Environ. Sci. Technol. 2009, 43, 6963–6968
Brominated Flame Retardants in Serum from the General Population in Northern China L I N G Y A N Z H U , * ,† B A O L I N G M A , † A N D RONALD A. HITES‡ College of Environmental Science and Engineering, Key Laboratory of Pollution Processes and Environmental Criteria, Nankai University, Ministry of Education, Tianjin, 300071, China, and School of Public and Environmental Affairs, Indiana University, Bloomington, Indiana, 47405
Received April 30, 2009. Revised manuscript received July 29, 2009. Accepted July 30, 2009.
In 2006, 128 serum samples were collected from three populations in Tianjin, China: office cleaners, university students, and policemen. These samples were all analyzed for polybrominated diphenyl ethers (PBDEs) and for other brominated flame retardants (BFRs). The median concentration of total PBDEs (sum of 41 congeners) was 7.1 ng/g lipid, ranging from 0.48 to 1980 ng/g lipid. Among these PBDE congeners, the median sum of the tri- to hepta-PBDE (ΣPBDE3-7) congener concentrations was 2.9 ng/g lipid, ranging from 0.48 to 20 ng/g lipid. The most common tri- to heptabrominated congeners were BDE-47 (30% of total), BDE-99 (24%), BDE183 (15%), BDE-153 (12%), BDE-28 (9.5%), and BDE-100 (6.2%). These levels of ΣPBDE3-7 were similar to those observed in Europe and Asia but were much lower than those observed in North America. Highly brominated BDE congeners were detected in some serum samples. In particular, BDE-209 was detected in 28 samples; the median BDE-209 concentration in these samples was 42 ng/g lipid, ranging from ND to 1770 ng/g lipid. The total PBDE levels in office cleaners were significantly higher than in university students and policemen. In addition, we also measured several other BFRs. Hexabromobenzene (HBB) was identified in 26 samples with a median concentration of 0.27 ng/g lipid, ranging from 0.11 to 1.50 ng/g lipid. Pentabromoethylbenzene (PBEB), hexabromocyclododecane (HBCD), 1,2-bis(2,4,6-tribromophenoxy)ethane (BTBPE), and decabromodiphenylethane (DBDPE) were not detected in any of these samples.
Introduction Brominated flame retardants (BFRs) are a group of diverse bromine-containing chemicals that are used to inhibit the burning of electronic equipment, construction materials, and upholstery (1). There are five major classes of BFRs: brominated bisphenols, diphenyl ethers, cyclododecanes, phenols, and phthalic acid derivatives (2). Among these compounds, polybrominated diphenyl ethers (PBDEs) are common; in 2001, their annual world market demand was over 67 000 t according to a report published by the Bromine Science and Environmental Forum (3). There were three kinds * Corresponding author. E-mail:
[email protected]. † Nankai University. ‡ Indiana University. 10.1021/es901296t CCC: $40.75
Published on Web 08/13/2009
2009 American Chemical Society
of PBDE commercial products: penta-BDE, octa-BDE, and deca-BDE. Toxicological studies in animal models suggest that the effects of PBDEs are similar to those of PCBs with increased risks of neurodevelopmental deficits, immunotoxicity, reproductive effects, teratogenicity, and endocrine disruption (4, 5). Penta-BDE and octa-BDE have been banned by the European Union (6) because of their biological effects and their increasing concentrations in the environment. Deca-BDE, however, is still being produced and is used globally. There are no restrictions on the production or use of deca-BDE in China. PBDEs have been recognized as ubiquitous environmental contaminants and they have been found in many environmental compartments (7, 8). Like polychlorinated biphenyls (PCBs), PBDEs are lipophilic and persistent, and they bioaccumulate. As a result, they have been found in biota such as fish (9), birds, and mammals, and in human milk (10), adipose tissue (11), and blood (12, 13). One particular public health concern is thatsunlike PCBs, the concentrations of which have steadily decreased in the environment, food, and people since their production stopped in 1977s the human body burdens of PBDEs have increased substantially over the last 30 years. A recent time trend study of United States residents showed increasing serum PBDE concentrations from the mid-1980s to 2002 (14). The majority of studies on human exposure are from North America, Europe, Japan, and Korea, and little is known about PBDE levels in the Chinese population, especially in northern China. There have been only three reports on PBDE levels in Chinese human serum (15-17), and all of them have focused on occupational exposures in the e-waste industry in Guangdong province, which is located in southern China. The objective of the present study was to investigate the levels of BFRs in three populations from Tianjin, a typical industrial metropolis in North China. The three populations were office cleaners, university students, and policemen; 128 samples were collected in 2006. Forty-one PBDE congeners and five non-PBDE BFR compounds were measured. The PBDE concentrations and congener patterns were analyzed as a function of occupational category, age, and gender. Comprehensive comparisons to other reports were made to illustrate the exposure levels and exposure pathways of the general Chinese population.
