Screening of platinum group metals; Pt, Rh and Pl

SWECO VIAK Screening Report 2007:2

Screening of platinum group metals; Pt, Rh and Pl Client

Swedish Environmental Protection Agency

Malmö 2007-12-14 SWECO VIAK AB Södra Regionen

Niklas Törneman Uppdragsnummer: 1270170200

SWECO VIAK Hans Michelsensgatan 2 Box 286, 201 22 Malmö Telefon 040-16 70 00 Telefax 040-15 43 47

Cleas Thuresson

SWECO VIAK Screening of WFD priority substances in Sweden

Contents Contents Sammanfattning Summary 1 Introduction 1.1 Background 1.2 Objectives 1.3 Platinum group elements 1.3.1 Occurrence and sources 1.3.2 Solubility and bioavailability 1.3.3 Toxicity 2 Methods 2.1 Sampling strategy 2.2 Sampling methods 2.2.1 Soil 2.2.2 Sediment 2.2.3 Sewage Treatment Plant (STP) sludge and water 2.2.4 Fish 2.2.5 Water 2.2.6 Moose 2.2.7 Cow 2.2.8 Raptor 2.2.9 Plants 2.2.10 Air 2.3 Analytical methods 2.3.1 Extraction and analysis 3 Results and discussion 3.1 Air 3.2 Soil 3.3 Sediment and fish 3.4 Surface water and groundwater 3.5 Sewage treatment plants 3.6 Higher animals 3.7 Plants 3.8 Comparison to earlier results 4 Conclusions and recommendations 5 References Appendix 1 sampling stations in the Stockholm area Appendix 2 Raw data tables (excel)

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Sammanfattning Bakgrund och metoder Inom screeningprogrammet 2006 har SWECO VIAK på uppdrag av Naturvårdsverket utfört mätningar för att kartlägga förekomsten av katalysatormetallerna Platinum (Pt), Palladium (Pl) samt Rhodium (Rh) i olika matriser i Stockholmsområdet samt i opåverkade bakgrundsområden i Sverige. Syftet med screeningstudien var att verifiera resultaten från tidigare studier från andra länder där höga halter av katalysatormetaller påvisats i urbana miljöer, att utöka kunskapen om halter av katalysatormetaller i opåverkade bakgrundsområden och i biologiska matriser, samt att mycket summariskt bedöma om katalysatormetaller i Sveriges yttre miljö utgör någon miljö- eller hälsorisk. I Stockholmsområdet/Mälardalen omfattade provtagningen jord, slam och inkommande vatten, sediment från dagvattendammar och från sjöar, grundvatten, ytvatten, dagvatten, luft, växter, fisk, nötkreatur, älg samt havsörn. I opåverkade bakgrundsområden omfattade provtagningen fisk, sediment, jord och luft. Som en generell indikator på urban påverkan valdes koppar, som därmed analyserades i alla biologiska och abiotiska prov för att fastställa om det fanns någon samvariation mellan koppar och katalysatormetaller. Slutsatser och rekommendationer De huvudsakliga slutsatserna från denna studie var att: • Pd påträffades i nästa alla biologiska prov medan Pt och Rh sällan eller aldrig återfanns. Resultat från abiotiska matriser visar även att Pd tycks vara det mest mobila ämnet. Detta bekräftar tidigare studier som har visat att Pd är den mest mobila och biotillgängliga katalysatormetallen. • Halterna av katalysatormetaller var betydligt högre i luftprover nära vägar i Stockholm jämfört med den regionala bakgrundslokalen Råö på västkusten. • Halterna av katalysatormetaller i jord avklingade kraftigt 15 – 40 m bort från vägkanterna i Stockholmsområdet. • Kvoten mellan Pt och Rh indikerade att fordonskatalysatorer var den främsta källan till katalysatormetaller även om vissa avvikelser förekom. • Sediment i dagvattendammar innehöll tydligt förhöjda halter av katalysatormetaller medan sedimentkoncentrationerna i en sjö i centrala Stockholm var på samma nivå som i de opåverkade bakgrundssjöarna. • Pd halterna i grundvatten var tydligt förhöjda, t.o.m. i högre än i dagvatten från starkt trafikerade vägar. Detta visar på den höga mobiliteten av Pd.

