Document ymaRE7kYpDOVaEweK9dy1pq64

Banning trichloroethylene: Responsible reaction or overkill? Frank D. Schaumburg Oregon State University Corvallis, OR 97331-2302 Trichloroethylene (TCE) has been used since the 1940s. Since the late 1970s TCE has been the subject of environ mental and public health concern and controversy. Common methods used by industry and government facilities for the disposal of chlorinated solvents prior to 1980 have resulted in wide spread groundwater contamination. This paper provides background infor mation on the use, disposal, fate, and impact of TCE from the 1940s to the present. From useful to hazardous substance TCE has been used in the United States for many years as an excellent degreasing agent, a popular dry clean ing solvent, an extraction agent in decaffeinating coffee, a general anesthetic in medicine and dentistry, and in nu merous other ways (I). Its uses were severely curtailed in 1976, however, when a study by the National Cancer Institute provided evidence that TCE, in very high experimental dosages, caused tumor growths in a sensitive species of mouse (2). It is interesting to note that subsequent studies by other researchers have failed to reproduce the carcinogenic response to TCE from any species of test animal (3, 4). Recent epidemiological studies in Michigan and California have failed to implicate TCE as a cause of cancer in humans (5, 6). Although no direct evidence existed in the past, or even now, that the inges tion of small amounts of TCE elicits a carcinogenic response in humans, the scientific community and environmen tal regulatory agencies concluded in 1976 that TCE was a "suspected car cinogen" and should be banned. In 1976, TCE was included on the everexpanding EPA list of hazardous sub stances. In recent years, TCE has been dis- covered in groundwater used for hu man consumption throughout the United States. It has become the subject of extensive governmental regulation and a target chemical in perhaps hun dreds of environmental litigations. However, little has been presented in the technical literature regarding the origin and development of the environ mental and public health problems cre ated by this once-beneficial substance. Properties of TCE An understanding of the origin and fate of TCE in the environment re quires some background knowledge of the properties and characteristics of this controversial substance. Trichloroethy lene (Cl2C=CHCl) is a synthetic, chlorinated organic chemical that ful fills all requirements for the ideal de greasing solvent (/, 7; see box). TCE is only slightly soluble in water (about 1100 ppm at 77 F) and forms an azeotrope with water, resulting in a mixture with a lower boiling point and vapor density. It is considered to be a "highly volatile" compound and favors environmental partitioning to the air rather than water (8). TCE is destroyed by photooxidation in the atmosphere, with a half-life of about one day. TCE, like other chloroethenes, trans forms through reductive dehalogenation very slowly in the soil or groundwater environment. Bouwer and McCarty noted that TCE can be trans formed slowly under methanogenic conditions at low concentration (9) and also very slowly under denitrification conditions (10). They noted that no degradation occurs under aerobic con ditions. These observations indicate why TCE persists in soil and groundwater for a considerable time. Some other chlorinated organic sol vents of current concern are perchlorethylene (PCE), trichloroethane (TCA), carbon tetrachloride, and methylene chloride. Sources of TCE contamination Over the years, TCE has been dis charged to the nation's surface waters and groundwaters by industry, com merce, and individual consumers. About 90% of the TCE produced in 1974 was used in industrial degreasing. EPA estimates that in 1974 approxi mately 310,200 tons of waste solvents were produced by degreasing opera- 0013-936X/89/0924-0017S02.50/0 1989 American Chemical Society SL 034878 Environ. Sci. Technol., Vol. 24, No 1, 1990 17 lions (ll). Meanwhile, lesser amounts of TCE were being used and discarded by dry cleaners, septic tank cleaners, and other operators of cleaning estab lishments that used chlorinated sol vents. Until recently, many commonly used consumer products included TCE. Some of these made their way into the environment by way of septic tanks, the sewer, or municipal landfills. Among these products were drain and pipe cleaners, shoe polish, spot removers, paint removers, upholstery cleaners, adhesives, and septic tank cleaners (12, 13). Discovery of TCE in groundwater TCE was discovered in the fall of 1979 in a groundwater aquifer in the vicinity of Sacramento, California (14). Although this was one of the earliest reported discoveries of TCE contami nation of groundwater, it does not mean that the contamination there, or else where, had just occurred. In fact, it was subsequently found that this aquifer had been contaminated with TCE for sev - jt'jnnjLw, *, v ' ,, .