Anal. Chem. 2004, 76, 3337-3364
Environmental Mass Spectrometry: Emerging Contaminants and Current Issues Susan D. Richardson
National Exposure Research Laboratory, U.S. Environmental Protection Agency, Athens, Georgia 30605 Review Contents Reviews on Emerging Contaminants and General Reviews PFOS and PFOA Brominated Flame Retardants (Polybrominated Diphenyl Ethers) Pharmaceuticals, Hormones, and Endocrine-Disrupting Compounds Drinking Water Disinfection Byproducts Mass Spectrometry and Homeland Security Chiral Contaminants Algal Toxins Pesticide Transformation Products Alkylphenol Ethoxylate Surfactants Organotins Perchlorate Methyl tert-Butyl Ether Arsenic Microorganisms Natural Organic Matter Literature Cited
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This review covers developments in environmental mass spectrometry over the period of 2002-2003. A few significant references that appeared between January and March 2004 are also included. This review is in keeping with a current approach of Analytical Chemistry to include only 100-200 significant references and to mainly focus on trends in analytical methods. As a result, this review will limit its focus to new, emerging contaminants and environmental issues that are driving most of the current research. Even with a more narrow focus, only a small fraction of the quality research publications could be discussed. Thus, this review will not be comprehensive, but will highlight new areas and only discuss representative papers in the areas of focus. I would welcome any comments you have, in particular regarding this more narrow focus, whether you find it more (or less) useful than a broader approach (
[email protected]). Numerous abstracts were consulted before choosing the best ones to present here. Abstract searches were carried out using the Web of Science. A table of acronyms is provided (Table 1) as a quick reference to the acronyms of analytical techniques and other terms discussed in this review. A table of useful websites is also provided (Table 2). Over the last two years, the overall trends in analytical methods for environmental analysis include an increased application of timeof-flight (TOF), quadrupole-ion trap, and Fourier transform (FT) mass spectrometers; increased use of chiral separations (usually with chiral gas chromatography (GC) or liquid chromatography (LC) columns or using capillary electrophoresis (CE)); more on10.1021/ac040060d Not subject to U.S. Copyright. Publ. 2004 Am. Chem. Soc.
Published on Web 04/24/2004
line coupling of extraction with separation/detection, such as solidphase extraction (SPE) or solid-phase microextraction (SPME) coupled with LC/mass spectrometry (MS); increased use of LC/ MS/MS and GC/MS/MS; and increased coupling of LC and ion chromatography (IC) with inductively coupled plasma (ICP)MS for inorganic applications. The use of matrix-assisted laser desorption ionization (MALDI)-MS and electrospray ionization (ESI)MS has also increased for the analysis of microorganisms. Research in this area is now going beyond simple fingerprinting and empirical matching of MALDI or ESI mass spectra to the organisms; papers are reporting increased development of modeling approaches for improving identifications, complete sequencing of protein biomarkers, and techniques to explore the structure and function of these microorganisms. MALDI- and ESI-MS are also increasingly being used to probe the structures of high molecular weight natural organic matter (i.e., humic materials). Previously, mass spectral analysis of humic material was only possible through the use of chemical and thermal degradative techniques, such as pyrolysis-GC/MS, which did not permit the analysis of the original, intact molecule. The availability of MALDIand ESI-MS, along with the use of high-resolution FT-ion cyclotron resonance (ICR)-MS and MS/MS, is allowing the analysis of intact humic materials for the first time by mass spectrometry. The last two years have also seen a combined approach of using size exclusion chromatography (SEC) to separate/purify molecular weight fractions prior to analysis by ESI-MS; this is designed to address the question about whether humic materials are selectively ionized, creating a low molecular weight bias. A few new analytical techniques have also been developed and applied to environmental analyses during