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• Resultaten styrker inte att katalysatormetaller i den yttre miljön utgör någon direkt hälso- eller miljörisk. De förhållandevis få proven i vissa matriser (framförallt luft och grundvatten) kombinerat med bristen på utförliga riskbedömningar och på ekotoxikologiska data gör ändå att det inte går att helt utesluta att dessa ämnen kan utgöra risker. Den höga transportbenägenheten och risken för bioackumulering av Pd komplicerar ytterligare riskbedömningen av katalysatormetaller. Denna studie visade tydligt att det förekom regional lufttransport av katalysatormetaller. Därför rekommenderas det att luftmätning av katalysatormetaller även sker i mer avlägsna bakgrundsområden, t.ex. Pallas. I nuläget finns inga data om bakgrundshalter av katalysatormetaller i organismer. Därför är det också svårt att bedöma vad de uppmätta Pd halterna i djur och växter innebär. Således rekommenderas det att katalysatormetaller analyseras i historiska biologiska prov från Naturhistoriska Riksmuseets miljöprovbank. Givet de tydligt förhöjda Pd halterna i grundvatten kan det också vara av intresse att analysera ett större antal antal grundvattenprov från urbana och/eller vägnära områden med avseende på katalysatormetaller eller enbart Pd. Detta kan förslagsvis samordnas med existerande miljöövervakning av grundvatten.

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Summary Background and methods Within the screening program of 2006 SWECO VIAK has had the assignment from the Swedish Environmental Protection Agency to measure the occurrence of Pt, Pd and Rh (Platinum Group Elements, PGEs) in various matrices in Stockholm and background areas in Sweden. The objectives of the project were to confirm the results from other studies regarding the occurrence of PGEs in abiotic matrices, to enhance the knowledge about PGE levels in biological matrices and to briefly assess whether the levels of PGEs found in the environment constitutes an environmental and/or health problem. A national sampling strategy was devised in which air, soil, sludge, run-off water, run-off water sediments, surface water, animals and fish were sampled in a region supposedly impacted by PGEs from traffic and industrial activities. Stockholm and its surroundings was chosen as the impacted region. Swedish environmental background levels of PGEs in fish and sediments were determined in reference lakes and in soils surrounding these lakes. The influence from human activities on these lakes is generally considered to be minimal. As an indicator of anthropogenic influence, copper was also measured in the same samples as PGEs. The sampling program is summarized in table 2-1. Conclusions and recommendations The main conclusions from this investigation were: • Pt and Rh were almost never detected in the biological samples while Pd was consistently detected above the limit of quantification. Most results indicated that Pd occurs in more mobile/soluble/bioavailable forms compared to Pt and Rh • There were considerable higher PGE levels in air samples collected close to heavily trafficked roads in Stockholm compared to a regional background locality (Råö). • PGE concentrations leveled off to background levels 15 – 40 m away from heavily trafficked roads in Stockholm. • The Pt/Rh ratio in soil and sediment samples mainly indicated automobile catalyst sources although some deviations occurred. • Urban run-off water pond sediments had highly elevated PGE concentrations while the concentrations in a lake in central Stockholm was at par with the concentrations at background localities in Sweden.

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• Pd was also a very dominating PGE in groundwater even far above the Pd concentrations in run-off water (ponds). • The results do not establish that the occurrence of these substances in the Swedish environment pose any direct risk towards humans and/or aquatic ecosystems. Few sampling points in each matrix, a lack of (eco)toxicological data as well as the bioaccumulative nature of Pd makes this conclusion very tentative. Regional air transport of PGEs was evident in this study and air sampling of PGEs at more remote location is recommended in order to determine the degree of (trans-) national air transport. There are no data on the background concentrations of Pd in biological samples which prohibits any conclusions based on the levels of Pd in biological samples found in this study. It is therefore recommended that PGEs are analyzed in older biological samples from the Environmental Specimen Bank at the Museum of Natural history. Given the elevated Pd levels in ground water it is also recommended that PGEs are measured in more groundwater samples from urban areas and/or in the vicinity of heavily trafficked roads. This could be coordinated with existing monitoring of groundwater.

