5.5Other intentional product/process uses
Table 5 169 Other intentional products/process uses: sub-categories with primary pathways of releases of mercury and recommended inventory approach
Chapter
|
Sub-category
|
Air
|
Water
|
Land
|
Product
|
Waste/
residue
|
Main inventory approach
|
5.5.1
|
Dental mercury-amalgam fillings
|
x
|
X
|
|
X
|
X
|
OW
|
5.5.2
|
Manometers and gauges
|
x
|
X
|
x
|
X
|
X
|
OW
|
5.6.3
|
Laboratory chemicals and equipment
|
x
|
X
|
|
X
|
X
|
OW
|
5.5.4
|
Mercury metal use in religious rituals and folklore medicine
|
X
|
X
|
X
|
X
|
X
|
OW
|
5.5.5
|
Miscellaneous product uses, mercury metal uses and other sources
|
X
|
X
|
X
|
X
|
X
|
OW
|
Notes: PS = Point source by point source approach; OW = National/overview approach;
X - Release pathway expected to be predominant for the sub-category;
x - Additional release pathways to be considered, depending on specific source and national situation.
5.5.1Dental mercury-amalgam fillings 5.5.1.1Sub-category description -
Dental amalgam fillings consist of an alloy of mercury, silver, copper and tin (typically about 44-51% mercury by weight). The alloy is typically supplied to the dentists either: 1) as pure mercury along with a powder mix of the other metals, which are weighed and mixed in an agitator in the clinic; or 2) as small capsules where mercury and the metal powder are present in the right formula and only need to be mixed (in the capsule before opening) in the clinic, prior to filling the cavity in the tooth (COWI, 2002). Other variants of the same principles may occur.
-
Mercury is released to air, water, and wastes during the production, use and disposal of the amalgam fillings (such as following the removal of fillings or teeth containing fillings during medical/dental procedures, or through lost teeth). Also, releases can occur at the end of life of a person with fillings. For example, dental amalgams are a major factor determining mercury releases to air from crematoria (see section 5.10.1).
-
In the dental clinic parts of the mixed amalgam filling is filled into the cavity, but there is always an unused rest, which is often collected for waste disposal or recycling (especially due to the silver value). Often the filling is adjusted in the surface which releases a little amalgam particles to the waste water system. Also at the routine renewal of amalgam fillings, the old filling is drilled out, and amalgam particles are lead to the waste water system. Often larger amalgam particles from such operations will be withheld in a mesh filter in the water suction system, from where they can be retrieved for waste disposal of recycling. In countries with strict waste water regulations for dental clinics, the clinics may have an additional central filter which is much more effective than the coarse mesh filter in retaining mercury amalgam from the waste water. In addition, teeth with amalgam fillings may be removed in the clinic, and disposed of as general waste or separately collected hazardous waste, or sent for recycling. In Denmark, and perhaps also in other countries, a substantial number of extracted teeth are sent to dental schools for the use in practical dentist teaching (Maag et al., 1996; Skårup et al., 2003).
5.5.1.2Main factors determining mercury releases and mercury outputs
Table 5 170 Main releases and receiving media during the life-cycle of dental mercury-amalgam fillings
Phase of life cycle
|
Air
|
Water
|
Land
|
Products
|
General waste
|
Sector specific treatment/
disposal *1
|
Production/supply of materials for fillings
|
|
|
|
X
|
|
|
Dental preparations and procedures at dental offices
|
x
|
X
|
|
|
X
|
X
|
Use (while in peoples mouths)
|
|
X
|
|
|
|
|
Disposal
|
|
X
|
|
|
X
|
X
|
Notes: *1: Separate collection for treatment as hazardous/medical waste or for recycling;
X - Release pathway expected to be predominant for the sub-category;
x - Additional release pathways to be considered, depending on specific source and national situation.
-
Releases of mercury could take place during processing/packaging of mercury and capsules at the producers/suppliers, but the releases may be minimal due to the simple processing. No emissions controls are known to be used in production in USA. Small fractions of mercury are released to air in the dentist clinic.
-
The most important aspects influencing mercury releases from dental amalgam are as follows:
-
The amounts of dental amalgam used per person (capita) in the country, reflecting both the general dental care standard in the population, and the extent of use of alternative dental filling materials (plastic composites, ceramics or cast gold crowns);
-
The presence of modern high-efficiency amalgam filters in the dental clinics waste water system. If present, they may collect 90 - 99.9 % of the amalgam input to the waste water in the clinic. If only the coarse mesh filters (strainers) are used, most of the amalgam - perhaps 80 - 90% based on the Danish studies - is lost to the public waste water system (or released to the environment if no such system exists);
-
The fate of amalgam waste (excess amalgam from new fillings, in collected filter material and in extracted or lost teeth). It may be collected separately for recycling or other treatment as hazardous/medical waste, or it may be disposed of with general waste to landfills, incineration or other waste treatment as prevailing in the country.
