Paul Robinson (TDARCOS@MCIMAIL.COM) writes: > I wanted to see if there was anything: > > % telnet > telnet> open whitehouse.gov 25 > Trying 188.8.131.52 ... > Connected to whitehouse.gov. > Escape character is '^]'. > 220 SMTP/smap Ready. > helo > 250 Charmed, Im sure. > vrfy hillary > 250 <hillary> > > "250" in this case, is an "ok" indicating the mail-server receiving > the request considers the address to be valid. So try that, then: > > firstname.lastname@example.org Alas, this will most probably not work. If you type vrfy foobar 250 <foobar> vrfy tdarcos 250 <tdarcos> [ Eh Paul ? Didn't know you worked there :-) ] etc. In fact, anything is accepted by the mailer, so that no new address can be traced before it is officially released. A finger request at that site returns a standard message; a "rup" of that site (to see "if the President is busy reading your beloved messages" :) returns a "port mapper failure". Still not ready to give up ? Okay, how about trying "talk email@example.com" ? The reply is: "No talk daemon on requested machine" I leave it to RISKS readers to find out if firstname.lastname@example.org is on Internet Relay Chat (IRC). :-) Olivier M.J. Crepin-Leblond, Digital Comms. Section, Elec. Eng. Department Imperial College of Science, Technology and Medicine, London SW7 2BT, UK Internet/Bitnet: <email@example.com> - Janet: <firstname.lastname@example.org> [Also noted by email@example.com (Bill Brykczynski) Dave Bachmann <firstname.lastname@example.org> tep@SDSC.EDU (Tom E. Perrine) Frederick W. Wheeler <email@example.com> Donald_L._Wegeng.firstname.lastname@example.org "Jonathan I. Kamens" <email@example.com> Pat Place firstname.lastname@example.org Mark.Maimone@A.GP.CS.CMU.EDU Jerry McCollom <email@example.com> "Albert Peters" <albert@cs.Stanford.EDU> Peter J. Scott <pjs@euclid.Jpl.Nasa.Gov> ]
Someone in the White House must be paying attention to RISKS Digest. In RISKS-14.69, Paul Robinson showed <> telnet> open whitehouse.gov 25 [...] <> vrfy hillary <> 250 <hillary> I just tried it and got back vrfy 500 Command unrecognized It looks like they sealed off this possible security risk. [Also noted by "Albert Peters" <albert@cs.Stanford.EDU>. Perhaps we need to add the White House to the RISKS LIST! PGN]
I am uploading a chapter from our new book Phantom Risk: Scientific Inference and the Las (MIT Press June 1993, Foster, Bernstein, Huber, eds.) Hopefully it adds something to the public concern about health effects of VDTs - and maybe some users will buy the book! K. R. Foster (firstname.lastname@example.org). From PHANTOM RISK: SCIENTIFIC INFERENCE AND THE LAW K. R. FOSTER, D.E. BERNSTEIN, P. W. HUBER, EDS. MIT PRESS JUNE 1993 Miscarriage and Video Display Terminals: An Update Kenneth R. Foster Dept. of Bioengineering Univ. of PA Phila. PA 19104 email@example.com The link between miscarriages and use of video display terminals (VDTs) became a public issue around 1980 with the reports of clusters of reproductive mishaps in women users of VDTs. In 1986 I traced the development of the VDT debate (Foster 1986). Now, six years later (and a decade after the controversy began), I describe the current state of the issue. All together, about a dozen clusters were reported. These included 7 adverse outcomes of 8 pregnancies at the offices of the solicitor general in Ottawa; 10 out of 19 at the offices of the attorney general in Toronto; 7 of 13 at the Air Canada offices at Dorval Airport, Montreal; 8 of 12 at Sears, Roebuck in Dallas, Texas; 10 of 15 at the Defense Logistics Agency in Atlanta; 3 of 5 at Pacific Northwest Bell in Renton, Washington; and 5 of 5 at Surrey Memorial Hospital in Vancouver. The problems included birth defects, spontaneous abortions, respiratory problems in the newborns, Down's syndrome, spina bifida, and premature birth. Despite attempts by health authorities to investigate the matter, the clusters were never adequately explained. I have been able to locate reports of a follow-up investigation by the U.S. Army Environmental Hygiene Agency of the cluster at the Defense Logistics Agency (Tezak 1981), and by the Centers for Disease Control (1981) of the cluster at Sears, Roebuck. Both verified the existence of a cluster; neither established any apparent link to the women's use of VDTs. The interpretation of a cluster is problematic. Any unexpected grouping of problems (a cluster) may indicate some problem of public health significance. More commonly, investigation by health authorities of a reported cluster fails to identify a problem that can be remedied by public health measures. However tragic the outcomes may be to the people involved, the grouping of cases may have been a statistical event with no epidemiologic significance. Roughly one pregnancy