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1 Introduction 1.1 Background At present there is a lack of knowledge regarding the emission, distribution and exposure for many of the chemicals emitted to the environment. The aim of the screening program financed by the Swedish Environmental Protection Agency is to alleviate this lack of knowledge by estimating the occurrence of different chemicals in the environment in relevant matrices (soil, water etc.). To maximize the information gained from the screening program measurements are made in many matrices at many sites, but with few samples per site. The Swedish EPA is responsible for the screening at the national level and selects the chemicals that are to be included. Within the screening program of 2006 SWECO VIAK has had the assignment from the Swedish Environmental Protection Agency to measure the occurrence of platinum group elements (PGEs) in various matrices in Stockholm and background areas in Sweden.

1.2 Objectives The objectives of the project were to: • Confirm the results from other studies regarding the occurrence of PGEs in abiotic matrices (soil, air, groundwater, surface water and sediment) in urban areas. • Investigate the levels of PGEs in biological matrices that have not been well investigated previously. • To very briefly assess whether the levels of PGEs found in the environment constitutes an environmental and/or health problem

1.3 Platinum group elements 1.3.1 Occurrence and sources This report concerns platinum (Pt), palladium (Pd) and rhodium (Rh) hereafter denoted as platinum group elements (PGEs). There are more elements included in the platinoid group that are not covered by this report. Platinum is used in automobile catalysts, jewellery, as an anti-tumour drug, in catalysts in the chemical industry, in electronics and in dentistry as alloys (Kristine et al. 2004). The main uses of palladium are in electronics, as industrial catalysts, in cir-

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cuitry, in dental alloys, in jewelry and in automobile catalysts (Kristine m.fl. 2004). Rhodium is mainly used with platinum in automobile catalysts and in catalysts in the chemical industry (Habashi 1997). In general, automobile catalysts are considered to be the dominating source of PGEs to the environment (Kristine et al. 2004). PGEs are the active components in automotive catalysts. Platinum and palladium oxidizes CO2 to CO and hydrocarbons to H2O3, while rhodium reduces NOx. In accordance, there seems to be a clear connection between the increasing use of automobile catalysts and increasing environmental PGE concentrations (Rauch and Hemond 2003). The occurrence of elevated PGE levels in a number of terrestrial and aquatic abiotic compartments such as soil, sediments, road dust, surface water, urban and arctic snow, sludge and air particles is very well established (Goméz et al. 2002, Kristine et al. 2004, Ravindra et al. 2004). These studies have shown that the concentration of PGEs in soils and dusts exposed to high-traffic density far exceeds the natural background levels Increasing levels in biotic compartment has also been established although there are considerable fewer measurements. Most biotic measurements have been made in grass and plants in urban areas and in human urine and blood (Goméz et al. 2002, Kristine et al. 2004, Ravindra et al. 2004). In comparison, investigations of PGE levels in animals are severely lacking. 1.3.2 Solubility and bioavailability The metallic forms of PGEs are practically insoluble in water and it was previously believed that PGEs in the environment were relatively inert. However, it has been shown that these metals undergo environmental transformations into more reactive species which may be more soluble, more mobile and more bioavailable. One important process in this regard is most likely complexation with natural organic matter (NOM), such as humic acids. Pt, Pd and Rh in the form of complexes of chloride and nitrate have also been shown to be relatively mobile and soluble in rainwater at a pH of 4 – 5 (Menzel et al. 2001) PGEs are bioavailable to plants to a variable extent depending on the type of plant, time of contact with the emission source, and the dispersion of the PGE species. Pd is more bioavailable than Rh and Pt and a major route of uptake is via the roots by binding to sulphur in low molecular weight species In a similar manner, Pd is more bioavailable to animals than Pt and Rh. The bioavailable fraction to rats of Pt originating from automobile catalyst may be in the range of 20–30%. Studies show that PGEs, especially Pd, is taken up in the liver and kidney of rats and eels exposed to PGE in the laboratory. It has also been shown that

