Contact Dermatitis, 1998, 39, 281–285 Copyright C Munksgaard 1998Printed in Denmark . All rights reserved

ISSN 0105-1873

Metal release from gold-containing jewellerymaterials: no gold release detectedC L1,2, M N3 L S2

1Department of Occupational and Environmental Dermatology,Stockholm County Council, Sweden

2National Institute for Working Life, Solna, Sweden3ANA Adelmetall, Helsingborg, Sweden

Metal release from 13 different gold-containing jewellery alloys stored for 1 and 3 weeks in artificialsweat was analysed. For chemical analysis, inductively-coupled plasma detection (ICP) and atomicabsorption spectrophotometry (AA), with flame and with furnace, were used. No release of goldwas detected. It is unlikely that skin contact with gold-containing metallic items such as jewelleryis responsible for inducing contact allergy to gold or allergic contact dermatitis due to the gold.The patch-test reactivity to gold sodium thiosulfate needs to be explained by some other mechan-ism(s).

Key words: gold; gold sodium thiosulfate; artificial sweat; release of metals; precious metals; chemi-cal analysis; bioavailability; jewellery alloys. C Munksgaard, 1998.

Accepted for publication 13 July 1998

Jewellery and other metallic items in prolongedcontact with the skin frequently cause certain well-known problems. Nickel allergy, both sensitizationand elicitation of allergic contact dermatitis, is thelargest problem, which is recognized by dermatol-ogists, consumers, producers and the EU (1–3).Silver turns black, copper may stain the skin black,and brass may give off verdigris. Compounds suchas sulfides and chlorides readily react with metalions to form chemical compounds which arestrongly blackening. Iron may rust in the hands ofsome people. These metals are easily ionized whenexposed to sweat, which creates the necessary con-ditions for the above problems.

The precious metals gold, platinum, rhodiumand palladium are frequently used in jewellery al-loys and platings, together with non-preciousmetals. Precious metals in the elemental form arestable and they are, according to experience, safein contact with the skin. Metallic gold in jewelleryhas been reported to cause allergic contact derma-titis in single cases only (4–6). Some precious-metalsalts and other precious-metal compounds, how-ever, are reactive and may be irritant or allergenicon skin contact. Occupational dermatitis has beenreported in workers exposed to precious-metalcompounds (7).

Several precious-metal compounds have beenused for patch testing in standard series, dental

screening and research. Some of these compounds,i.e., gold sodium thiosulfate and palladium chlor-ide, cause positive patch test reactions in many der-matitis patients (8–12). The clinical relevance ofthese reactions has however been questioned. Reac-tivity to gold sodium thiosulfate has recently beenshown to be as frequent among control subjects asamong dermatitis patients, and with no associationto dental or therapeutic gold or ear-piercing (13).The reactivity to palladium chloride is seen mainlyamong nickel-sensitive subjects and, based on ani-mal experiments, cross-reactivity has been sug-gested as the explanation (14–16). Are these patch-test substances and the reactions relevant to skin ex-posure to the precious metals in elemental form?

The aim of the present study was to analyse therelease of gold, but also of other precious and non-precious metals, from different gold-containingjewellery materials stored in artificial sweat.

Materials and Methods

Metal discsTogether with representatives of the Swedish Gold-smiths’ Association, different types of gold-con-taining materials frequently used in jewellery wereselected for the study. The materials representedprecious-metals items as well as fashion jewellery,

282 LIDEN ET AL.

and different levels of gold content were included.The materials are shown in Table 1.

Material nos. 1–13 were alloyed and discs wereprepared by the ANA Adelmetall AB certified lab-oratory (ANA Adelmetall AB, Helsingborg,Sweden). The discs were 15 mm in diameter andca. 1 mm thick. Their composition was verified bychemical analysis (see below).

Metal release

Solutions and reagents. Nitric acid, 10% and 25%;deionized water, and artificial sweat were used.

