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Survey and health assessment of chemical substances in jewelleries

7 Exposure scenarios and risk assessment

• 7.1 Assumptions and uncertainties related to the exposure calculations
  • 7.1.1 Two exposure periods – 16 and 24 hours
  • 7.1.2 Migration analysis for sweat is presumed also to apply saliva
  • 7.1.3 Inorganic metal compounds
  • 7.1.4 Highest value chosen in duplicate determinations
  • 7.1.5 Migration is presumed constant over time
• 7.2 Dermal exposure
  • 7.2.1 Results – dermal exposure
• 7.3 Oral exposure
  • 7.3.1 Results – oral exposure
• 7.4 Total health risk by using jewelleries

Jewelleries are used by a large part of the population and they are often in direct contact with the skin for many hours at the time – in some cases even 24 hours a day. This means that possible heavy metals/problematic substances in the jewelleries can penetrate the skin and induce toxic effects.

Another form of exposure can arise by sucking the jewelleries. Some people (probably mostly children) have a tendency to suck their pendants on the necklace and thereby absorb the migrating heavy metals/problematic substances directly.

Furthermore, there can be a risk for children, as well as for adults, that small jewelleries by accident can be swallowed. The seriousness of this is confirmed by a recent death of a 4 year old boy. The boy had by accident swallowed a heart-shaped jewellery containing more than 99% lead. The episode let to a voluntarily recall of 300,000 examples of the mentioned jewellery (Berg et al., 2006).

During the migration analysis the amount of heavy metal that can migrate to sweat and thereby potentially be absorbed via the skin is found. Migration tests for eight chosen heavy metals in 25 different jewellery parts have been performed.

Yet only 4 metals (Cu, Pb, Ni and Cd) showed to migrate in a concentration above the detection limit. For these 4 metals a health and risk assessment has been performed in which the TDI values plus the oral and dermal absorption rates for the metals deduced in chapter 6 are used.

For use in the following risk assessment the data below are applied:

Table 7-1: TDI values plus dermal and oral absorption rates for the 4 metals.

Table 7-2: Margin to TDI values for the 4 metals (µg/kg bw/day).

7.1 Assumptions and uncertainties related to the exposure calculations

7.1.1 Two exposure periods – 16 and 24 hours

During the calculations of exposure through the skin it is conservatively presumed that the jewelleries are in direct contact with the skin during all the time they are worn, e.g. there are for instance no textile between the jewellery and the skin. Some jewellery is worn 24 hours a day, for instance rings and piercings, whereas other jewelleries such as necklaces, bracelets etc. in general are presumed to be removed when the person sleeps. Thus, two different periods of use are applied (16 and 24 hours respectively) depending on whether the jewelleries are removed during the night or not.

7.1.2 Migration analysis for sweat is presumed also to apply saliva

The migration analysis is performed to artificial sweat because this is the type of exposure that most frequently will occur. The results from the migration analysis to artificial sweat are also presumed to be able to be used in the oral exposure calculation because the solutions for artificial sweat and saliva do not deviate significantly from each other.

The solutions consist both primarily of salt water which means that one can expect that the surface tension is approximately the same. Furthermore, metals are positively charged in aqueous solutions and therefore will not form complexes with sodium/potassium, thus the difference in concentration of these has no importance. The temperature in both solutions is approximately the same and the concentration of chloride ions, which is presumed to be the component that primarily forms metal compounds, is also in approximately the same dimensions.

There is approximately 5 times as much urea in the sweat solution as in the saliva solution, but because the urea is not expected to form complexes with the metal it is presumed that this difference is of no importance. Likewise there is much more lactic acid in the saliva solution than in the sweat solution but because lactic acid is not expected to form complex compounds with the metal it is presumed to be of no importance.

Because the pH value in the saliva solution is lower than in the sweat solution (5 versus 6.5) it is presumed that more metal chloride compounds are formed in the saliva solution. This assumption is supported by a study made by Strandesen et al. (2007) where a model is developed to simulate the formation of metal compounds in different aqueous system. This study shows that for salt water with a pH value of 5 3-4% more lead chloride compounds are formed than in salt water with a pH value of 6.5. This means that by using the results from the sweat test in the oral exposure calculations the exposure is underestimated to a certain degree. However, this small difference of 3-4% is not expected to have crucial influence on the results and will probably lie within the measurement uncertainty.