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PGEs bind to metal binding proteins (metallothioneins) in liver and kidney. The in vitro solubility of a model substance of Pt particles was only 0.4% in pure water while solubility was 10% in a 0.9% NaCl solution. This is particularly interesting given that in organisms conditions similar to those in a 0.9% NaCl solution are likely to exist. 1.3.3 Toxicity Most studies have focused on allergy related toxicity in the work place environment. The metallic forms of PGE elements are essentially biologically inert. However, the halogenated PGE compounds have a high allergenic potential and the allergic response to Pt salts increases with increasing number of chlorine atoms, (Ravindar et al. 2004). Soluble PGE salts are toxic, and chronic industrial exposure to them is responsible for a syndrome characterized by respiratory and cutaneous hypersensitivity (Platinosis) (Ravindra et al. 2004). The prevalence of allergic reactions resulting from Pt salt exposure in refineries and in the catalyst production industry is relatively high (Merget and Rosner 2001). Certain Pt compounds are also known to be cytotoxic, mutagenic and have carcinogenic effects (Merget and Rosner 2001). There are also several Pt based anticancer drugs (most noticeable cisplatin) that exhibit a number of different biological effects that are outside the scope of this report. The ecological effects and human health problems caused by PGE emissions to the environment is largely unknown. There are no scientific reports on any health effects related to non-occupational exposure to allergenic Pt compounds (Merget and Rosner 2001). However, given the low levels found to cause sensitization effects, the levels found in the urban environment may be of concern. The German workplace MAK/TLV value of 2 µg/m3 has been recommended as a ceiling value, which should not be exceeded (DFG 1995) and WHO (1991) has suggested that a no observed effect level (NOEL) should be based on the maximum concentrations of soluble Pt measured in low exposure areas in the work environment of production facilities (1.5 ng/m3). Since only 0.1 – 1 % of the total Pt in air constitutes soluble Pt salts, a guidance value of 15 – 150 ng/m3 in ambient air has been derived (Merget and Rosner 2001). There are no reported data on ecotoxicological effects of PGEs on terrestrial organisms. The effects of PGEs on aquatic organisms are better researched and aquatic ecotoxicological effects levels are presented in Table 1.1. Singer et al. (2005) demonstrated that Pd, Rh and Pt were 3 – 4 times more potent than Cd and Pb in inducing biochemical responses at the cellular level in zebra mussel which is a clear sign that the aquatic ecotoxicity of these compounds may be high. Ecotoxicological and toxicological data for the PGE are summarized in Table 1.1.

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Table 1.1 Toxicological properties of PGE compounds Substance

Properties

Toxicological Information

Guideline values

Ecotoxicological Information

Source

Platinum (Pt) Pt is a group VIII platinoid element of the second Transition series. A range of oxidation states are known although the principal oxidation states are II and IV.

The acute toxicity of Pt salts increases with solubility. Rodent oral LD50 for a range of Pt salts varies between 10 to > 1100 mg/kg. Repeated dose toxicity gives a NOEL for administration of PtCl4 for 13 days of 13 mg Pt/kg/day.

PDE (permitted daily exposure for patients, EMEA 2002) = 2.6 µg/kg/day. TLV = 0.002 µg/m3 NOEL (Pt salts) = 1.5 ng/m3 Guideline value for ambient air 15 – 150 ng/m3 (total Pt content)

LC50 Fish 96h: 2,5 mg/l EC50 Daphnia 48h: 0,082 mg/l EC50 Bacteria: 0.025 mg/l LC50 Scud 196 h: 0.11 mg/l

EMEA 2002 Ravindra et al. 2004 Prevent Database Merget and Rosner 2001 ECOTOX database (http://cfpub.ep a.gov/ecotox/)

Palladium (Pd)

Rat oral LD50=5 – 170 mg/kg. in vitro micronucelus assays did not demonstrate any genotoxicity Several reports of Pd allergy through dental alloy exposure

PDE (permitted daily exposure for patients, EMEA 2002) = 2.6 µg/kg/day (based on Pt due the lack pf Pd data)

LC50 Scud 196 h: > 1 mg/l LC50 Scud 196 h: 0.57 mg/l EC50 Tubifex worm 24 h: 0.24 mg/l EC50 Tubificid worm 48 h: 0.142 mg/l

EMEA 2002 Ravindra et al. 2004 ECOTOX database (http://cfpub.ep a.gov/ecotox/)

Rat oral LD50=200 and > 500 mg/kg. Rhodium (Rh) Rh is a group VIII platinoid element of Simple Rh compounds (i.e. RhCl3) the second Transition have been reported as genotoxic series. Its principal oxidation states are I, II and III

PDE (permitted daily exposure for patients, EMEA 2002) = 2.6 µg/kg/day (based on Pt due the lack pf Pd data)

LC50 Scud 196 h: 0.8 mg/l LC50 Scud 196 h: > 3.2 mg/l

EMEA 2002 Ravindra et al. 2004. ECOTOX database (http://cfpub.ep a.gov/ecotox/)

Pd is a group VIII platinoid element of the second Transition series. Its principal oxidation states are II and IV.

