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Barbara Sibbald
City bans medical devices that contain mercury
CMAJ 2003; 168: 78 [Full text] [PDF]
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[Read eLetter] Labelling All Sphygmomanometers
Phillip J. Colquitt   (13 January 2003)

Labelling All Sphygmomanometers 13 January 2003
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Phillip J. Colquitt,
Independent Technical Advisor
Self-employed

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Re: Labelling All Sphygmomanometers

philjquitt{at}hotmail.com Phillip J. Colquitt

Editor,

Please allow me to comment at some length on the brief article in Jan 7 2003 edition of eCMAJ by Sibbald[1], as some of the ideas therein, though “newsy” in style, deserve further treatment, and readers may be interested in an Australian perspective.

The report by Sibbald[1], on the very welcome Duluth action to ban medical mercury, cites a recent study[2] in support of the accuracy of the aneroid sphygmomanometer - the alternative to the mercury(Hg) sphygmomanometer. However, your readers may not be aware of another more recent aneroid confirming US study[3]. More recently again, a UK study[4] raised questions about the claimed[2,3] accuracy of aneroid gauges, based on the idea that blood pressure gauges must be reading accurately as the Hg falls down the graduated glass tube - that is, dynamically, not statically.

The two above mentioned US based studies[2,3] used static calibration, whereas the UK study[4] used “dynamic” calibration against “gold standard” Hg gauge, with a small sample of just 39 aneroid gauges, in an obstetric setting. None of these three recent studies gave accurate information about make and model of gauges used, and as such give little useful information about availability of quality aneroid gauges. From my observations in Australian hospitals, two manufacturers seem to dominate present aneroid purchasing; Tycos – a Welch Allyn company, and Accoson.

While good quality Hg columns may well be accurate in static mode, it remains debatable whether either the Hg or aneroid medical gauge, can read out accurately “as the Hg falls” – there being an important difference between indicating that pressure is falling, on the one hand, and measuring that falling pressure, on the other. One reason the aneroid gauge may falter is because it contains moving parts that may be subject to “sticking”. The Hg gauge contains only one moving part – the liquid Hg itself, yet may falter because of it’s predisposition to “bouncing” of the moving Hg. Thus, Hg gauges are deliberately dampened by a semi-permeable membrane atop the graduated glass tube – this membrane has been found to create errors[5]. The present Hg sphygmomanometer has changed little in over 70 years, yet, as recently as 1960, Brombacher et al stated….“Mercury column instruments have little application in making dynamic pressure measurements.…..”[6].

Sibbald’s article refers to the FDA position as being one of believing exposure to Hg from sphygmomanometers to be “rare”. The opposite is most certainly the case, as the literature, and reporters of same, have largely left the sphygmomanometer and it’s main users(nurses), out of the relevant reports. Williams et al[7] found hospital Hg vapour levels of 710 µgs/m3 in general air - seven times the then allowed limit(100 µgs/m3), they acknowledged thermometers as contributing sources, but omitted any mention of the sphygmomanometer. Notani-Sharma et al[8] mentioned the sphygmomanometer among their list of equipment sources of hospital Hg, then omitted further mention of the sphygmomanometer, and made the unsupported and highly questionable claim, that these equipments had come under considerable scrutiny in previous mercury studies.

Ide[9] reported the first Hg poisoning in sphygmomanometer repairers in 1986. He recommended aneroid substitution, but made no comment on the unsealed design of the sphygmomanometer and associated hazards to sphygmomanometer users(nurses). Twelve years later, when the current debate arose, Ide reported that legal action against the employer of the index case of his earlier report had been necessary[10].

Goldberg et al[11] reported from New York a further poisoning of a sphygmomanometer repairer in 1990 - the repairer had a Hg urine level of 600 ug/L- 30 times the normal range(0-19 µg/L). They then surveyed 11 acute care municipal hospitals and 2 larger chronic care facilities in New York City, finding airborne levels of Hg in 6 out of 13 facilities exceeded the 50 µgs/m3 Hg vapour limit. No citation of the earlier study by Ide[9] was given, and nursing, the most numerically represented occupation in hospitals by far, was omitted from the six occupation categories participating in the survey.

