Environ. Sci. Technol. 2010, 44, 7723–7728
Occupational Exposure to Airborne Perfluorinated Compounds during Professional Ski Waxing B A A R D I N G E G E R D S S O N F R E B E R G , †,‡ LINE SMÅSTUEN HAUG,§ RAYMOND OLSEN,† HANNE LINE DAAE,† MERETE HERSSON,† CATHRINE THOMSEN,§ S Y V E R T T H O R U D , † G E O R G B E C H E R , §,⊥ P A A L M O L A N D E R , †,⊥ A N D D A G G . E L L I N G S E N †,* National Institute of Occupational Health, P.O. Box 8149 Dep, N-0033 Oslo, Norway, The Norwegian Biathlon Union, Servicebox 1, US, N-0840 Oslo, Norway, Norwegian Institute of Public Health, P.O.Box 4404 Nydalen, N-0315 Oslo, and Department of Chemistry, University of Oslo, P.O.Box 1033 Blindern, N-0315 Oslo, Norway
Received June 17, 2010. Revised manuscript received August 16, 2010. Accepted August 25, 2010.
The concentration levels of 11 perfluorinated carboxylic (PFCA) and eight sulfonic (PFSA) acids were determined in the serum of 13 professional ski waxers. The same components were also determined in workroom aerosols and in fluoro containing solid ski waxes and ski wax powders. The highest median concentration (50 ng/mL) was detected for perfluorooctanoic acid (PFOA), which is around 25 times higher than the background level. For the first time perfluorotetradecanoic acid (PFTeDA) has been found in human serum. Positive statistically significant associations between years exposed as ski waxer and seven different PFCAs were observed. The serum concentrations of the PFCAs with carbon chain lengths from C8 to C11 were reduced by around five to 20% on average during the eight month exposure free interval, whereas the reduction was substantially larger when the carbon chain lengths were smaller than C8 or larger than C11. This study links for the first time PFCAs in the ski waxers serum to exposure from the work room aerosols. Not only professional ski waxers but also the significant larger group of amateur skiers and waxers are potentially exposed to these compounds.
Introduction In winter sports such as cross-country skiing, downhill skiing and biathlon, ski waxes are applied to the skis to increase performance. Ski teams performing at high levels have highly skilled professional ski waxers in their employment, and professional ski waxers are also employed at certain sport shops and ski centers. Professional ski team waxers are exposed to aerosols and to some extent vapors when working in poorly ventilated small cabins during the skiing season * Corresponding author phone: + 47 23 19 53 77; e-mail:
[email protected]. † National Institute of Occupational Health. ‡ The Norwegian Biathlon Union. § Norwegian Institute of Public Health. ⊥ University of Oslo. 10.1021/es102033k
2010 American Chemical Society
Published on Web 09/10/2010
from November until March, in particular when applying gliders. Today only a few use full facepiece respirators regularly, in previous years the use was limited to primitve models. Worldwide, the number of professional ski waxers is not known. In addition to professional ski waxing, a substantial number of people consume such products in preparation to leisure activities. The number of people potentially exposed to ski waxing products containing perfluoro-n-alkanes (PFA), either professionally or in relation leisure activities, is unknown. Waxes with different chemical characteristics fit different snow and temperature conditions, and can crudely be divided into gliders and grip waxes. Gliders are applied to the skis to reduce resistance between the skis and the snow and to improve water repellency. The exact composition of gliders is rarely disclosed by the producers. However, modern gliders, available as solid blocks or as powders, consist mainly of petroleum-derived straight-chain aliphatic hydrocarbons with 20-80 carbon atoms and PFAs, that is, alkanes with 12-24 carbon atoms where all hydrogen are substituted by fluorine (1, 2).The solid block gliders may also contain various percentages of polyfluorinated n-alkanes, that is, not fully fluorinated alkanes CH3(CH2)n(CF2)mCF3, where n varies from 9 to 23 and m from 3 to 11, as additives (2). The powders are sprinkled on to the skis, while the solid blocks are melted and dripped on the ski using a heated iron. After application, the gliders are heated with an iron for the preparation of a smooth surface. The working temperature of the iron is typically between 120 and 180 °C. The gliders melt and to some extent evaporate during heating, and when cooled, they will nucleate and form small particles that will grow by condensation and coagulation (3). Aerosol concentrations from 0.62 to 2.36 mg/m3 generated during the heating process have been measured previously (4). Descriptions of the production processes of gliders are lacking in the scientific literature. However, it is likely that parts of the synthesis process are similar to those generally used in industrial processes of perfluorinated alkylated substances. These substances are synthesized by two different methods (5). The older method of electrofluorination has low process selectivity and results also in branched carbon chains. The method of telomerization is based on the polyaddition of tetrafluoroethylene to trifluoromethane iodide. It has been described that some production processes result in breakdown products, such as perfluorinated carboxylic