The artificial sweat (17) consisted of deionizedand aerated water containing sodium chloride0.5% m/m, lactic acid 0.1% m/m and urea 0.1% m/m. Ammonia was used to adjust the pH to 6.5.The solution was used within 3 h of preparation.

Equipment. 50 ml polyethylene vessels with lid;laboratory glass pearls (6mm diameter) to beplaced on the bottom of the test vessels to ensurethat the solution reached both sides of the discs,and plastic forceps for handling the discs.

Pre-treatment. The test vessels, the glass pearlsand the forceps were pretreated by being stored in10% nitric acid overnight and then rinsed thor-oughly with deionized water. The discs werecleaned by ultrasound in ethanol at 60æC for 2 min.

Metal-release procedure. The method developedby CEN/TC 283/WG 4 in the preparation of a con-trol standard for the EU Nickel Directive ‘‘Refer-ence test method for release of nickel’’ was used(17). Metal release from discs stored in artificialsweat was analysed. The major deviation from thedraft standard was the addition of a 3-week releaseperiod to the original 1-week period.

1 disc, 10 ml artificial sweat and 14 glass pearlswere placed in each vessel. Vessels were also pre-pared as blanks, without disc. Vessels with the 13different materials and 2 blanks were prepared in

Table 1. Gold-containing materials used in the study; composition according to analysis by atomic absorption spectroscopy

Composition of base alloy

No. Type of material and carat (K) metals gold content (%)

1 coin metal, red gold (23 K) Au, Cu 97.52 red gold, medium (18 K) Au, Ag, Cu 75.03 red gold, bright (18 K) Au, Ag, Cu 75.04 red gold, extra bright (18 K) Au, Ag, Cu 75.05 red gold, casting (18 K) Au, Ag, Cu, Zn 75.06 red gold, medium (14 K) Au, Ag, Cu, Zn 58.67 white gold (18 K) Au, Ag, Pd, Cu, Zn 75.08 white gold (18 K) Au, Ag, Pd, Cu 75.09 white gold (14 K) Au, Ag, Pd, Cu, Zn 58.6

10 solder, red gold (18 K) Au, Ag, Cu, Zn, Cd 74.511 solder, white gold (18 K) Au, Ag, Cu, Zn, Ni 80.612 gold-plated brass Cu, Zn 013 rhodium plated white gold (No. 8) Au, Ag, Pd, Cu 75.0

duplicate and were stored in an oven at 30æC for 3weeks. After 2 weeks an identical set-up of vesselswas prepared and was stored for 1 week in thesame oven.

At the end of the release period, each disc wasremoved from its vessel and rinsed with 100 ml de-ionized water which was added to the solution. 0.4ml 25% nitric acid was also added to prevent depo-sition of dissolved metals on the surface of test ves-sels. The blanks were treated equally.

The metal-release procedure was carried out inour laboratory, at the National Institute for Work-ing Life, Solna.

Chemical analysis

Composition of metal discs. The composition of themetal discs used in the study was analysed by ANAAdelmetall AB using an atomic absorption spec-trophotometer (Spectra AA-10, Varian). The goldcontent of the base alloys is shown in Table 1.

Metal release from discs. The metals in the arti-ficial sweat after the release procedure were ana-lysed by Analytica AB (Analytica AB, Taby,Sweden). The laboratory has great experience inanalysis of gold and other precious metals at lowconcentrations, and also in analysis of metals inartificial sweat. The equipment used and the re-porting limits for the different metals are shown inTable 2.

The release rate of each metal was calculated,based on the mean values of the 1-week samplesfrom each material (samples A and B), and wasexpressed as mg/cm2/week.

