MANAGEMENT OF MERCURY WASTE IN DENTAL CLINICS

Talwar Sangeeta*, Nawal Roongta Ruchika**, Verma Mahesh***

Introduction:

Dental amalgam is an alloy composed of a mix­ture of approximately equal parts of elemental liq­uid mercury and an alloy powder, containing pow­dered metals, silver, copper, zinc , and tin. The firstuse of amalgam was recorded in the Chinese litera­ture in the year 659, and for the last 150 years, ithas been the must pupular and effective restorativematerial used in dentistry. This popularity of amal­gam mainly arises from its excellent long term per­formance , ease of use and low cost,

However despite the long history and popularityof dental amalgam as a restorative material, one ofits major components, mercury, is ofparticular con­cern due to its potential adverse effects on humansand the environment.' ? This has been the subject ofa number of previous pub licat ions , expert panelmeetings, national and international conferences.

The purpo se of om p:-Jp~r if: to review the cur­rent state ofknowledge on dental amalgam with spe­cial emphasis on recognizing the potential sourcesof mercury contamination in the dental office. Wereview the current safety guidelines and mercuryhygiene recommendations for judicious use uf thisrestorati ve material.

Why should we be concerned abou t mercury?Mercury and the environment.

Concern about the effects of mercury in the en­vironment has increased over the years . Human be­ings are constantly exposed to mercury in the envi­ronrncntn from n I1llllt ill l,k, ",r , ' " 111 ,1 " /I ., /I 1"" I/,, rboth natural emissions and human pollution. Theexposure includes the breathed air, consumed wa­ter, ingested food, medical and dental products.

*PraJessar & Head aJDepartment**Seniar Resident***Principal-Directar, Maulana Azad Institute aJ Dental Sci­ences, New Delhi

Ch emically, mercury exists in three majorforms: elemental (valence 0), inorganic (valence +1and +2) and organic (alkyl and aryl). These threeforms are different in their physical and chemicalproperties, their rates of absorption, excretion, andtheir distribution patterns in tissues. The chemi­cal fo rm of mercury, therefo re, determ ines itstoxico logical p rofi le.

Elemental mercury is the most volatile of thethree, and mercury vapor in air is the predominantform of elemental mercury. In dentistry, only themetallic form is av ailable. Critical times arewhen met allic mercury exists in liquid/vaporform, rather than bound in a set amalgam. As a vapor,metallic me rcury can be inhaled and absorbedthrough the alveoli in the lungs at 80% efficiency.After cellular absorption, this metallic mercury iscon verted into mercuric ions which can produ cetoxic effec ts.

Sources of mercury in drinking water and foodare generally inorganic and organic mercury com­pounds, with organic compounds like methyl mer­cury being particularl y associated with seafoodt.Thisis the form of mercury that humans and other ani­mals ingest when they eat some types of fish. Me­thyl-m ercury is particularly dangerous because itbio-accumulates in the environment. Though, we asdentists do not directly use this form of mercury,but improper disposal of amalgam waste productsIroui dental offices, leads to mercury deposits inthe water. Once 1llt:I l.:UI Y is deposit ed into lakes andetrsnmu, bacterin convert noma of the ",.-.r'·,lI ly ill l"the organic form, methyl-mercury .

The main sources of mercury from the dentaloffice into the environment are: (Fig . 1)

• Mercury vapor in the air (elemental mercury)

• Amalgam waste products : solid trash , wastewater sludge

JPFA, Vol. 23, September, 2009 107

Ifproper mercury disposal measures are not fol­lowed, the amalgam waste products can pollutethe environment through the following mainroutes:

• Mercury in medical waste incinerators

Mercury is a very volatile metal that evaporateseasily. When a mercury containing product fmdsits way into a medical waste red bag and is incin­erated, the mercury becomes gaseous and exitsthrough smoke stacks into the air. The mercurythen settles on land and in water where it can bechanged into its organic form, methylmercury. Itis very important to educate employees about thedangers of putting amalgam wastes in the redmedical waste bags to prevent this contamination

• Mercury in solid waste str eam:

If waste amalgam is placed in the garbage,it could potentially be incinerated, and the

mercury will volatilize and enter the atmosphereas described above. If the solid waste is sentto a landfill, the mercury may volatilize outwith the methane gas that is released from thelandfill.

