Inernatonal Archives of
Int Arch Occup Environ Health 47, 263-268 (1980)
(e'lliptlti Oitlu I , and
I *iltolim't © Springer-Verlag 1980
Identification of Potential Carcinogens in Technical Grade 1,1,1-Trichloroethane D Henschler, D Reichert, and M Metzler Institut fiir Pharmakologie und Toxikologie der Universitat, Versbacher Str 9, D-8700 Wdirzburg, Federal Republic of Germany
Summary Gas chromatography and gas chromatography-mass spectrometry were employed to analyze 22 samples of technical grade 1,1,1-trichloroethane for impurities Eighteen contained vinylidene chloride (,l-dichloroethylene) (30-900 Vg/ml) and further contaminants were identified as 1,1-dichloroethane (11), trichloroethylene (12), and 1,1,2-trichloroethane (9) Nitromethane ( 18), 1,2-epoxybutane (19), tert butanol ( 7), and dioxane (10) were detected as stabilizers It is recommended that the manufacturers should eliminate vinylidene chloride and stabilizers which carry a carcinogenic and/or mutagenic risk, from technical samples of l,l,l-trichloroethane. Key words: 1,1,l-Trichloroethane 1,2-Epoxybutane Antioxidants
Methyl chloroform
Vinylidene chloride -
Halogenated aliphatic hydrocarbons have created considerable concern in recent years Olefinic structures, such as vinyl chloride l10, 11, 17 l, vinylidene chloride l10, 18l, and allylic halides l4 l, as well as saturated compounds like chloroform l14l, carbon tetrachloride l6 l, l,1,l-trichloroethane l 19l, 1,2-dichloroethane l15 l and 1,2-dibromoethane l2 l have been demonstrated to be carcinogenic in animal experiments; some of them are proven human carcinogens Others, such as trichloroethylene and perchloroethylene, exert mutagenic properties and are discussed as potential carcinogens. Some major industrial products cannot be easily substituted by non-halogenated alternatives for a variety of reasons Much effort is therefore being expended in the search for "safe" halogenated aliphatic hydrocarbons, in particular for use as organic solvents One of these potential alternatives may be 1,1,1-trichloroethane (methyl chloroform) which has been investigated extensively in many toxicological studies, with humans as well as with a variety of animal species (for reviews see l1, 5 l) On the other hand, we have recently provided evidence in the case of trichloroethylene, another potential alternative, that the Offprint requests to: Prof Dr D Henschler (address see above)
0340-0131/80/0047/0263/$ 1 20
D Henschler et al.
264
observed mutagenic and carcinogenic activity may likely be due to contaminants with high genotoxic potential, e g , epichlorohydrin and epoxybutane which are added as stabilizers l9 l. We report here on an analytical study in which 22 commercial batches of technical grade 1,1,1-trichloroethane were tested for potentially mutagenic and carcinogenic contaminants.
Materials and Methods Chemicals Technical grade 1,1,1-trichloroethane samples were kindly supplied by eight different manufacturers (FRG, Switzerland, and France) and four dealers (FRG) Vinylidene chloride and all
Table 1 Contaminants determined by GC and GC-MS analyses in 22 samples of technical grade 1,1,1-trichloroethane Vinylidene chloride, 1,1l-dichloroethane, trichloroethylene, and 1,1,2trichloroethane on a quantitative, all others on a qualitative scale Sample no
Vinyl idene chloride
1,l-Di chloro ethane
Tri chloro ethylene
1,1,2-Tri chloro ethane
1,2 Epo xy
,Lg/ml
Itg/ml
Pig/ml
pg/ml
butane
1,800
1,350
1,350
+
1
450
2
nda
+
3
100
+
tert Buta nol
Ni tro me
Di To Others oxane luene (not identified)
thane + +
+
+
I 1
+ +
I
+
2
4
150
+
S
nda
+
+
6
30
+
+
+
7
90
+
+
+
8
340
+
+
9
450
6,300
2,700
+
+
+
I
10
900 530
530
2,120
1,060
+
+
+
0
11
270
540
1,350
405
+
+
+
0
12
100
+
+
13
250
125
1,000
14
240
480
2,160
1,680
15
370
740
1,850
370
16
670
1,340
4,020
17
300
600
600
18
150
300
600
19
400
20
nda
21
60
22
nda
480
> 600
+
+
1
1 3 2
3 O I
+
+
+
0
3,015
+
+
?
0
1,200
+
+
+
I
300
+
+
+
0 1
800 ? ?