in five ends in spontaneous abortion (the reported rates vary widely, depending on how early pregnancy is diagnosed); roughly one child in a hundred is born with a major birth defect. Simple calculations will show that many clusters will occur every year among the 10 million North American women who use VDTs. The issue, so easily raised, took a decade to resolve. In the remainder of this chapter, I will summarize two lines of evidence related to the possible reproductive risks from use of VDTs. The first is the many studies on possible teratological effects of electromagnetic fields; the second is the series of progressively more sophisticated epidemiologic studies searching for a possible link between adverse pregnancy outcomes and use of VDTs. Electromagnetic Fields Public concern about VDTs has focused on several factors. As judged by contemporary newspaper articles, initial fears concerned possible X-ray emissions from the terminals, no doubt reflecting the scare in the late 1960s about X-ray emission from color television sets (Foster 1986). However, measurements by several government agencies on thousands of terminals showed that X-ray emissions are extremely low and in the overwhelming majority of cases are unmeasurable (Zuk et al. 1983). Emissions of ultraviolet, visible, and infrared radiation are also small, and far below recommended exposure limits. VDTs produce no measurable microwave radiation, notwithstanding one early (incorrect) report by an investigator to the contrary. In their coverage of the issue, the lay media has frequently mentioned possible effects of low-frequency magnetic fields that are present near the terminals. These fields include components at power-line frequency (50-60 Hz) associated with the power supply, and fields with a more complex time dependence from the coils that move the electron beam around the screen. The power-frequency fields from VDTs are comparable with those from other appliances; at a distance of 30 cm from the terminal, typical field strengths are a few v/m (electric field) and 4-7 Mg (magnetic flux density) (Jokela et al. 1989). The fields from the beam deflection coils are more complex. If displayed on an oscilloscope, they would resemble a sawtooth wave with a repetition frequency of approximately 20 Khz (for the coils responsible for horizontal beam movement) and 60 Hz (vertical motion). The field from the vertical deflection coil has a peak amplitude of about 10-15 Mg at a distance of 30 cm from the screen (Jokela et al. 1989); that from the horizontal deflection coil is smaller but at a higher frequency. The corresponding electric field strength is typically a few volts per meter at a distance of 30 cm from the terminals. These field strengths are far below the levels associated with known hazards of electromagnetic fields (excessive heating of tissues or nerve excitation and shock) and far below recommended exposure limits. In Vitro and In Vivo Studies Two lines of evidence are related to the question of possible reproductive risk from VDTs: animal studies and epidemiologic observations on human populations. I consider the first and most confusing of these: animal tests for possible teratogenic effects of low-frequency magnetic fields. In 1982 Delgado and colleagues reported that chicken eggs exposed to pulsed magnetic fields showed a striking number of malformations in the embryos inside (Delgado et al. 1982; Ubeda et al. 1983). The fields were comparable in strength with those from VDTs but weaker than the earth's magnetic field. Further, the investigators claimed, small changes in the waveshape of the field made a large difference in the rate of the malformations that were induced. Four independent attempts to confirm the findings were unsuccessful (Maffeo et al. 1984; Stuchly et al. 1988; Sandstrom et al. 1986; Sisken et al. 1986). Delgado's findings were widely reported in the lay media, often with speculation about their possible significance to hazards from fields from VDTs and other appliances. The unsuccessful attempts at replication received little media attention. Project HenHouse To address the questions that the Delgado studies raised, the US Office of Naval Research commissioned at great expense a multi- laboratory replication of the original study, under the name Project HenHouse. Six laboratories in the United States, Canada, and Europe conducted replicate experiments, using the same techniques, identical exposure apparatus, and precisely measured fields (Berman et al. 1990). Each experiment involved the exposure of fertilized chicken eggs to pulsed magnetic fields, and subsequent examination of the embryos. The outcome of Project HenHouse was very puzzling. Four of the laboratories--including that of