7.1.3 Inorganic metal compounds

It is presumed that it is primarily inorganic metal compounds (as metal chlorides) that are being formed in sweat having contact with the jewelleries, which is the reason why oral and dermal absorption rates as far as possible are based on information concerning relevant inorganic metal compounds. The background for the assumption is found partly in an article by Menné (1994) quoted from ATSDR (2005a) who claims that nickel alloys being in contact with the skin forms nickel chlorides and partly in the risk assessment from the Danish EPA from 2005 (Andersen et al., 2005a), which claims that corrosion of metal in sweat primarily is dependent on the content of chloride and oxygen.

The values for oral and dermal absorption are in this way associated with some uncertainty because it is not known for sure exactly which metal compounds that will be formed when the jewelleries are in contact with sweat (and saliva). The optimum would be to conduct studies that demonstrate  precisely which metal compounds that are formed and which oral and dermal absorption these can expect to have. However, it has not been possible within the scope of this project to perform these kind of comprehensive studies.

7.1.4 Highest value chosen in duplicate determinations

In situations where the duplicate determinations differed significantly the highest value has been used. In Table 4-1 the results from the migration analysis for all samples are presented. In this table it is also illustrated which samples showed significant difference in the duplicate determinations. A significant difference is defined as a difference of approximately 50% or more.

7.1.5 Migration is presumed constant over time

During the risk assessment it is presumed that the migration is constant over time. It should be mentioned here that a piece of jewellery cannot be expected to release the same amount of metal per hour during several years. The migration will decrease with time. Based on the analysis performed in this project it is, however, not possible to determine how fast the migration will decrease and therefore it is assumed that in a period of days/weeks the migration will stay relatively constant.

7.2 Dermal exposure

The potential dermal intake (the exposure) by wearing a piece of jewellery can be expressed through the following equation (European Commission, 2003):

Where:

For use in these exposure scenarios the formula can be rewritten to:

Where:

M_der represents the amount (µg) of chemical substance (here metal) which migrates per gram of jewellery during a period of 4 hours, i.e. the result of the migration analysis.

W represents the real weight of the part/s of the jewellery which can be assumed to have a problematic content of heavy metal, i.e. textile strings etc. are deducted. W is defined by looking at the metal content of the different jewellery parts of the jewellery (from the XRF-screening) and based on this information perform an individual assessment of which metal parts of the jewellery that can be assumed to have a problematic content, i.e. the weight of the jewellery parts which resemble the analysed part. In other words, it is here determined (by comparing the results from the XRF screening) which metal parts of the jewellery that resemble the part on which a migration analysis was made - and thus can be expected to have the same content of metal (and migration).

In cases where a migration test is performed on two different jewellery parts (with a different result) belonging to the same piece of jewellery, separate calculations are made where W is set to the weight of each of the two jewellery parts. Finally, the two results (U_der) are added to give a total dermal absorption by wearing the specific jewellery.

F_der represents the part of the weight (W) of the jewellery which has contact to the skin. F_der is determined based on a visual assessment of each jewellery. However, in most cases it is assumed that 50% of the jewellery has contact to the skin.

T_contact represents the time period of which the jewellery has contact with the skin. Two scenarios are taken into consideration (16 and 24 hours respectively) as it is assumed that some types of jewelleries (as for instance rings, piercings etc.) are worn day and night while other types of jewelleries (as for instance large necklaces and earrings etc.) are most probably removed  during the night.

BW represents body weight in kilograms. Based on TGD, it is here assumed that children weigh 20 kg while adults weigh 60 kg. The value of 60 kg is chosen as it is assumed that it is primarily women who wear jewelleries. According to TGD values for adults of both 60 and 70 kg can be used.

O_dermal represents the dermal absorption (in percentage) of the specific metal. Theses values are different from metal to metal (see Table 7-1) and are described during the health assessment of the different metals.

