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Possible Control of EU Priority Substances in Danish Waters 4 Assessment of cadmium
4.1 Definition of the reference state4.1.1 IntroductionCadmium (CAS no. 7440-43-9) is an element, and it is therefore not degradable in nature. Important cadmium compounds include cadmium chloride (CAS no. 10108-64-2), cadmium acetate (CAS no. 543-90-8), cadmium oxide (CAS no. 1306-19-0), cadmium sulphide (CAS no. 1306-23-6) and cadmium sulphate (CAS no. 10124-36-4). Environmentally, cadmium is a heavy metal with high toxicity. Compared with other heavy metals, cadmium and cadmium compounds are, , relatively water soluble. They are therefore also more mobile in e.g. soil, generally more bioavailable and tend to bioaccumulate. The mobility depends heavily on the pH-level and the sorption capacity of the soil in question /1/. 4.1.2 Main uses and pollution sourcesThe quantitatively most important use of cadmium is as a component in NiCd-batteries. However, intentionally cadmium is also used as pigments in plastics, ceramics and glasses, as plating on other metals in particular steel, as an element in alloys with zinc, copper, and lead and in low temperature alloys and solders. Unintentionally, cadmium is consumed with fossil fuels, phosphate-based fertilizers, agricultural lime and cement besides being a natural contaminant in zinc. In 1996, the consumption of cadmium in Denmark was estimated at 43-71 tonnes /2/. Intentional uses were responsible for a consumption of 37-61 tonnes/year, while unintentional uses counted for about 5.4-9.5 tonnes /2/. The most important pollution sources of cadmium to the environment may briefly be listed as follows: Air Water Soil 4.1.3 Releases to and state of the aquatic environmentThe most important sources of releases of cadmium to the water environment comprise (according to /2/):
Sacrificial anodes made of zinc are designed to be dissolved thereby protecting steel structures against corrosion. The structures in question includes oil extraction platforms, harbour structures, steel boats etc. The zinc anodes contains about 0.05 % cadmium by weight, which will be dissolved together with the zinc. The amount of cadmium released to the water environment in 1996 was estimated at 0.6 tonnes /2/. Sacrificial anodes are likely to be the most important single source for contamination of the water environment by cadmium in Denmark (mainly coastal/marine environment). Effluents from sewage treatment plants as well as discharge of stormwater obtain their contents of cadmium from a number of sources. The most important source probably being corrosion of zinc used for corrosion protection of steel in road infrastructure installations such as pylons for lamps and signboards, fences etc. besides galvanized mailboxes, and eaves gutters and downpipes made of zinc. Other sources include releases from galvanization and foundry plants. Atmospheric deposition from sources within Denmark and abroad adds to the amount of cadmium emitted from sewage treatment plants and by stormwater drainage by being washed off impervious surfaces by rain. Atmospheric deposition, furthermore, is an important direct source of cadmium to Danish interior waters. The contribution in 1996 was estimated at 2.3 tonnes yearly primarily due to burning of oil for power and heating. The majority of the atmospheric deposition is considered to originate from sources outside Denmark. Leaching from agricultural soils is believed to be a further source of cadmium releases to many Danish freshwater streams and lakes as these soils contain cadmium from the use of phosphate fertilisers and from atmospheric deposition during many years. There are observations indicating exceedance of the phosphorus-binding capacity of the soils. Table 4-1 Monitoring data for cadmium (average values). The values in parenthesis are the 95 % percentiles. Sources: /4/ /5/.
