | 0.017 | 30.65 | 1.17 | 6.67 | 1.48 | 6.37 | 1.62 | 8.73 | 0.16 |
BDEs were found in 75 of the 100 blood samples (Table
Blood PBDE levels by congener (ng/g of blood lipid).
Participant | BDE 28 | BDE 47 | BDE 99 | BDE 100 | BDE 153 |
---|---|---|---|---|---|
1 | 4.8 | 110 | 32 | 25 | 14 |
2 | 0.98 | 8.4 | ND | ND | 3.2 |
3 | 1 | 18 | 4.2 | 4.2 | 6.1 |
4 | 2.1 | 24 | 3.2 | 1 | 4.2 |
5 | 0.48 | 3.5 | 0.3 | 0.3 | 6.9 |
6 |
|
6.6 | ND | ND | ND |
7 | 0.87 | 13 | 2 | 2.8 | 1.2 |
8 | ND | 30 | 4.2 | 4.8 | 3.3 |
9 | 1.9 | 71 | 19 | 23 | 43 |
10 | 2.2 | 22 | 4.8 | 2.6 | 5.4 |
11 | ND | 32 | 9.4 | 5.2 | 8.5 |
12 | 0.98 | 17 | 2.6 | 2.6 | 6.3 |
13 | ND | 1.8 | ND | ND | 2.4 |
14 | ND | 4.2 | ND | 54 | 3.4 |
15 | 1.2 | 8.7 | 3 | 1 | 5.5 |
16 | ND | 31 | ND | 1.9 | 7.6 |
17 | ND | 5.8 | ND | ND | 2.2 |
18 | ND | 19 | ND | 1.9 | ND |
19 | 0.92 | 10 | 1.1 | 0.37 | ND |
20 | ND | 3.1 | ND | ND | 4.7 |
Geometric mean and selected percentiles of concentrations in blood (ng/g of blood lipids).
BDE 28 | BDE 47 | BDE 99 | BDE 100 | BDE 153 | |
---|---|---|---|---|---|
Mean | 0.72 | 19.42 | 3.34 | 8.87 | 5.28 |
50th percentile | 0.77 | 16.00 | 1.33 | 1.90 | 5.10 |
75th percentile | 1.03 | 24.61 | 3.90 | 5.99 | 6.44 |
90th percentile | 1.84 | 34.43 | 8.54 | 25.48 | 8.62 |
95th percentile | 2.19 | 48.87 | 13.61 | 36.09 | 11.29 |
Mean blood levels for PBDE congeners in the BUS and NHANES studies [
Because the BUS study tested for 120 chemical toxicants [
Perspiration PBDE levels by congener (ng/g of perspiration).
Participant | BDE 28 | BDE 47 | BDE 99 | BDE 100 | BDE 153 |
---|---|---|---|---|---|
1 | 0.05 | 5.2 | 8.1 | 1.6 | 0.84 |
2 | 0.01 | 0.31 | 0.18 | 0.044 | 0.015 |
3 | 0.006 | 0.3 | 0.3 | 0.053 | 0.029 |
4 | 0.023 | 0.82 | 0.44 | 0.1 | 0.025 |
5 | 0.022 | 0.79 | 0.47 | 12 | 0.032 |
6 |
|
IP | IP | IP | IP |
7 | 0.013 | 0.73 | 0.64 | 0.14 | 0.052 |
8 | ND | 0.044 | 0.046 | 0.0094 | 0.0056 |
9 | 0.031 | 2.3 | 3.1 | 0.6 | 0.38 |
10 | 0.0011 | 0.039 | 0.036 | 0.046 | 0.047 |
11 | 0.014 | 1.2 | 1.4 | 0.26 | 0.15 |
12 | 0.014 | 1.1 | 0.95 | 0.23 | 0.078 |
13 | 0.0032 | 0.071 | 0.066 | 0.013 | 0.082 |
14 | 0.0034 | 0.074 | 0.052 | 0.013 | 0.004 |
15 | 0.004 | 0.14 | 0.11 | 0.021 | 0.009 |
16 | 0.041 | 1.8 | 1.4 | 0.32 | 0.13 |
17 | 0.004 | 0.13 | 0.11 | 0.025 | 0.094 |
18 | 0.052 | 0.3 | 0.28 | 0.064 | 0.028 |
19 | IP | IP | IP | IP | IP |
20 | IP | IP | IP | IP | IP |
Geometric mean and selected percentiles of concentrations in perspiration (ng/g of perspiration).