*.'. '^ &'.- TCE: The ideal degreasing solvent and why - -,*-> TCE has high solvency for oils, greases, waxes, tars, resins, lubri- . -"cants, and coolants generally found in the metal-processing indus- i.*-.try. ; . ' >',TCE will not attack steel, copper, zinc, or other metals used in indus try. TCE was considered to have low toxicity; until the mid-1970s, the air ^ standard for environmental exposure ranged from 100 to 200 ppm. *TCE Is nonflammable and nonexplosive at ordinary temperatures. TCE has a high vapor density (4.5 times that of air); this results in %-maintenance of a distinct vapor level near condensing coils in de- 'j S greasing tanks and prevents excessive vapor losses to the surround ing atmosphere. i; ' /:TCE is highly stable In the presence of common chemical stabilizers. ^" TCE has a low boiling point (87.1 C); this permits low heat input and ^^facilitates handling of work following degreasing operations. eral years, perhaps since as early as the 1950s, but the problem had defied dis covery. Four different, but related, historical reasons for this lag in discovery of the TCE problem in the Sacramento area are identified and discussed below. The environmental consciousness of U.S. citizens was not awakened until the mid-1960s. A general knowledge of the fate of TCE in the environment and its po tential deleterious effects on human health was absent until the late 1970s. The capability to reliably measure FIGURE 1 Impact of development on environment paralleled by social and governmental response 8000 8 6000 -r? aj 3 iL 69 Q_ Z O 4000 - g *- to c c0) Eao 2000 ii.So & 0L Source: Reference 15. 18 Environ. Sci. Technol., Vol. 24, No. 1, 1990 Year SL 03487g trace concentrations of TCE in aque ous samples was not developed until the mid-1970s. - Specific laws and regulations for TCE were not promulgated until the late 1970s to early 1980s. Environmental consciousness Immediately following World War II and through the mid-1960s, the prevail ing interest in the United States was ec onomic recovery and prosperity. Little attention was paid to the rapidly de grading and abused environment. The graph in Figure 1 (15) shows how envi ronmental contamination paralleled re source development in the United States during the 1950s and 1960s, Few people at the time were aware that eco nomic growth, based on the exploita tion of natural resources, would pro duce enormous quantities of residues that had to come to rest somewhere in the environment. And this phenome non, which could have been predicted from the basic laws of thermodynam ics, resulted in serious water, air, and land pollution nationwide (16). By the mid-1960s, in the absence of effective regulations and enforcement, environmental degradation had become severe and was no longer tolerated by the citizenry as an acceptable trade-off for economic gain. This change in atti tude toward environmental quality marked the beginning of the environ mental movement in the United States. This change is quantified in Figure 1 by the growth in membership in the Sierra Club, a national environmental organi zation, This change is also demon strated in Figure 2 by the increase in environment-related articles in the press during the late 1960s. As public concern about the environ ment intensified, the Congress became responsive to public demands and en acted an increasing number of rigorous environmental laws. Some of the major legislation is shown in Figure 1. TCE viewed as a hazard During the past 50 years, several trends in environmental focus or inter est can be identified, as shown in Fig ure 3. The chart plots the number of articles that were indexed in the Jour nal of the Water Pollution Control Fed eration about selected categories of chemical contaminants. (Each year the JWPCF publishes an index of the world literature that relates in some way to the field of water quality.) The articles are contributions from university research ers, governmental regulators, waste treatment facility operators, equipment representatives, and, on occasion, con cerned citizens. The numbers of artic les about detergents, pesticides, and heavy metals plotted in Figure 3 are close approximations because duplica tions of listings were not determined and because the selection of articles was based solely on the abstracted de scriptions in the literature review. It is my contention that an increase in the number of publications about a sub ject area represents an increase in soci etal awareness or concern about that subject. The number of articles pub lished and the areas of emphasis also reflect the availability of research fund ing from government and other sources. It is interesting to note that each of the four trends identified in Fig ure 3 was initiated by societal concern and action rather than by farsighted leadership by universities. Universities have generally only responded to prob lems and have focused research primar ily where