+
+
+
+
1
+
+
3
+
+
+
n.d = not detected (less than O 55 g/ml) b This sample constitutes a 1: -mixture of 1,1,l-trichloroethane and petrol
> 23 b
265
Carcinogens in Technical 1,1,1-Trichloroethane
w
c
C
a
z
4, c 0
4-,
0
E
4,
C ,
0
w U
z
0
0
4,
c.
E 0 U
w
I-
C-
w
C
0
A
0
5
10
15 10
I
20
min
Fig 1 Gas chromatogram of a typical 1,1,l-trichloroethane sample (sample 1 in Table 1)
other compounds necessary for comparison were purchased from Merck (Darmstadt, FRG) and were of the highest purity available.
Analytical Conditions Separation of contaminants was carried out using a Packard Instruments 470 gas chromatograph (GC) with a flame ionization detector The conditions were as follows: glass column 1.8 mx 3 mm I D packed with 30% squalane on 80/100 Chromosorb W AW DMCS; oven temperature 80 ° C, isothermal; injection port and detector each 150° C; nitrogen flow 30 ml/min. Contaminants were identified by co-chromatography and gas chromatography-mass spectrometry (GC/MS) with authentic reference compounds GC/MS was performed with a Varian CH 7 mass spectrometer coupled to a Varian 2700 gas chromatograph (GC) Mass spectra were recorded at 70 eV The total amount of vinylidene chloride was determined by GC analysis using standard stock solutions as references I,l-Dichloroethane and 1,1,2-trichloroethane concentrations were estimated by comparison of the respective GC-peak areas with that of vinylidene chloride.
Results The first qualitative analytical evaluation of the 22 samples of 1,1,1-trichloroethane showed vinylidene chloride ( 1,1-dichloroethylene) to be the most frequent contaminant (Table 1) Therefore, we focused on a quantitative analysis of vinylidene chloride in all samples during the next step of the evaluation The other chlorinated contaminants were determined on a semiquantitative scale only.
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266
The results are listed in Table 1 The following impurities have been identified (number of positive samples in brackets): vinylidene chloride ( 18); 1,1-dichloroethane (11 + 1 doubtful); trichloroethylene (12); 1,1,2-trichloroethane (9); nitromethane (18); 1,2-epoxybutane (19); tert butanol (7); dioxane (10 + I doubtful); toluene (I); and up to three additional compounds which have not been further identified There is no indication of any overall relationship or links between the occurrence of pairs or groups of compounds No sample was free of contaminants; the least contaminated samples contained three or more impurities, the highest number of contaminants being nine (out of 12) A typical gas chromatogram is shown in Fig 1. In four samples, no vinylidene chloride was detected Quantitative determination of vinylidene chloride revealed a remarkably wide concentration range of 30-900 l g/ml The semi-quantitative evaluation of other chlorinated aliphatic hydrocarbons indicated-in most cases-larger quantities as compared to vinylidene chloride (Table 1), without any identifiable trend in the type or amount. The exception with sample no 22 is due to the fact that it consisted of a 1: 1 mixture of 1,l,l-trichloroethane and petrol; this mixture is used as a solvent for correcting typographical errors.
Discussion Obviously, some of the contaminants have been added to the technical samples of 1,l,1-trichloroethane as stabilizers These are nitromethane, tert butanol, 1,2epoxybutane, dioxane, and possibly toluene One of these, 1,2-epoxybutane, has been identified as a mutagen l9 l; it is used, or has been used, as a stabilizer in technical trichloroethylene l9 l, and possibly in technical tetrachloroethylene as well. Some other chlorinated compounds may be regarded as impurities stemming from the technical synthesis; this process is initiated with vinylidene chloride The resulting impurities are vinylidene chloride, ,l-dichloroethane, trichloroethylene, 1,1,2-trichloroethane, and most probably the other unidentified compounds The main contaminant, vinylidene chloride, may also originate from decomposition, especially under alkaline conditions: H Cl I I Cl C -C Cl
H
H
Cl -HCI H
C
>
Cl
C H
We investigated freshly supplied samples only; one would not be surprised to find much larger amounts of vinylidene chloride during and after technical use of 1,1,1trichloroethane, in particular if repeated recycling were practised. Vinylidene chloride has been identified unequivocally as a mutagen l8 l and carcinogen in animal experimentation l18 l The potency of its carcinogenic potential is under discussion; the existence of a threshold for its carcinogenic effect is claimed l7l but not unconditionally accepted.
