Sodium hexahydroxoantimonate

Endpoint summary

Description of key information

Calculated and measured concentrations

The concentrations of antimony in the environment can be estimated via calculations or via available measured data.

Based on the available monitoring data, ambient background concentrations in the different compartments can be calculated. The calculated ambient concentrations will consist of the natural background (present only due to natural causes) and the emission of metal from diffuse sources of human origin (present due to anthropogenic activities, both historical and present).

The modelled PEC_regional values are steady state concentrations based only on the estimated total emissions of antimony. However, as the time for reaching steady state is not taken into consideration and the natural background concentrations are not included, the modelled PEC_regional values do not represent the current situation. In addition, they only include antimony from the compound being considered, and not all potential sources of antimony to the environment. Therefore, the background concentrations based on measured data will be used instead of the calculated PEC_regional in the calculations of local PECs.

This approach was used in the EU RAR for ATO and is in accordance with the methods used in risk assessments for other metals (ICMM, 2007). We have therefore also used this approach for the risk assessment of antimony metal and compounds.

Reasonable worst case ambient concentration

A reasonable worst case (RWC) ambient concentration to be used in the regional risk characterisation were calculated as follows:

RWC-ambient PEC_country: median value of all 90^th percentiles that have been derived for different sites, rivers/catchments or regions within a country. The median value from the 90^th percentiles has actually been used for PEC regional for environmental risk assessment as stipulated by the ECHA guidance R16.4.2.

In cases where the amount of data for a country were too limited for deriving site/river/catchment-specific 90^th percentile values, the 90^th percentile of all relevant data was considered as the RWC-ambient PEC. For countries with only one ambient data point, that single value was used as an initial estimate for the RWC-ambient PEC_country. Measured values coming from polluted sites or mining areas were not included for the derivation of a regional RWC-ambient PEC, since those values are influenced by point sources and are therefore not representative for ambient (i.e., diffuse) contamination on a regional scale.

RWC ambient country-specific data were only available for a limited number of EU countries, when compared to the FOREGS database which includes measurements from the majority of the EU countries + Norway. However, since the FOREGS database is made up of measurements corresponding to low anthropogenic pressure, the use of country-specific measurements from the FOREGS database for those countries lacking RWC ambient data may result in an underestimation of the environmental concentrations intended to represent PEC_regional. This was investigated in the EU RAR for ATO. The results indicated that for water and sediment the FOREGS data were lower than the 90^th percentiles based on other data sources and therefore inclusion of the FOREGS data reduced the PEC_regionalsignificantly. For this reason the FOREGS data were not included in the calculation of PEC_regional for water or sediment. Although the FOREGS soil data were less influential on the PEC_regional, the same approach to that for water and sediment was followed for consistency.

A literature review has been conducted to identify any literature published since the EU RAR for ATO. Several new monitoring studies were identified. In addition, GEMAS soil monitoring data has become available since the EU RAR. The data from these new sources have been added to the data that were presented in the RAR and evaluated to conclude that the PEC_regional values defined in the RAR are still suitable for use.

RWC-ambient concentrations based on the available measured data are presented in Table below.

Compartment	Concentration
Freshwater	0.72 µg Sb/L
Sediment	0.65 mg Sb/kg ww
Soil	1.5 mg Sb/kg ww
Air	2.6 ng Sb/m^3
Marine water	0.20 µg Sb/L
Marine sediment	0.65 mg Sb/kg ww

Additional information

Levels in surface water

Baseline background concentrations of antimony in stream waters measured in the FOREGS project resulted in values that ranged over about three orders of magnitude, from <0.002 to 1.21 µg Sb/L (excluding two outliers up to 2.91 µg Sb/L), with a median value of 0.07 µg Sb/L.

Measured antimony concentrations in rivers, lakes, groundwater and precipitation from other sources besides the FOREGS database were reported in the EU RAR. A RWC-ambient PEC of 0.72 µg Sb/L was calculated in the EU RAR using ambient data from eight countries.The country-specific FOREGS 90^th percentile values range from similar (Sweden) to about 18 times lower (France) when compared to measured ambient concentrations. Vesely et al. (2001) gave additional data to that in the RAR that could be used to update the RWC-ambient background. Samples were taken from 119 river sites in the Czech Republic, but no range or 90^th percentile is reported, only a median value of 0.33 Sb µg/L. INERIS (2009) collated antimony water monitoring data from EU member states. Data was available from the Czech Republic, Germany, Spain, France, Portugal, Greece and the UK. Over 95% of samples were from rivers, with the remainder from transitional waters, lakes and coastal waters. The 90^th percentile of nearly 5000 samples was 0.06 µg Sb/L.

The median value from the 90^th percentiles was used for PEC regional for environmental risk assessment as stipulated by the ECHA guidance R16.4.2. The EU RAR for ATO concluded that the RWC-ambient background concentration of antimony in freshwater (dissolved) was 0.72 Sb µg/L. There are no newly available data to suggest that this value should be adjusted. We will therefore also use the 0.72 Sb µg/L RWC-ambient background.

The concentrations measured in marine waters, adjacent to the EU, are normally within the range of 0.20-0.40 µg Sb/L. Filella et al. (2002a) concluded that the concentration of antimony in oceans is about 0.2 µg Sb/L, and that the decrease in antimony concentrations as well as in data scatter with time reflect the parallel improvement of the analytical techniques available. The relatively lower concentrations measured in the brackish waters of the Baltic Sea have been attributed to a higher particle flux and longer water residence time, compared to the oceans (Andreae and Froelich, 1984).

