The Colour of Money
#6 -- 1998 Published by the Nickel Development Institute
What Nickel Gives to
Coinage
Nickel Contact Dermatitis
Coinage and Nickel
Euro-coinage
Dermal Nickel Sensitization Workshop
Summary
Endnotes
During the thousands of years of metal coinage, a hierarchy of value developed based on the colours of metals of different scarcity. Even though those metals are today largely absent from coinage, their colours still influence the appearance of coins.
Based on their relative scarcity:
- Gold was used for high value coins and the "yellow" of gold remains an indication of high value.
- Silver was used for middle value coins and the "silver" colour is still used for middle-rank coins.
- Copper (and its alloys) was relatively common and low in the hierarchy of coinage values. The "red" or
"copper" colour is still common for low-value denominations, and the metal itself (unlike gold and silver)
still has a significant role.
These groupings reflected the attitude that the intrinsic value of a coin should equal, as closely as possible, its face value.
There were two problems with this, and silver provides the best example. The European discovery of the empires of Central and South America in particular led to enormous and unpredictable fluctuations in the supply of silver, which led to fluctuating understandings of its scarcity and hence of its value. Silver is also an easily alloyed metal. Thus there were many "silver" coins which, from country to country, from denomination to denomination, and from year to year, would vary significantly in both the amount of silver and the value of that amount. Governments did not help when, faced with financial difficulties, they "debased" their currency: "silver" coins were issued which contained less silver.
In these circumstances, the notion gradually gained acceptance that the intrinsic value of a coin need not match its face value. This paralleled the idea that paper money need not represent an exact equivalent amount of gold in the national treasury.
This change of attitude to the value of coinage led to the search for a metal that possessed the same valued properties of silver for coinage but was less costly and less liable to manipulation. First in the 1850's in Switzerland and Belgium, and thereafter around the world, nickel was recognized as the ideal metal.
Nickel in coinage was not new even in the 1850s. Long before nickel was identified as an element (in 1751 by the Swedish scientist Axel Cronstedt), nickel was part of coinage: the ancient Chinese alloy 'paitung' was an coinage material of nickel, copper and zinc.
For modern coinage, many alloys were made and tested in the search for the best substitute for silver. The Swiss and Belgian coins were made of an alloy 75% copper and 25% nickel. That alloy, cupro-nickel, is today the single most common alloy of nickel for coinage in the world.
In 1881, Switzerland introduced pure nickel coins after certain metallurgical problems in the processing of pure nickel into coins were overcome. The wear resistance of these pure nickel coins was so great that coins from the 1880s still in circulation in the 1960s were almost indistinguishable from new counterparts minted at that time.
The dominance of nickel and nickel-containing materials in medium and high value coins is easily explained:
- in appearance, both pure nickel and cupro-nickel have the same silvery whiteness and bright metallic
luster that is associated with the "value" of "silver"coins;
- the high corrosion resistance of nickel prevents tarnishing or dulling of coins so that they maintain
their silvery whiteness and metallic luster while in circulation;
- in the foundries, the alloy is easy to work with, is not prone to contamination by other elements and, as
a result, produces a very consistent, colour-stable product;
- the "weight" of nickel or cupro-nickel coins reflects a similar "medium" density that is psychologically
associated with the "worth" and "value" of "silver" coins;
- the high malleability and formability of nickel and cupro-nickel allows a deep and accurate "strike" of
the coin "impression" in a minting press that is as good or better than silver coins;
- the "toughness" of nickel provides even greater wear resistance, durability and longevity than silver
coins; and
- the magnetic properties of nickel are exploited to minimize fraudulent use of low-value tokens or counterfeit coins in vending machines. This latter attribute is assuming a greater importance as the values of the denominations in circulation increase.
Allergies are very common in industrialized societies. The number of agents (allergens) that can lead a person to first become sensitized and, in subsequent exposure, provoke an allergic reaction, is measured in the thousands. Not all allergens have the same potency, however, and nickel is one of a number classed as "moderate" allergens. Nickel has attracted attention, however, because it is so common in our society. There are tens of billions of coins in circulation which contain nickel in some form, and nickel-containing items and utensils are common in our everyday lives.
The number of individuals sensitized to nickel varies by sex and origin. In Europe, where the issue has attracted the greatest attention, the figures generally quoted by dermatologists are 1-2% of men,10-12% of women, and with higher figures for young women (up to 20%). The percentages for young men has also been growing along with the prevalence of male body-piercing. Only a minority of those sensitized subsequently experience an allergic reaction, and most of those are of a minor nature. The most common symptoms being a redness, itchiness or scaliness of the skin where an object containing nickel in a form capable of releasing nickel ions has been in direct and prolonged contact with the skin. Earring posts or clips are the classic examples. The symptoms disappear when the irritant is removed.
In some cases, however, more extreme symptoms express themselves in hand eczema, a condition which can be persistent, recurring and requiring medical attention and management.