* Highways /6/ Studies of ground water have shown 50 % percentile values of cadmium of 0.008 μg/l, while the 90 % percentile value is 0.08 μg/l /3/. Based on the median values in sewage and in stormwater runoff presented in table 4-1, the total Danish releases of cadmium to the aquatic environment can be estimated at about 55 kg/year and 110 kg/year, respectively. EQS proposal The most rigorous of the EQS values for cadmium in the aquatic environment presently proposed for the Daughter Directive on priority substances are AA-EQS = 0.08 μg/l (inland surface waters) and MAC-EQS = 0.45 μg/l (all surface waters). The background concentration in freshwater used in the elaboration of the EQS proposal for cadmium was 0.003 μg/l ("dissolved"), a value determined for the river Rhine. 4.1.4 Existing legislation/regulation and their impactStatutory Order no. 1199 of 23 December.1992 from the Ministry of the Environment and Energy on the prohibition of sale, import and manufacture of cadmium-containing products. This Order prohibits the import, sale and manufacturing of products in which cadmium is present as plating, pigment or stabilizer in plastics in concentrations above 75 ppm in homogeneous materials. A number of exemptions from the ban are established. Assessment This Order replaces the original Danish ban on cadmium from 1983 and implements a corresponding EU Directive. The effect of the order is that the amount of cadmium-containing products directed to waste incineration or steel recycling is slowly being reduced thereby also slowly reducing the amount of cadmium which could be emitted to the air or leached from residual products. However, the dominant source of cadmium to waste incineration is assumed to be NiCd-batteries, which are not covered by the ban. Statutory Order no. 223 of 5 April.1989 from the Ministry of the Environment on the content of cadmium in phosphorus-containing fertilizers This Order limits the maximum content of cadmium in phosphate fertilisers to 110 mg Cd/kg phosphorous. Assessment Statutory Order no. 998 of 12 October 2004 from the Ministry of Food, Agriculture and Fisheries on feedstuff This Order limits the maximum content of cadmium in feedstuff to between 0.5 and 10 mg Cd/kg feedstuff depending on the type of animal in question. Assessment Statutory Order no. 183 of 15 December.1975 from the Ministry of Employment on the prohibition of the use of certain soldering products which contain cadmium. This Order limits the maximum content of cadmium in solders to 0.1% by weight. Assessment Act no. 414 of 14 June.1995 on a charge on lead accumulators (closed nickel-cadmium batteries) and Act no. 404 of 14 June.1995 (as amended by Act 1105 of 29 December 1999) on remuneration in connection with collection of hermetically sealed nickel-cadmium accumulators (closed nickel-cadmium batteries). NiCd-batteries have to be labelled and are subject to a sales tax, which, in turn, is used to finance a payment arrangement for a return system for batteries. Assessment The acts render NiCd batteries financially less attractive to the costumer and encourage collection organisations to collect these batteries for recycling purposes. Thereby both acts contribute to the objective of reducing the amount of batteries turning up in waste incineration plants and the emission of cadmium to the air etc. caused by such batteries. It is difficult to assess the collection rate of used NiCd batteries but it is believed to be at least 50%. Statutory Order no. 298 of 30 April 1997 by the Ministry of the Environment on certain requirements for packaging The sum of the concentration levels of lead, cadmium, mercury and chromium (VI) present in packaging and packaging components used in Denmark must not exceed 100 ppm by weight. Assessment Statutory Order no. 1042 of 17 December 1997 from the Ministry of the Environment on restricting the sale and use of certain dangerous chemical substances and products for specially stated reasons Assessment Statutory Order no. 1008 of 12 October 2004 from the Ministry of the Environment on import and sale of electric and electronic equipment. Equipment containing lead, cadmium, mercury, chromium (VI), polybrominated biphenyls (PBB) or polybrominated diphenylethers (PBDE) is prohibited from 1 July 2006. Assessment Statutory Order no. 489 of 12 June 2003 from the Ministry of the Environment on cosmetic products. The order prohibits the use of cadmium and compounds in cosmetics. Assessment The order has no significant impact on the water environment as the consumption of cadmium for cosmetics is insignificant. Other regulations relevant for cadmium include:
