MULTISPECTRAL METHO AND RISK COMMUNI O
ne grain of rye in 100 tons of wheat. A needle in five telephone poles. Contaminants can be detected in samples at parts-perbillion and parts-per-trillion concentrations, and techniques for measuring chemicals with greater accuracy and sensitivity are constantly being developed. Many of these techniques can be used to study components of water, soil, and air that may pose environmental threats. Multispectral analysis recently evolved from GC/MS, which was first used in the late 1960s and early 1970s to identify more than 100 organic compounds in water, including 2,3,7,8-tetrachlorodibenzo-£-dioxin. During the next 10 years, the procedure became the accepted method for the identification of target analytes in aqueous samples. EPA protocols, such as Methods 624 and 625 for 114 specific organic "priority pollutants," were developed for lab-to-lab standardization. In 1971 an automated program for the spectral identification of approximately 9000 compounds was developed through the collaboration of re-
searchers at Battelle Northwest Laboratories and John McGuire at the Environmental Research Laboratory, EPA, Athens, GA (1, 2) to help experienced analysts identify analytes in water samples. Based on an algorithm developed by Harry Hertz, Ronald Hites, and Klaus Biemann at the Massachusetts Institute of Technology (3), the program led to the establishment of a reference library of mass spectra of identified compounds
FOCUS and made it possible to identify a target compound by matching its spect r u m to those in the reference library. This procedure is still used to identify compounds in water, soil, and air. The reference library at the National Institute of Standards and Technology currently contains about 50,000 spectra (4). Although this identification process is reliable in theory, it has practical limitations. Often, too little time is spent comparing a spectrum
with those in the reference library. Lab managers report that an identification requiring the comparison of an unknown chromatogram to reference spectra usually is done in less than 30 s, often by technicians who are not expert at interpreting mass spectra (5). Unfortunately, inaccurate identifications occur when inadequately trained personnel either fail to distinguish overlapping peaks or do not recognize the significance of the presence or absence of certain peaks. The use of GC/MS has other limitations. Compounds not extracted from the sample never reach the detector; polar compounds of low molecular weight, or compounds of high molecular weight, such as lignins, are not detected; and compounds whose mass spectra are not in the reference libraries are not identified. A multispectral analysis approach for the identification of these nonreferenced compounds was recently described by McGuire (5). Used in conjunction with conventional GC/MS and GC/IR, the multispectral method incorporates high-accuracy mass de-
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FOCUS termination for identification of the elemental composition of ions, FT-IR spectroscopy for recognition of submolecular structure, and chemical ionization MS for determination of molecular weight. These techniques are applied when attempts to match a GC/MS spectrum with the reference spectra fail to produce a reliable identification of an analyte. The results are melded together to give a total picture of the structure of the molecule. When identifications made by IR and MS agree, a structure can be postulated with a reasonable amount of confidence. McGuire comments, "Surprisingly, spectral matching has been successful more often than not, in spite of the fact that a reference library of even 100,000 spectra is but a small fraction of the 10,000,000 compounds that have been reported." He describes the multispectral analysis approach for determination of the s t r u c t u r e of an unknown as "just good analytical chemistry." The multispectral approach was used to elucidate the structure of an unidentified u n s a t u r a t e d aldehyde for which neither MS nor IR library spectra existed. Spectra from GC/MS, IR, chemical ionization MS, a n d high-accuracy MS analyses led to the determination of the location of the olefinic bond and a positive identification of trans- 2 -octenal. In another sample, GC/FT-IR established the presence of a - O H group in a compound previously identified by GCV MS alone as methylbenzofuran, leading to the correct identification of indenol. In another application, alkyl and chloroalkyl phosphates were pre cisely identified in the effluent of a manufacturing plant (6). The usefulness of this technique is also demonstrated in the reanalysis of a sample described in a contract laboratory report (7). The report correctly identified three target compounds, and it tentatively identified three other compounds. However, it failed to identify 16 other compounds that represented some of the largest peaks in the GC/MS chromatogram. F u r t h e r analysis of the sample by high-accuracy MS, chemical ionization MS, and GC/FT-IR led to the conclusion that only one of the tentative identifications was correct and that the other two assignments actually corresponded to compounds that had never been reported and therefore did not have spectra in the reference library. The three peaks were i d e n t i f i e d as s u b s t i t u t e d d i b e n zofurans. Now identified, their spectra can be added to the reference li-
brary, and their identification in the future will be easier. Unfortunately, the multispectral approach is time consuming and requires expensive i n s t r u m e n t a t i o n . McGuire estimates that 200 h was spent in the reanalysis, confirmation, and identification of the six substances reported in the contract laboratory sample. Together, a highaccuracy mass spectrometer and a GC/IR instrument cost approximately $500,000-$750,000. A laboratory would need a strong incentive to purchase such costly equipment, and at this time there are only ~ 100 labs in the United States, including three EPA labs, so equipped. However, the expertise needed to meld the information together is not always found in the same laboratory, and, when it is, "turf" conflicts between m a s s spectrometrists and molecular spectroscopists may prevent its use. Fortunately, a sample determination can be a collaborative effort with more than one laboratory involved in a single analysis. McGuire emphasizes, however, t h a t the multispectral approach is necessary only when components cannot be identified. Currently, nonidentified components are ignored, even though they may represent highly toxic or carcinogenic compounds. Because the multispectral approach can help to identify such components, it has great potential in the field of environmental analytical chemistry. Identification of previously unreported compounds in environmental samples raises additional concerns. What happens when they are mixed with other chemicals? What happens while they spend years in a dumpsite? What happens to animals and humans exposed to them? Frequently t h e s e questions cannot be a n swered, and, thus, the risks associated with human exposure cannot be assessed. But if human exposure is possible, or h a s already occurred, these concerns become very real. These are issues with which persons involved with risk assessment and communication struggle. Risk assessment involves evaluation of the safety hazard posed by the use of, or exposure to, a chemical, and is usually extrapolated from available laboratory and/or epidemiological data. Risk communication is the presentation of this information to the concerned community. According to Vincent Covello, director of Columbia University's Center for Risk Communication, the public's perception of the health risk posed by chemicals has changed in