 

It is reasonable to think that at least some of the Sb in marine waters is due to anthropogenic activity. For the EU RAR for ATO a (high) estimate of 0.2 µg Sb/L was chosen as an ambient background of antimony in marine waters (dissolved). The same value is used in this Chemical Safety Report.

Levels in sediment

Baseline background concentrations of antimony in stream water sediments measured in the FOREGS project result in values that range over three orders of magnitude from < 0.02 to 34.1 mg Sb/kg dw, with a median value of 0.615 mg Sb/kg dw.

Measured antimony concentrations in sediments from other sources besides the FOREGS database were reported in the EU RAR for ATO. A RWC-ambient PEC of 3 mg Sb/kg dw (0.65 mg/kg ww) in freshwater sediments was calculated in the EU RAR using ambient data from five countries.The country-specific FOREGS 90P values range from similar in size (Italy and UK) to eight times smaller (Austria) when compared to measured ambient concentrations. The new data that are not influenced by point sources (Grahn et al., 2006, control site from Solà and Pratt 2006) do not suggest that the RWC-ambient PEC in the EU RAR needs to be altered. INERIS (2009) collated antimony sediment monitoring data from EU member states. Data was available from the Czech Republic, Germany, Spain, France, Portugal, Greece and the UK. The 90^th percentile of nearly 500 samples was 2.8 mg Sb/kg dw whole sediment. This data also does not suggest that the RWC-ambient PEC used in the EU RAR needs to be altered.

The median value from the 90^th percentiles has actually been used for PEC regional for environmental risk assessment as stipulated by the ECHA guidance R16.4.2. In conclusion, the RWC-ambient background concentration of antimony in freshwater sediments used in this risk assessment is 3 mg Sb/kg dw (0.65 mg Sb/kg ww).

Measured antimony concentrations in marine sediment were reported in the EU RAR. The information on antimony concentrations in marine sediments is scarce, which is why the concentration chosen for freshwater sediments was also used for the marine sediments in the EU RAR for ATO. The ambient background concentration of antimony in marine and freshwater sediments used in the RAR for ATO was 3 mg Sb/kg dw, corresponding (with EUSES default conversion factors) to 0.65 mg Sb/kg ww. The newly available marine sediment data (Cal-Prieto et al. 2001) do not suggest that the RWC ambient concentration needs to be adjusted.

WWTP levels

The levels of antimony in 48 municipal wastewater treatment plants have been reported by Eriksson (2001). The levels found were in the range 0.6 mg Sb/kg_dw to 18 mg Sb/kg dw, with the median level being 1.3 mg Sb/kg dw, and the 90^th percentile 3.4 mg Sb/kgdw. The samples were collected spring-early summer 2000. The sample with the highest concentration of antimony was collected from wastewater treatment plants (Borås) that had a possible contribution from the textile industry.

Sternbeck et al. (2002a) studied 4 municipal wastewater treatment plants that differed substantially in type of loading. The emission of antimony calculated as person equivalents (pe) was similar for the three WWTP, with the lowest concentrations ranging from 0.039 to 0.078 g Sb/pe and year (equivalent to 0.57-3.1 mg Sb/kg dw), while this substantially increased to 1.2 g Sb/pe and year (16 mg Sb/kg dw) for the WWTP connected to the textile industries.

Levels in soil

Antimony, being a natural element, will naturally occur in soils as a result of weathering parent rock material. The concentrations of antimony in soils are highest in soils from sedimentary rocks such as argillaceous sediments and shale (Fergusson, 1990). The average concentration of antimony in the earth’s crust is approximately 0.2 - 0.3 mg/kg (Lisk, 1972;Bowen, 1979; Wedepohl, 1995). The average concentration of antimony in soils is about 0.5 mg/kg (Reiman and Caritat, 1998) to 1 mg/kg (Bowen, 1979), but wide ranges have been reported.

Baseline background concentrations of antimony in soil (topsoil and subsoil) measured in the FOREGS project result in values in topsoil that range over three orders of magnitude, from <0.02 to 31.1 µg Sb/kg dw, with a median value of 0.60 mg Sb/kg dw. The median ratio topsoil/subsoil is 1.15

Measured antimony concentrations in european soils fro mother sources beside the FOREGS database were reported in the EU RAR for ATO. Since publication of the EU RAR for ATO. For instance, data from a European-wide monitoring programme GEMAS has become available (Reimann et al, 2009). Over 2000 samples were taken from both agricultural and grazing soils. Pristine sample sites were not selected but point sources were avoided as far as possible. The median values of the 90^th percentiles per country are 0.63 Sb mg/kg and 0.70 Sb mg/kg for agricultural and grazing land respectively. The median value from the 90^th percentiles has actually been used for PEC regional for environmental risk assessment as stipulated by the ECHA guidance R16.4.2.

A RWC-ambient PEC of 1.7 mg Sb/kg dw (1.5 mg/kg ww) in soil is calculated in the EU RAR for ATO using ambient data from 7 countries .The country-specific FOREGS 90P values range from a factor of two larger (Spain and Sweden) to a factor of almost three lower (Germany and UK) when compared to measured ambient concentrations. The newly available monitoring data from sites without point sources are in the same range as those reported in the EU RAR. The GEMAS monitoring data also do not suggest that the RWC-ambient needs to be refined. Therefore, the same RWC ambient used in the EU RAR was used in this Chemical Safety Report.

Levels in air

The EU RAR for ATO calculated a RWC-ambient background concentration of antimony in air of 2.6 ng Sb/m³ based on these data. As no additional data were identified this value was also used in this Chemical Safety Report.