Assessment The Orders may have a direct impact on the releases to the aquatic environment depending on the rules actually established for reducing the environmental loads of cadmium from various sources. 4.1.5 Conclusion on the need for further regulationThe data presented in table 4-1 show that the proposed AA-EQS and MAC-EQS for cadmium have already been met as only minor dilution of the most important discharge categories is required. Hence, there is no further need for progressive reduction in Scenario A while in Scenario B the regulatory measures already implemented (the above statutory orders) can be considered to be "progressive reduction" measures as they will undoubtedly contribute to slowly but steadily decreasing concentrations of cadmium in emissions and discharges into the environment. However, as cadmium is classified as a priority hazardous substance, further regulatory measures need to be considered in order to ensure the cessation or phasing out of emissions, discharges and losses (within a timeframe of 20 years in Scenario B). Possible measures are described in the following. The gradual implementation of the measures could at the same time be regarded as "progressive reduction" measures in Scenario B. 4.2 Possible reduction/elimination measures4.2.1 Technical measures to reduce/eliminate cadmiumThe following options for further reduction of Danish releases of cadmium to the water environment may be considered:
4.2.2 Possible synergies with other (priority) substancesAs mentioned in section 4.1.3, the dominant source of release of cadmium to the aquatic environment appears to be stormwater runoff from separate systems. Therefore, an initiative to reduce this input could be considered though it is considered technically as well as economically unrealistic to introduce measures specifically for cadmium in stormwater runoff. However, the majority of the PS/PHS, including cadmium, are characterised by properties such as lipofilicity and significant sorption onto particulate (organic) matter. Therefore, it is assessed that technological measures that aim to detain suspended particles in surface runoff will significantly reduce the loads of cadmium and many other PS/PHS on the aquatic environment. Since this type of measure is not substance specific, it is described technically and assessed economically in a separate chapter (Chapter 12). 4.2.3 Summary and assessment of technical possibilitiesCadmium is classified as a priority hazardous substance, PHS, for which the 2005 draft proposal of the Daughter Directive stipulates that the discharges, emissions and losses into the aquatic environment must cease within 20 years after the date when the Daughter Directive enters into force (Scenario B). The dominant future source of cadmium release to the aquatic environment in Denmark is assessed to be the discharge of stormwater runoff from paved surfaces and roofs. To meet the requirements for ceasing "discharges, emissions and losses" of cadmium within 20 years (Scenario B), action must be taken against releases caused by stormwater. The most obvious way of doing this is by introducing detention basins and similar technological arrangements by which particulate matter in the effluent is retained prior to the discharge into the aquatic environment (see Chapter 13). Further, in Scenario B, replacement of old zinc gutters and downpipes should be considered to the extent they are still in use 20 years after the entry into force of the Daughter Directive. With regard to Scenario A, it is assessed, based on the interpretation of the obligations in the WFD, that mandatory replacement of old zinc gutters and downpipes is not realistic and that the "natural" replacement due to weathering can be considered to be an appropriate measure. With regard to both scenario A and B elimination of cadmium in sacrificial zinc anodes could be considered. 4.3 Economic AssessmentThe technical assessment has identified elimination of the use of zinc for sacrificial anodes as one of the few realistic technical measures specifically targeted at cadmium. This can be achieved by substituting aluminium or magnesium anodes for the zinc anodes. This measure is technically possible and will mean little or no loss of quality or functionality of the anodes. These anodes contain indium instead of cadmium. Table 4-2 below shows the contents - and thereby the potential losses - of cadmium and indium in the two types of anodes. Table 4-2 Aluminium anodes compared to zinc anodes, same protection of steel surface
If the average of the chemical composition in Table 4-2 is used, the total content of cadmium and indium in the two types of anodes are: Zink 95 %: 11.2 kg x 0.05 % Cd = 5.9 g Cadmium /kg anode material Aluminium 90 %: 3.2 kg x 0.02 % In = 0.7 g Indium /kg anode material The volume of aluminium anode material will only be about 1/3 compared to zinc anode material because of the much higher capacity of the former. In sum, there will be a much lower release of indium than of cadmium after a total substitution of anodes. The main use of anodes is on boats. On small boats and yachts the typical amount of anodes is 0.5 to 10 kg per boat. That means an effect of substitution per boat of between 2.8 and 59 g cadmium. On larger ships and fishing vessels the typical amount is 50 to 2000 kg. For the remaining underwater uses such as floodgates, gutters at seawater intakes and protection of steel constructions in brackish water and pipelines, the amounts used are all quite small and data is limited. To implement a fully effective substitution scheme to abandon zinc anodes, the scheme would also have to include foreign small ships entering Danish waters. The market for sacrificial anodes for larger ships and fishing boats is already dominated by aluminium anodes. Almost all large vessels and harbours use aluminium anodes today, since they are slightly cheaper and the change of production technology has already been effected.