acids (PFCA) containing two to seven carbon atoms, as well as longer chain products (6), and that considerable fragmentation of the carbon chain occurs (7). Lack of isomeric purity is a signature of some of the processes (8). The producers of the gliders buy different components in bulk from various chemical suppliers, often in “technical” quality. Thus, the purity may be sometimes questionable. Polyfluorinated compounds have been used during the last 50 years in many commercial applications including surfactants, lubricants, paints, polishes, paper and textile coatings, food packaging, and fire-retarding foams (9). Concerns about the persistence and bioaccumulative properties of polyfluorinated compounds were raised when the widely used surfactant perfluorooctylsulfonate (PFOS) was found to be ubiquitously distributed in wildlife (10, 11) Several PFCAs and perfluorinated sulfonic acids (PFSA) have been detected in human blood from general populations worldwide (8, 12). Higher levels of perfluorooctanoic acid (PFOA) were reported in residents living near a fluoropolymer production facility and in residents exposed to contaminated drinking water (13, 14). VOL. 44, NO. 19, 2010 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
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Studies addressing the chemical work environment among professional ski waxers are in general scarce, also with respect to fluorinated compounds. Nilsson et al., however, found elevated levels of some PFCAs with carbon chain lengths from C4 to C11 in whole blood from ski waxers using fluorinated ski wax in a recent study (15). The highest PFOA concentration was 535 ng/mL. Occupationally exposed workers manufacturing PFCAs and PFSAs, had PFOA serum concentrations ranging from 50 to 80 000 ng/mL (16). No studies have yet distinctly described any link between fluorinated compounds in human serum and in ski waxes or occupational air samples during ski waxing. The aims of this study were to assess the serum levels of perfluorinated compounds in ski waxers. Furthermore, it was a goal to determine the levels of these compounds in air samples collected during work in waxing cabins, and finally to determine the content of these compounds in commonly used modern gliders.
Materials and Methods Study Design and Participants. Professional ski waxers were recruited from two national winter sports teams participating in world cup competitions. Thirteen men were asked to participate in the study. Participation in the study was voluntary, but all subjects accepted. Their mean age was 40.6 years (range 28.3-52.9), and they had worked as professional ski waxers for seven years (range 2-13) on average. The study was approved by the local ethical committee for medical research. An informed written consent was obtained from the participants. The design of the study was to include the subjects at the end of season I (March 2008) for blood sampling. A second blood sample of the same subjects was collected eight months later at the beginning of the next season (season II) (October/ November 2008). The third and final blood sample was collected at the end of season II (March 2009). In addition to the blood samples, six air samples that had been collected during a health survey (parallel to this study) to assess ski waxers’ pulmonary health were analyzed for the content of PFCAs and PFSAs. Finally, 11 solid waxes and 11 powders from six different manufacturers were analyzed to assess the contents of PFCAs and PFSAs in these ski waxing products. Sampling Procedures. A 10 mL tube without additives (BD Vacutainer, Belliver Industrial Estate UK) was used to collect whole blood at each sampling session. The blood samples were stored at room temperature for 45 min before centrifugation at 2300 rpm for 20 min. The serum was pipetted into a 4.0 mL NUNC polyethylene cryotube, and stored at -20 °C until analysis. Air Sampling with Direct Reading Respicon Sampler. The air samples were collected with a photometric direct reading Respicon sampler (Helmut Hund GmbH, Wetzlar, Germany) in six different waxing cabins selected at random during World Cup competitions in Norway during the season 2007-2008. This sampler is a 3.1 L/min multistage virtual impactor with an annular slit aerosol inlet. The instrument is designed to simultaneously collect the three health related aerosol fractions: (a) the coarser inhalable fraction, defining the aerosol fraction that may enter the nose and mouth during breathing; (b) the intermediate thoracic fraction, defining the fraction that may penetrate beyond the larynx and so reach the lung; and (c) the finer respirable fraction, defining the fraction that may penetrate to the alveoli of the lung (17). In addition the sampler separate the three fractions on filters, thus in total 18 filters were collected. A detailed description of the instrument has been published previously (18). The sampler was placed in the middle of the waxing cabin for area sampling during day time for approximately 5-8 h. Chemicals. The following analytes were included in the study: Perfluorobutanoic acid (PFBA), perfluoropentanoic 7724