When U_{der, pot} is calculated the value is compared with the “Margin to TDI” value which is described in Table 7-2. As earlier described, the “Margin to TDI” value shall be regarded as the tolerable daily dose of metal which people  can tolerate, deducted the exposure which the Danes are already exposed to through food, beverages and air. If the U_{der, pot} value exceeds this ”Margin to TDI” value it means that the total exposure (from food, beverages, air and jewelleries) is higher than the tolerable daily intake. In these cases, there might be a potential health risk by wearing the jewelleries. Here it must be mentioned that the “Margin to TDI” value is multiplied by the oral absorption rate (belonging to the specific metal) before it is compared with the dermal exposure as dermal exposure shall be regarded as an absorption of the metal and not an intake which TDI values are normally based on. At an intake (ingestion) some of the metal is excreted through for instance the faeces and is thus not absorbed in the body, while the amount “coming in” through the skin shall be regarded as absorbed in the body (i.e. in plasma, blood, organs etc.).

Example of a calculation of absorption through dermal exposure

Below the exposure- and risk calculation for cadmium exposure from jewellery no. 62 is described. The calculations are made by extrapolating the result from the migration test of the jewellery part (belonging to the specific jewellery) to apply to all the metal parts of the jewellery which can be expected to have the same content of metal as the jewellery part examined (i.e. W). The exposure scenario is 16 hours and valid for children (20 kg). The migration analysis showed that 3 µg cadmium migrated per gram of jewellery during 4 hours. The part of the whole jewellery which is assumed to have a problematic content of metal (W) - i.e. the weight of jewellery parts resembling the analysed part - weighed 40 gram of which 50% is assumed to have skin contact while the dermal absorption rate is 0.6%.

Therefore, the following formula is valid:

Here it shall be noted that the migration analysis is made during a period of 4 hours and therefore the calculations are multiplied by 4 to illustrate an exposure scenario of 16 hours (and 6 for exposure scenarios related to 24 hours).

The TDI value for cadmium is set to 0.5 µg/kg bw/day. If the amount of cadmium which an average child (4-6 yours) is exposed to daily through air, food and beverages (0.39 µg/kg bw/day) is deducted, a “Margin to TDI “ value of 0.11 µg/kg bw/day is achieved (see Table 7-2). This “Margin to TDI” value is multiplied by the oral absorption rate for cadmium (8.9%) in order to “imitate” a TDI value for absorbed metal. I.e. the value with which the dermal exposure shall be compared is (0.089x0.11) 0.00979 µg/kg bw/day.

Therefore the following applies:

In this situation the dermal exposure exceeds the “Margin to TDI” value and therefore the result is below 1, i.e. there might be a potential health risk for a child who wears this jewellery for 16 hours.

Here it shall be emphasized that a TDI value is an expression of what a person may get on a daily basis through an entire lifetime without experiencing health related effects. Thus, for a shorter period the TDI value can be exceeded without this causing any effects, if the person in a corresponding period later in life takes in an equivalent lesser amount. Thus, to wear the above-mentioned jewellery for 16 hours during a single day will not result in effects harmful to health unless an amount equal to the TDI value is taken in every day for the rest of the life.

7.2.1 Results – dermal exposure

Background exposure - average

In the tables below the results of dermal exposure of the jewelleries for 16 and 24 hours respectively at children and adults are presented – at an average background exposure of the four metals.

Table 7-3: Results for dermal exposure at children for 16 and 24 hours respectively – at an average background exposure

NB: Dark grey fields indicate that the TDI value is exceeded while pale grey fields indicate that the TDI value is close to being exceeded.

The results show that for nearly all the jewelleries from where cadmium migrated in an amount above the detection limit, there is a potential health risk for children (who already are exposed to an average background exposure) by wearing the jewelleries for 16 and 24 hours respectively a day. For two of the jewelleries the total tolerable daily dose is exceeded by a factor of 10. I.e. children wearing these jewelleries get 10 times the tolerable dose of cadmium a day. However, here it shall again be mentioned that the daily tolerable dose (TDI) is an expression of what a person may daily get through an entire lifetime without this causing health related effects. Thus, for a shorter period, the TDI value can be exceeded without this causing any effects if in a corresponding period later in life an equally lesser amount is taken in.