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the past 10 years (8). His research shows that 10 years ago most people in the United States believed t h a t 10% of all cancers were caused by lifestyle factors such as smoking, diet, and lack of exercise; that another 10% were caused by exposure to chemicals in the environment; and that the remaining 80% were attributable to fate or natural causes. Today, however, most people still believe t h a t 10% of all cancers are caused by lifestyle factors, but they attribute 5% to fate and the remaining 85% to chemical exposure. An even more alarming finding is that most science teachers believe t h a t 80% of all cancer cases result from chemical exposure. Covello explains that the general public has many negative impressions about chemicals. For example, people perceive that most chemicals in the home are found u n d e r the kitchen sink or in the bathroom medicine cabinet and are a source of danger. He says that most people fail to realize that chemistry is involved in all facets of daily living—from toothpaste to living room carpet to computer chips to bedroom slippers. Covello a s s e r t s t h a t more effective communication is needed about our dependence on chemicals in daily life. Covello's results also indicate that during the past 10 years industry and government have lost substantial credibility in the eyes of the public, in part because of the public's perception that government has not been honest, is not competent, does not care about environmental issues, and is not committed to solving envir o n m e n t a l problems. This loss of trust and credibility makes it even more difficult for government and industry to communicate effectively with the public about issues of chemical safety. Covello proposes three steps for bridging this credibility gap. First, government and industry must make a concerted effort to win back the public's t r u s t a n d credibility by showing that they are honest, competent, caring, and committed to solving environmental problems. Second, they must draw on the credibility of those whom the public still trusts, such as medical doctors and university scientists. Third, government officials need to improve their risk communication skills. As these improved skills are utilized, the public's understanding of chemical safety and risk will increase. Covello explains that effective com munication about the important role played by chemicals in daily life is a
requirement for discussion of chemi cal risk. Such communication does not occur without effort; it is a skill that must be learned, developed, and practiced. The process must include scientists, media specialists, chemi cal manufacturers, government offi cials, and regulatory representatives, and it must be directed toward the general public. The goal must be to make the public a partner in deci sions affecting the use of chemicals in the market, the workplace, and the environment. An important point t h a t Covello makes is that the public must under stand that no chemical can be certi fied as completely safe, but that its risks can be evaluated. An educated public should ask, "How safe is it?" rather than "Is it safe?" Information about chemicals must be presented honestly and clearly. Covello stresses that teachers and schools must also become involved. Issues such as chemical testing, haz ard evaluation, and risk assessment should be taught in the schools. Cur ricula for these topics for all grade levels need to be developed. Covello summarizes, "Given the
high degree of public concern about environmental issues and the high level of public distrust of those in in dustry and government, people re sponsible for assessing and manag ing chemical risks have no choice but to improve their risk communication skills." Evaluation of environmental risk begins in the lab. Through a battery of analytical techniques and new de velopments, such as multispectral analysis, compounds found in the en vironment can be detected and iden tified. Only when compounds are identified can t h e i r benefits and risks can be assessed. After chemical risks are evaluated and discussed, decisions regarding use and exposure can be made. In some cases the bene fits may outweigh the risks; in others they may not. But a decision made by an educated, informed public is the result of effective risk assessment and communication. Such decisions are possible only when scientists, manufacturers, regulatory officials, media representatives, and the gen eral public deliberate together, using the best possible analytical informa tion. Jane K. Baker
References (1) McGuire, J. M. Prog. Water Technol. 1975, 7, 23-31. (2) Hoyland, J. R.; Neher, M. B. Implemen tation of a Computer-Based Information Sys tem for Mass Spectral Identification; U.S. Environmental Protection Agency, 1974; EPA-660/2-74-048. (3) Hertz, H. S.; Hites, R. Α.; Biemann, K. Anal. Chem. 1971, 43, 681-91. (4) Lias, S. G. /. Res. Nat. Inst. Stand. Techol. 1989, 94, 25. (5) McGuire, J. M. Presented at the 21st International Symposium on Environ mental Analytical Chemistry, Jekyll Is land, GA, May 1991. (6) Thruston, A. D., Jr.; Richardson, S. D.; Collette, T. W.; McGuire, J. M. /. Am. Soc. Mass Spectrom., in press. (7) McGuire, J. M.; Collette, T. W.; Thrus ton, A. D., Jr.; Richardson, S. D.; Payne, W. D. Multispectral Identification and Con firmation of Organic Compounds in Waste water Extracts; U.S. Environmental Pro tection Agency, 1990; EPA/600/S4-90/ 002. (8) Covello, V. T. Presented at the 21st In ternational Symposium on Environmen tal Analytical Chemistry, Jekyll Island, GA, May 1991. Suggested reading Effective Risk Communication: The Role and Responsibility of Government and Nongov ernmental Organizations; Covello, V. T.; McCallum D.; Pavlova M, Eds.; Plenum Press: New York, 1989.
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