Results

The results of analysis of the metals silver, gold,cadmium, copper, nickel, palladium, rhodium andzinc in the artificial sweat after 1 week and 3 weeks

283METAL RELEASE FROM GOLD-CONTAINING MATERIALS

Table 2. Equipment used for analysis of metals released from 13 gold-containing materials stored in artificial sweat for 1 week(samples A and B) and for 3 weeks (samples C and D)

ReportingEquipment Metal limit Material no. and sample

inductively-coupled plasma detection, ICP (Liberty Vacuum Ag 0.02 mg/ml nos. 1–13, sample A-D200 ICP-AES, Varian) Au, Cu, Ni, Pd, Rh 0.05 mg/ml

atomic absorption spectrophotometer, AAS, with a furnace Au 5 mg/l nos. 1–13, sample C(Spectr AA 800Z, GTA 100, Varian)

atomic absorption spectrophotometer, AAS, flame (Spectr Cd 0.01 mg/l no. 10, sample DAA 200, Varian) Zn 0.01 mg/l nos. 5–7, 9–12, sample C

Table 3. Metals detected in artificial sweat after storage of 13 gold-containing materials in the solution for 1 week (samples A andB) and 3 weeks (samples C and D), respectively, and calculated release rate: Ag, Au, Cda), Cu, Ni, Pd, Rh and Znb) were analysedfor; Au, Pd and Rh were not detected in any sample

1 week 3 weeks

sample C sample D Calculatedsample A sample B (mg/ml for Ag, Cu, Ni; (mg/ml for Ag, Cu, Ni; release (mg/cm2)

Material no. (mg/ml) (mg/ml) mg/l for Zn) mg/l for Cd) after 1 weekc)

1 Cu 0.095 Cu 0.088 Cu 0.141 Cu 0.136 Cu 0.272 Cu 0.152 Cu 0.153 Cu 0.188 Cu 0.192 Cu 0.453 Cu 0.108 Cu 0.106 Cu 0.148 Cu 0.135 Cu 0.324 Cu 0.079 Cu 0.083 Cu 0.105 Cu 0.104 Cu 0.245 Cu 0.245 Cu 0.241 Cu 0.288 Cu 0.276 Cu 0.72

Zn 0.076 Ag 0.023 Ag 0.033 Ag 0.048 Ag 0.030 Ag 0.08

Cu 0.197 Cu 0.213 Cu 0.249 Cu 0.225 Cu 0.61Zn 0.08

7 Cu 0.032 Cu 0.040 Cu 0.043 Cu 0.049 Cu 0.11Zn 0.04

8 Cu 0.041 Cu 0.044 Cu 0.048 Cu 0.046 Cu 0.139 Cu 0.049 Cu 0.047 Cu 0.048 Cu 0.045 Cu 0.14

Zn 0.0610 Cu 0.231 Cu 0.212 Cu 0.295 Cd 0.05 Cu 0.66

Zn 0.05 Cu 0.62111 Cu 0.084 Cu 0.103 Cu 0.109 Cu 0.109 Cu 0.28

Ni 0.303 Ni 0.302 Ni 0.325 Ni 0.271 Ni 0.90Zn 0.40

12 Cu 81.6 Cu 110 Cu 146 Cu 110 Cu 290Zn 53

13 Cu 0.015 Cu 0.020 Cu 0.018 Cu 0.010 Cu 0.05blank 1 – – – – –blank 2 – – – – –

Reporting limit: Ag: 0.02 mg/ml; Au: 0.05 mg/ml (sample A, B, D) and 5 mg/L (sample C); Ni: 0.05 mg/ml; Pd: 0.05 mg/ml; Rh: 0.05mg/ml.Calculated reporting limit for release rate: Ag 0.06; Au 0.15; Cu 0.03; Ni 0.15; Pd 0.15; Rh 0.15 mg/cm2 and week.a) Cd was analysed in material no. 10 after 3 weeks only (sample D).b) Zn was analysed in materials nos. 5–7 and nos. 9–12 after 3 weeks only (sample C).c) Based on the mean values from samples A and B.–: no metal was detected.

of storage of the 13 gold-containing materials inthe solution are shown in Table 3.

Gold, palladium and rhodium were not detectedin any sample by the ICP analysis. Gold was alsoanalysed in the 3-week samples (sample C) by AASwith increased sensitivity (reporting limit 5 mg/l,Tables 2, 3), but none was detected.