Materials and Methods Chemicals. All standard solutions were purchased from Wellington Laboratories (Ontario, Canada). The standard mixture contained 41 PBDE congeners at different concentrations and pentabromoethylbenzene (PBEB), hexabromobenzene (HBB), 1,2-bis(2,4,6-tri- bromophenoxy)ethane (BTBPE), decabromodiphenylethane (DBDPE), and hexabromocyclododecane (HBCD) at concentrations of 50 µg/mL each. Surrogate standards, BDE-77 and 13C12-BDE-209, were used to monitor the method recovery of PBDEs. The internal standard, BDE-118, was used for the quantitation of the trito hepta-BDEs, and 13C12-BDE-206 was used for the quantitation of the octa- to deca-BDEs. All solvents were pesticide grade. n-Hexane and dichloromethane were purchased from Fisher Scientific, Loughborough, UK; methyl tert-butyl ether (MTBE), and 2-propanol were from Sigma Chemical Co., St. Louis, MO, and sulfuric acid and hydrochloric acid were from Merck (Darmstadt, Germany). Alumina (50-200 µm, MP BioMedicals, Solon, OH) and anhydrous sodium sulfate (Merck) were baked at 600 °C for 12 h before use. VOL. 43, NO. 18, 2009 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
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TABLE 1. Characteristics of the Study Groups, Given As the Median Value with the Range in Parentheses. Height, Weight, and BMI Data for the Cleaners Was Not Available group sex number age weight (kg) height (cm) BMIa (kg/m2) a
cleaners M 17 35 (22-51)
F 13 41 (22-49)
students M 25 22 (21-24) 77 (52-100) 175 (164-190) 25.2 (17.8-32.1)
F 44 22 (21-24) 55 (42-75) 165 (152-175) 20.2 (16.2-25.6)
M 29 32 (21-52) 81 (55-95) 178 (172-184) 26.8 (18.0-30.4)
BMI is a person’s weight in kilograms divided by that person’s height in meters squared.