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2 Methods 2.1 Sampling strategy A national sampling strategy was devised based on four objectives: • • • •

Determine the environmental concentrations of PGEs in Sweden. Verify elevated levels in urban areas by sampling in the Stockholm region. Investigate background levels by sampling in background areas from Northern to Southern Sweden. Since few PGE measurements have been made in higher animals, determine the PGE concentrations in fish, cow, moose and raptor.

Air, soil, sludge, urban run-off water, urban run-off water sediments, surface water, animals and fish were sampled in the Stockholm area which was hypothesized to have elevated levels of PGEs due to high traffic intensity. Environmental background levels in fish and sediments were determined in samples from background reference lakes where the influence from human activities are considered to be minimal; Lake Abiksojaure in the northernmost part of Sweden, Ljusacknen in the middle part of Sweden and Krageholmsjön in the southernmost part of Sweden (Figure 2-1). Soil was also sampled from the areas around these lakes. Background air samples were taken at Råö (Figure 2-1) which is an air sampling station used in the national monitoring for air pollutants, the co-operative program for monitoring and evaluation of long range transmission of air pollutants in Europe (EMEP), and in the Arctic Monitoring and Assessment Program (AMAP). As a general indicator of anthropogenic influence, copper was also measured in the same samples as the PGEs. The sampling program is summarized in Table 2.1.

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Figure 2.1 Background sampling stations.

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Table 2.1 Number of samples from different localities and in different matrices Air Soil Background

Urban

Abiskojaure

1

Sediment Fish Ground water Surface STP sludge water 1

STP Flora water

Animals Total

1

3

Ljusacknen

1

1

1

3

Krageholmssjön

1

1

1

3

Råö

1

1

Hornsgatan

1

1

Essingeleden

1

1

Norrtull

3

Hanveden Västra Haninge

1

4

1

1

3

3

Sorbusdammen (run-off water pond)

1

1

2

Linneaholm (runoff water pond)

1

1

2

Lake Trekanten

1

3

Bromma STP

2

2

4

Lake Mälaren (prästfjärden)

1

1

Lake Fysingen

2

2

Mälardalen

4

4

Mälardalen (moose)

3

Sea eagle

1

Mälardalen (cattle)

3

3

7

42

3

9

6

6

2

2

2

2

4

2.2 Sampling methods Sampling instructions were given to all personnel. These explained sampling procedures and handling of samples during transport. One important issue was that all sampling personnel should avoid ring jewelry since the presence of different metals, especially gold and silver, could contaminate the samples. 2.2.1 Soil Soil was sampled from the topmost layer (0-3 cm) after the removal of dead and living plant parts. Also, stones and larger objects were avoided. Soil samples were collected into diffusion tight clean sampling plastic bags and sent to the laboratory within a day of sampling. Samples were stored frozen until analysis.