the last 2 years, including the use of low-pressure GC with GC/MS, which allows for much shorter analysis times (see discussion under the Organotins section); a rapid on-slide proteolytic digestion of microorganisms for MALDI-MS analysis (see discussion under the Microorganisms section); and a new Supersonic GC/MS technique that enables enhanced molecular ions and a rapid measurement of pesticides in complex matrixes (see discussion under Pesticide Transformation Products). A pollutant that is currently receiving a great deal of attention by the U.S. Environmental Protection Agency (EPA) and others is perfluorooctanoic acid (PFOA). PFOA is a used to make fluoropolymers (PTFE) and fluoroelastomers (PVDF) that are used in a wide variety of commercial products. Perfluorooctanesulfonate (PFOS), a related compound, initially received much attention due to its unexpected toxicity, persistence, and bioaccumulative ability. Early research is revealing PFOA to also be persistent in the environment and to be toxic and carcinogenic. Analytical Chemistry, Vol. 76, No. 12, June 15, 2004 3337
Table 1. List of Acronyms ACS APCI APEO ASMS BMX BMX-1 BEMX-3 BSTFA BTEX CCL CE CI DBPs DEHP DMA DNPH ECD ECNI EDCs EI EPA ESA ESI FOSA FT GC HAAs IC ICP ICR LC MALDI MCL MIMS MRM MS MTBE MTBSTFA MX NICI NDMA
American Chemical Society atmospheric pressure chemical ionization alkylphenol ethoxylates American Society for Mass Spectrometry brominated forms of MX 3-chloro-4-(bromochloromethyl)-5-hydroxy-2(5H)-furanone (E)-2-bromo-3-(dibromomethyl)-4-oxobutenoic acid bis(trimethylsilyl)trifluoroacetamide benzene, toluene, ethylbenzene, and xylenes Contaminant Candidate List capillary electrophoresis chemical ionization disinfection byproducts di(2-ethylhexyl)phthalate dimethylamine 2,4-dinitrophenylhydrazine electron capture detection electron capture negative ionization endocrine disrupting compounds electron ionization Environmental Protection Agency ethanesulfonic acid electrospray ionization heptadecafluorooctane sulfonamide Fourier transform gas chromatography haloacetic acids ion chromatography inductively coupled plasma ion cyclotron resonance liquid chromatography matrix-assisted laser desorption ionization maximum contaminant level membrane introduction mass spectrometry multiple reaction monitoring mass spectrometry methyl tert-butyl ether N-(tert-butyldimethylsilyl)-N-methyltrifluoroacetamide 3-chloro-(4-dichloromethyl)-5-hydroxy-2(5H)-furanone negation ion chemical ionization nitrosodimethylamine
NMR NOM NP NP1EO NP1EC NP2EC NPEOs OA OP OP1EO PBBs PBDEs PCBs PFBBr PFDA PFDoA PFHpA PFHxS PFNA PFOA PFOS PFOSA PFTA PFUnA PVC Q-TOF QIT SEC SPE SPMDs SPME TAME TBA TBF TCAA THMs THM4 TOF TOX
nuclear magnetic resonance natural organic matter 4-nonylphenol nonylphenol monoethoxylate nonylphenol monocarboxylate nonylphenol dicarboxylate nonylphenol ethoxylates oxanilic acid 4-tert-octylphenol octylphenol monoethoxylate polybrominated biphenyls polybrominated diphenyl ethers polychlorinated biphenyls pentafluorobenzyl bromide perfluorodecanoic acid perfluorododecanoic acid perfluoroheptanoic acid perfluorohexanesulfonate perfluorononanoic acid perfluorooctanoic acid perfluorooctane sulfonate perfluorooctanesulfonamide perfluorotetradecanoic acid perfluoroundecanoic acid poly(vinyl chloride) quadrupole time of flight quadrupole ion trap size exclusion chromatography solid phase extraction semipermeable membrane devices solid phase microextraction tert-amyl methyl ether tert-butyl alcohol tert-butyl formate trichloroacetic acid trihalomethanes four regulated THMs (chloroform, bromoform, bromodichloromethane, chlorodibromomethane) time of flight total organic halide
Table 2. Useful Websites website www.epa.gov http://www.epa.gov/OGWDW/ccl/cclfs.html www.epa.gov/ogwdw/methods/methods.html www.epa.gov/epaoswer/hazwaste/test/new-meth.htm#8323 www.epa.gov/athens/publications/EPA_600_R02_068.pdf http://www.epa.gov/safewater/mdbp/mdbp.html www.chbr.noaa.gov/CoastalResearch/algaeInfo.htm www.dhs.ca.gov/ps/ddwem/chemicals/NDMA/NDMAindex.htm www.epa.gov/mtbe www.epa.gov/OGWDW/mtbe.html www.epa.gov/safewater/arsenic.html www.epa.gov/endocrine/
