Mercury Release from Dental Amalgam

Release of Mercury from "Silver" Dental Amalgam

(In Descending Chronological Order )

Influence of amalgam fillings on Hg levels and total antioxidant activity in plasma of healthy donors. Pizzichini M, Fonzi M, Gasparoni A, Mencarelli M, Rocchi G, Kaitsas V, Fonzi L. Bull Group Int Rech Sci Stomatol Odontol 2001 May-Sep;43(2):62-7. (11799720)
Mercury and selenium concentrations in maternal and neonatal scalp hair: relationship to amalgam-based dental treatment received during pregnancy.Razagui IB, Haswell SJ. Biol Trace Elem Res (2001) Jul;81(1):1-19. (11508328)
Mobilization of mercury and arsenic in humans by sodium 2,3-dimercapto-1-propane sulfonate (DMPS). Aposhian (1998). Environ. Health Perspect. 106:1017-1025. (9703487)
Mercury in biological fluids after amalgam removal. Sandborgh-Englund et al., (1998). J. Dent. Res.77:615-624. (9539465)
The absorption, blood levels, and excretion of mercury after a single dose of mercury vapor in humans. Sandborgh-Englund et al., (1998). Toxicol. Appl. Pharmacol. 150:146-153.(9630463)
Toxicological aspects on the release and systemic uptake of mercury from dental amalgam. Ekstrand et. al., (1998). Eur. J. Oral Sci.106:678-686.(9584901)
The influence of amalgam fillings on urinary mercury excretion in subjects from Apulia. Soleo et. al., (1998). G. Ital. Med. Lav. Ergon. 20:75-81.(9658238)
Systemic transfer of mercury from amalgam fillings before and after cessation of emission. Halbach et. al., (1998). Environ. Res. 77:115-123.(9600804)
Mercury as a potential hazard for the dental practitioner. Kostyniak (1998).N.Y.State Dent. J.64:40-43.(9613096)
Methylmercury and inorganic mercury in serum-correlation to fish consumption and dental amalgam in a cohort of women born in 1922. Bergdahl et. al., (1998). Environ. Res. 77:20-24.(9593624)
Mercury and dental amalgam fillings. Lygre et. al., (1998). Tidsskr. Nor. Laegeforen 118:1698-1701.(9621758)
The absorption, blood levels, and excretion of mercury after a single dose of mercury vapor in humans. Sandborgh-Englund et. al., (1998). Toxicol. Appl. Pharmacol. 150:146-153.(9630463)
Mercury in saliva and feces after removal of amalgam fillings. Bjorkman et al., (1997). Toxicol. Appl. Pharamcol.144:156-162. (9169079)
Effect of Pd and In on mercury evaporation from amalgams. Okabe et. al., (1997). Dent. Mater. J.16:191-199. (9555257)
Mercury exposure from dental amalgam fillings: absorbed dose and the potential for adverse health effects. Mackert and Berglund (1997). Crit. Rev. Oral Biol. Med. 8:410-436.(9391753)
The future of dental amalgam: a review of the literature. Part 2: Mercury exposure in dental practice. Eley (1997). Br. Dent. J. 182:293-297.(9154707)
The future of dental amalgam: a review of the literature. Part 3: Mercury exposure from amalgam restorations in dental patients. Eley (1997). Br. Dent. J. 182:333-338.(9175289)
Effect of Pd and In on mercury evaporation from amalgams. Okabe et. al., (1997). Dent. Mater. J.16:191-199.(9555257)
Patterns of mercury release from amalgam fillings into the oral cavity. Motorkina et. al., (1997). Stomatologiia (Mosk.)76:9-11.(9381508)
Compartmental transfer of mercury released from amalgam. Halbach et al., (1997). Hum. Exp. Toxicol.16:667-672. (9426369)
Impact of nocturnal bruxism on mercury uptake from dental amalgams. Isacsson et. al., (1997). Eur. J. Oral. Sci.105:251-257.(9249192)
Dissolution of mercury from dental amalgam at different pH values. Marek (1997). J. Dent. Res.76:1308-1315.(9168865)
Intial mercury evaporation from amalgams made with In-containing commercial alloys. Nakajima et. al., (1996). Dent. Mater. J. 15:168-174.(9550014)
Influence of chewing gum consumption and dental contact of amalgam fillings to different metal restorations on urine mercury content. Gebel and Dunkelberg (1996). Zentralbl. Hyg. Umweltmed.199:69-75.(9409909)
Long-term use of nicotine chewing gum and mercury exposure from dental amalgam fillings. Sallsten et. al., (1996). J. Dent. Res.75:594-598.(8655765)
Mercury exposure from "silver" tooth fillings: emerging evidence questions a traditional paradigm. Lorscheider et al., (1995). FASEB J.9:504-508. (7737458)
Mercury levels among dental personnel in Isreal: a preliminary study. Steinberg et al., (1995). Isr. J. Med. Sci.31:428-432. (7607870)
People with high mercury uptake from their own dental amalgam fillings. Barregard et al., (1995). Occup. Environ. Med.52:124-128. (7757165)
Sodium 2,3-dimercaptopropane-1-sulfonate challenge test for mercury in humans: II. Urinary mercury, porphyrins and neurobehavioral changes of dental workers in Monterrey, Mexico. Gonzalez-Ramirez et. al., (1995). J. Pharmacol. Exp. Ther. 272:264-274.(7815341)
