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The Elements in the Second Rank

4 Evaluation of Potential Impacts

4.1 Evaluation of the 11 metals

As mentioned in chapter 3, the metals are used in very different quantities and the also the concentration in the waste streams vary greatly. In the following, the metals are evaluated one by one by collating information related to exposure (uses, consumption, dispersal and levels in the environment) with their inherent potential for adverse environmental effects.

4.1.1 Antimony

Among the metals in the second rank, antimony is the one which is used in highest amounts in Denmark. The use of antimony in batteries, pigments, plastic and cosmetics can result in losses to and dispersal in the environment. Especially sewage sludge and solid waste contain antimony. Energy production based on fossil fuels will result in atmospheric emission of antimony and antimony in stack gas cleaning residuals.

In the waste streams analysed in this study, relatively high concentrations of antimony were found in leachate and sewage sludge. The concentration in leachate of 8 µg/L is under the lowest NOEC-value for living organisms found in the literature. Adverse environmental effects from percolation of leachate are therefore not expected to be due to the content of antimony.

In sewage sludge the concentration of antimony is on the same level as the background concentration found for soil, while the concentration in compost is in the low end of the concentration range in soil. Use of these types of biowaste for fertilisation or soil improvement is not expected to increase the concentration of antimony in the affected areas.

Inhalation of antimony as antimony trioxide is dangerous and can result in CMR-effects.

4.1.2 Beryllium

The light-alloy metal beryllium is known as damaging to human health, and exposure to high concentrations of beryllium is known as a problem in the working environment. It is classified as carcinogenic and sensitizing.

Beryllium is used in e.g. electronics, but due to the low use of beryllium it is unlikely that the exposure will result in adverse effects on health and environment. In the working environment toxic effects from beryllium have been observed.

The concentration of beryllium is under the detection limit in leachate and treated waste water. Emission of stack gas from MSW incineration is regarded as an important way of dispersal. However, the concentration measured in stack gas is approx. 40 times below the limit value of 0.1 mg/m³. The emission of beryllium from stack gas is in the form of beryllium oxide. This compound is relatively immobile in the pH interval found in most soils. Low concentrations of beryllium is found in compost, sewage sludge and sludge from sediment from road runoff retention basins.

Critical exposure of beryllium primarily occurs in the working environment and use of beryllium in e.g. electronics is not expected to result in adverse effects on health or environment.

4.1.3 Bismuth

The use of bismuth in e.g. electronics, pigments, plastic and cosmetics can result in environmental exposure, and especially sewage sludge and solid waste contain bismuth. Bismuth can be used instead of antimony in electronic equipment. The consumed amount of bismuth is approx. 36 tonnes/year, or 20 times less than the consumption of antimony.

Coal and oil contain bismuth. Therefore, energy production based on fossil fuels contributes to the overall emission of bismuth.

In this study, bismuth was found in low concentrations in sewage sludge, sediment from road runoff retention basins and leachate. The amount of data regarding the environmental toxicity is too sparse for proper evaluation of its effects on health and in the environment. Due to the potential for bioaccumulation bismuth might cause adverse environmental and health effects if the consumption increases.

4.1.4 Boron

Boron in the form of sodium borate is used as bleaching agent in detergents. Boron compounds are also used in e.g. plastic, flame retardants and as dietary supplement. On a weight basis, borate is the most important use of boron Waste water and sewage sludge contain high boron concentrations.

The concentration of boron is high in all waste products analysed as part of this study. Of the 11 metals in the second rank, boron is the metal found in the highest concentration in all types of waste except sediment from road runoff retention basins. Based on the collected information regarding aquatic toxicity, boron is not regarded as dangerous to aquatic organisms. The concentration in treated municipal waste water is a factor 100 lower than the NOEC-value for Daphnia magna.

No quality criteria exist for the concentration of boron in soil and compost. Boron is added to farmland when sewage sludge is applied as a soil improving agent, but there is not sufficient data to evaluate its effect on soil organisms. Being an essential micro-nutrient, no adverse effects of boron are expected at the concentrations found in this study.

The use of domestic products containing boron can possibly cause sensitization.