However, there is little known about the sources of PFOA and exposure pathways or environmental occurrence and fate. As a result, PFOA has emerged as a high-priority contaminant for the U.S. EPA, and research is exploding in this area. Polybrominated diphenyl ethers (PBDEs) are also emerging as important environmental contaminants. These compounds are widely used as flame retardants in furniture (particularly in the foam cushions used in chairs), textiles (including children’s 3338 Analytical Chemistry, Vol. 76, No. 12, June 15, 2004
comments U.S. EPA’s website; provides a searchable link to U.S. EPA regulations and methods U.S. EPA’s Contaminant Candidate List (CCL) link to U.S. EPA’s Office of Ground Water and Office of Research and Development drinking water methods link to new U.S. EPA Method 8323 for organotins link to Nationwide DBP Occurrence Study U.S. EPA’s microbial and DBP Rules NOAA’s website for algal toxin information California Department of Health Services site for NDMA information U.S. EPA website for MTBE information U.S. EPA Office of Ground Water and Drinking Water information on MTBE in drinking water U.S. EPA’s website for arsenic U.S. EPA’s website for EDCs
clothing), plastics, paints, and electronic appliances. PBDEs are environmentally persistent, having been found in human milk, human blood, birds, fish, marine mammals, air, and sediments, and there is concern about potential adverse developmental effects from exposure to PBDEs. The majority of PBDE studies have been from Europe, which has a Directive to control emissions of these compounds. Although there were a few early measurements of PBDEs in the United States in the late 1970s and early 1980s,
they have not been regulated in the United States. However, interest has increased dramatically in the last two years, with a new interest by the U.S. EPA and new reports of PBDEs in human maternal and fetal blood samples, as well as adipose tissues. Endocrine disrupting compounds (EDCs) continue to be an important issue. Although EDCs can hardly be considered an “emerging” issue (there has been concern about EDCs since the early 1990s), most EDC research has been conducted only in the last seven years, and the last two years has seen substantial growth. As time goes on, more chemicals are being discovered to be endocrine disrupting. In the United States, the Food Quality Protection Act and the Safe Drinking Water Act Amendments (published in 1996) helped to promote new research on EDCs. These two legislative acts require that the U.S. EPA develop a screening and testing strategy for estrogenic substances and other EDCs. Publication of the book Our Stolen Future in 1996 also helped to publicize this area of concern, much as Rachel Carson’s book, Silent Spring, helped to launch the beginnings of the environmental movement in the 1960s. Another area of recent interest is the study of pharmaceuticals in water. In addition to concern about potential estrogenic effects to wildlife, there is also concern about potential estrogenic effects in humans and the development of bacterial resistance. Due to improved analytical methods (typically LC/MS) that can measure highly polar pharmaceuticals at the low levels required, there has been an explosion of research in this area. Researchers are not only measuring their occurrence in waters but also studying their fate in wastewater treatment plants. Several studies are, in fact, showing that there has been incomplete removal of some pharmaceuticals at wastewater treatment plants, and therefore, there is the possibility that they could enter source waters for drinking water. In fact, pharmaceutical contamination of tap water in Germany and in the United States has been recently shown. As a result, various pharmaceuticals are currently being considered as possible future drinking water contaminants for the U.S. EPA’s Contaminants Candidate List (CCL), a list of unregulated contaminants that are to be monitored in drinking water systems and considered for future regulation (based on their occurrence and health effects) (http://www.epa.gov/OGWDW/ccl/cclfs.html). The current list of CCL contaminants is also available in ref 2. As in the preceding two years, herbicides and pesticides continue to be studied more than any other environmental contaminant. However, current research is focusing more on their degradation products, with the recognition that that these degradation products (often hydrolysis products) can be present at greater levels in the environment than the parent pesticide itself. Studies are