colleagues of Delgado--found no statistically significant differences in the rate of malformations in the exposed versus control eggs. A fifth laboratory reported a borderline-significant increase. The sixth reported a statistically significant increase (but a smaller one than originally reported by Delgado et al.). If the results of all six studies are combined, they indicate a borderline significant increase in rate of malformations in the exposed eggs--in contrast with the very striking effect originally reported by Delgado et al. (Berman et al. 1990). Thus, the results of Project HenHouse were neither clearly positive nor clearly negative. The simplest interpretation is that five of the six studies were negative, and that the one positive study was different in some important respect from the other five. Whether the sixth was in error or whether there is something important in its results is a question that cannot at present be answered. The latest development in this episode is the preliminary report by Litovitz et al. (1992) of a teratogenic effect of weak magnetic fields on chicken eggs. Litovitz claimed that the critical variable of exposure is the "coherence" of the field. As of this writing these results have not been published; whether they will be confirmed and accepted by other scientists remains to be seen. In retrospect, Delgado's study probably did not merit the widespread attention it received. The biological system (fertilized chicken eggs) differs too much from human embryos for the test to have much value for risk assessment; on the other hand it is too complex to be of much use for basic scientific research on mechanisms of interaction of fields with a biological systems. Chickens are not inbred, and are notoriously variable in the frequency of chick malformations and fertility of eggs. Finally, a project officer from the Office of Naval Research who visited Delgado's lab (Thomas C. Rozzell, private communication) told me that the initial experiment was crudely done and the applied fields were poorly characterized. After ten years of research on the "Delgado effect" with so little to show for it, funding agencies and most scientists have lost interest in the matter. As well they should. Other Animal Studies Since the early 1980s, at least 17 animal studies have been searched for effects of pulsed magnetic fields on animal embryos. (Berman 1990 provide a comprehensive review.) The literature is very inconsistent, with some studies reporting effects and others (including attempts to replicate earlier positive findings) finding none. Berman concludes ... we cannot clearly relate an increase in the incidence of abnormal embryos resulting from exposure to pulsed magnetic fields to any patterns of pulse frequency, field intensity, pulse shape, or rate of change in the intensity.... Until the important variables in pulsed magnetic fields are determined and the mechanism of effects is identified, it may not be possible to extrapolate such effects to humans. (1990, p. 47). This conflates two issues. The first is the absence of any clearly reproducible phenomena. Until some reproducible phenomenon appears, with some defined relation between dose and response, that can be consistently observed by independent investigators, it will be difficult to draw any conclusions from the data. The second is the relevance of these results to human health, assuming that the effects themselves are real. That depends on the biological similarity between the animal subjects and humans, the exposure conditions, and other factors. Whether these studies will point to a mechanism for human injury is, at present, a matter of speculation. Epidemiologic Evidence A much clearer picture has emerged from the epidemiologic studies. By now, a dozen epidemiologic studies have been conducted in the United States, Canada, Finland, Sweden, and elsewhere on reproductive problems associated with use of VDTs. (A good, but dated, review is Blackwell and Chang 1988.) They have been overwhelmingly--but not totally--negative, finding no links between use of VDTs and spontaneous abortion or birth defects. The studies vary widely in their methods, and I will not review them in detail here. Table 6.1 summarizes their results in terms of the relative risk, which is the risk (probability) of an undesired consequence in a VDT user, divided by the probability of the same consequence for an otherwise similar nonuser (see chapter 1). The table also shows the 95 percent confidence intervals, i.e. margins of sampling error in the studies. Virtually all of the results indicate no increase in risk associated with use of VDTs. But some of these studies did report positive or equivocal findings, which has helped to keep the