• Mercury in waste water stream

Mercury amalgam that is not captured by a trapin dental office will travel to the local wastewatertreatment plant. Once mercury enters thewastewater treatment plant , most of it concen­trates in wastewater bio-solids during treatment.Since most treatment plants dispose of gener­ated solids by land spreading, mercury enters theterrestrial environment by this process. Someof this mercury spread on land may, over Lime,be volatilized to the atmosphere. This mercurymay then be deposited into lakes and streams,methyla ted, and ingested by fish , eventuallyreaching wildlife and humans.

~J.bdiulw.ut~ Sclid wut~

~ / -

M:U(lI£}'vo:q)(.r in

n"nfilol" ffi,,,,

AIR

1i

II

(Elemen ml mercury) ~--...... water bodies ~ CONVERTED INTO

ORGANIC HG

Figure 1: Sources of mercury into environment from dental office.

108 JPFA, Vol. 23, September, 2009

• Mercury cycle in dentistry

The primary challenge in dentistry for the con­tinued use of amalgam as restorative material istherefore management of mercury waste. Thepath of dental mercury from the purchase of theamalgam product to the end of the clinical life­time of a restoration has been rnonitored".(Fig. 2)

• The types ofamalgam waste created hence maybe listed as the following types :

• Major amalgam particles: (> lOOflm)

o Non contact amalgam (scrap): this constitutesthe surplus of triturated amalgam

o Contact amalgam: is amalgam that has been incontact with the patient. Examples are extractedteeth with amalgam restorations, carving scrapcollected at chair side, and amalgam capturedby chair side traps, filters or screens

• Minor amalgam particles: « lOOflm)o Amalgam sludge is the mixture of liquid and

solid material collected within vacuum pump fil­ters or other amalgam capture devices .

o Empty amalgam capsules are the individuallydosed containers left over after mixing pre-cap­sulated dental amalgam.

Who is affected? Safety concerns regardingdental amalgam:

Having recognized that chronic exposure to highlevels ofmercury vapor generated during dental pro­cedures can be a potential health hazard, we need toknow at what levels we can be affected. The adversehealth effects of mercury used in dental offices canmainly affect the following three groups:• Dental patients• Dental professionals in the dental operatory en­

vironment• Environmental pollution

New amalgamfillingsMercury in

dental practiceSurplus of

triturated amalgam •

Carved aurplusof amalgam

Collection/re-cycling

Removal of oldf---+ amalgam fillings

Central vacuumsystem

Los t/extracte df-----.. teeth with fillings

Amalgam fillings ..c~t-t. In deceased persons -----.

Minor amalgamparticles

Waste

Interment

Cremation

sludge

Drain/sewage

Figure 2: Mercury cycle ill dentistry.

JPFA, Vol. 23, September, LUUY lVY

Dental patients and exposure to Hg fromamalgam:

Dental patients are believed to be exposed to themercury vapor through the following routes:

• During all amalgam manipulation procedures

• From the existing mercury levels in the envi­ronment.

• Chronic mercury exposure from existing amal­gam restorations in mouth .

During the amalgam procedures, both the place­ment and removal of amalgam restorations can re­sult in significant levels of intraoral mercury vapor."An early study using copper amalgam and proce­dures reported that intraoral mercury vapor canreach up to 388 flg/m3 of air during the insertion ofan amalgam restoration? Other studies have shownthat dry polishing of amalgam restorations resultedin the release of 44 ug of mercury vapor per resto­ration, while removal of amalgam in vivo initiatedthe rclcaac of 15 to 20 flg of mercu ry vapor per res­tor ation". Th is mercury vap or in is inhaled in thebudy .unl <lUCiUlUtlJ tlu uu gh lhtl ulveul i. 'I lu: sliurtduration of these exposures, however, is consid­cred inadequate to caus e any adverse health ef­f eels and the pluoemcut uiul rornuvul U[ umulgururestorations alone does not appear to constitute asignificant health concern to patients. In addition,studies have demonstrated that up to 90 percent ofthe mercury vapor generated during restorative pro­cedures can be effectively eliminated by using ahigh-volume evacuator.

Another aspect, on which recent research has[Ul;USt:U UIl, is mercury released [rum amalgam res­torations after insertion in .the body. This consti­tutes the chronic mercury exposure experiencedby patients. With the development of highly sensi­tive techniques, measurement of mercury releaseti-OI11 amalgam restorations has become possible.Studies have shown that average daily mercury dosefrom amalgam restorations is in the range of 4.5 ug/dny". This mercury release is also linearly COlT C­

luted to time and the surface area of restorations.