Only one piece of jewellery was close to the TDI value of lead while another piece of jewellery was close to the TDI value of nickel. The results indicate that there is no health risk associated with the content of copper in the jewelleries.

Table 7-4: Results for dermal exposure at adults for 16 and 24 hours respectively – at an average background exposure.

For adults being exposed to an average background exposure the TDI value related to cadmium is exceeded for two of the examined jewelleries, when they are worn over a period of 24 hours. Five other jewelleries are close to the TDI value.

None of the jewelleries gave problems related to lead and copper. Three other jewellery parts were close to the TDI value for nickel.

Background exposure – 95 percentiles

In the tables below the results of dermal exposure of the jewelleries for 16 and 24 hours respectively at children and adults are presented – at a background exposure corresponding to the 95 percentile. Copper is not included as no background exposure corresponding to the 95 percentile for copper exposure in Denmark was found.

Table 7-5: Results of dermal exposure at children for 16 and 24 hours respectively – at  a background exposure corresponding to the 95 percentile.

NB: A red field indicates that the TDI value is already exceeded without including the contribution from jewelleries.

No calculations are performed for cadmium as the TDI value for cadmium is already exceeded for the 5% of Danish children being exposed to the maximum background exposure of cadmium.

Three jewellery parts are close to the TDI value related to lead.

Table 7-6: Results of dermal exposure at adults for 16 and 24 hours respectively – at background exposure corresponding to the 95 percentile.

The results show that for the 5% adults being exposed to the maximum background exposure of cadmium (i.e. the value belonging to the 95 percentile or higher) the TDI value is exceeded for four of the jewelleries when they are worn for a period of 24 hours, while only two of them exceed the TDI value when they are worn for only 16 hours.

None of the jewelleries gives problems related to lead while two jewellery parts  exceed the TDI value related to nickel when they are worn for 16 and 24 hours respectively.

Added results for jewelleries which had jewellery parts with different migration results

For 5 jewelleries a migration analysis has been made on two different jewellery parts belonging to the same jewellery. To get a correct picture of the potential skin absorption on these jewelleries it is necessary to add the results for the two different jewellery parts. Below the added results are presented. These calculations are only relevant to carry out for dermal exposure as it is not expected that humans will have two different charms in the mouth at the same time. As an explanation of the table it can be mentioned that among the jewelleries showing a migration there was a jewellery from where nickel migrated from two different jewellery parts (jewellery no.91). There was no case of a jewellery showing migration of cadmium from two different parts on the same jewellery and therefore there are no results for cadmium.

Table 7-7: Added results for the 4 jewelleries which each had two jewellery parts with different migration of metals. Dermal exposure time: 24 hours. Background exposure: the 95 percentile.

* At exposure of 16 hours the value is 0.4.

It is seen that jewellery no. 91 exceeds the total TDI when adults wear it for 24 hours (and 16 hours). This is valid for the 5% of adults in Denmark being exposed to maximum background exposure of nickel.

As the results from this project show that there might potentially be a hazardous health risk by wearing just one piece of jewellery at a time it shall of course be emphasised that if several different jewelleries are worn at the same time the exposure will increase and the potential health risk of course increase as well.

7.3 Oral exposure

When people suck jewelleries (as for instance a pendant) the metals, which migrate from the jewellery, will be ingested directly. In these cases, the total amount of migrated metal (measured in the migration analysis) will be ingested (though not necessarily absorbed in the body).

The TDI value, which is used during the risk assessment, is based on studies that indicate an effect at a certain amount of ingested metal. Thus, during the risk assessment in this project the amount of ingested metal is compared directly to the TDI value (i.e. an oral absorption rate is not multiplied, as in the calculations related to dermal exposure).

