Sodium polysulfide aluminosilicate with a SOD-type framework structure

Toxicity to soil microorganisms

Administrative data

Endpoint:

toxicity to soil microorganisms

Data waiving:

study scientifically not necessary / other information available

Justification for data waiving:

other:

Justification for type of information:

JUSTIFICATION FOR DATA WAIVING
The study does not need to be conducted because of the following reasons:

Ultramarine Blue (UMB) pigment is a sodium aluminum sulfosilicate having a typical formula Na(AlSiO)S which is prepared from kaolin, a natural aluminosilicate source which is mainly constituted by kaolinite but also for other minor silicates and oxides (micas, feldspaths, iron or titanium oxides). UMB is an inorganic substance considered environmentally and biologically inert due to its physico-chemical properties and low bioavailability which resembles to the naturally occurring Lazurite (1302-83-6/ 215-111-1)(major component of Lapis Lazuli). Other analogous sodium silicoaluminates, derived from natural sources, occur in soils and sediments.
The silicates, owing to their abundance on Earth, constitute the most important mineral class. Approximately 25 percent of all known minerals and 40 percent of the most common ones are silicates; the igneous rocks that make up more than 90 percent of Earth’s crust are composed of virtually all silicates.
As a major constituent of Earth’s crust, aluminum follows only oxygen and silicon in importance. The radius of aluminum, slightly larger than that of silicon, lies close to the upper bound for allowable fourfold coordination in crystals. As a result, aluminum can be surrounded with four oxygen atoms arranged tetrahedrally, but it can also occur in sixfold coordination with oxygen. The ability to maintain two roles within the silicate structure makes aluminum a unique constituent of these minerals. (https://www.britannica.com/science/mineral-chemical-compound/Silicates).
Aluminium, as the most abundant metal in the lithosphere and ubiquitous in the environment, is a major constituent of many rock-forming minerals, and the weathered products of aluminium minerals include secondary clay minerals, and aluminium-hydroxides, which may control the equilibrium concentration of aluminium in soil solution, groundwater and stream water. The speciation of aluminium in the environment is determined by pH, mineralogical composition, and the abundance of organic complexing agents. Under most environmental conditions, aluminium has a low mobility. However, decreasing pH (below pH 5.5) increases the mobility of aluminium ions (Salminen et al. 2005 and references therein).
Monitoring data for elemental aluminium background concentrations in soil is provided by the FOREGS Geochemical Baseline Mapping Program. Baseline aluminium levels in topsoil range from 3,700 to 267,000 mg Al2O3/kg (1,958 to 141,304 mg Al/kg) with a mean of 105,000 mg Al2O3/kg (55,569 mg Al/kg) and a 90th percentile of 160,000 mg Al2O3/kg (84,676 mg Al/kg) (Foregs Geochemical Atlas (gtk.fi)).
Additionally, aluminium concentration of agricultural soils was determined in the GEMAS project (Geochemical Mapping of Agricultural and Grazing land Soil). Aluminium levels of agricultural soil range from 351.6 to 64,527.0 mg Al/kg with 5th, 50th and 95th percentiles of 2,508.0, 10,769.4 and 23,999.1 mg Al/kg, respectively. In grazing land, soil concentrations of aluminium range from 627.3 to 62,541.8 mg Al/kg with 5th, 50th and 95th percentiles of 2,335.6, 10,506.8 and 25,326.4 mg Al/kg, respectively.
Based on the FOREGS dataset, the 90th percentile of 84,676 mg Al/kg can be regarded as representative background concentration of aluminium in topsoil of EU countries. Representative aluminium concentrations (95th percentile) of agricultural and grazing land soil (i.e. ambient levels) amount to 23,999.1 and 25,326.4 mg Al/kg, respectively, according to the GEMAS dataset.
Aluminium or silicates are abundant in soil environments and soil organisms are well adapted to the presence. The addition of aluminium or silicates to soil as result of the manufacture or use of the substance is not expected to be relevant for respective total and bioavailable soil concentrations and toxicity. Thus, additional soil testing is not expected to provide any further insight.