110 JPFA, Vol. 23, September, 2009

There still is considerable controversy regarding theextent to which mercury from amalgam contributesto our total daily exposure to mercury. Further re­finement of measurement techniques, appropriateexperimental design and judicious data analyses willaid in reaching a consensus on this issue.

Another significant question is whether mer­cury released from dental amalgam results insignificant adverse health effects, as mere expo­sure is not synonymous with ill effects to health.Hence, it is of considerable importance that weemphasize on carefully designed research requiredto investigate potential biological effects resultingfrom low level Hg.

Dental professionals and exposure to mer­cury in dental office: occupational exposure

Chronic exposure to mercury vapor owing to .inappropriate handling of dental amalgam can be apotential health hazard in the work place. The mainfaotorn that oontribute to the occupational II g ex­posure in the dental office include:

During mnn ipulntion of ama lgam :

+ Trituration, placement, condensation

• Polishing of amalgam

• Removal of old amalgam fillings

• Vaporization of Hg from contam inated instru ­ments

However, the exposure to mercury vapor duringthe above manipulation procedures ofamalgam res­torations is found to be minimal when appropriatehygiene procedures are followed, and hence can bereduced considerably",

Occupational risk in dental offices is mainly as­sociated with improper handling ofamalgam includ­ing:

• Accidental mercury spills (Fig. 3)

• IUllJIUlJt:l handling aud direct skin contact

... Squeezing of amalgam in cloth to remove cs­ccas mercury,

Figure 3: Accidental Mercury spill ill delltaloffice around amalgamator.

• Malfunctioning amalgamator

• Leaky amalgam capsules

• Malfunctioning bulk Hg dispenser

It is important to note that all sources of mer­cury are likely to affect the dentist. Also, the ex­posure of the dentist is long s tandi ng andchronic. Many studies have shown that dental prn­fessionals can minimize unnecessary exposure to~km~nta l mercury simply by following recom ­mended mercury hyg iene procedures e r. :lr.r.0rd­ing to one study, mercury vapor in the breathing zoneof the dentist was found to be minimal (1 to 2 J.tglm3) when the high volume evacuator was used: with­out high-volume evacuation, however, mercury·,' ;\IJ'.·I lw',' w1I: WWI W I·....v Iv 1:; tirnun hiuhur thun thuTT,v as defined by WH06, The generally acceptedthreshold limit value (TT.Y) for r.xpmmrr. to mer­cury vapor for a 10 hour work week is 50J.tglcubio m."

111. 111.v, 1111. iIlILJVI I"uv" v[jJl .tl. lil.i ll\: 111 1/1 ml IlIl1Icury hygiene measures cannot be stressed uponmore.

Mercury hygiene measures

From the above discussion, we can conclude thatthe most important issue to be dealt with regardingmercury hazard in dentistry is the emphasis onjudi­cious use ofamalgam rather than its use as a whole.

The hazards from mercury can be significantly re­duced and brought well within the recommendedTLV levels if proper mercury hygiene measures areemployed. These measures include :

• Trained dental personnel :

Train all personnel involved in the handling ofmercury and dental amalgam regarding the po­tential hazards of mercury vapor and the neces­sity of observing good mercury hygiene prac­tices

• Office engineering

• Hygiene measures during manipulation ofmercury

• Filtration

• Storage

• Re-cycling

Office engineering:

During designing of the dental offices , the fol­lowing steps should be kept in mind to createhealthier working atmosphere and reduce the amountof mercury vapor.

Dental clinics should be designed such that theyare well-venti lated, with fresh all' exchanges andoutside exhaust. If the work areas are air-condi­tioned,the air-conditioning filters should be replacedperiodically.

Work area should be properly designed to fa­nilirnto spill nnntninmrnt nnd r.1 rnnllr PI,; ,;)" ,-,-,WI'­in s should be nonabsorbent, seamless and easy toclean . Use ofcarpeting in operatories, where an ac­cidenral merr.llry sp ill might oc cur, is not recom­mended. Chemical decontamination of carpetingis not effective, as mercury droplets can seepthro ugh the l.ullJd aud i curaui U I <lu ..essi b le tu thedecontaminant. Removal of the contaminated 'car­pet is the only way to ensure decontamination.

Periodically check the dental operatory atmos­phere for mercury vapor. This may be done usingdosimeter badges or through the use of mercuryvapor analyzers for rapid assessment after any mer­cury spill or cleanup procedure.