It is assumed that as a worst case jewellery is sucked for a period of maximal two hours per day. Calculations regarding oral ingestion are based on the equation for migration of substances from a product to food/beverages, which is then ingested (European Commission, 2003). However, sucking jewellery is not fully comparable with the situation of which the above mentioned equation is based, thus the equation is adjusted.

Thus, oral ingestion can be calculated based on the following equation (European Commission, 2003):

Where:

By oral exposure of the jewelleries the equation can be adjusted to:

Where:

M_der, W, and BW represent the same as described in the section regarding  dermal exposure calculation.

F_oral represents the part of the weight of the jewellery (W) (which has a problematic content of heavy metal) that can be assumed to be sucked. F_oral is determined by visually judging how large a part of each jewellery that realistically can be assumed to be put into the mouth. Thus, for jewelleries such as rings, bracelets and piercings F_oral is 0 since these jewelleries are not assumed to be put into the mouth.

T_contact represents the duration of the exposure which here is assumed to be 2 hours.

When I_{oral, pot} is calculated, the value is compared to the value representing “Margin to TDI” which is described in Table 7-2. The “Margin to TDI” value must, as described earlier, be regarded as the amount of metal which people can tolerate to take in on a daily basis, subtracted the amount of metal which the Danes already take in via food, beverages and air – in other words, the “Margin to TDI” value must be thought of as the extra amount of metal which people can tolerate on a daily basis without experiencing health related effects. If the I_{oral, pot} value exceeds this “Margin to TDI” value there is a potential health related risk by sucking the jewelleries.

Example of a calculation on uptake via oral exposure

Below is described how the exposure calculation related to lead is performed for jewellery no. 62. The calculation is performed by extrapolating the result derived from the migration test of the jewellery part (belonging to that specific jewellery) to account for the metal part of the jewellery which can be expected to be put into the mouth.

The duration of the exposure (T_contact) is 2 hours and the “target” of interest is children (20 kg). The migration analysis showed that 39 µg lead migrated per gram of jewellery during a period of 4 hours. The part of the jewellery which is assumed to have a problematic content of metal (W) – i.e. the weight of the part of the jewellery, which resembles the analysed part – weighs 40 gram. The part of W, which is assumed to be put into the mouth (F_oral) is 0.50 (since the pendant is of such a size that it is judged that only half of it can be put into  the mouth) – thus the weight of the part of the jewellery that can be put into  the mouth is 20 gram.

Thus, the following equation is valid:

It should be noted that the migration analysis is performed during a period of 4 hours. In order to illustrate an exposure scenario of 2 hours a factor of 0.5 is therefore multiplied in the calculations.

The TDI value for lead is set at 1.8 µg/kg bw/day. If the amount of lead, which an average child (4-6 years) is exposed to on a daily basis via air, food and beverages (0.49 µg/kg bw/day) is subtracted, a “Margin to TDI” value of 1.31 µg/kg bw/day arises (see Table 7-2).

Thus, the result is as follows:

In this case the result is below 1, which indicates that there is a potential health related risk related to lead for children who suck this particular jewellery for a period of 2 hours per day. This is only valid for children that are exposed to an average background concentration of lead.

It should be pointed out that a TDI value represents the amount of substance that a person can tolerate to take in per day during an entire lifetime, without the occurrence of health related effects. Thus, it is possible for a short period of time to exceed the TDI value without this causing any effects, provided that in a similar time period later in life the person takes in an equivalent lesser amount. Thus, sucking the above mentioned jewellery for a period of 2 hours per day will not result in health related effects unless the person every day for the rest of his/her life takes in an amount corresponding to the tolerable daily dosage (the TDI value).

7.3.1 Results – oral exposure

Background exposure - average

The table below presents the results related to oral exposure of the jewelleries during a period of 2 hours per day in adults and children respectively – who already are exposed to an average background exposure of the four metals.

Table 7-8: Results related to oral exposure during a period of 2 hours in adults and children respectively – calculated in scenarios representing an average background exposure.

The results show that when sucking the jewelleries for a period of 2 hours potential health related risks related to cadmium, nickel and lead arise. It is most pronounced for lead and cadmium since almost all of the jewelleries (which showed migration of the specific metal) exceeded the TDI value related to lead and cadmium. This is valid for children and adults exposed to an average background exposure.