Copper was detected in all samples. The highestlevel was found in the samples from disc no. 12,the gold-plated brass, with 100¿ higher values

than the other samples. The artificial sweat solu-tion of disc no. 12 had turned blue by the end ofthe release period, indicating formation of coppersulfate.

Zinc was detected in all samples where it was ana-lysed. The highest level was found in the samplefrom disc no. 12, the gold-plated brass, with a 100 to1 000¿ higher value than the other samples.

Cadmium was detected in the sample from discno. 10, red gold solder containing cadmium.

284 LIDEN ET AL.

No major difference in metal release into the ar-tificial sweat solution was shown when comparingthe results from samples A and B (1 week) withsamples C and D (3 weeks), and there was goodcorrespondence between the duplicates.

The calculated metal release per area after 1week (mg/cm2/week) is also shown in Table 3. Theonly nickel-containing material was white gold sol-der (no. 11), with a nickel release of 0.90 mg/cm2/week.

Discussion

It has been claimed that positive patch-test reac-tions to gold sodium thiosulfate represent contactallergy to gold (8–10). The clinical relevance of thereactivity to gold sodium thiosulfate and its poss-ible connection to skin contact with gold-contain-ing metallic items has however not yet been proven(7, 13).

Bioavailability of allergens is essential for in-ducing contact allergy and for eliciting allergiccontact dermatitis. How far are precious metals bi-oavailable on skin contact with jewellery?

In the present study, we were not able to showany release of gold from a number of frequently-used gold-containing jewellery materials stored inartificial sweat. It was not even possible when therelease period was extended from 1 week to 3weeks and when the sensitivity of the analyticalmethod was increased. No rhodium or palladiumrelease was detected either.

Ionization of metals in contact with electrolytessuch as sweat is a complex matter (18). Metal re-lease has previously been studied under differentconditions concerning the composition of the arti-ficial sweat solution, and the temperature and timefor the release procedure. We used the only stan-dardized method (17), with which we also haveprevious experience (2, 19).The more precious ametal is, the more stable and resistant to ionizationit is. Metals in alloys and metals in contact withother metals behave differently from the puremetals when they are in contact with sweat, due toa galvanic effect. Well-known examples are the lownickel release from stainless steel of the 18/8 type,versus higher nickel release from sulfur-rich stain-less steels and pure nickel, and high release fromcopper-nickel (18, 20, and Liden and Carter to bepublished). The presence of a precious metal en-hances the ionization of non-precious metals.

Some precious-metal compounds have beenshown in sensitization experiments to be potentsensitizers (14, 21, 22) or to cause contact derma-titis in occupationally exposed workers (7). Butmetallic gold, rhodium and palladium have rarelybeen reported to cause contact dermatitis. Similar

examples may be presented for some non-preciousmetals. Hexavalent chromium has been one of themost common causes of occupational contact al-lergy, while metallic chromium is harmless on skincontact. Contact allergy to thimerosal is generallynot interpreted as contact allergy to metallic mer-cury.

Thus, the hazard presented by a metal com-pound or an alloyed metal may be completely dif-ferent from the hazard of the same pure metal inelemental form.

No gold release from different gold-containingjewellery materials stored in artificial sweat wasshown in the present study. It is therefore con-sidered unlikely that skin contact with gold-con-taining metallic items such as jewellery is respon-sible for induction of contact allergy to gold orallergic contact dermatitis due to the gold. Thepatch-test reactivity to gold sodium thiosulfatemust be explained by other mechanism(s) thanskin exposure to metallic gold. Dental alloys con-taining gold and other precious metals, often incombination, should possibly be subjected to re-lease studies in artificial saliva.

Acknowledgements

We thank the Swedish Goldsmiths’ Association forfruitful discussions concerning gold-containingmaterials and their use in jewellery, and for econ-omic support to cover the costs of materials. Fin-ancial support was received from the SwedishCouncil for Work Life Research.

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Address:

Carola LidenDepartment of Occupational and Environmental DermatologyKarolinska HospitalSE-171 76 StockholmSweden