To my knowledge, the first report describing illegal levels of Hg vapour(85 µgs/m3; Australian TLV=50 µgs/m3) in the breathing zone of a hospital patient, emanating from functioning(not broken) sphygmomanometers, came in 1995[12,13]. This[12] was dismissed by the hypertension establishment[14,15], who have shown little interest in ensuring that hazard warning labels be applied to the Hg sphygmomanometer.

Using the reported 9 Kg/year of Hg ordered in to repair sphygmomanometers in one large Australian hospital without evidence of Hg spill retrieval[16], together with the estimated 24,000 hospitals in the USA reported in Goldberg et al[11], potentially upwards of 200 tons of Hg are being ordered into hospitals to repair sphygmomanometers in USA each year. If used hospital Hg is unaccounted for, as is reported to be the case in Quebec hospitals[17], then the unaccounted for Hg may be assumed to have polluted the immediate hospital environment, thence to pollute the greater environment. The above considerations may moderate the optimistic perspective given in Sibbald[1] regarding coal-fired power plants in the US releasing 51 tons of mercury into the atmosphere there every year, and that medical Hg is a “relatively minor source”.

The nursing profession’s contribution to the Hg safety debate, as distinct from the Hg environmental debate, has been almost insignificant, and at times inept. Wilson[18] claimed that inorganic Hg is….”a rather mild toxin”. and…”more troublesome if it becomes methylated”. Ondeck[19] made the claim .….”In order to reach toxic levels, the individual must come into contact with approximately 30 milligrams of mercury, far more than the average thermometer”….. In fact, a single thermometer typically contains one gram Hg, that is, 1000 milligrams - some 33 times Ondeck’s estimate.

These inaccurate assertions from the nursing profession, are incongruent with experimental data and case reports. Experimentally, a single 0.1 ml droplet of Hg begins to form vapour levels of 300 µgs/m3 within 2 seconds of being spilled[20]. A 2.0-5.0 mg droplet of Hg adhered to a jewellery item such as a gold ring, if heated to remove the Hg, will result in a Hg vapour level exceeding a threshold limit value of 100µgs/m3 in an average room of 30 m3[21]. Human fatalities in the domestic environment have been caused by the breakage of a single thermometer[22], and morbidity requiring chelation therapy in other such single thermometer cases has occurred[23]. A recent tragic death from Hg poisoning was caused by a single drop of super- toxic dimethyl mercury[24]. Here, the argument about “mild” forms of Hg[18] was nullified, because the victim was an expert professor in heavy metals, and would have drawn the distinction between the different toxic effects and properties of different forms of Hg. Why did precautions fail?

Though the Australian nursing and medical professions both were represented in the creation of the Australian standard for sphygmomanometers[25], they have not taken any initiative to ensure the labelling described therein. Indeed, nursing registration councils[26] seem to prefer pictures of the Hg sphygmomanometer as a perennial filler to pad out pages of their journals.

The present need is for appropriate and honest labelling of all existing sphygmomanometers. Those not containing mercury should be so labelled[27]. Those not willing to comply with such ethical and reasonable consumer needs, are unlikely to contribute well to the debate. Mercury can not be disposed of, because in it’s simplest form(the element) it remains toxic. It is an eternal poison.

Phillip J. Colquitt Independent Technical Advisor New Farm, Queensland, Australia.

Refs:

[1] Sibbald B. City bans medical devices that contain Hg. CMAJ. 2003 Jan 7;168(1):78.

[2] Canzanello VJ, Jensen PL, Schwartz GL. Are aneroid sphygmomanometer accurate in hospital and clinic settings? Arch Intern Med. 2001 Mar 12;161(5):729-31.