issue alive. The most widely publicized of these studies was that of Goldhaber et al. (1988), who reported a 1.8-fold increase in risk of miscarriage among women who worked with VDTs for more than 20 hours a week during their first trimester of pregnancy. This increase was at the edge of statistical significance. Goldhaber's study was generally well done, but it had one major weakness that resulted from its retrospective design. To determine the subjects' use of VDTs during pregnancy, the investigators sent them a questionnaire, as much as three years after their pregnancies. The investigators did not independently verify the subjects' actual use of the terminals. At the time the study was conducted, the possible reproductive hazards of VDTs were well publicized; it is likely, as the investigators themselves suggested, that women with adverse pregnancy outcomes might have been more likely than other women to report using VDTs. Goldhaber's study was widely reported in the lay media, without the careful reservations of the investigators, and usually without mention of the negative findings of the other studies. The most recent, and undoubtably the best, study on reproductive risk of VDTs was published early in 1991 in the New England Journal of Medicine by Schnorr and colleagues. The investigators, working for the National Institute for Occupational Safety and Health (NIOSH), conducted a retrospective cohort study that compared groups of telephone operators who used VDTs with telephone operators in otherwise similar jobs who did not. The investigators found no link between spontaneous abortion and use of VDTs during the first trimester of pregnancy. Whether this study will end the VDT debate remains to be seen. The epidemiologic literature on the VDT-miscarriage question frequently mentions the great difficulty of measuring reproductive risk. These problems are not reflected in the 95 percent confidence intervals in the table, which show only the statistical uncertainties due to sampling error. For example, several of the papers listed in the table discuss at length the problem of reporting bias, which might be introduced if not all of the subjects in a study were equally likely to report use of VDTs during their pregnancies. Two studies (Goldhaber et al. 1988; McDonald et al. 1988) mentioned this as a possible explanation for a small apparent excess of miscarriages among VDT users. Another problem is the difficulty of reliably detecting miscarriages that occur early in pregnancy. Because of this difficulty, an investigator has a choice of including only miscarriages that occur after a month or more of pregnancy (and thus missing a large fraction of all miscarriages), or of including earlier miscarriages and finding some way to determine precisely when the subjects became pregnant. Most studies choose the former approach. A final difficulty arises from the many different birth defects that can occur. A study that retrospectively examines medical records for any association between birth defects and use of VDTs can, therefore, make many different comparisons. However, by the statistical tests that most scientists adopt, 1 comparison out of 20 will show a difference that is statistically significant--even if there is no real difference in the groups being compared. (This problem is discussed in chapter 1, and again in chapter 4.) Because of these and other problems, one can never achieve complete consistency in epidemiologic studies--but the dozen studies summarized in the table come pretty close. They certainly rule out the large increases in risk that some people inferred from the clusters. Recently, public concern has shifted to the much more difficult question of possible risks from the fields associated with the terminals, which these studies do not directly address. In the NIOSH study, for example, both the VDT and non-VDT operators were exposed to similar levels of 60 Hz electromagnetic fields from the equipment they used. Consequently, the study is inconclusive on the question of hazard from fields. This point was raised in a letter to the editor of Science News from the president of a company that makes radiation shields for VDTs (Doilney 1991). An adequate epidemiologic study on reproductive risk from 60 Hz fields from VDTs would be very hard to mount. The NIOSH investigators measured the fields from the terminals, and found them to be comparable to those from many other sources in the environment. The latest development in this issue is a preliminary report of a Finnish epidemiologic study (Hietanen et al. 1992) of a 3.5- fold increase in risk of miscarriage in VDT operators who were exposed to extremely low frequency magnetic fields greater than 9 Mg from the terminals. The