Silver concentrations in human tissues. Their dependence on dental amalgam and other factors. Drasch et. al., (1995). J. Trace Elem. Med. Biol.9:82-87.(8825980)
An estimation of the uptake of mercury from amalgam fillings based on urinary excretion of mercury in Swedish subjects. Weiner and Nylander (1995). Sci. Total Environ. 168:255-265. (7644912)
Mercury vaporization from amalgams with varied alloy compositions. Ferrancane et. al., (1995). J. Dent. Res. 74:1414-1417.(7560393)
Combined estimation of mercury species released from amalgam. Halbach (1995). J. Dent. Res.74:1103-1109.(7782541)
Estimation of mercury dose by a novel quantitation of elemental and inorganic species released from amalgam. Halbach (1995). Int. Arch. Occup. Environ. Health 67:295-300. (8543376)
Human exposure to mercury and silver released from dental amalgam restorations. Skare and Engqvist (1994). Arch. Environ. Health49:384-394. (7944571)
Mercury concentrations in the urine of children with and without amalgam fillings. Schulte et al., (1994). Schweiz Monatsschr Zahnmed 104:1336-1340. (7984991)
Mercury burden of human fetal and infant tissues. G. Drasch ,I. Schupp , H. Höfl , R. Reinke , G. Roider. European Journal of Pediatrics. Volume 153 Issue 8 (1994) pp 607-610.
Amalgam tooth fillings and man's mercury burden. Halbach (1994). Hum. Exp. Toxicol. 13:496-501.(7917507)
Long-term mercury excretion in urine after removal of amalgam fillings. Begerow et. al., (1994). Int. Arch. Occup. Environ. Health 66:209-212.(7814102)
Evaluation of the safety issue of mercury release from dental fillings. Lorscheider and Vimy. (1993). FASEB J. 7:1432-1433. (8262327)
The relationship between mercury concentration in human organs and different predictor variables. Weiner and Nylander (1993). Sci. Total Environ. 138:101-115. (8259485)
An in vitro and in vivo study of the release of mercury vapor from different types of amalgam alloys. Berglund (1993). J. Dent. Res. 72:939-946.(8501292)
Mercury release from amalgam into saliva. An in-vitro study. Lussi (1993). Schweiz. Monatsschr. Zahnmed. 103:722-726.(8322057)
Urinary mercury after administration of 2,3-dimercaptopropane-1-sulfonic acid: correlation with dental amalgam score. Aposhian et al., (1992). FASEB J. 6:2472-2476. (1563599)
Mercury concentration in the mouth mucosa of patients with amalgam fillings. Willershausen-Zonnchen et. al., (1992). Dtsch. Med. Wochenschr. 117:1743-1747.(1425293)
Side-effects: mercury contribution to body burden from dental amalgam. Reinhardt (1992). Adv. Dental Res. 6:110-113.(1292449)
Dental amalgam: the materials. Marshall and Marshall (1992). Adv. Dent. Res. 6:94-99.(1292469)
Quantitation of total mercury vapor released during dental procedures. Engle et. al., (1992). Dent. Mater. 8:176-180.(1521706)
Daily dose calculations from measurements of intra-oral mercury vapor. Olsson and Bergman (1992). J. Dent. Res. 71:414-423.(1556301)
Mercury exposure of the population. IV. Mercury exposure of male dentists, female dentists and dental aides. Zander et. al., (1992). Zentralbl. Hyg. Umweltmed. 193:318-328. (1290562)
The mercury exposure of the population. III. Mercury mobilisation by DMPS (Dimaval) in subjects with and without amalgam fillings. Zander et. al., (1992). Zentralbl. Hyg. Umweltmed. 192:447-454.(1554403)
Release of mercury vapor from dental amalgam. Berglund (1992). Swed. Dent. J. Suppl. 85:1-52.(1475757)
Factors influencing mercury evaporation rate from dental amalgam fillings. Bjorkman and Lind (1992). Scand. J. Dent. Res. 100:354-360. (1465570)
Amalgam fillings-a considerable source of exposure to heavy metals. Skare and Engqvist (1992). Lakartidningen 89:1299-1301. (1579001)
Daily dose estimates of mercury from dental amalgams. Lorscheider and Vimy. (1991). J. Dent. Res. 70:233-237. (1999563)
The dental amalgam issue. A review. Hanson and Pleva (1991). Experientia 47:9-22.(1999251)
Toxicological assessment of amalgam components released in immersion tests. Weiland and Nossek (1991). Dtsch. Zahnarztl. Z. 46:547-550.(1817927)
Significance of hydrogen ion concentration on the dissolution of mercury from dental amalgam. Soh et. al., (1991). Quintesence Int. 22:225-228.(2068263)
Thermal effect on dissolution of mercury from two dental amalgams. Soh et. al., (1991). J. Oral Rehabil. 18:179-183.(2037941)
Long-term dissolution of mercury from a non-mercury-releasing amalgam. Chew et. al., (1991). Clin. Prev. Dent. 13:5-7.(1860296)
The mercury release of different amalgams in vitro. Lussi and Schoenberg (1991). Schweiz Monatsschr Zahnmed. 101:1405-1408.(1962164)