4.1.5 Gallium

Electronic equipment is the most important source of exposure to gallium and, hence, solid waste, stack gas and gas cleaning residuals from waste incineration are expected to contain gallium. The consumption is expected to increase, and this will possibly also increase gallium concentration in the waste streams. This was confirmed from the analyses conducted in this study. Gallium was found primarily in sewage sludge, compost from municipal household waste and leachate.

Due to the content of gallium in fossil fuels, energy production based on this energy source will add to the total emission of gallium.

The environmental toxicity of gallium in not well documented. Hence, it was not possible to evaluate if gallium in emissions or waste products pose any risk. Because of the low consumption of gallium, it is not expected to cause adverse effects on health or environment at present.

4.1.6 Indium

The global consumption of indium is increasing faster than any of the metals included in this study. The yearly use in Denmark is only about 1 ton. Indium is used in LCD-displays, batteries and electronics. The most important route of dispersal to the environment is through solid waste and residuals from waste incineration.

The concentration of indium was low in all samples from the analysed waste types. No data was found regarding environmental toxicity of indium, and, consequently, the possible environmental impacts of indium can not be assessed. However, due to the low consumption of indium and the low concentrations found in waste, the actual risk of adverse effects on environment and health is considered to be low.

4.1.7 Lithium

Lithium is used in e.g. electronics, perfume, plastic and in the pharmaceutical industry. The wide application spectrum means that lithium is found in many waste types. Lithium discharged with waste water or disposed at landfills can be found in the treated waste water and landfill leachate due to its high solubility in water.

According to the analyses conducted during this study, leachate from landfills contain 50-200 µg/L of lithium, while leachate from landfills with gas cleaning residuals contain approx. 300 µg/L. Compost and sewage sludge contain high concentrations of lithium.

Compared to the aquatic toxicity, the concentration of lithium in treated waste water is approx. 10 times lower than the NOEC for fish. Compared to the quality criteria for soil, the concentration in sewage sludge and compost is approx. a factor of 100 lower. Lithium seems not to show adverse effects on the environment at the present level and pattern of dispersal.

Experiments with experimental animals have shown that lithium can have reprotoxic effects, and increasing consumption might therefore result in adverse effects on health and environment.

4.1.8 Molybdenum

With a yearly consumption of 275 tonnes, molybdenum is among the most used among the second rank metals. Molybdenum is used in alloys of steel and to specialty steel/stainless steel, as flame retardant, and in colour pigments, plastic and dietary supplements. Due to this wide spectrum of uses, molybdenum can be found in both waste water, sewage sludge and landfill leachate.

The acute toxicity measured in test with Daphnia magna is low and moderately low for algae. However, the data is not sufficient to allow a thorough evaluation. The level in waste water is approx. a factor of 1000 lower than the LC₅₀ for daphnia, but close to the limit in drinking water. The content in sewage sludge and compost exceed the soil quality criteria of 2 mg/kg. The content in stack gas from municipal solid waste incineration and leachate from landfills with waste gas residuals is high.

Based on the high concentration of molybdenum in all analysed waste types, the exposure of the environment to molybdenum is regarded as significant. The limited amount of data regarding its toxicity makes it impossible to evaluate the potential for adverse environmental and health effects from molybdenum exposure.

4.1.9 Palladium

The use of palladium in Denmark is at present limited with a consumption of only 2.4 tonnes per year. The consumption is expected to increase. The main use is in printed circuit boards, catalysts and metal alloys.

The date regarding environmental toxicity is very limited. From the data presented in the data sheet, it can be seen that palladium chloride has a very low effect concentration on Tubifex tubifex and should as such be regarded as very toxic to aquatic organisms.

In the examined waste streams palladium was found in leachate, treated waste water and sewage sludge. The concentration in treated waste water is approx. a factor of 100 lower than the EC₅₀-value for the organism mentioned above.

The environmental toxicity of palladiums is not well documented, and the concentration found in especially waste water can therefore not be evaluated properly with regard to possible environmental impact.