-
Losses of mercury from fillings during use (while still in the mouth) are taking place continuously at very low rates. Until recently, these mercury outputs have been deemed negligible by some researchers, but a 2001 study from the capital of Sweden, Stockholm, indicated that about 44% of the total mercury inputs to waste water treatment originated from amalgam fillings in the mouth, while only about 21% of the total mercury inputs to waste water treatment originated from dental clinics (Sörme and Lagerkvist, 2002; Sörme et al., 2003). The mercury release estimates from amalgam in the mouth of inhabitants were based on excretion rates of 60 μg/ (day*person) with faeces and urine (citing Skare and Engquist, 1994), and did not include contributions from food intake (Sörme and Lagerkvist, 2002; Sörme et al., 2003). These results should be seen in the context that other mercury input sources to waste water are likely minimal in Sweden compared to many other places in the world (Sweden is perhaps one of the countries where mercury has been regulated most strictly for several decades).
Table 5 171 Overview of activity rate data and mercury input factor types needed to estimate releases from dental mercury-amalgam fillings
Life-cycle phase
|
Activity rate data needed
|
Mercury input factor
|
Production of ingredients
|
Mercury purchased for the
production per year
|
Mercury loss per Kg mercury purchased for production
|
Preparations of fillings in the teeth at dentist clinics
|
Number of amalgam fillings
made per year
or
National population
|
g mercury used for preparation of one amalgam filling
or
Estimated mercury consumption for amalgam fillings per capita
|
Use
(while in peoples mouths)
|
National population
|
Estimated mercury excretion per capita per year
|
Disposal
|
Number of amalgam fillings made per year 10-20 years ago
or
National population
|
g mercury used for preparation of one amalgam filling
or
Estimated mercury consumption
for amalgam fillings per capita
10-20 years ago
|
-
Based on data from Denmark, depending on size and type of filling, about 0.4-1.2 g of mercury is used per filling on average, including excess amalgam; about 0.4 g mercury for a one surface filling and about 1.2 g for a filling on three surfaces of the tooth. Based on detailed Danish data on the types of fillings actually made, the average mercury consumption per filling is about 0.8 g Hg/filling (based on Maag et al., 1996, and Skårup et al., 2003). Similar quantities per filling may be used in other countries.
Table 5 135 Reported annual mercury consumption for dental fillings in selected countries, in total and per inhabitant *1
|
Denmark, 1983
|
Denmark, 1993
|
Denmark, 2001
|
Sweden, 1991
|
Sweden, 2003
|
Norway, 1995
|
Norway, 1999
|
USA, 1996
|
Reported mercury
consumption with amalgam fillings, Kg/year
|
3100
|
1800
|
1200
|
1700
|
103
|
840
|
510
|
31000
|
Population, millions *2
|
5.4
|
5.4
|
5.4
|
8.9
|
8.9
|
4.5
|
4.5
|
281
|
Annual mercury consumption with
dental amalgam,
g per inhabitant
|
0.57
|
0.33
|
0.22
|
0.19
|
0.01
|
0.19
|
0.11
|
0.11
|
Notes: *1 Denmark: Mercury amalgam has been gradually substituted for by other filling materials. Since 1994,
amalgam fillings have been banned except for adult's molar teeth on surfaces with tough wear (Skårup
et al., 2003). Sweden: In the early 1990's a quick shift towards alternatives made the amalgam
consumption drop, since then the consumption has dropped more slowly (Kemi, 1998). Dental amalgam in Sweden and the reduction of the used amounts has declined significantly the last 5-6 years. In 1997 the sold amounts of mercury to dental amalgam was 980 kg and in 2003 it was 103 kg (Kemi, 2004). Norway: Norwegian Pollution Control Authority, as cited by Maag et al. (2001). USA: Mercury consumption for amalgam fillings reported as almost constant between 1980 and 1996 (Sznopek and Goonan, 2000);
*2 CIA'a World Fact Book (accessed 2003 at http://www.odci.gov/cia/publications/factbook/index.html ).
-
Rothenburg and Katz (2011) suggested that basing estimation of mercury inputs with dental amalgam on input factors as shown above in combination with population numbers only, might produce too high estimates for countries with lower dental restoration frequency than the developed countries mentioned above. They suggested to further adjust such mercury input estimates with a factor describing the number of dental personnel present in the country of interest, as compared to the number of dental personnel in the countries from which the mercury consumption per capita were derived. This adjustment was applied in Inventory Level 1 and can also be used in Inventory Level 2 if desired; see also Section 5.6.1.5 below. The latest available aggregated estimates of the number of dental personnel in most countries of the world are reported by the WHO (2006). Annex 8.4 to this Reference Report shows the WHO's estimates of the density of dental personnel per 1000 inhabitants. For a few countries, such estimates were missing, and approximations were made here as described in the Appendix notes. Some dental personnel data, in combination with WHO's description of the background for the estimates, indicate that reported dental personnel data for some countries may be vulnerable to reporting errors and estimation principles (in the context of this Toolkit). Reported dental personnel densities below the 20% percentile for non-OECD countries (i.e. some developing countries) were therefore replaced by the same 20% percentile in the appendix (see the appendix).