JPFA, Vol. 23, September, 2009 111

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\

Hg hygiene during manipulation:

• Use only pre-capsulated amalgam alloys. It isrecommended against the use of bulk alloy andbulk elemental mercury, also referred to as liq­uid or raw mercury, in the dental office .

• Use an amalgamator with a completely enclosedarm.

• If possible, recap single-use capsules after use ,store them in a closed container and recyclethem.

• Use care when handling amalgam. Avoid skincontact with mercury or freshly mixed amalgam.

• Use high-volume evacuation systems (fitted withtraps or filters) wh en finishing or removingamalgam.

In case of an accidental mercury spill:

• Never use a vacuum cleaner ofany type to cleanup the mercury.

• Never use household cleaning products to cleanup the spill, part icularl y those containing ammo­nia or chlorine.

• Never pour mercury, or allow it to go, down thedrain

• Never usc a broom or a lJd illll11 u :-.lI III c lea u Ill'the mercury.

• Never allow people whose shoes may be contaminated with mercury to walk around or leavethe spill area until thl': mercury-contaminateditems have been removed.

Filtration: Capturing amalgam ami mercurywastes (Fig. 4)

In order to reduce the amount of mercury fromamalgam particles entering the sewer system orlandfill , it is recommended that you use an amal­gam trap. There are several filtration devices avail­able to capture amalgam at the source of genera­tion. These include:

• Chair side traps capture amalgam waste dur­ing amalgam placement or removal procedures(traps from dental unit s dedicated strictly to hy-

112 JPFA. Vol. 23. September. 2009

Figure 4: Filtration devices in dental unit.

giene may be placed in the regular garbage).First, disinfect the trap for 24 hours using a mini­mum amount of disinfectant. Then, remove allvisible amalgam and store it in an airtight con­tainer , lab eled "WAST E AMALGAM." The dis­infected trap can then he reused . Recycl e thewa~tc amalgam as outlined for the scrap arnulgam.

• Vacuum pump filters or traps contain amalgamsludge and water. Some recyclers will acceprwhol e trlt ers , whil e oth ers will require specialhandling of this material. Change these filters atleast once a mo uth , Ul mo re frequently ifneeded. DO NOT dispo se uf the filters as regu­lated medical waste. Place facial tissue or tow­ols inside to ubsorb the liquid .

• Amalgam separators: Chair-side traps andvacuum pump filters generally remove 40 to 80pe rcent of the amalgam particles from thewastewater stream; however, some amalgamwaste particles still enter the sewer system (11).Amalgam separators are devices designed to re­move amalgam waste particles in dental officedischarge. Amalgam particles in dental officewastewater can range in size from colloidal par­ticles (smaller than 0.45 micrometers) to thoselarger than 3 millimeters. To remove these vari­ous-sized particles from waste discharge, amal­gam separator units can use several separation

techniques, alone or in combination: sedimen­tation, filtration, centrifugation or ion exchange.

Storage:

Mercury in liquid or gaseous form is very mo­bile and has high diffusion rate. This allows it topenetrate through fine spaces. Mercury containingproducts hence should not be stored in open but inclosets/cabinets. Storage locations should be neara vent that exhausts air out of the building.

Excess amalgam remaining at the end of a pro­cedure should be stored in an air-tight containerlabeled "SCRAP AMALGAM.". The containershould be filled till the brim with spent fixer or un­der water. At one time only a small bottle should bepresent in the clinic. This scrap amalgam should thenbe carefully packaged and sent for re-cycling.

Re-cycling

The stored waste amalgam can be re-used andhence should be carefully packaged and sent for re­cycling. Extracted teeth with amalgam restorationsare mixed with body fluids such as saliva, blood, orother poLcnLiully inf ecti ous material . These shouldbe first chemically disinfected and then packaged[VI 10;-1"vvliuu,

CONCLUSION

So is amalgam safe? For a material to be safe itis required, that it has a low incidence of adversereactions or significant side effects when used ac­cording to adequate warnings and directions. Inher­ent in this definition are considerations of the risk­vs.-benefit relationship of the material. In relationto mercury exposure [10m dental amalgam, avail­able data have not identified any significant sideeffectte), other than the rare allergic reaction , afterruuic tlrau 150 years uf usc. Based U11 this UVCI- .

whelming body of scientific data supporting thesafety and efficacy of dental amalgam, and the ab­sence of any similar database attesting to the safetyand efficacy ofan alternative material, there appearsto be no justification for discontinuing the use ofamalgam. The issue of prime importance is 'to

promote judicious use of amalgam and properamalgam waste disposal. We need to take pruden­tial steps in the following direction :

• Laying down clear guidelines and educating pro­fessionals about the same for observing propermercury hygiene measures in the dental officesand proper mercury disposals.