Whole-body imaging of the distribution of mercury released from dental fillings into monkey tissues. Hahn et al., (1990). FASEB J. 4:3256-3260. (2227216)
Estimation by a 24-hour study of the daily dose of intra-oral mercury vapor inhaled after release from dental amalgam. Berglund (1990). J. Dent. Res. 69:1646-1651.(2212208)
Exposure to mercury in the population. I. Mercury concentrations in the urine of normal subjects.. Zander et. al., (1990). Zentralbl. Hyg. Umweltmed. 190:315-324. (2080963)
Exposure to mercury in the population. II. Mercury release from amalgam fillings. Zander et. al., (1990). Zentralbl. Hyg. Umweltmed. 190:325-334. (2080964)
Maternal-fetal distribution of mercury (203Hg) released from dental amalgam fillings. Vimy et. al., (1990). Am. J. Physiol. 258:R939-R945.(2331037)
Mercury release of silver amalgams in vitro. Hellwig et. al., (1990). Dtsch. Zahnarztl. Z. 45:17-19.(2257794)
Mercury release from amalgam: a study in vitro and in vivo. Ahmed and Stannard (1990). Oper. Dent. 15:207-218.(2095533)
Mercury as a pollutant in the dental profession. I. Its biological cycle, toxicity and monitoring. Valerio et. al., (1990). Minerva Stomatol. 39:625-628.(2287331)
Mercury exposure of different origins among dentists and dental nurses. Skare et al., (1990). Scand. J. Work Environ. Health 16:340-347. (2255875)
Mercury, selenium, and glutathione peroxidase before and after amalgam removal in man. Molin et al., (1990). Acta Odontol. Scand. 48:189-202. (2368614)
The influence of dental amalgam placement on mercury, selenium, and glutathione peroxidase in man. Molin et al., (1990). Acta Odontol. Scand. 48:287-295. (2220337)
Dental "silver" tooth fillings: a source of mercury exposure revealed by whole-body image scan and tissue analysis. Hahn et al., (1989). FASEB J. 3:2641-2646. (2636872)
Mercury vapor from dental amalgams, an intro study. Derand (1989). Swed. Dent. J. 13:169-175.(2814828)
Dental "silver" tooth fillings: a source of mercury exposure revealed by whole-body image scan and tissue analysis. Hahn et. al., (1989). FASEB J. 3:2641-2646.(2636872)
Dental amalgam: a review of the literature. Eggleston (1989). Compendium 10:500-505.(2700133)
Comparison of release of mercury from three dental amalgams. Chew et. al., (1989). Dent. Mater. 5:244-246.(2638267)
Dental amalgam and mercury. Aronsson et. al., (1989). Biol. Met. 2:25-30.(2485649)
Effect of admixed indium on mercury vapor release from dental amalgam. Powell et. al., (1989). J. Dent. Res. 68:1231-1233. (2632609)
Dissolution of metallic mercury in artificial saliva and eleven other solutions. Takahashi et. al., (1989). Dent. Mater. 5:256-259.(2638269)
Dental amalgam and mercury. Aronsson et al., (1989). Biol. Met. 2:25-30. (2485649)
Prospective study on the mercury uptake of dental students. Part 1: Increase in mercury excretion during simulated training. Pieper et. al., (1989). Dtsch. Zahnarztl. Z. 44:714-716.(2637853)
Determination of the rate of release of intra-oral mercury vapor from amalgam. Berglund et. al., (1988). J. Dent. Res. 67:1235-1242.(3166008)
Mercury concentrations in the human brain and kidneys in relation to exposure from dental amalgam fillings. Nylander et. al., (1987). Swed. Dent. J. 11:179-187.(3481133)
Examination of blood levels of mercurials in practicing dentists using cold-vapor atomic absorption spectrometry. Chang et. al., (1987). J. Anal. Toxicol.11:149-153.(3626527)
Potential health hazard of use of mercury in dentistry: critical review of the literaure. Enwonw (1987) Environ. Res. (1987). 42:257-274.(3542524)
Metal release from dental biomaterials. Brune (1986). Biomaterials 7:163-175.(3521750)
Estimation of mercury body burden from dental amalgam: computer stimulation of a metabolic compartment model. Vimy et. al., (1986). J. Dent. Res. 65:1415-1419.(3465771)
Intra-oral air mercury released from dental amalgam. Vimy and Lorscheider (1985). J. Dent. Res.64:1069-1071. (3860538)
Serial measurements of intra-oral air mercury: estimation of daily dose from dental amalgam. Vimy and Lorscheider (1985). J. Dent. Res.64:1072-1075. (3860539)
A model for recording mercury relaease from an amalgam surface. Brune (1985). Biomaterials6:357-359.(4052550)
Man's mercury loading from a dental amalgam. Brune and Evje (1985). Sci. Total Environ.44:51-63.(4023695)
Initial corrosion of amalgams in vitro. Brune an Evje (1984). Scand. J. Dent. Res. 92:165-171.(6585923)
Mercury toxicity and dental amalgam. Wolff et. al., (1983). Neurotoxicology4:201-204.(6361623)
Corrosion of amalgams. Brune (1981). Scand. J. Dent. Res. 89:506-514.(6951250)
Release of mercury from amalgam fillings into salival. Mayer and Diehl (1976). Dtsch. Zahnarztl. Z. 31:855-859.(1068794)