also focusing on pesticides that are endocrine disrupting and on the occurrence/degradation of chiral isomers. Chiral chromatography (using either chiral GC or LC columns or CE with mass spectrometry) is being used to study the occurrence and environmental fate of pesticides that are chiral. Typically, one pesticide enantiomer is the active one, and the other is inactive. In addition, one pesticide enantiomer is typically degraded differently in the environment (their fate is not the same). Therefore, with the manufacture and use of pesticides containing racemic mixtures, there was the potential for one form of the pesticide to accumulate in the environment and cause
unintended effects on nontarget species. Because earlier fate research studied racemic mixtures, there was also the potential for an incorrect assessment of the pesticide’s half-life in the environment; i.e., the rate of degradation may give the impression that the pesticide would completely degrade, when only one form may be degrading. It is also interesting that the ability to separate pesticide enantiomers has also led pesticide manufacturers to offer a particular enriched chiral isomer commercially. Accordingly, there are studies that have observed this “switch”, where only one enantiomer is predominantly found. This production and use of specific pesticide enantiomers is expected to increase and may potentially have a benefit to the environment by reducing the amount of pesticide needed to control pests and undesirable plants/weeds. The discovery of nitrosodimethylamine (NDMA) as a disinfection byproduct (DBP) in drinking water treatment (and also as a contaminant) has received much interest due to its known cancer potency. Other recently identified DBPs are also receiving attention. These include halonitromethanes, which have been shown to be more genotoxic than most of the DBPs currently regulated, as well as iodinated DBPs, such as iodotrihalomethanes and iodo acids, which are predicted to be potent genotoxins. Lower detection limits, improved analytical instrumentation and methods, and new derivatization procedures are allowing significant advances in an area that has been active for 30 years. Organotins are receiving renewed attention partly because of a new study showing that they can leach out of poly(vinyl chloride) (PVC) pipe into drinking water at continuous ppb levels and also a recent study suggesting that they may leach from polyethylene plastic containers used in the making of wine. Organotins were previously regarded as an ecological threat, due to leaching from antifouling paints used on ships. New research is indicating that there is a potential threat of human exposure through drinking water. Although not considered as great a toxicological risk, methyl tertbutyl ether (MTBE) is also still receiving significant study, due to its impact on groundwater sources (and entry into drinking water) from leaking underground gasoline storage tanks. Perchlorate contamination in groundwater has also recently been shown to be significant, and its use in some fertilizers has been a recent concern. Arsenic research has also seen a continuous increase, with the development of improved analytical methods permitting the study of specific species of arsenic in water, foods, and biological samples. The ability of mass spectrometry to measure polar, higher molecular weight compounds has also permitted the analysis of algal toxins in environmental samples. Many algal toxins are peptide related; e.g., microcystins are cyclic peptides produced by blue green algae (cyanobacteria). Algal toxins have been responsible for large fish kills, poisoning of shellfish, other animal deaths, and illness in people. Cyanobacteria, other freshwater algae, and their toxins are currently on the U.S. EPA’s CCL. Another group of emerging contaminants included in this review are alkylphenol ethoxylate surfactants, which are widely used in detergents and are endocrine disrupting. Finally, a section on MS and Homeland Security was added to this year’s review, as interest has dramatically increased in this area due to the renewed terrorism threats and the events of September 11, 2001. Rapid detection methods being developed for field detection of these Analytical Chemistry, Vol. 76, No. 12, June 15, 2004