funding is available. Figure 3 shows that the middle to late 1960s might be termed the "era of de tergents" in environmental history. De tergents provoked public ire when foam and scum were visible on rivers, lakes, and harbors. The problem was essen tially solved by the replacement of nonbiodegradable detergents with biode gradable formulations that had FIGURE 3 Number of articles in the world literature on chemical contaminants11 Number of articles SL 034880 Environ. Sci. Technol., Vol. 24, No. 1, 1990 19 FIGURE 4 Articles on TCE in the world literature'' Number of articles 'As indexed by the Journal of the Water Pollution Control Federation. comparable cleaning properties. Soci etal interest then declined significantly, as did the number of publications on the subject. The "era of pesticides" began in the late 1960s and was prompted, in large measure, by the popular book Silent Spring by Rachel Carson (17). The era of pesticides has continued to the present because these chemicals remain in common use and are considered to be toxic, hazardous substances. The "era of heavy metals" is shown in Figure 3 to have begun in the early 1970s. In 1969 fewer than 50 articles about heavy metals appeared in the lit erature. By contrast, nearly 700 articles were published on this subject in 1977. Early concerns about chromium from tanning and dyeing intensified as the metal plating industry developed. Plat ing wastes included chromium, zinc, cyanide, and other highly toxic chemi cals. Later concerns focused on lead in gasoline and paint products, cadmium, mercury (causing Mikimoto disease), and other heavy metals. Heavy metals continue to be used extensively by in dustry and in homes, and serious prob lems of environmental contamination are prevalent throughout the country. The final era identified in the chart in Figure 3, and shown in expanded scale in Figure 4, might be referred to as the "era of chlorinated solvents," which began in the late 1970s in response to the infamous Love Canal situation. Prior to the 1980s, the paucity of tech nical literature about this category of chemicals suggests that there was little concern about chlorinated solvents in university research programs, regula tory agencies, industry, or the general public. Recently however, considerably more interest in these chemicals has been generated, as many have now been identified as hazardous substances that have been, and continue to be, used in industry (as solvents), in commerce (in dry cleaning), and in homes (in cleaners, cosmetics, and other common household products) (13). Availability of analytical methods The analytical capability for detect ing and measuring environmental con taminants has expanded greatly in re cent years in both precision and sophistication. This has resulted in the discovery of environmental contamina tion which has heretofore existed but which could not have been detected by less sensitive analytical techniques and devices. Such is the case with TCE. Prior to the mid-1970s, there were no analytical methods available to environ mental analysts to measure, or even de tect, specific chlorinated solvents such as TCE in water. The Fujiwara colori metric method of TCE determination was commonly used, but had many shortcomings--most notably its inabil ity to distinguish TCE from other chlo rinated solvents (18). Other limitations included the need to keep all reagents absolutely dry, the need for precise vol umetric measurement, and the rapid de cay of color density--the basis for mea surement. Then in 1974, Bellar and Lichtenberg (19) described a gas chro matographic method that could separate and detect chlorinated solvents in water in the parts-per-billion range. As a con sequence of this and other develop ments in analytical capability, environ mental regulators were able to test water samples for TCE. They found the substance in groundwater aquifers na tionwide. The evolution of techniques for the measurement of chlorinated substances in aqueous samples is illustrated in the semiquantitative plot in Figure 5. The plot reflects the methodology generally available to the environmental profes sion as evidenced in the bible of water analysis, Standard Methods for the Ex amination of Water and Wastewater. (Standard Methods is published jointly by the American Public Health Associ ation, the American Water Works Asso ciation, and the Water Pollution Control Federation and is edited and updated approximately every five years. New methods of analysis that are proposed for inclusion in the publication must first be thoroughly evaluated by quali fied environmental chemists in selected laboratories.) Figure 5 shows that Standard Meth ods did not include any methods for the analysis of chlorinated pesticides or chlorinated solvents prior to the 12th edition in 1965 (20). This edition made a brief reference to gas-liquid chroma tography as a "potential" method of pesticide analysis. It was not until the 13th edition in 1971 (21), however, that even a "tentative" method was adopted; and this method was only for pesticides. A method for chlorinated solvents did not appear in Standard Methods until the 15th edition pub lished in 1980 (22). There is little doubt that the signifi cant improvements in analytical sophis tication and detection sensitivity have profoundly affected our ability to evalu ate and manage environmental quality. It is highly likely, however, that our ability to detect and measure contami nants far exceeds our ability to properly and responsibly evaluate the impacts of those concentrations on human health, on other biological life, and on overall environmental quality. Industrial standards of practice Environmental management in the United States has long featured prob lem identification by society; legal mandate by Congress; detailed regula tion by appropriate governmental pol lution control agencies; response to regulation by industry, municipalities, and other dischargers of waste; and conflict resolution in the courts. This management approach, by default or by design, has placed the responsibility for environmental problem evaluation and resolution on government. It is regret table that our universities and technical. 20 Environ. Sci Technol., Vol. 24, No. 1, 1990 SL 034881 professional, and scientific societies have not assumed a stronger leadership role in environmental protection. Over the years, industries that pro duced wastes generally sought to dis pose of them by the most readily availa ble and economical methods consistent with environmental regulations in effect at that time. That practice continues to this day. The methods of treatment and disposal that were commonly used throughout an industry or segment of an industry are referred to as "industry standards of practice." History has shown that as environmental laws and regulations became more rigorous, and as new and better methods for treat ment and disposal were developed, the standard of practice for industry (and municipalities) increased in sophistica tion and rigor. In retrospect, it is very tempting to criticize industries for standards of practice for handling hazardous sub stances that were adopted in the 1940s, 1950s, 1960s, and even into the 1970s, because as a result of those practices we now find contaminated groundwater throughout the country. But to judge fairly, one must determine whether the methods used for waste management in the past were "reasonable" for the level of knowledge at that time. A good example is the handling and disposal of TCE, It continued to be used for several reasons in addition to its solvent properties. TCE was considered to be safe for human contact because it was being used by the health profession through the 1970s as an anesthetic. It was also approved for extensive use in food production by the Food and Drug Administration through the late 1970s. There were no federal, state, or local laws or regulations that restricted or banned TCE in liquid effluents until the late 1970s. There were no analytical methods available to test for this substance in low concentrations until the mid to late 1970s, so detection in groundwater would have been impossible had it been suspected. It was not until the mid-1970s that TCE was determined to be a "sus pected carcinogen." TCE was disposed of directly onto the land at military installations through the 1970s (Figure 6), yet the military had the same responsibilities for environmental protection as in dustry or municipalities. The nation's universities did not pro vide educational opportunities in haz ardous-waste management until the 1980s, so few people in government and industry were trained to identify and effectively react to hazardous- FIGURE 5 Development of analysis methods for chlorinated pesticides and TCE* JAs published in References 20,21, and 22. Year of publication FIGURE 6 Land disposal of TCE at military installations v - .y*t? McClellan AFB, CA (pits) Mather AFB, CA (landfill, ditch) Whidbey Island, WAa (landfill, trench, pit) Miramar, CA* (spray) Castle AFB, CA (landfill, pits) Keyport, WAa (landfill) Bremerton, WAa (on ground) Vandenberg AFB, CA (to grade) Naval bases 1940 1950 1960 1970 Year 1980 1990 waste problems. Figure 7 shows the increase in availability of hazardouswaste courses at U.S. universities. Summary The case against the use of TCE in the work place and its disposal in small quantities in the environment is shaky at best. However, the current environ mental regulatory posture of our soci ety apparently is: "If we err, err on the side of conservatism." But this con servatism is not without huge societal costs. Toxic tort litigations involving TCE are running in die billions of dollars; remedial actions involving groundwater and soil cleanup to essentially nondetectable levels are costing billions of dollars; and, perhaps most impor tantly, the populace has been unduly traumatized by overreactive publicity and allegations