Mercury Release from Dental Amalgam

The IADR/AADR/CADR 80th General Session (March 6-9, 2002) San Diego, California

Dental Materials: VII - Others-Metallic

11:00 AM-12:15 PM San Diego Convention Center Exhibit Hall C, Poster Session
Amalgam
3438 / Effect of Composition on Mercury Vapor Release from Pd-Containing Amalgams
A.L. NEME1, J.L. FERRACANE2, and B.B. MAXSON1, 1 University of Detroit Mercy, USA, 2 Oregon Health & Science University, USA
3439 / Mercury Vapor Release in Various Capsule Designs
J.T. VETTRAINO, and A.L. NEME, University of DetroitMercy, USA
3440 / Hg Release After Abrasion of Pd-Containing Amalgams with Varied Cu
J.L. FERRACANE1, J.D. ADEY1, and T. OKABE2, 1 Oregon Health & Science University, USA, 2 Baylor College of Dentistry, Texas A&M University System, Health Science Center, USA
3441 / The Effect of Bleaching Agents on Mercury Release from Spherical Dental Amalgam
F.J. CERTOSIMO, F.J. ROBERTELLO, M.V. DISHMAN, R.E. BOGACKI, and M. WEXEL, Virginia Commonwealth University, USA
3442 / TCLP Analysis and Residual Mercury Levels in Dental Wastewater Lines
M.E. STONE, J.C. KUEHNE, R.S. KARAWAY, J.M. GULLETT, and J.C. RAGAIN, Jr., Naval Dental Research Institute, USA
3443 / Evaluation of an amalgam under AFM after Nd:YAG laser appliction
M. TANASIEWICZ, and T. KUPKA, Silesian University of Medicine, Poland
3444 / WITHDRAWN
3445 / Longitudinal assessments of urinary mercury levels in the Casa Pia Study
M.D. MARTIN1, B.G. LEROUX1, T. BENTON1, J. LEITAO2, M. BERNARDO2, H. SOARES LUIS2, N. BRAVEMAN3, J.S. WOODS1, L. SIMMONDS1, and T.A. DEROUEN1, 1 University of Washington, USA, 2 University of Lisbon, Portugal, 3 National Institute of Dental and Craniofacial Research, USA
3446 / Effects of compositional variations of dental gallium alloys on corrosion and mechanical properties
Y.-J. PARK1, Y.-R. LEE1, D.-J. LEE1, B.K. NORLING2, and H.R. RAWLS2, 1 Chonnam National University, South Korea, 2 University of Texas Health Science Center at San Antonio, USA