4.1.10 Platinum

Consumption of platinum for catalytic combustion of exhaust gas from e.g. car engines (both gasoline and diesel powered) is regarded as the quantitatively most important use of platinum. Platinum is also used in the electronics industry, the petrochemical industry and the pharmaceutical industry. 1.3 tonnes of platinum is used in Denmark yearly, and the consumption is expected be relatively constant.

Despite of the variety of uses of platinum, the concentration found in all waste streams were low.

The data on the environmental toxicology of platinum is very limited. Hexachloro platinum acid has an effect concentration on Tubifex tubifex of 61 µg/L and is therefore very toxic to this aquatic organism. In treated waste water the concentration was found to be approximately 1,000 times lower. It is expected that the consumption should increase significantly before adverse health and environmental effects from platinum exposure can be observed.

4.1.11 Vanadium

Approximately 100 tonnes/year of vanadium is used in Denmark in e.g. alloys, catalysts, pigments and dietary supplement. The many different uses and the large amounts can result in dispersal of vanadium from most waste streams.

Vanadium is found in fossil fuels and is emitted from coal-fired power plants and this is assumed to be the main source of emission to the environment. From the 6.7´ 10⁶ tonnes of coal consumed in Denmark in year 2000 (Danmarks Statistik 2001) and an average concentration of vanadium of 60 mg/kg (Sternbeck and Östlund 1999), the total amount of vanadium in emissions and residuals from coal based energy production was approx. 400 tonnes.

Compost, sewage sludge and sediment from road runoff retention basins contain high concentrations of vanadium. Compared to antimony (the metal with highest consumption in Denmark among the second rank metals, the concentration of vanadium was higher in all the analysed waste streams. Due to the high background concentration in soil, the use of sewage sludge as a soil improving agent is not expected to result in adverse effects despite its high vanadium concentration.

Vanadium is regarded as toxic to aquatic organisms. However, only limited data regarding environmental toxicity exist. It is especially the solid waste that contains much vanadium, and vanadium is therefore not regarded as a significant potential risk for the aquatic environment. Certain vanadium compounds are carcinogenic, mutagenic and/or reprotoxic.

4.2 The classic heavy metals versus the second rank metals

An overlap in the use areas for the second rank metals and e.g. lead, cadmium, chromium and mercury exists. The amounts consumed of especially lead and chromium are much higher than the consumption of the second rank metals, see Table 3.1 and Table 4.1.

Table 4.1
Uses and consumption of the classic heavy metals.

1Miljøstyrelsen (1996), 2Miljøstyrelsen (2000), 3Miljøstyrelsen (1985), 4Miljøstyrelsen (1996a).

The effects of the traditional heavy metals on health and environment are well known. Table 4.2 gives an overview of health effects and environmental toxicology for lead, cadmium, chromium and mercury. Especially lead, cadmium and mercury have significant adverse effects on health and environment.

Table 4.2
Selected adverse effects of heavy metals on health and environment. From Miljøstyrelsen (1995).

Also some of the metals in the second rank have significant adverse health and environmental effects, e.g. beryllium, which is carcinogenic. To provoke such effect, inhalation of beryllium over an extended period of time is required. Certain boron, molybdenum, platinum and vanadium compounds have adverse health effects on health, e.g. sensitizing effects. Information regarding gallium, indium, palladium, platinum and vanadium was too limited for evaluation on their health and environmental effects.

The consumption of beryllium, gallium, indium, palladium and platinum is relatively low. Therefore, the use of these metals poses only a little risk for adverse environmental effects. The use of fossil fuels can result in significant dispersal due to emissions from stack gas and gas cleaning residuals.

4.3 Data quality

The elements in the second rank have until now not received as much attention as the classic heavy metals with regard to adverse effects on human health and the environment. Thus, the data on environmental toxicity was lacking both depth and width, i.e. test results for organisms on more than one trophic level and several tests with the same organism. The data found in the data sheets are therefore in most cases not sufficient for conducting a thorough evaluation.

The second rank metals can be used in many organic and inorganic compounds. Data on the organic compounds have not been included in this study due to low importance in relation with production, use and waste disposal, which is the issue of this report. All the inorganic compounds have been included in the description and evaluation of the health and environmental effects of each metal. However, the behaviour of each single metal species regarding solubility and thus exposure of test organisms was not considered.

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