[13] There is a short-term, added financial cost of production of aluminium anodes for small ships compared with zinc anodes. This would mean a higher cost for a small production due to the sunk cost of the investment in new production technology. But in the case of a total change-over of production the average cost can be expected to be slightly lower as is the case with anodes for large ships and harbours. In consequence, there must be one or more barriers that prevent the change-over of production even though it appears to be attractive to both producers and consumers. One Danish producer points to consumer conservatism and sluggish demand to explain the situation. In other words, zinc anodes will still be favoured even when a slightly cheaper alternative with identical functional quality and appearance exists. The assessment warrants a further investigation, but this would entail information campaigns targeting consumers. Further, industrial reconversion policies could be helpful in bringing about substitution of the zinc anodes in small ships anodes. Another possibility in relation to further progressive reduction is to replace old zinc gutters and downpipes. Before further refining of zinc was started in the late 1970's, gutters, downpipes and hot dip galvanizing in zinc generally contained about 1000 ppm cadmium or more as zinc used for these purposes was not refined in order to reduce the content of cadmium. However, concerns related to the impact of cadmium on humans in the late 1970's led to the adoption of a 100 ppm limit on the cadmium content of zinc used for hot dip galvanising of pipes for drinking water. This limit was adopted by zinc manufacturers all over Europe. During the 1980's the cadmium content of zinc was further reduced by many zinc manufacturers to a level about 10 ppm or even below. Zinc manufactured and installed before 1978 in use in the Denmark today includes gutters and downpipes in zinc and zinc used for hot dip galvanising in particular for road infrastructure, such as e.g. lamp standards. The costs and effects for Denmark of replacing gutters and downpipes in zinc installed before 1980 are estimated based on the following assumptions:
To these figures should be added the cost of replacing gutters and downpipes on dwelling units, institutions, offices and commercial buildings. No detailed investigations have been made of the investments required in this context. However, it seems fair to assume that such investments could well add an extra 10 - 50% to costs considering the fact that the number of buildings in question is probably small compared to detached houses whereas replacement costs in most cases will be significantly higher due to the height of the buildings in question. This investment can be assumed to take place over a five-year period. The outcome of this investment would be a strong reduction (>90%), estimated to be around 120 - 480 kg/year, of the yearly release of cadmium to wastewater in the years following the investment /2/. Table 4-3 below presents the result of the estimated cost of a replacement policy meeting the deadline in 2025 (Scenario B). Note that the figures are quoted in billion DKK. In Scenario A/C it is assumed that the ordinary rate of replacement of gutters ("natural replacement") will be sufficient. Table 4-3 Replacement of downpipes in zinc
* A discount rate of 3 % is used. If 6 % is used the results for Scenario B will be DKK 0.6-4.0 billion The financial cost of Scenario B would be between 0.4 and 2.9 billion DKK compared to Scenario A at between 0.2 and 1.4 billion DKK. The corresponding welfare-economic cost is DKK 1.0-6.6 billion in Scenario B and 0.6-4.2 billion DKK in Scenario A. The welfare-economic cost has been calculated on the assumption that the replacement scheme is financed by public funds. If replacement is to be exclusively funded by private house owners, the welfare-economic cost should not include marginal costs of public funds, and roughly estimated the cost would be 20% lower. The potentially high costs related to replacing old hot dip galvanized items, including road infrastructure (signposts, crash barriers, lamp standards etc.) have not been estimated as a significant fraction of these probably only has a marginal impact on water quality, and the rest is of a diffuse nature that can be addressed through stormwater retention arrangements (Chapter 13). The cost of general action against suspended matter/pollutants in stormwater runoff is estimated after the substance-specific chapters in this report. 