3438 Effect of Composition on Mercury Vapor Release from Pd-Containing Amalgams
A.L. NEME1, J.L. FERRACANE2, and B.B. MAXSON1, 1 University of Detroit Mercy, USA, 2 Oregon Health & Science University, USA

The addition of a small amount of Pd has been shown to reduce mercury release from amalgam during setting (Neme, IADR #3218, 2000).
Objective:
The aim of this study was to evaluate the effect of Cu content on Hg release during setting of amalgams with 1.5 wt% Pd using two collection methods; closed bottle (CB) and Intraoral Flow (IOF).
Methods:
Five amalgam alloys produced by Special Metals (Ann Arbor, MI) were evaluated (wt %): CU1=Ag-60.3, Sn-28.2, Cu-10; CU2=Ag-59.1, Sn-28.4, Cu-11; CU3=Ag-57.9, Sn-28.6, Cu-12.0; CU4=Ag-56.8, Sn-28.8, Cu-13; CU5=Ag-55.6, Sn-28.9, Cu-14. Five Class I cavities were restored for each of the alloys and individually placed in 25-mL glass bottles sealed with a rubber septum (CB). Vapor was extracted by a syringe and analyzed using the Jerome 411 Mercury Analyzer at 1, 3, and 5 hrs after trituration and daily for 5 days. An additional 5 Class I cavities were restored for each of the alloys and placed in a typodont. Ten-second vapor readings were taken at 10 min., 0.5, 1, 2, 3 and 5 hrs after trituration using a customized impression tray attached to the mercury analyzer with a flow rate of 125 cc/10 sec (IOF). The data were analyzed by ANOVA and Tukey HSD (a=0.05).
Results:
A significant difference in Hg vapor release was determined among alloys and time. The alloy with the highest Cu content yielded lower total Hg vapor release (11.7 ng) compared with the alloy with the lowest Cu content (15.2 ng) in the CB method. A similar trend was reported in the IOF method, however not significant.
Conclusion:
In conclusion, Hg vapor release significantly decreased with increasing Cu content in Pd-containing dental amalgams in the CB collection method. Supported in part by NIH/NIDCR grant DE07644.

3439 Mercury Vapor Release in Various Capsule Designs
J.T. VETTRAINO, and A.L. NEME, University of DetroitMercy, USA

Since the introduction of capsulated amalgam, some attention has been given to the potential hazards associated with residual mercury in the capsule waste.
Objective:
It was the purpose of this investigation to evaluate the amount of mercury vapor released from different amalgam capsules in a closed system following trituration.
Methods:
Three different capsule designs each with double-spill regular set alloys were evaluated (Dispersalloy, Tytin, and Valiant PhD). Forty capsules of each material were triturated, the amalgam scrap was discarded, and the unsealed waste capsules were placed in 1-gallon jugs and sealed (n=5). Additionally D and T were evaluated with their capsules resealed and stored as above. Vapor was measured using the Jerome 411 Mercury Vapor Analyzer with a 10:1 dilution module. Measurements were taken at baseline (time 0), 1, 2, 3, 24, 48 and 72 hours after trituration. Average mercury vapor levels and total vapor released were calculated and the data were analyzed by ANOVA and Tukey HSD at a=0.05.
Results:
There was no significant difference in total amount of Hg vapor released among materials with open capsules (D=68.67 m g, T=61.02 m g, V=79.66m g). A significant difference was observed between open and closed capsules in both material D and T, however no significant difference was found between closed capsules (D=8.35m g, T=6.98m g).
Conclusions:
In conclusion, although no significant differences were determined among the three capsule designs investigated when unsealed, resealed amalgam capsules released significantly less Hg vapor compared with open capsules of the same design. Funded in part by Kerr Corp.