study has not been published as of this writing and there is no way to judge its quality; perhaps the issue of reproductive risk from VDTs will remain alive. Other Problems Associated with Use of VDTs Of greater concern to many scientists and health authorities have been diverse ergonomic and psychosocial problems associated with the use of computers in the workplace (World Health Organization 1989). Ergonomic problems include workstation design, glare, legibility of display, seating, and keyboard height. A panel assembled by the U.S. National Research Council judged radiation hazards to be highly unlikely, and focused in its report on issues such as glare, legibility of video displays, and background lighting (National Academy of Sciences 1983). Perhaps more important still are psychosocial problems. To my mind the fundamental problem is that many clerical workers using VDTs simply have lousy jobs. A data entry operator who spends the day keying numbers into a computer, with every keystroke counted, little opportunity for personal interaction, and rigid performance standards to meet might well experience emotional and perhaps physical problems. If only radiation shielding could fix such problems! Carpal tunnel syndrome (CTS) is a painful condition associated with repetitive motions of the hand, that afflicts workers in many occupations, including VDT operators. CTS arises from compression of the median nerve as it passes through a small opening (the carpal tunnel) in the wrist (Spinner et al. 1989); and can be relieved by a simple operation. The problem has been reported among workers in diverse occupations, including meat cutting and clerical workers, but there are few reliable data on its incidence and the medical literature on CTS is sketchy and anecdotal. The syndrome is clearly a matter of concern to VDT operators and their employers, and might be prevented by better keyboard design or other ergonomic considerations. Clearly, more study on CTS is needed. Other, less well defined, health problems have been reported from use of VDTs (Bergqvist 1989; Council on Scientific Affairs 1987). Since the mid-1980s, there have been scattered reports of rashes and other skin problems among VDT users; follow-up studies have been unable to find the cause of the problem or associate it with the terminals or other factors in the office environment. This has, however, led to at least one lawsuit (see "The Legal Context" at the end of Part I). On reviewing the history of the VDT debate, I am struck by the great disparity between the ease with which concerns about reproductive hazards from the terminals were raised, and the great difficulty in adequately addressing them. The clusters, in retrospect, were probably chance events of no epidemiologic significance. But the question of whether use of VDTs increases reproductive risk took ten years and a dozen studies to address, and (from a recent preliminary report) it has still not been settled. It is time to focus instead on the more serious ergonomic and psychosocial problems associated with use of computers in the workplace. References Berg, M. 1988. Skin problems in workers using visual display terminals--a study of 201 patients. 19 Contact Dermatitis 335- 341. Bergqvist, U. 1989. Possible health effects of working with VDUs. 46 Br. J. Indus. Med. 217-221. Berman, E., L. Chacon, D. House, B. A. Koch, W. E. Koch, J. Leal, S. Lovtrup, E. Mantiply, A. H. Martin, G. I. Martucci, K. H. Mild, J. C. Monahan, M. Sandstrom, K. Shamsaifer, R. Tell, M. A. Trillo, A. Ubeda, and P. Wagner. 1990. Development of chicken embryos in a pulsed magnetic field. 11 Bioelectromagnetics 169- 187. Berman, E. 1990. The developmental effects of pulsed magnetic fields on animal embryos. 4 Repro. Toxicol. 45-49. Blackwell, R., and A. Chang. 1988. Video display terminals and pregnancy. A review. 95 Br. J. Obstet. & Gynaecol. 446-453. Brandt, L. P. A., and C. V. Nielsen. 1990. Congenital malformations among children of women working with video display terminals. 16 Scand. J. Work Environ. & Health 329-33. Bryant, H. E., E. J. Love. 1989. Video display terminal use and spontaneous abortion risk. 18 Int. J. Epidemiol. 132-8. Butler, W. J., and K. A. Brix. 1986. Video display terminal work and pregnancy outcome in Michigan clerical workers. In Allegations of reproductive hazards from VDUs. Nottingham UK: Humane Technology 67-91. Centers for Disease Control, Family Planning Evaluation Division. 981. Cluster of spontaneous abortions. Report EPI-80-113-2. Council on Scientific Affairs. 1987. Health effects of video display terminals. 257 J. Am. Med. Assn. 1508-1512. Delgado, J. M. R., J. Leal, J. L. Monteagudo and M. G. Gracia. 1982. Embryological changes induced by weak extremely low frequency electromagnetic fields. 