In this regard, the results of the exposure assessment (CSR, endpoint record 13.1) demonstrate the absence of or no significant exposure of the soil throughout the life cycle of the substance.
Based on CSR assessment, the concentration of the substance released from all sources (all assessed uses or scenarios) in agricultural soil for a regional scale (regional PEC) is estimated to be 1.85E-05 mg/kg dw. For widespread uses, the estimated local PEC in agricultural soil is 1.62E-04 mg/kg dw.
These estimated concentrations confirm how irrelevant is the contribution of the released substance to the soil compared to the above-mentioned background concentration of aluminium in topsoil or agricultural and grazing land soils.
Moreover, based on studies into the weathering of analogue substance Zeolite A in natural waters by hydrolysis, forming natural aluminosilicates (Cook et al., 1982; endpoint record 5.1.2_003) it can be anticipated that the substance reaching the aquatic and terrestrial compartments will ultimately turn into natural constituents of waters, sediments and soils.
Furthermore, Zeolites are used in agriculture due to their ability to hydrate and rehydrate which have a significant impact on maintaining proper water balance in the soil and prevent drying of soils and soil-like substrates (Szerement et al., 2014).
It is also demonstrated that Zeolites improves soil structure, reduces water and fertilizer costs by retaining beneficial nutrients and moisture in the root zone (Polat et al., 2004).
Ultramarine Blue is registered as an inert ingredient in PPP by US EPA, so considered as it hasn’t any effect on plants (System of Registries | US EPA).
As mentioned above, Ultramarine Blue pigment is an inorganic substance considered environmentally and biologically inert due to its physico-chemical properties: low water solubility (endpoint record 4.8) and low partition coefficient (Kow) (endpoint record 4.7), that indicates a low bioavailability.
The poor water solubility and low partition coefficient of the Ultramarine Blue pigment is expected to determine its behaviour and fate in the environment, and subsequently its potential for ecotoxicity.
In this sense, Ultramarine Blue pigment is not classified as dangerous for the aquatic environment, an aquatic PNEC is not required, thus not indicating a hazard to the aquatic environment. In these circumstances there are also no unclassified hazards to the soil compartment because toxicity to aquatic organisms is used as an indicator of concern for soil organisms and a screening risk characterization (using the equilibration partitioning method to derive a PNEC for soil) does not need to be undertaken either. Thus, Ultramarine Blue pigment does not have a “non-classified hazard” potential to the soil compartment.
In summary, considering the ubiquitousness of aluminium and silicates and their essentiality in soil, irrelevance of contribution of the released substance in soil compared to background concentrations of aluminium or silicates, low water solubility, low partition coefficient and low bioavailability, lack of toxicity to aquatic organisms and lack of unclassified hazards to the soil compartment, it is concluded that a toxicity study to terrestrial organisms does not need to be conducted.

References:
Cook TE et al. (1982). Zeolite A hydrolysis and degradation. Environ. Sci. Technol,1982, 16 (6), pp 344-350.
Polat E et al. (2004). Use of natural zeolite (clinoptilolite) in agriculture. Journal of Fruit and Ornamental Plant Research vol. 12, 2004 Special ed.
Geochemical Atlas of Europe. FOREGS-Euro Geo Surveys Geochemical Baseline Database. Salminen, R. (Chief-editor), Part 1. Statistics, Methodology and Maps. http://www.gtk.fi/publ/foregsatlas/
EU GEMAS: Geochemical mapping of agricultural and grazing land soil at the continental scale in Europe. https://www.eurogeosurveys.org/projects/gemas/.
Szerement J. Use of zeolite in agriculture and environmental protection. A short review / J. Szerement, A. Ambrożewicz-Nita, K. Kędziora, J. Piasek // Вісник Національного університету "Львівська політехніка". Теорія і практика будівництва. - 2014. - № 781. - С. 172-177. - Режим доступу: http://nbuv.gov.ua/UJRN/VNULPTPB_2014_781_34.