Background exposure – 95-percentiles

The table below presents the results related to oral exposure of the jewelleries during a period of 2 hours per day in children and adults respectively exposed to a background exposure corresponding to 95-percentiles.

Table 7-9: Results related to oral exposure during a period of 2 hours in children and adults respectively exposed to a background exposure corresponding to 95-percentiles.

NB: a red box indicates that the TDI value is exceeded without taken into account the contribution from sucking jewelleries.

As described in section 7.2.1 5% of the Danish children are already exposed to an amount of cadmium which exceeds the tolerable daily dosage. Thus, no calculations are performed for cadmium.

However, almost all of the jewelleries (which showed migration of lead) exceed the TDI value for lead in children as well as adults. Finally, one jewellery exceeds the TDI value related to nickel in situations where adults suck the jewellery for a period of 2 hours.

Table 7-10 shows the content of lead in those jewelleries, where the results from the migration analysis indicated a potential health related problem by sucking them for a 2-hour period. The table also shows the time period of which a person can suck the jewelleries before the total TDI value is exceeded.

Table 7-10: Oral exposure calculations for lead in relation to content of lead in the specific jewelleries. Calculated for persons that are exposed to an average background exposure.

NB: The content of Pb is determined by an XRF-screening and therefore only gives an approximate estimate of the content of lead (see section 3.4.1 for description of the uncertainty). A line indicates that no migration occurred, thus it was not possible to calculate a TDI/I_{oral, pot} value.

The results show that the lowest content of lead, which causes potential health related problems by sucking the jewelleries for a period of 2 hours, is a lead content of 1.77%, i.e. a great deal above the claim of a maximum content of 0.01% lead stated by the new Statutory order on ban on import and sale of products containing lead. At the same time it is seen that none of the jewelleries containing a maximum amount of 100 ppm lead cause potential health related problems.

The table above likewise shows the number of minutes of which an adult/child can suck the jewelleries before the tolerable daily dosage is exceeded. For jewellery no. 138.1 it can be seen that children as a maximum can suck the jewellery for 1 minute before the tolerable daily dosage is exceeded. It is here interesting to note that this jewellery proved to have the lowest content of lead (out of the jewelleries that showed migration of lead). Of this can be concluded that in general it must be recommended not to suck jewelleries.

7.4 Total health risk by using jewelleries

Based on the findings of this project it cannot be excluded that by wearing or sucking some of the metal jewelleries examined in this project potential health risks related to especially cadmium and nickel arise. This is valid for people exposed to the background exposure found in Denmark. For lead there are primarily problems when sucking the jewelleries. None of the jewelleries examined caused problems related to copper.

The health related risks associated with the three metals are effects on the kidneys (cadmium), increased mortality risk on foetuses (nickel) and reduced IQ at children (lead).

If the jewelleries comply with the legal demand related to content of lead, the results in this project indicate that no health related risks arise by wearing or sucking the jewelleries.

A number of reservations are decisive in terms of health related problems arising. Among others, the jewellery must be worn/sucked every day over an extended period of time, since a short-term exceeding of the tolerable daily dosage not necessarily results in health related effects, unless during the remaining life time the person takes in an amount equal to the tolerable daily dosage. Furthermore it is assumed in the calculations, that the migration of metals from the jewelleries is constant. The migration will in time decrease.

Additionally, the findings of this project show that no correlations seem to exist between the appearance of the jewellery (i.e. gold coated, silver-like etc.) and the content/migration of heavy metals. Based on the findings of this project there is thus no reason for avoiding for instance silver-like or gold coated jewelleries. Though, it should be mentioned that jeweller jewelleries (genuine silver and gold), that is jewelleries submitted to control by the Precious Metal Assay and Inspection, generally are not expected to contain heavy metals at a problematic level.

Finally it is in the project concluded that there exist textile necklaces on the Danish market, which contain benzidine in amounts exceeding the allowable.

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Version 1.0 October 2008, © Danish Environmental Protection Agency