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2.2.2 Sediment Sediment samples from both run-off ponds and lakes were collected by means of a kajak sampler. All sediment samples were transferred to clean plastic jars and sent to laboratory within one or two days of collection. They were stored frozen until analysis. 2.2.3 Sewage Treatment Plant (STP) sludge and water The staff at the sewage treatment plants collected the sludge samples from the anaerobic chambers in clean plastic jars or in acid rinsed pre burned glass bottles. All STP samples were sent to the laboratory within one or two days of collection. They were stored frozen until analysis. 2.2.4 Fish Only perch (perca fluviatilis) was used in this study. Fish from Ljusacknen were collected using fishing net. Samples from all other lakes were supplied from the Environmental Specimen Bank at the Museum of Natural history (A. Bignert and colleagues). When the fish was gutted glass knives were used to avoid metal contamination. All fish samples were stored frozen until analysis. 2.2.5 Water Unfiltrated water was collected in clean plastic jars or in acid rinsed pre-burned glass bottles. Water samples were kept frozen until analysis. 2.2.6 Moose Moose samples were taken from three animals; one heifer from a relatively remote area (Dalarna) and a bull and a cow from areas relatively more exposed to traffic (Sörmland). As moose range over large areas, it is difficult to obtain samples that are certain to be from background areas or areas influenced by anthropogenic activities. Moose samples were kindly provided by the Swedish Association for Hunting and Wildlife Management (Niklas Holmqvist). 2.2.7 Cow Liver samples from cows were supplied from one slaughterhouse/breeder where the cow breeding is based on organic/ecological farming principles (in Swedish, KRAV märkt kött). Despite this, the organically bred cows had some of their pastures close to a heavily trafficked road. The other two liver samples originated from conventionally bred cows. 2.2.8 Raptor Muscle from a white tailed eagle was supplied from the Environmental Specimen Bank at the Museum of Natural history (A. Bignert and colleagues).

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2.2.9 Plants Birch leaves and blueberries were collected close to a road with medium traffic density and 200 m further away from the road. The samples were collected in clean plastic jars and stored frozen until analysis. 2.2.10 Air Urban air sampling was performed by the company SLB Analys. Samples were collected using a low volume air sampler with a PM10 collector using an airflow of 0.96 m3 / h. Samples were collected on a GN-4 Metricel Membrane filter (0.8 µm) intended for air monitoring applications. The filters were automatically changed once every 24-hour period using an automatic exchange mechanism. In total 13 filters was used giving a total sampling volume of 302 m3 and 317 m3 for Hornsgatan and Essingeleden respectively (Figure 2.1). Air sampling at the background station (Råö) was performed by the Swedish Environmental Research Institute (IVL). Samples were collected using a high volume air sampler with a flow of approximately 14 m3 / h giving a total volume of sampled air of 12 900 m3. After sampling, the filters were wrapped in aluminum foil and sent to the laboratory where they were stored frozen until analysis.

Hornsgatan

Essingeleden

Figure 2.1 Low volume air samplers used for air sampling at two urban sites in Stockholm.

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2.3 Analytical methods 2.3.1 Extraction and analysis AGS Analytica AB was responsible for all analytical work. Determination of Cu and PGE in environmental samples was done by ICP-SFMS (ELEMENT2, ThermoFisher, Bremen, Germany) equipped with high-efficiency introduction system and with methane addition to the plasma (Rodushkin et al. 2005). Measurements were performed by combination of low and high-resolution modes using operation conditions and measurement parameters described in details elsewhere (Rodushkin et al. 2004). Prior to measurement stage, solid samples were digested using MW-assisted procedure (Aqua Regia+HF). For PGE analysis, analyte preconcentration was accomplished using ion exchange chromatography.

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3 Results and discussion 3.1 Air PGEs occurred in the air samples at both of the urban sites and at the background locality (figure 3.1). As expected the levels were much higher in the urban areas most likely due to direct impact of traffic related emissions at the urban sites (figure 2.1). Copper levels as indications of anthropogenic influence also co-varied with PGE levels (figure 3.2). It should be noted that the PGE levels at the urban and background localities are not directly comparable because PM10 sampling was used at the urban sites while particles of all sizes were sampled at the background locality. The PM10 fraction is believed to be a more bioavailable fraction than the whole particle fraction (Gómez et al. 2002) which makes it appropriate for air sampling of pollutants. The urban PGE concentrations were at the upper range of values found in a number of previous investigations in the urban environment (Table 3.1). Previous PGE analysis of the PM10 fraction of urban air samples in Gothenburg yielded levels of 1 – 19, 0.1 – 10 and 0.3 – 4 pg/m3 of Pt, Pd and Rh respectively (Rausch et al. 2001) which is well below the ranges found in this study. This may be because the samplers in this study were placed very close to the traffic (Figure 2.1).

Air 30.1

14

6.5 Pd (pg/m3)

6

Pt (pg/m3)

PGE concentrations (pg/m3)

5

Rh (pg/m3) 4.30

4 3.1 3

2

1