[3] Yarows SA, Qian K. Accuracy of aneroid sphygmomanometers in clinical usage: University of Michigan experience. Blood Press Monit. 2001 Apr;6(2):101-6.

[4] Waugh JJ, Gupta M, Rushbrook J, Halligan A, Shennan AH. Hidden errors of aneroid sphygmomanometers. Blood Press Monit. 2002 Dec;7(6):309- 12.

[5] Shaw A, Deehan C, Lenihan JM. Sphygmomanometers: errors due to blocked vents. Br Med J. 1979 Mar 24;1(6166):789-90.

[6] Bromcacher WG, Johnson DP, Cross JL. 1960;May:21. Mercury Barometers and Manometers. National Bureau of Standards Monograph 8.

[7] Williams HL, Majer AJ, Custer JL, Miller FC. A survey of mercury vapor hazards in hospitals. Am Ind Hyg Assoc J. 1968 Mar-Apr;29(2):186-8.

[8] Notani-Sharma P, Chiva RK, Katchen M. Little-known mercury hazards. Hospitals. 1980 Jul 1;54(13):76-8.

[9] Ide CW. Hg hazards arising from the repair of sphygmomanometers. Br Med J (Clin Res Ed). 1986 Nov 29;293(6559):1409-10.

[10] Ide CW. Demise of Hg manometer. Scott Med J. 1998 Oct;43(5):133.

[11] Goldberg M, Klitzman S, Payne JL, Nadig RJ, McGrane J. Mercury exposure from the repair of blood pressure machines in medical facilities. Appl Occup Environ Hyg. 1990;5(9):604-10.

[12] Colquitt PJ. Unlucky leaks. New Sci 145 (1964): 50-50 FEB 11 1995

[13] Colquitt PJ. The effect of occupational exposure to Hg vapour on the fertility of female dental assistants. Occup Environ Med. 1995 Mar;52(3):214.

[14] Langford NJ, Ferner RE. Toxicity of mercury. J HUM HYPERTENS 13 (10): 651-656 OCT 1999.

[15] OBrien E. Will mercury manometers soon be obsolete? J HUM HYPERTENS 9 (12): 933-934 DEC 1995.

[16] Colquitt PJ. Will the millimetre of Hg be replaced by the kilopascal? J Hypertens. 1999 Feb;17(2):305-6.

[17] Guerrier P, Weber J-P, Cote R, Paul M & Rhainds M. The accelerated reduction and elimination of toxics in Canada: the case of mercury-containing medical instruments in Quebec hospital centres. Water, air, and soil pollution 80:1199-1202 (1995).

[18] Wilson TM, Wilson M. Can we afford to loose the battle of mercury? Hypertension- Canada. 2001;Sept Bull 69:1 –6.

[19] Ondeck BA. The right to know: Mercury thermometer breakage: Hazardous of not? Home Health Care Manage Prac. 1999;11(4):63-64.

[20] Kulshrestha MK, Aw TC. Dealing with spilt mercury. Occup Med (Lond). 1996 Feb;46(1):91-2.

[21] Washington C. Mercury spillage. The Pharmaceutical Journal. 1986 Oct 4: 384.

[22] Jaeger A, Tempe JD, Haegy JM, Leroy M, Porte A, Mantz JM. Accidental acute mercury vapor poisoning.Vet Hum Toxicol. 1979;21 Suppl:62 -3.

[23]von Muhlendahl KE. Intoxication from mercury spilled on carpets. Lancet. 1990 Dec;336:1578.

[24] Toribara TY. Analysis of single hair by XRF discloses mercury intake. Hum Exp Toxicol. 2001 Apr;20(4):185-8.

[25] Standards Australia. Homebush NSW. AS 3655-1989 : Sphygmomanometers. Sec.13.1(e).

[26] Queensland Nursing Forum. Queensland Nursing Council. December 2002.

[27] Colquitt PJ. Electronic sphygmomanometers: are they a source of Hg in hospitals? Hypertension. 2002 Mar 1;39(3):e21.