-
Amalgam fillings typically have a lifetime of 10-20 years (for adult's teeth), which means that current mercury outputs due to disposal of “spent" fillings typically reflect consumption at about 10-20 years ago. NJ MTF assumed a half-life of about 15 years per filling (NJ MTF, 2002).
5.5.1.4Examples of mercury in releases and wastes/residues -
In detailed Danish studies (Skårup et al., 2003; Maag et al., 1996) it was estimated that in Denmark about 60% of the consumed (new) amalgam is built into fillings, while about 25% is excess amalgam (a little more is mixed than used), and about 15% is sucked out of the mouth and goes to waste water (or to a filter) during the filling and shaping process. In the same study it was estimated, based on a mass balance approach, that about 70% of the mercury in old fillings were drilled out and went to waste water (or to waste via filters), while about 20% was extracted (mainly from adults) or lost (mainly from children) and went to waste, and about 10% remained with deceased people and was released to soil (cemeteries) or to the atmosphere (from cremation) (COWI, 2002). Regarding amalgam wastes following the waste water produced in the dental clinics, an estimated 80% of the dental clinics in Denmark have high efficiency central filters which can retain about 95% of the amalgam waste in the waste water, while the remaining 20% or so of the clinics are not assumed to have these filters (Skårup et al., 2003). For the clinics which have coarse mesh filters only, and do not have high efficiency filters, it is roughly estimated that only 20 - 50% of the mercury in the waste water is retained in the filters and disposed of to hazardous waste, municipal waste or recycling (based on Skårup et al., 2003, and their citations from Arenholt-Bindslev and Larsen, 1996).
-
NJ MTF reports that tests of wastewater from dental offices in 6 US cities and one European city suggest that an average of about 0.1 g of mercury per dentist is released per day from dental offices (Bill Johnson, 1999, as cited in NJ MTF, 2002). However, the data indicate that the amount released by each dentist varies considerably (NJ MTF, 2002). A study in Massachusetts USA (MWRA, 1997) estimated that 0.06 - 0.34 g mercury is released per facility per day to wastewater (MWRA, 1997, as cited in NJ MTF, 2002).
-
Some dental clinics have filters collecting varying fractions of the mercury in the clinic's waste water (up to about 95%). Excess amalgam and sometimes the filter fraction may be collected and processed to recover the silver. The amount of mercury discharged by a dentist office is dependent on various factors, including whether filters (or “chairside traps”) are used. One study reports that an average of 2 g mercury per dentist per day is discharged if no filtration is used (Drummond et al., 1995, as cited in NJ MTF, 2002). If chairside traps are used, about 60 - 70% of the mercury is captured and does not get released to waste water (NJ MTF, 2002). Some facilities also use additional filter systems such as vacuum filters or air/water separators which collect additional, smaller mercury particles (NJ MTF, 2002).
-
In NJ, the mercury-contaminated material captured by traps and other control devices is typically released in MSW or recycled (NJ MTF, 2002).
-
The total amount of mercury used in the dental industry in the USA in 1995 was 32 metric tons (Plachy, 1996, as cited in US EPA, 1997a). A report by Perwak, et al. (1981) estimated that 2% of the mercury used in dental applications is emitted to the atmosphere (from the clinics). Using the 2% figure, 1995 mercury emissions were estimated to be 0.64 metric tons in the USA (US EPA, 1997a).
-
There are slow releases of elemental mercury vapours throughout the lifetime of the filling, which can be released directly to air or wind up in human wastes (such as in urine and faeces) (Barr, 2001).
-
In addition to the above mentioned, the mercury amalgams also lead to significant releases during crematoria (described in section 5.10.1) and in cemeteries (see section 5.10.2).
5.5.1.5Input factors and output distribution factors -
Based on the information compiled above on inputs and outputs and major factors determining releases, the following preliminary default input and distribution factors are suggested for use in cases where source specific data are not available. It is emphasized that the default factors suggested in this Toolkit are based on a limited data base, and as such, they should be considered subject to revisions as the data base grows.
-
The primary purpose of using these default factors is to get a first impression of whether the sub-category is a significant mercury release source in the country. Usually release estimates would have to be refined further (after calculation with default factors) before any far reaching action is taken based on the release estimates.