134 J. Anat. 533-551. Doilney, J. A. 1991. Science News 387. June 22. Letter to the editor. Ericson, A., and B. Klln. 1986. An epidemiological study of work with video screens and pregnancy outcome: II. A case- control study. 9 Am. J. Indus. Med. 459-475. Foster, K. R. 1986. The VDT debate. 74 Am. Scientist 163-168. Goldhaber, M. K., M. R. Polen, and R. A. Hiatt. 1988. The risk of miscarriage and birth defects among women who use visual display units during pregnancy. 13 Am. J. Indus. Med. 695-706. Hietanen, M., M. L. Lindbohm, P. von Nandelstadh, P. Kyyrnen, and M. Sallmn. 1992. Effects of exposure to magnetic fields of VDTs on miscarriages (abstr), 1st Congress of the European Bioelectromagnetics Association, Brussels, Belgium. January. Jokela, K., J. Aaltonen, and A. Lukkarinen. 1989. Measurements of electromagnetic emissions from video display terminals at the frequency range from 30 Hz to 1 Mhz. 57 Health Physics 79-88. Edstrm, R., and B. Klln. 1985. Dataskarmsarbete och graviditet. 82 Lakartidningen 687-688. Kurppa, K., P. C. Holmberg, K. Rantala, and T. Nurminen. 1984. Birth defects and video display terminals, 2 The Lancet 1339. Kurppa, K., P. C. Holmberg, K. Rantala, T. Nurminen, and L. Saxen. 1985 Birth defects and exposure to video display terminals during pregnancy. 11 Scand. J. Work Environ. Health 353-356. Maffeo, S., M. W. Miller and E. L. Carstensen. 1984. Lack of effect of weak low frequency electromagnetic fields on chick embryogenesis. 139 J. Anat. 613-618. Mackay, C. J. 1989. Work with visual display terminals: psychosocial aspects and health. 31 J. Occup. Med. 957-968. McDonald, A. D., N. M. Cherry, C. Delorme, and J. C. McDonald. 1986. Visual display units and pregnancy: evidence from the Montreal Study. 28 J. Occup. Med. 1226-1231. McDonald, A. D., J. C. McDonald, B. Armstrong, N. Cherry, A. D. Nolin, and D. Robert. 1988. Work with visual display units in pregnancy. 45 Br. J. Indus. Med. 509-515. Miller, D. A. 1974. Electric and magnetic fields produced by commercial power systems. In J. G. Llaurado, A. Sances, and J. H. Battocletti, eds., Biologic and clinical effects of low-frequency magnetic and electric fields 62-70. C. Thomas. National Academy of Sciences. 1983. Video displays, work, and vision. Washington DC: National Academy Press. Nurminen, T., and K. Kurppa. 1988. Office employment, work with video display terminals, and course of pregnancy. Reference mothers' experience from a Finnish case-referent study of birth defects. 14 Scand. J. Work Environ. Health 293-298. Sandstrom, M., K. H. Mild, and S. Lovtrup. 1986. Effects of weak pulsed magnetic fields on chick embryogenesis. In Proceedings of the International Scientific Conference: Work with video display units 60-63. Stockholm: Swedish National Board of Occupational Safety. Schnorr, T. M., B. A. Grajewski, R. W. Hornung, M. J. Thun, G. M. Egeland, W. E. Murray, D. L. Conover, and W. E. Halperin. 1991. Video display terminals and the risk of spontaneous abortion. 324 N. Eng. J. Med. 727-733. Sisken, B. F., C. Fowler, J. P. Mayaud, J. P. Ryaby, J. Ryaby, and A. Pilla. 1986. Pulsed electromagnetic fields and normal chick development. 5 J. Bioelec. 25-34 (1986). Slesin, L., and M. Zybko. 1983. Video display terminals: Health and safety. New York: Microwave News 41-46. Spinner, R. J., J. W. Bachman, and P. C. Amadio. 1989. The many faces of carpal tunnel syndrome. 64 Mayo Clinic Proc. 829-836. Stuchly, M. A., et al. 1988. Teratological assessment of exposure to time-varying magnetic field. 38 Teratology 461-466. Ubeda, A., J. Leal, M. A. Trillo, A. Jimenez, and J. M. R. Delgado. 1983. Pulse shape of magnetic fields influences chick embryogenesis. 137 J. Anat. 513-536. Tezak, R. W. 1981. Investigations of adverse pregnancy outcomes. Service Report 66-32-1359-81. Aberdeen Proving Ground MD: U.S. Army Environmental Hygiene Agency, Defense Contract Administration. Wahlberg, J. E., and C. Lidn. 1988. Is the skin affected by work with visual display terminals? 6 Occup. Dermatoses 81-85. Westerholm, P., and A. Ericson. 1987. Pregnancy outcome and VDU-work in a cohort of insurance clerks. In B. Knave, P. G. Widebck, eds., Work with display units 86, at 87-93. Amsterdam: Elsevier. Windham, G. C., L. Fenster, S. H. Swan, and R. R. Neutra. 1990. Use of video display terminals during pregnancy and risk of spontaneous abortion, low birth-weight, or intrauterine growth retardation. 18 Am. J. Indus. Med. 675-688. Zuk, W. M., M. A. Stuchly, P. Dvorak, and Y. Deslauriers. 1983. Investigations of radiation emissions from video display terminals. Public Affairs Directorate, Dept. of Health and Welfare Canada, Report 83-EHD-91.
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