This ability of nickel to sensitize and the potential for allergic reaction has attracted medical, media, and regulatory attention. Sensitivity to nickel is associated primarily with inexpensive, nickel-plated earrings and other nickel-plated items that come into direct and prolonged contact with the skin, variously including some bracelets, necklaces, buttons and zippers. There has been some association with certain types of stainless steel (the so-called "high sulphur" varieties) occasionally found in some watch parts and bands.
For sensitization to occur, there must be a release of nickel ions. The result of continuous skin contact with nickel over a period of hours or more, particularly in the presence of sweat, can be free nickel ions which can penetrate the skin.
Most people exposed to nickel ions will not become sensitized. The level of exposure may be insufficient. There may not be, in the individual, a disposition towards nickel sensitivity. The individual may have developed an immunity to nickel through early childhood exposures (e.g. nickel-containing dental brace materials)1. If the nickel is isolated from contact with the skin by a coating, or if the nickel is in the form of an alloy that resists attack by sweat, then no nickel is released and no sensitization or skin effects result.
Nickel or copper-nickel coins have been in widespread use for almost 150 years without apparent harm to society. This positive record is possible because nickel-containing coins meet some but not all of the conditions needed for the development of nickel allergy. Although nickel is present and in a form susceptible to releasing nickel ions when acted upon by sweat, a coin does not remain in one person's hand for long periods of time. Even occupationally exposed groups (e.g., cashiers) come in contact with individual coins for only very brief periods of time. The contact is not prolonged.
What little sweat that may be transferred from the hand to the coin will be minuscule and temporary. The action of the sweat on the surface of the coin will be equally small and will cease when the sweat dries. Used coins have been shown to have lower levels of nickel release than coins when they first enter circulation, probably because of surface dirt, oils and fats from the skin, and products of corrosion (eg., nickel oxide).2, 3
Notwithstanding this human experience, a linkage has been made by some between the existence of nickel allergy and the presence of nickel in coinage. Some authorities have acted on the basis of this assumption to alter the composition of their coinage.
Sweden has largely removed nickel from its coinage and, in the recent decision on the new European coinage (the Euro), Sweden argued for the total removal of nickel and nickel alloys from consideration for the new coinage. While the scientific advice was that nickel in coinage did not pose an undue health risk (see below), the Swedish representations resulted in a broader political decision to greatly reduce the number of new coins that will have nickel as a constituent. In place of the traditional nickel alloys for the middle value coins, a trademarked alloy used in Swedish coins called Nordic Gold has been mandated by the European Union. Nickel alloys remain important constituents, however, in the high-value 1 and 2 Euro coins.
"At the request of the [European] Commission, the Scientific Committee for the Toxicity and Ecotoxicity of Chemical Compounds has considered the risk arising from handling coins containing nickel. The committee agreed that there was no evidence to suggest that current coinage had been associated with the initiation of sensitization. As for people already sensitized, analysis of the very limited information available led the scientific committee to the conclusion that very few cases of dermatitis may be caused by the release of nickel from present day coins, both in the average consumer and in workers professionally handling coins." -- Commissioner de Silquy, 6 October, 1997
Dermal Nickel Sensitization Workshop
Partly because of recently heightened attention focused on nickel dermatitis, the Nickel Producers Environmental Research Association, NiPERA, sponsored a two-day workshop on nickel dermatitis in Brussels in 1997. Invited participants in this workshop included some of the leading authorities on nickel dermatitis from universities, hospitals and research organizations, together with medical and other representatives of the world's major primary nickel producers.
At the conclusion of the workshop, a number of "Consensus Positions on the on the Role of Nickel in Dermal Sensitization" were prepared, reviewed and accepted. In the section most relevant to coinage, the view was:
"Transient, short term contact with nickel containing articles such as coinage, keys, handles, tools and other equipment does not appear to be a factor in the induction of an allergic contact dermatitis within the general population. If the contact is of short duration and also infrequent, the risk of sensitization is negligible, and the risk of the elicitation of dermatitis is limited. Conversely, if the contact is frequent and/or continuous, it may elicit dermatitis in certain highly sensitive or previously sensitized individuals. When an end-use of nickel has the potential to produce elevated levels of nickel release in normal use, nickel producers or manufacturers should inform their customers of this potential and work with them to manage or remove the risk to nickel sensitive individuals." 4
Nickel-containing coinage does not make individuals -- even those who handle large volumes of coins on a daily basis -- allergic to nickel.
Of those who become allergic to nickel by other means and who have a high occupational exposure to nickel-containing coinage, such coinage might cause a reaction among a very small fraction of highly sensitive individuals. In these rare instances where hyper-sensitivity and high occupational exposure occur, those who might react should wear cotton gloves while handling coins.
The selection of any material for use in coinage involves a number of criteria. In this context, the mechanical, security, aesthetic, and economic advantages of nickel-containing coinage are uncontested.
1 "Reduced frequency of nickel allergy upon oral nickel contact at an early age", Hoogstraten
et al, 1991
2 "Hygiene Characteristics of Nickel", Bozec et al, 1992
3 "Nickel Coin Dermatitis", Hussain, 1977
4 "Proceedings of the NiPERA Dermal Nickel Sensitization Workshop", Nickel Producers Environmental
Research Association, 1998.