regarding the deleteri ous health effects of TCE. It is interest ing to note that some "accepted" alter natives to TCE for degreasing since the mid-1970s have been trichloroethane (TCA) and freon. TCA is now on the EPA list of suspected carcinogens, and freon is implicated in the destruction of the ozone layer. Although Figure 4 shows an increas- SL 03^^ Environ. Sci. Technol., Vol. 24, No. 1, 1990 21 WATER TESTING REAGENTS AND SOLUTIONS FIGURE 7 Increase in hazardous-waste courses at U.S. universities Number of universities so---------------------------------------------------------- 70 - 60 50 - 40 - 30 20 10 - 01------------- 1----------- 1974 Source: AFfP Register, Vol HI-VI. 1981 Year 1984 1989 From Ferrous Ammonium Sulfate to Densotropic Solvent, Anderson Laboratories can supply the water testing reagent to fit your particu lar need, no matter how common or how rare. Anderson Laboratories has a large selection of water testing reagents in stock with many more available. Reagents and solutions are available for: EPA (Clean Water Act); ASTM; AOAC; APHA; and USGS recommended tests. WE SHIP WTTHIN 48 HOURS: Because of our large network of dealers throughout the U.S. we can fill and ship your order within 48 hours. We have dealers in every major metropolitan area in the U.S. Your BANCO dealer is listed in the yellow pages under Laboratory Equipment and Supplies or call to find the dealer nearest you. BANCO9 STANDARDIZED- Anderson Laboratories, Inc. 5901 Fitzhugh Avenue Fort Worth, Texas 76119 Telephone: (817) 457-4474 ^a CIRCLE 3 ON READER SERVICE CARD 22 Environ. Sci Technol., Vol 24, No. 1, 1990 ing number of publications relating to chlorinated solvents during the 1980s, the absolute numbers remain quite small in comparison to those that reflect other chemicals of environmental con cern (Figure 3). This suggests that the level of interest in and concern about chlorinated solvents remains relatively low; and low government priority has meant a low funding level for basic and applied research. Another factor affecting a rise in in terest in chlorinated solvents is the lack of compelling evidence of significant harm to human health or environmental quality. Only in the courts has this sub stance taken on dimensions of enor mous significance. References (1) "Status Assessment of Toxic Chemicals. Trichloroethylene" U.S. Environmental Protection Agency. U.S. Government Printing Office: Washington, DC, 1979; EPA-600/2-79-210m. (2) "Carcinogenesis Bioassay of Trichlo roethylene"; National Cancer Institute; Washington, DC, 1976; CAS No. 79-016, NCI-CG-TR-2, (3) Henschler, D.t et al. J. Cancer Res. Clin. Oncol. 1984, 104, 149. (4) Van Duuren, B, L. et al. J. Natl. Cancer Inst. 1979, 63, 1433-39. (5) Freni, S. C.; Bloomer, A. Report on the Battle Creek Health Study; Michigan De partment of Public Health, Lansing, MI, 1988. (6) Baker, D. B. et al. Arch, of Env. Health 1988, 43, 325-34. (7) Leroy, J.M. Modern Metal Degreasing', Dow Chemical of Canada: Sarna, On tario, Canada, 1952. (8) "An Exposure and Risk Assessment for Trichloroethylene"; U.S. Environmental Protection Agency. U.S. Government Printing Office: Washington, DC, 1981; EPA-440/4-85-019. (9) Bouwer, E. J.; Rittmann, B. E.; Mc Carty, P. L. Environ. Sci. Technol. 1981, 15. 595-99. (10) Bouwer, E. J.; McCarty, P. L. Appl. Env. Microbiology 1983, 45, 1295-99. (11) "Organic Solvent Cleaners: Background Information for Proposed Standards"; SL 034883 U.S. Environmental Protection Agency, U.S. Government Printing Office: Wash ington, DC, 1979; NTIS #PB80-137912. (12) Fishbein, L. The Science of the Total En vironment 1979, 11, 111-61. (13) "Sources of Toxic Compounds in House hold Wastewater"; U.S. Environmental Protection Agency. U.S. Government Printing Office: Washington, DC, 1980; EPA-600/2,80-128. (14) Munter, J. E.; DeVries, S. P, Toxics Law Reporter Jan. 14, 1987, 874. (15) Schaumburg, F, D. J. Environmental Sys tems 1979, 9. 89-98. (16) Schaumburg, E D. Prog. Water Technol. 1975, 7. 121-26. (17) Carson, R. Silent Spring; Riverside Press: Cambridge, MA, 1962. (18) Camisa, A. G. J. Water Pollut. Control Fed. 1975, 47, 1021-31. (19) Bellar, T. A.; Lichtenberg, J. J. J. Am. Water Works Assoc. 1974, 66, 739-44. (20) Standard Methods for the Examination of Water and Wastewater, 12th ed.; Ameri can Public Health Association: Washing ton, DC, 1965. (21) Standard Methods for the Examination of Water and Wastewater, 13th ed.; Ameri can Public Health Association: Washing ton, DC, 1971. (22) Standard Methods for the Examination of Water and Wastewater, 15th ed.; Ameri can Public Health Association: Washing ton, DC, 1980. Frank D. Schaumburg is professor ofen wronmental engineering and head of the Civil Engineering Department at Oregon State University. He earned a Ph.D. in en vironmental engineeringfrom Purdue Uni versity in 1966. His interests include the legal and political implications of hazard ous-waste management and the human di mension of engineering.