4.4 Conclusion on CadmiumAccording to the monitoring data available, the concentrations of cadmium in various discharges as well as in surface waters do not appear to pose a problem in relation to compliance with the proposed EQS values, and therefore there is no need for further progressive reduction measures in Scenario A. The existing regulatory measures contribute to the decreasing trend of cadmium concentrations in emissions and discharges into the environment and could, thus, possibly fulfil the Scenario B obligation of progressive reduction even after EQS compliance has been achieved. However, cadmium is categorised as a priority hazardous substance (PHS), and therefore in Scenario B action needs to be taken to ensure cessation of discharges, emissions and losses to the aquatic environment (with a timeframe of 20 years). In Scenario A, additional measures must be taken based on considerations of all technical reduction options with the aim of fulfilling the cessation/phase-out obligations. The possible means of achieving this include in Scenario A and B substitution of aluminium anodes for sacrificial zinc anodes. Sacrificial zinc anodes for corrosion protection are considered one of the main sources of emissions of cadmium. Three potentially relevant uses of zinc anodes were considered, i.e. on large ships and steel sheet piling and the like in harbours; on smaller ships and yachts; and on metal piping. As it can be seen in Table 4-4 below, only anodes on small ships are relevant for further consideration. There are good technical and economic possibilities of substituting zinc anodes for aluminium anodes as production costs will not increase even if a total change-over of the production is effected. In fact, the change-over to production of aluminium anodes for large ships have resulted in slightly lower production costs and thus in somewhat lower prices. However, there seems to be barriers preventing the change-over of the production of anodes for small ships in Denmark. Table 4-4 Overview of potential substitution of zinc anodes
The financial cost of replacing cadmium in sacrificial zinc anodes is estimated to be low or even to give a slight welfare-economic and financial gain in Scenarios A and B. This is a tentative, preliminary estimate. Aluminium anodes for larger ships already dominate the market, and there is no difference in quality or functionality. The price is slightly lower than the price of traditional zinc anodes. In the short-term, substitution of zinc anodes still used for smaller ships would entail investments to be made by producers and slightly higher costs to consumers. However, the long-term cost would probably be 0 or it would lead to a slight financial and welfare-economic benefit. Public expenditure to overcome barriers preventing the change-over of production is foreseen. The possible replacement of downpipes in zinc manufactured before 1978 and with high cadmium content was also investigated. In scenario A/C it is assumed that the ordinary rate of replacement of the gutters will be appropriate. The potential cost of a substitution scheme was estimated to be quite high as the financial cost of Scenario B would be between DKK 0.4 and 2.9 billion. The corresponding welfare-economic cost is DKK 1.0-6.6 billion. The outcome of this investment would be a strong reduction (>90 %) in the yearly release of cadmium to wastewater (presently 120-480 kg) in the years following the investment /2/. It should be noted that this is the cost of an example of a replacement campaign based on Swedish experiences. A campaign could be conducted on a smaller scale, but the effects would be unknown. A campaign at a scale similar to the Swedish one is assessed to be a cost-effective measure, but this needs further investigation. A final option is to reduce the level of cadmium in stormwater discharges (common measure affecting a significant number of PS/PHS), which is the largest direct source of releases to surface waters in Denmark. With regard to potential measures targeting stormwater discharges in scenarios A and B, the subject is discussed in technical and economic detail in Chapter 13. 4.5 References/1/ Hansen, E. and C. Lassen (2003). Cadmium review. Nordic Council of Ministers, Copenhagen. /2/ Drivsholm, T.; J. Maag, E. Hansen and S. Havelund (2000). Substance flow analysis for cadmium. Environmental project no. 557, 2000. The Danish Environmental Protection Agency. (in Danish) /3/ GEUS (2004). Grundvandsovervågning 2003. /4/ Miljøstyrelsen (2004). Punktkilder 2003. /5/ MST (1997). Miljøfremmede stoffer i overfladeafstrømning fra befæste- de arealer. Miljøprojekt nr. 355. /6/ Miljøstyrelsen (2002). Bearbejdning af målinger af regnbetingede udledninger af NPO og miljøfremmede stoffer fra fællessystemer i forbindelse med NOVA 2003. Miljøprojekt 701. /7/ Bøgestrand, J. (red.) (2002): Vandløb 2001. NOVA 2003. Danmarks Miljøundersøgelser. - Faglig rapport fra DMU 422 : 39 s. (elektronisk). /8/ DMU (2004). Søer 2003. Faglig rapport fra DMU nr. 515 (elektronisk). /9/ Statistikbanken 2006. Statistik om byggeri og boliger - BOL3. Danmarks Statistik. /10/ Jensen, Ib 2006. Personal communication with Ib Jensen, Randbøldal VVS, Ny Nørup, September 2006. Footnotes[13] Based on interview with main Danish producer and one mayor shipping company. [14] No data available. Tentative assumption based on selected observations and interviews by COWI in 2006.
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