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agents also has a benefit to their detection for environmental purposes. REVIEWS ON EMERGING CONTAMINANTS AND GENERAL REVIEWS A number of reviews over the last 2 years covered emerging contaminants. The previous Environmental Mass Spectrometry review published in 2002 focused on emerging contaminants and current issues for the 2000-2001 period (1). This review covered topics similar to that of the current review, with discussions of the U.S. EPA’s CCL, pharmaceuticals, EDCs, chiral contaminants, PBDEs, algal toxins, drinking water DBPs, MTBE, organotins, perchlorate, arsenic, natural organic matter, and microorganisms. A review on Water Analysis published in 2003, included a discussion of emerging contaminants and current issues that are important for water, as well as a discussion of the new regulations and regulatory methods that have been developed (2). This Water Analysis review covered developments from 2001 to 2002. Ferrer and Thurman published an excellent book, entitled Liquid Chromatography/Mass Spectrometry, MS/MS, and Time-of-Flight MS: Analysis of Emerging Contaminants, which resulted from a symposium held at the 225th American Chemical Society (ACS) meeting in Orlando, FL (3). This book focuses on LC/MS/MS and TOF-MS techniques, which are now being adopted by the environmental community, with a focus on topics including pesticides, pharmaceuticals, surfactants, disinfection byproducts, aromatic hydrocarbons, humic substances, plasticizers, steroids, hormones, and their degradation products. Many of the chapters in this book are groundbreaking and are discussed in various sections of this review. As a leadoff chapter to this book, Ferrer and Thurman wrote a review on the analysis of emerging contaminants (4). This overview chapter focused on the importance of emerging contaminants and their presence in the environment and summarizes the advances presented in this book. Thurman and Ferrer also wrote a chapter comparing quadrupole (Q)-TOF, triple quadrupole, and ion trap MS/MS for the analysis of emerging contaminants (5). In this chapter, the unique features of each of these instruments is presented, along with examples showing their complimentary nature. For example, Q-TOF-MS/ MS allows exact mass measurements (1-2 millimass units) for molecular ions and fragments that aid in the identification of unknowns; triple quadrupole-MS/MS permits the measurement of neutral loss, which aids in the identification of unknowns that are structurally related; and quadrupole ion trap-MS/MS allows MSn measurements, which help elucidate fragmentation pathways and unknown chemical structures. A special issue of TrAC, Trends in Analytical Chemistry published in November 2003 focused on emerging pollutants in water analysis. In this issue, Petrovic et al. discussed the analysis and removal of emerging contaminants in wastewater and drinking water through the use of activated sludge treatment, membrane bioreactors, advanced oxidation processes used for wastewater treatment, and ozonation, granular activated carbon filtration, and other processes used for drinking water treatment (6). As for the book by Ferrer and Thurman, this special issue of TrAC, Trends in Analytical Chemistry contains many important papers on the subject of emerging contaminants; as a result, several of these papers will be discussed in various sections of this review. 3340
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Farre and Barcelo reviewed the testing of wastewater and sewage sludge by biosensors, bioassays, and chemical analysis (7). Fractionation schemes that combine sample preparation and chemical analysis (including LC/MS and GC/MS) with biological measurements were presented and reviewed. In early 2004, Petrovic et al. published an excellent review on a survey of new monitoring and occurrence data for endocrine disrupting compounds and other emerging contaminants in the environment (8). An overview of toxicity identification and evaluation procedures used for the effect-based analysis of EDCs is presented, along with future trends in advanced chemical analysis of EDCs and other emerging contaminants. This paper was part of a special issue in Analytical and Bioanalytical Chemistry devoted to EDCs. De Alda et al. published a review on LC/MS and LC/MS/MS methods for measuring emerging pollutants (steroid hormones, drugs, alkylphenol