Carcinogens in Technical 1,1,1-Trichloroethane
267
On the other hand, 1,1,1-trichloroethane per se has been shown to be noncarcinogenic in rats in a 12-month inhalation experiment with concentrations of 1,750 ppm and 875 ppm l13 l A feeding study in rats and mice with "maximum tolerated doses" revealed no increase in tumor incidences although this result cannot be regarded as definite because the survival time of treated animals was shortened to a degree which precludes extrapolation and prediction l3l There are two other reports on a slight mutagenic potential in vitro of l,l,l-trichloroethane: one in Salmonella typhimurium strain TA 100, with and without addition of mammalian metabolizing enzyme system l16l, and another one with a rat embryo cell system l12 l In both cases, insufficient information is provided on the purity of the samples used Therefore, it is concluded that at present there is no evidence for a carcinogenic potential of pure 1,1,1-trichloroethane. Based on our analytical findings and on the reports in the literature of the genotoxic potential of some of the identified impurities, we recommend that producers and users of 1,1,1-trichloroethane eliminate vinylidene chloride as well as stabilizers suspected of carrying a carcinogenic risk from the technical grade compound.
References 1 Aviado DM, Zakhari S, Simaan JA, Ulsamer AG (1976) Methylchloroform and trichloroethylene in the environment CRC Press, Cleveland, OH 2 Background information on ethylene dibromide (1975) Office of Occupational Health Surveillance and Biometrics, National Institute for Occupational Safety and Health (NIOSH), July 7, 1975 3 Bioassay of 1,1,1-trichloroethane for possible carcinogenicity NCI-CG-TR-3, US Department Health, Education, and Welfare Bethesda, Maryland, 1977 4 Bioassay of allylchloride for possible carcinogenicity NCI-CG-TR-73, US Department Health, Education, and Welfare Bethesda, Maryland, 1978 5 Criteria for a recommended standard (1976) Occupational exposure to l,1,1-trichloroethane. US Department Health, Education, and Welfare Washington, DHEW Publication No. (NIOSH) 76-184, 1976 6 Eschenbrenner AB, Miller E (1946) Liver necrosis and the induction of carbon tetrachloride hepatomas in strain A mice J Natl Cancer Inst 6:325-341 7 Reitz RH, Watanabe PG, McKenna MJ, Quast JF, Gehring PJ (1980) Macromolecular effects of vinylidene chloride in rats and mice Implications for carcinogenic risk estimation. Society of Toxicology, 19th Annual Meeting, Washington, DC, March 9-13 8 Greim H, Bonse G, Radwan Z, Reichert D, Henschler D (1975) Mutagenicity in vitro and potential carcinogenicity of chlorinated ethylenes as a function of metabolic oxirane formation Biochem Pharmacol 24:2013-2017 9 Henschler D, Eder E, Neudecker T, Metzler M (1977) Carcinogenicity of trichloroethylene. Fact or artifact? Arch Toxicol 37:233-236 10 Lee CC, Bhandari JC, Winston JM, House WB, Dixon RL, Woods JS (1978) Carcinogenicity of vinyl chloride and vinylidene chloride J Toxicol Environ Health 4:15-30 11 Maltoni C, Lefemine G (1975) Carcinogenicity bioassays of vinyl chloride Current results. Ann NY Acad Sci 246:195-218 12 Price PJ, Hassett CM, Mansfield JI (1978) Transforming activities of trichloroethylene and proposed industrial alternatives In Vitro 14:290-293 13 Rampy LW, Quast JF, Leong BKJ, Gehring PJ (1977) Results of long-term inhalation toxicity studies on rats of l,1,1-trichloroethane and perchloroethylene formulations International Congress on Toxicology, Toronto, April 1977
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14 Report on carcinogenesis bioassay of chloroform (1976) Carcinogenesis program, division of cancer cause and prevention, National Cancer Institute, National Institutes of Health. Bethesda, MD, March 1, 1976 15 Report on carcinogenesis bioassay of 1,2-dichloroethane US Department of Health, Education, and Welfare National Cancer Institute Washington, DHEW Publication No. (NIH) 78-1305, 1978 16 Simmon VF, Kanhanen K, Tardiff RG (1977) Mutagenic activity of chemicals identified in drinking water In: Scott D, Bridges BA, Sobels FH (eds) Progress in genetic toxicology. Elsevier/North-Holland Biomedical Press, Amsterdam, pp 249-258 17 Viola PL, Bigotti A, Caputo A (1971) Oncogenic response of rat skin, lungs, and bones to vinyl chloride Cancer Res 31:516-522 18 Viola PL, Caputo A (1977) Carcinogenicity studie, on vinylidene chloride Environ Health Perspect 21:45-47 19 Weisburger EK (1977) Carcinogenicity studies on halogenated hydrocarbons Environ Health Perspect 21:7-16 Received May 19, 1980 / Accepted October 6, 1980