3440 Hg Release After Abrasion of Pd-Containing Amalgams with Varied Cu
J.L. FERRACANE1, J.D. ADEY1, and T. OKABE2, 1 Oregon Health & Science University, USA, 2 Baylor College of Dentistry, Texas A&M University System, Health Science Center, USA

Objective:
We recently reported reduced Hg release from Pd-containing amalgams (Adey, IADR:#428, 1999). The aim of this study was to compare the Hg release after abrasion from 5 amalgams containing 1.5 wt% Pd, and to relate the amount of Sn in the g1 to Hg release and Cu content.
Methods:
Alloys were produced by Special Metals (Ann Arbor, MI)(wt %): CU10=Ag-60.3/Sn-28.2/Cu-10; CU11=Ag-59.1/Sn-28.4/Cu-11; CU12=Ag-57.9/Sn-28.6/Cu-12.0; CU13=Ag-56.8/Sn-28.8/Cu-13; CU14=Ag-55.6/Sn-28.9/Cu-14. Amalgams (4mm dia) were made with 42% residual Hg (n=10), aged 1 month and tested for Hg release every 30-60s after abrasion until reaching zero (Jerome 411). Sn wt% was determined with EPMA. Total Hg release was determined by integration (ng) and compared with Tytin (Kerr).
Results:
Means with the same superscript were not different (ANOVA/Tukey’s; p<.05).
CU10 / CU11 / CU12 / CU13 / CU14
Hg release / 373(156)a / 790(427)a,b / 990(400)b / 1050(318)b,c / 1567(673)c
%Sn in g1 / 2.62(0.38) / 2.17(0.19) / 2.15(0.28) / 1.80(0.16) / 1.57(0.13)
Pd significantly reduced Hg vapor emission for all alloys compared to Tytin (2182 ± 544). There was a significant correlation between increased Sn in g1 and lower Hg release (R2=0.932). EPMA identified a Cu-Pd-Sn phase that increased with higher wt% Cu. We hypothesize that when Cu content is low, Cu preferentially reacts with Pd (instead of forming Cu-Sn), thus freeing Sn to deposit in the g1. When Cu content is high, more Sn reacts with Cu and is unavailable for the g1 matrix.
Conclusion:
This study verified that a small amount of Pd (1.5%) in amalgams can significantly reduce Hg release. The reduction is due to an increased Sn in the g1. Supported by NIH/NIDCR Grant DE 07644.

3441 The Effect of Bleaching Agents on Mercury Release from Spherical Dental Amalgam
F.J. CERTOSIMO, F.J. ROBERTELLO, M.V. DISHMAN, R.E. BOGACKI, and M. WEXEL, Virginia Commonwealth University, USA

Objective:
To investigate the effect of carbamide peroxide, hydrogen peroxide and over-the-counter home bleaching products on the release of mercury from spherical dental amalgam (Tytin(R)).
Methods:
One hundred fifty amalgam specimens were prepared in acrylic blocks, aged for 1 week at 37°C, and placed in individual polystyrene jars containing 20 ml of saline. The specimens were divided into three groups of 50(A, B, and C) and bleached in 8 hour cycles. The groups were removed from the saline, blotted to remove moisture, and each subgroup of 10 specimens was covered with Opalescence (Op), Day White 2 (Dw), Contrast pm Plus (Pm), or Rembrandt Dazzling White (Rb). After 8 hours of bleaching, the specimens were cleaned with a toothbrush, rinsed with deionized water, and returned to the saline for 24 hours. Group A was tested for mercury release after 8 hours of bleaching, Group B after 40 total hours of bleaching, and Group C after 80 total hours of bleaching. A reducing agent, SnCl2, was added to change mercury in solution to mercury vapor. The headspace was then analyzed with a Gold Film Mercury Vapor Analyzer.