BDE 28 | BDE 47 | BDE 99 | BDE 100 | BDE 153 | |
---|---|---|---|---|---|
Mean | 0.02 | 0.90 | 0.95 | 0.55 | 0.12 |
50th percentile | 0.02 | 0.61 | 0.63 | 0.15 | 0.09 |
75th percentile | 0.04 | 1.28 | 1.13 | 0.47 | 0.12 |
90th percentile | 0.05 | 1.98 | 2.01 | 0.99 | 0.23 |
95th percentile | 0.05 | 2.40 | 2.99 | 2.21 | 0.35 |
Effectiveness of perspiration induction interventions for PBDE excretion.
Type of Intervention | Overall mean blood : sweat ratio | ||||
---|---|---|---|---|---|
BDE 28 | BDE 47 | BDE 99 | BDE 100 | BDE 153 | |
Exercise ( |
137.2 | 25.5 | 4.8 | 16.9 | 26.9 |
Infrared sauna ( |
17.9 | 32.1 | 3.25 | 94.6 | 71.8 |
Steam sauna ( |
69.5 | 26.3 | 5.6 | 2.4 | 121.2 |
Insufficient perspiration samples are not included.
Of the 25 blood tests that tested negative for PBDE congeners, 16 were positive in the corresponding perspiration tests (Table
Comparison: PBDE congeners detected in participants’ blood and sweat.
BDE 28 | BDE 47 | BDE 99 | BDE 100 | BDE 153 | |
---|---|---|---|---|---|
No PBDEs in blood | 9 | 0 | 8 | 5 | 3 |
No PBDEs in blood, PBDEs in sweat | 6 | 0 | 6 | 3 | 1 |
No PBDEs in blood, no PBDEs in sweat | 1 | 0 | 0 | 0 | 0 |
No PBDEs in blood, insufficient |
2 | 0 | 2 | 2 | 2 |
Findings have implications in two important areas: biomonitoring of PBDEs and human elimination of toxicants. Concern for human bioaccumulation of PBDEs and the impact of these pollutants on human health, particularly the health of neonates and children, has already resulted in the banning of these substances in many jurisdictions. Biomonitoring and estimation of body burden, however, remain a concern, particularly in North America where levels remain high.
While blood is commonly used for testing PBDE body burdens [
In addition to supporting previous studies which indicate that congener concentrations vary across body fluids and excretion rates vary for different congeners [
The first and critical line of defense when dealing with PBDEs is undoubtedly to reduce exposure through better understanding exposure pathways, strategies to limit exposure to products containing PBDEs in homes, schools, and work environments, and legislative action [
Emerging evidence for the fetotoxic and reproductive effects of PBDE exposure [
There are limitations associated with study design: participants were tested for only five PBDE congeners, and the small sample size does not allow extrapolation of findings to a larger population. Methods for perspiration sample collection may also impose limitations: perspiration originating from different parts of the body may excrete different concentrations of PBDEs; excretion rates may be impacted by participant’s sweating duration; and factors such as ambient temperature and humidity, diet, hydration, and/or pharmaceutical and supplement use may influence excretion of PBDEs in perspiration. It is also not possible to determine whether the measured perspiration was tainted by elements originating from sebum as well as directly from skin tissue. Although it is possible that inadvertent contamination of samples occurred, precautions were taken to minimize this risk; for example, quality controls and blanks were analyzed simultaneously. Finally, it should be noted that the study did not assess health outcomes associated with PBDE elimination.
This is the first study, to our knowledge, to assess mechanisms for the elimination of bioaccumulated PBDEs from the human body. Our objectives were to determine the efficacy of three body fluids, blood, urine, and perspiration, as PBDE biomonitoring mediums, to assess the excretion potential of identified congeners into urine and sweat, and to explore the potential of induced perspiration as a means to decrease bioaccumulated PBDEs. None of the five tested PBDE congeners (28, 47, 99, 100, and 153) were found in participants’ urine samples, suggesting that urine testing is not useful for biomonitoring or elimination of these common congeners. In this paper, we therefore focused on the results of blood and perspiration testing.
Although blood is commonly used for testing PBDE body burdens, our findings suggest that, in isolation, this approach provides only a partial understanding of human PBDE bioaccumulation. Testing of both blood and perspiration may be important for a better understanding of PBDE accrual in the human body. Moreover, it is evident that induced perspiration facilitates excretion of the five common PBDE congeners included in the study, with different rates of excretion for different congeners. We cannot draw conclusions with respect to the rate at which induced perspiration will diminish total body PBDE burden as there is currently no means to accurately assess PBDE load in the spectrum of human tissues. Nonetheless, given the relative absence of studies exploring PBDE elimination or clinical detoxification in humans, as well as the scientific consensus about the negative impact of PBDEs on human health, this study provides important baseline evidence suggesting that regular sessions of induced perspiration may facilitate the therapeutic elimination of PBDEs. Serious concerns about the fetotoxic and reproductive effects of PBDE exposure highlight the importance of further research in this area.
The authors declare no conflicts of interest regarding the publication of this paper.