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acid (PFPeA), perfluorohexanoic acid (PFHxA), perfluoroheptanoic acid (PFHpA), PFOA, perfluorononanoic acid (PFNA), perfluorodecanoic acid (PFDA), perfluoroundecanoic acid (PFUnDA), perfluorododecanoic acid (PFDoDA), perfluorotridecanoic acid (PFTrDA), perfluorotetradecanoic acid (PFTeDA), perfluorobutane sulfonic acid (PFBS), perfluorohexane sulfonic acid (PFHxS), perfluoroheptane sulfonic acid (PFHpS), PFOS, perfluorodecane sulfonic acid (PFDS), perfluorooctane sulfonamide (PFOSA), N-methylperfluorooctane sulfonamide (MeFOSA) and N-ethylperfluorooctane sulfonamide (EtFOSA). The analytes were purchased from Wellington Laboratories (Guelph, Ontario, Canada). The 12 isotope labeled internal standards used and all other chemicals used are described elsewhere (19). Methanol (GC-MS grade) used in extraction of waxes and powders was obtained from Sigma Aldrich. Chemical Analysis. Sample Preparation. Serum. Serum samples were prepared according to a previously described method (19). In brief, 150 µL of serum was transferred to a centrifugation tube, added internal standards and methanol to make up a total volume of 150 µL methanol for precipitation of proteins, and then mixed using a whirl mixer. The samples were subsequently centrifuged and the supernatant was transferred to a glass autosampler vial, added 500 µL 0.1 M formic acid and mixed on a whirl mixer. Ski Waxes: Solid Blocks and Powders. Ski wax samples were extracted by initially transferring 1 g of the solid blocks or 3 g of the powders to 12 mL glass vials with a screw cap. Ten mL of methanol were added to the vials. The vials were subsequently sonicated for 45 min. Every 15 min, the samples were manually shaken for 20 s. After the sonication, the samples were cooled to room temperature. Four mL of the methanol extracts were transferred to a 10 mL centrifugation tube and the samples were subsequently centrifuged at 2000 rpm for 15 min. Finally, an aliquot of 50 µL of the methanol extracts were added internal standards, and 950 µL 0.1 M formic acid, and mixed on a whirl mixer. Aerosol Filters. The aerosol collecting filters were stored in 4 mL glass vials. The sample preparation was based on a previously described method (20). In brief, 2 mL of methanol was added to the vials, and mixed thoroughly on a whirl mixer and put in an ultrasonic bath for 10 min. The methanol extracts were then filtered through an empty precleaned SPE cartridge (3 mL Supelco) fitted with two frits (20 µm polyethylene) and collected in glass. Two mL 0.1 M formic acid were also passed through the filters and collected. A portion of 1 mL of the filtered extract was added internal standards and mixed on a whirl mixer. Each filter was analyzed separately. Chromatographic Determinations. For the serum determinations, the calibration solutions were prepared in serum from newborn calves, which has been shown to be an acceptable surrogate matrix for human serum (19). For the determinations of the PFCAs and PFSAs in the ski waxes and aerosol samples the calibration solutions were prepared in a mixture of methanol and 0.1 M formic acid (1:1, v/v). The samples and calibration solutions were analyzed by injection of 400 µL extract on a column switching liquid chromatography (LC) system coupled to a triple quadrupole mass spectrometer (MS) as described in detail elsewhere (19). For quantification of PFOS, the total area of the linear and branched isomers was integrated. The quantitative method for determination of PFCAs and PFSAs in serum has been thoroughly validated (19). For serum the limit of quantification (LOQ) was restricted by the lowest calibration point and set to 0.050 ng/mL for all PFCAs and PFSAs except for perfluorobutanoic acid (PFBA) for which it was 0.10 ng/mL (19). The methods for determination of PFCAs and PFSAs in ski waxes and aerosol samples are to be considered semiquantitative as no method validation has
TABLE 1. Median Concentrations (in ng/mL) and Ranges of Perfluorinated Compounds in Serum of 13 Professional Ski-Waxers According to Seasona
PFBA PFHxA PFHpAb,c PFOAb PFNA PFDAb PFUnDAb PFDoDAb,c PFTrDAb PFTeDAb,c PFHxSb PFHpS PFOSb PFOSA
after season I
before season II
after season II
march 2008
november 2008
march 2009
median
range
median
range
median
range
Nd 0.08 2.2 50 13 7.5 0.96 2.0 0.26 1.2 1.6 0.49 27 Nd
Nd-3.7 Nd-0.31 0.4-11.0 20-174 3.6-37 2.1-28 0.32-3.4 0.51-9.1 0.11-1.0 0.26-4.4 0.83-6.2 0.16-1.7 11-91 Nd-4.5
Nd Nd 0.74 53 13 6.8 0.88 1.2 0.17 0.40 1.4 0.40 24 Nd
Nd-Nd Nd-Nd 0.14-9.1 15-173 3.3-38 1.7-28 0.16-3.5 0.32-7.3 0.09-0.65 0.03-2.10 0.84-6.2 0.21-1.4 8.7-86 Nd-1.3
Nd Nd 1.5 57 12 6.8 0.88 1.3 0.21 0.36 1.5 0.40 26 Nd
Nd-5.4 Nd-Nd 0.21-12.0 20-162 3.9-33 2.3-27 0.21-3.3 0.46-8.3 0.06-0.76 0.11-2.9 0.80-6.4 0.13-1.5 10-86 Nd-2.1
a Nd ) not detected. b p < 0.05 between “After season I” and “Before season II”. c p < 0.05 between “Before season II and “After season II”. Nd: not detected < LOQ ) 0.050 ng/mL, except PFBA 0.10 ng/mL.
been performed. A 100% extraction effiency is used in the calculations. The quality of the PFCAs and PFSAs determinations in serum was controlled by analyzing reference samples (n ) 3), and the results were within the SD of the consensus concentrations (21). Method blanks, including extracts of filters used for aerosol collection, were analyzed simultaneously with the samples. The LOQ was calculated to 48, 67, and 82 ng/g dust for the respirable, thoracic, and inhalable aerosol fractions, respectively. For the gliders the LOQ was calculated