surfactants) in aquatic environmental samples (9). This review includes instrumental considerations, as well as sample preparation aspects, with a special focus on advanced techniques, such as immunosorbents, restricted access materials, and molecular imprinted materials. In early 2004, Zwiener and Frimmel published a two-part review, on LC/MS analysis in the aquatic environment and in water treatment. The first part covered instrumentation and general aspects of analysis and detection (10). This review discussed the current status and future perspectives of mass analyzers (which includes a discussion of quadrupole, ion trap, and TOF mass spectrometers), ionization techniques to interface LC with MS (which includes a discussion of ESI, atmospheric pressure chemical ionization (APCI), and atmospheric pressure photoionization), and methods for preconcentration and separation for water analysis (which includes a discussion of SPE with different sorbents, reversed-phase-LC, and on-line and miniaturized sample extraction and introduction approaches). Issues of compound identification, matrix effects, development of MS libraries, and connecting analysis with toxicity bioassays are also addressed. The second part covered applications of LC/MS for emerging contaminants and related pollutants, microorganisms, and humic acids (11). Several reviews of a more general nature are also worthy of note. Koester et al. published their biennial review of Environmental Analysis (covering the period of 2001-2002), which included a review of sample collection and extraction methods, separation and detection techniques (including LC/MS and ICPMS), emerging detection techniques (nuclear magnetic resonance spectroscopy (NMR) and MS), and analytes of emerging interest (12). This article not only reviews key papers published in those areas but also gives detailed discussions on the advantages and disadvantages of the analytical techniques, making this article a must-read for analytical chemists desiring the latest developments in environmental analysis. In 2003, the Journal of Chromatography, A published a special issue on A Century of Chromatography commemorating their 100th volume of the journal. This issue included papers on LC/ ESI-MS, LC/APCI-MS, LC/ICPMS, and GC/MS. Reemtsma covered LC/MS strategies for trace-level analysis of polar organic pollutants (13). This review discusses the selection of appropriate LC conditions and the most sensitive ionization mode for various polar analytes. Rosenberg reviewed the potential of LC/MS for speciation analysis (14). In this article, a brief review on the
fundamentals of atmospheric pressure ionization techniques is given, followed by a discussion of recent applications, use of ESIMS for structural elucidation of metal complexes, and characterization and quantitation of small organometallic species. MontesBayon et al. reviewed the use of LC/ICPMS for elemental speciation studies (15). Included in this article are a discussion of the basic principles of LC/ICPMS, its historical development, and ways in which this technique can be applied to the speciation of environmental samples. Santos and Galceran wrote a review on recent developments and applications of GC/MS for analyzing persistent pollutants and emerging contaminants in environmental samples (16). In this review, advantages and limitations of GC/ MS methods are discussed, as well as recent developments in field-portable GC/MS. Membrane introduction mass spectrometry (MIMS) was the subject of another review by Ketola et al. (17). In this review, the authors summarize the measurements of environmental volatile organic compounds using MIMS, developments for semivolatile compounds, and possible future directions of MIMS for environmental applications. Schmidt et al. reviewed the state-of-the-art, prospects, and future challenges of compound-specific stable isotope analysis of organic contaminants (18). The use of GC- and LC-isotope ratio-MS approaches for compound-specific isotope analysis is discussed. In another review, Heumann discussed the conditions in which ICP-isotope dilution-MS can be used as a routine method for trace element and element-speciation analysis (19). Included in this review are discussions on the use of GC, LC, laser ablation, electrothermal vaporization, and microwaveassisted isotope dilution methods. Becker reviewed