Serum Sampling and Preparation. One hundred and twenty-eight serum samples were collected at a hospital in Tianjin, China in 2006. The participants were “samples of opportunity”, who happened to be in the hospital for routine physical tests when we were sampling. All subjects were given information about PBDEs, and they voluntarily agreed to participate in the investigation. After this informed consent, basic data (such as age, gender, height, body mass index (BMI), and occupational history) were collected. The participants included 30 office cleaners (17 males and 13 females, 21-51 years old), 69 university students (25 males and 44 females, 21-24 years old), and 29 policemen (all males, 2152 years old). Detailed information on each participant is given in Supporting Information (SI) Table S1, and aggregated information is given in Table 1. About 5-10 mL of blood was collected from each person in serum tubes without an anticoagulant; the blood was allowed to clot for 20 min and centrifuged for 15 min at 4000 rpm. Serum was transferred into solvent-rinsed glass vials and stored at -20 °C until analysis. Serum samples were thawed before analysis and transferred into clean centrifuge tubes. BDE-77 (1 ng/sample) and 13C12-BDE-209 (2.5 ng/sample) were added as surrogate standards. Hydrochloric acid (6 M, 0.5 mL) was added, and the sample was rigorous blended on a vortex mixer. Three mL of 2-propanol was then added, and the sample was mixed again. The samples were subsequently extracted twice with a 1:1 hexane/MTBE mixture (5 mL each). The organic fractions were combined and evaporated under a gentle stream of nitrogen. After measuring the lipid content gravimetrically, the lipids were removed by adding 4 mL of concentrated sulfuric acid, and this mixture was washed with 3 mL hexane twice. The combined hexane fraction was blown down to 0.5 mL with nitrogen and loaded on a 6.5 × 1.9 cm (i.d.) alumina column. Two fractions of 8 mL each were collected using hexane and 40% dichloromethane in hexane. The second fraction was reduced to ∼0.1 mL, and internal standards (0.5 ng of BDE-118 and 1 ng of 13C12-BDE-206) were added. Instrumental Parameters. The samples were analyzed on a Hewlett-Packard 6890 gas chromatograph coupled to an Agilent 5973 mass spectrometer (Agilent Technologies, Santa Clara, CA) with helium as the carrier gas. One µL injections were made in the pulse splitless mode with a purge time of 2.0 min. The injection port was held at 285 °C. An Rxi-5 ms fused silica capillary column (15 m × 0.25 mm i.d., 0.25 µm film thickness; Restek Corporation, Bellefonte, CA) was used to separate the PBDE congeners and other BFRs. The GC oven temperature program was as follows: isothermal at 100 °C for 2 min, 25 °C/min to 250 °C, 3 °C/min to 270 °C, 25 °C/min to 325 °C, and held at 325 °C for 8 min. The ion source and transfer line temperatures were 150 and 280 °C, respectively. The mass spectrometer was operated in the electron capture negative ionization (ECNI) mode using methane as the reagent gas. Selected ion monitoring (SIM) used both bromine isotopes at m/z 79 and 81 for the BFRs; m/z 719.5 and 721.5 for BDE-201; m/z 408.8 and 410.8 for 6964
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BDE-197; m/z 561.7 and 563.7 for BDE-203; m/z 486.8 and 488.8 for BDE-204 and BDE-206 to BDE-209; and m/z 494.6 and 496.6 for 13C12-BDE-206 and 13C12-BDE-209. Quality Assurance/Quality Control. Four quality control criteria were used to ensure the identification of BFRs congeners in the serum samples: First, retention times matched with those of the authentic reference compounds. Second, the isotope ratios of the two characteristic ions were within (15% of the theoretical values. Third, the signal-tonoise (S/N) ratio was greater than three for the selected ions. Fourth, if interferences were present in the blank samples, the amount of the analytes in the sample had to be at least two times that in the blank sample. If any of these four criteria failed, the sample was excluded. The recovery of the analytical method was monitored using BDE-77 and 13C12-BDE-209 as surrogate standards. The average recoveries of BDE-77 and 13C12-BDE-209 were 78-84% and 55-67%, respectively. A procedural blank was run in parallel with every batch of 5-9 samples. Low levels of BDE-47, -99, -153, and -209 were detected in some blanks, and 13 of the 128 samples were excluded because of these high blanks. Average blank levels were subtracted from each sample when appropriate. If a congener was below the limit of detection (LOD, defined as a signal-to-noise ratio of 3), its concentration was assumed to be zero. Through the use of spiked serum samples, the recoveries of other BFRs were determined, and they were >86%. None of these BFRs were detected in procedural blank samples. The LODs of the major PBDE congeners and other BFRs are given in SI Table S2. Statistics. An analysis of variance (ANOVA) calculations using Minitab 15swas used to test for group differences. In addition, correlations between PBDE concentrations and BMI and age, respectively, were tested using the Pearson coefficient of determination. In all cases, statistical significance was defined as a probability of