• Set up of proper mercury re-cycle plants whichcan collect mercury from all sources and re-useit.

• Further refinement of measurement techniques,appropriate experimental design are required togive an accurate idea of how much mercury isexposed to the air from dental practices.

• Carefully designed research required to investi­gate potential biological effects resulting fromlow level Hg.

How call we help? Educate and implement

• Recommend strict mercury hygiene measuresin our set-ups

• Encourage the development and use of mercuryamalgam nltcrnntivcs

• Seminars, continuing education courses on mer­euryhygiene

• Participate in a bulk mercury collection program

• Develop and distribute a pamphlet on amalgamwaste reduction and recycling

• Form a Dental Task Force on Mercury Minimi­zation

References:

1. Bauer JG, First HA. The toxicity ofmercury in dentalarualgams, COli. J I~o2; 10(6):47-61

2. Langan DC. Fan PL. HOQ~ All.. The uscof mercury indentistry: a critical review nt'thp. f P (,pot literature. JADA1987; 115:867-80.

3. McHugh WD. Statement: effects and side-effects ofdental restorative materials. Adv Dent Res 1992;6:139-44.

4. World Health Organization. Environmental Health Cri­teria 101, Methyl-mercury. Geneva, Switzerland: WorldHealth Organization; 1990.

Jrr'A, Vol. 23, September, 2009 11]

5. Arenholt-Bindel v D. denta l ama lgam- environmentalaspects, Adv Dent Res 1992; 6: 125-130

6. Eng le JH, Ferracane JL, Wichmann J,Okabe T. .Quantitation oftotal mercury vapor released during den­tal procedures. Dent Mater 1992; 8(3) :176-80.

7. Frykho lm KO. Mercury from dental ama lgam: its toxicand allergic effects and some comments on occupa­tional hygiene. Acta Odontol Scand 1957; 15(22):5 -108 .

8. Pohl L, Bergman M. The dentist's expos ure to elemen­tal mercury vapor during clinicalwork with amalgam.Acta Odontol Scand 1995; 53(1):44-8.

9. Halbach S. Combi ned est imation of mercury mercuryspecies released from amalgam. J Dent Res 1995;74(4):1103-9.

10. World health organization: Environmental Health crite­ria 118: inorganic mercury, Geneva, Switzerland, 1991,WHO

II. Adegbembo AO, Watson PA, Lugowski SJ. The weightofwastes generated by removal ofdenta l amalgam res­toratio ns and the concentration of mercury in dentalwastewater. J Can Dent Assoc 2002; 68 : 553-8.

JOURNAL OF PIERRE FAUCHARD ACADEMYINDIA SECTION

AN APPEAL

With great pleasure and satifaction we are glad to inform you that the Journal Pierre Fauchard Acad­emy ofIndia Section has entered 23rd year of uninterrupted publication. During the last 22 years of itspublication of Journal of Pf A has received commendable recognition in the scientific forum nation­ally as well as outside the country.

Journal of PFA India Section is published quarterly (March, June Septermber & December) carryingscientific articles, case report s, book reviews, abstracts and information about the PFA, India Sectionand international office. This is sent to all the fellows of PFA, all the Dental Colege and MedicalColle ges in India awl tv the subscriber Iioui India and aborad. Fin ancial implications of con tinuedpublication of such an organ need not be over emphasised, I would like to appeal all the fellows, Ilcadsof Dental Institutions, dental manufacturers, traders and allied companies to voluntarily come forwardand extend their helping hand in continued publication of this journal by advertising in it. Donation tothe Ionrn al fn nrl IIfp 1I 1 ~ () 111P1r:'0 m p ,

Looking forward for an early response.Dr. V.P. Jalili

Chiif. Editor

Note: Addressull your correspondence co the ChiefEditor. D.D. I' Cheque may be drawn in fuvourII}' .I1"'''lUi II}' J11,:Ji . J.'/(I 'IIIIII/ /IJ Intluru.

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114 JPFA, Vol. 23, September, 2009