-
Due to lack of data, no default factors can be set for the production and supply of the amalgam ingredients.
a) Default mercury input factors -
Actual data on number of amalgam fillings prepared annually will lead to the best estimates of releases. This number can be multiplied with average mercury amount used per filling: 0.8 g Hg/filling, as described above for the Danish situation.
If no information is available on the number of amalgam fillings prepared annually, a first estimate can be formed by using the default input factors selected in Table 5 -172 below (based on the data sets presented in this section). Because consumption vary so much, it is recommended to calculate and report intervals for the mercury inputs to this source category. The low end default factors has been set to indicate a low end estimate for the mercury input to the source category (but not the absolute minimum), and the high end factor will result in a high end estimate (but not the absolute maximum).
Table 5 172 Preliminary default input factors for mercury use in preparation of dental amalgam fillings
|
Default input factors;
g mercury consumed per inhabitant per year;
(low end - high end)
|
Mercury used annually for
dental amalgam preparations
|
0.05 - 0.2
|
-
Note that if it is desired to use the default factors above in combination with adjustment for number of dental personnel in the country as described above in Section 5.6.1.3, it is recommended to use the high end default input factor (0.2 g mercury consumed per inhabitant per year), multiply it with the countries’ estimated dental personnel density (as shown in Annex 8.4) and divided by the dental personnel density of Denmark. This approach is used in the Inventory Level 1 spreadsheet (automatically) and has been implemented as an option in the Inventory Level 2 spreadsheet as well (manually). Note that Annex 8.4 also includes population data for most countries of the World.
b) Default mercury output distribution factors -
The default output factors defined below are primarily based on the Danish data above, as they provide correlated input and output data sets and are based on detailed investigations.
-
Note that the mercury outputs should calculated based on mercury inputs with dental fillings at different times (as shown in the table below) for the different life cycle phases of the amalgam fillings, due to the long lifetime of amalgam fillings. If the supply of mercury for preparation of dental amalgam fillings is known to have been relatively constant over the last 20 years, current supply data can be used as an input approximation.
-
Because the waste disposal routines will vary much between countries, an artificial, even distribution among the waste types was chosen to raise the signal that significant mercury outputs may take place through both of these outputs. If more specific information is available regarding the waste management practices, individual adjustments can be made to the calculations. In countries with a general lack of special management practices for hazardous or medical wastes, the full output to waste should likely be allocated to "general waste".
Table 5 173 Preliminary default mercury output distribution factors for dental amalgam
Phase in life-cycle
|
Default output distribution factors, share of Hg input
|
Air
|
Water
|
Land
|
Products
2*
|
General waste *1
|
Sector specific treatment/
disposal *1
|
Preparations of fillings in the teeth at dentist clinics (share of current mercury supply for amalgam fillings)
|
0.02
|
0.14
|
|
0.6
|
0.12
|
0.12
|
Use - from fillings in the mouth (share of mercury supply for fillings 5-15 years ago) *3
|
|
0.02
|
|
|
|
|
Disposal - via clinics and households and death (share of mercury supply for fillings 10-20 years ago) *4:
|
- in countries where most dental clinics are equipped with high efficiency amalgam filters (95% retention rate)
|
|
0.02
|
|
0.06
|
0.26
|
0.26
|
- in countries where only dental chair filters/strainers are used in most clinics
|
|
0.3
|
|
0.06
|
0.12
|
0.12
|
Notes: *1 Because the waste disposal routines will vary much between countries, an artificial, even distribution
among the waste types was chosen to raise the signal that significant mercury outputs may take place
through both of these outputs. Sector specific treatment may be recycling, disposal as hazardous
waste, or disposal as medical waste;
*2 The actual fillings when in the teeth. For the disposal phase, the mercury released with "products" is
the mercury remaining in fillings by the time of the persons death; this mercury will be released to
cemeteries of via cremation.
*3 This is a very rough estimate of mercury release from dental fillings in the mouth based on the data
from Sweden described above (based on Sörme and Lagerkvist, 2002; Sörme et al., 2003; and their
citation of Skare and Engquist, 1994); the conversion from amounts in the mouth to Hg supply is
based on the data from Denmark (see above) indicating that 60% of the supply of Hg for dental fill
ings end up in the mounted fillings, while 40% is lost during the preparation of the fillings.
*4 The factors here reflect that only about 60% of the original supplies were built into the fillings when
they were made.
c) Links to other mercury sources estimation -
No links suggested.
5.5.1.6Source specific main data -
The most important source specific data would in this case could be some or all of the following:
-
Data on total amount of mercury used in dental sector in the country, or
-
Data on average amount of mercury used by each dentist per year;
-
Data on percent of dentist clinics that use high efficiency amalgam filters;
-
Average number of fillings per person in a country (as an indication of the general dental care standards; and
-
Data on the distribution of dental amalgam wastes from dental clinics between general waste, and recycling, hazardous waste, or medical waste.
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