the state of the art and progress of different inorganic MS techniques (including ICPMS, laser ablation-ICPMS, thermal ionization-MS, glow discharge-MS, secondary ion-MS, resonance ionization-MS, and accelerator-MS) for determining long-lived radionuclides in environmental and other samples (20). Finally, Bacon et al. published an annual review on atomic MS, covering developments from 2002 to 2003 (21). PFOS AND PFOA Fluorinated surfactants have been manufactured for many years, but they are surface-active and inherently difficult to extract and measure. As a result, their measurement in environmental and biological samples was only recently made possible through the development of LC/MS techniques. One of these fluorinated surfactants, PFOA (CF3(CF2)6COOH), is currently receiving a great deal of attention as an emerging contaminant in the United States (as well as in other countries). PFOA is a used to make fluoropolymers (PTFE) and fluoroelastomers (PVDF) for use in soil, stain, grease, and water-resistant coatings used on textiles, carpet, cookware, and automobiles. PFOA is also widely used in fire-fighting foams. Perfluorooctanesulfonate, PFOS (CF3(CF2)7SO3-), a related compound, initially received much attention due to its unexpected toxicity, persistence, and bioaccumulative ability. PFOS has been previously used in refrigerants, surfactants, polymers, pharmaceuticals, flame retardants, lubricants, adhesives, cosmetics, paper coatings, and insecticides. PFOS had also been previously found in the blood of the general population and in wildlife. As a result, the manufacturer (3M) discontinued production of PFOS in 2000. Immediately afterward, the U.S. EPA
expanded its investigation to include other fluorochemicals, including PFOA, to determine whether its use would be of concern since 3M had also found PFOA in human blood during the initial studies of PFOS. Early research is showing PFOA to be persistent in the environment and also to be toxic and carcinogenic. However, there is little known about the sources of PFOA and exposure pathways or environmental occurrence and fate. Currently, the analytical technique of choice for measuring PFOA is LC/ESI-MS/MS, which can provide ppb- tp ppt-level detections in a variety of environmental and biological samples. Recent measurements of PFOA include measurements in human samples (serum, blood, liver), animals (polar bears, ringed seals, arctic fox, mink, birds, fish), surface water, and groundwater. A review of fluorinated alkyl surfactants was published by Schultz et al. in 2003, which focused on the analysis and occurrence of fluorinated surfactants that have been observed in the environment (22). Research needs, such as the elucidation of transport processes and the development of new methods for efficiently treating wastewaters, are outlined. Sottani and Minoia report a new LC/APCI-MS/MS method for measuring PFOA in human serum at a detection limit of 10 ng/mL (23). Ion pairing was used to facilitate the extraction of PFOA, and this method was used to quantify PFOA in serum from employees exposed to fluorochemicals used in polymer production. Blood levels were found to vary between 100 and 986 ng/mL. Olsen et al. carried out an occupational exposure study of employees at a fluorochemical manufacturing plant, where serum PFOA, PFOS, and other fluorochemical levels were measured using ion pair extraction and LC/ESI-MS/MS (24). The geometric mean for the 126 employees sampled was 899, 941, 180, 8, 81, 13, and 22 ng/mL for PFOA, PFOS,perfluorohexanesulfonate(PFHxS),ethylperfluorooctanesulfonamidoacetate, N-methyl perfluorooctanesulfonamidoacetate, perfluorooctanesulfonamide (PFOSA), and perfluorooctanesulfonamidoacetate, respectively. In another study, Olson et al. measured serum concentrations of PFOA and PFOS in employees from two perfluorooctanyl-manufacturing plants in Belgium and in the United States (25). Mean concentrations were 1780 and 910 ng/ mL (ppb), respectively, in U.S. employees; mean concentrations were ∼50% lower in employees from Belgium. Human donor liver and serum measurements of nonoccupationally exposed people were the focus of another study by Olsen et al. (26). Thirty-one donors were sampled for PFOA, PFOS, and PFHxS. LC/ESI-MS/MS measurements revealed liver PFOS concentrations ranging from 4.5 to 57.0 ng/g and serum PFOS levels of
