Talc (Mg3H2(SiO3)4)

Endpoint summary

Description of key information

Talc (Mg3H2(SiO3)4) is found abundantly in nature in soils and sediments. The material is an inorganic non-biodegradable substance, retaining its structure in the environment. At normal environmental pH’s this material is stable. In addition it is unlikely through normal use patterns that exposure to natural sediments would occur. Soil and sediment degradation studies are not considered to be applicable as the test material is essentially insoluble in water and consists of materials which occur naturally in these compartments. 

Additional information

Environmental fate and pathways

 

 

Talc (Mg3H2(SiO3)4) is found abundantly in nature in soils and sediments. The material is an inorganic non-biodegradable substance, retaining its structure in the environment. At normal environmental pH’s this material is stable. In addition it is unlikely through normal use patterns that exposure to natural sediments would occur. Soil and sediment degradation studies are not considered to be applicable as the test material is essentially insoluble in water and consists of materials which occur naturally in these compartments. 

 

Talc (Mg3H2(SiO3)4) has low vapor pressure ( 1.48E-020 Pa) indicating significant amounts of Talc (Mg3H2(SiO3)4) are unlikely to be present in the atmosphere for photodegradation. If released to air, a vapor pressure of 1.11E-022 mm Hg  at 25 deg C (1.11E-022 mm Hg is equivalent to a vapour pressure of 1.48E-020 Pa) indicates significant amounts of Talc (Mg3H2(SiO3)4) are unlikely to be present in the atmosphere for photodegradation and therefore Talc (Mg3H2(SiO3)4) is not expected to be susceptible to direct photolysis by sunlight. 

Using the AOPWIN QSAR model, the photochemical degradation rate of Talc (Mg3H2(SiO3)4) in the atmosphere is 6.9000 E-12 cm3/molecule-sec, with a resultant predicted half live of 18.602 Hrs ( 1.550 Days (12-hr day; 1.5E6 OH/cm3))

 

 

Talc (Mg3H2(SiO3)4 is  insoluble in water. Hydrolysis is not expected to be an important environmental fate process since this compound lacks functional groups that hydrolyze under environmental conditions. Hydrolysis is a chemical reaction during which molecules of water (H2O) are split into hydrogen cations (H+, conventionally referred to as protons) and hydroxide anions (OH−) in the process of a chemical mechanism).

Talc (Mg3H2(SiO3)4) is almost insoluble in water. 

On this basis, Talc (Mg3H2(SiO3)4) does not have a potential for Hydrolysis and Magnesium ion will not hydrolise. 

 

Biodegradation is not applicable to these inorganic substances. Natural silica/silicates are one of the most abundant materials in the earth's surface. Potential for environmental persistence does not exist. As the substance is inorganic, assessment of persistence is not applicable according to REACH Annex XIII.

Standard biodegradation tests (e.g., ready biodegradability studies conducted according to OECD guidelines) are not applicable to metal-containing inorganic substances because the methods are based on carbon oxidation.

 

 

No potential for bioaccumulation. Due to its inherent chemical-physical properties, such as absence of lipophilicity as well as the capability of the organism to excrete absorbed SiO2 components, bioaccumulation can be disregarded.Magnesium is widespread in living cells and does not bioconcentrate in aquatic organisms According to “ANNEX IX- STANDARD INFORMATION REQUIREMENTS FOR SUBSTANCES MANUFACTURED OR IMPORTED IN QUANTITIES OF 100 TONNES OR MORE , a bioaccumulation study need not be conducted if: — the substance has a low potential for bioaccumulation (for instance a log Kow ≤ 3) and/or a low potential to cross biological membranes, or — direct and indirect exposure of the aquatic compartment is unlikely. The estimated Log BCF of magnesium is 0.5  (BCF = 3.162 L/kg wet-wt) As the substance is inorganic, assessment of bioaccumulation is not applicable according to REACH Annex XIII.

 

 

The log of the adsorption coefficient (KOC) of Talc (Mg3H2(SiO3)4) was estimated to be log KOC = 1.5027 which is equal to a KOC value of 31.82 using the KOCWIN v2.00 QSAR method.

 

According to “ANNEX IX- STANDARD INFORMATION REQUIREMENTS FOR SUBSTANCES MANUFACTURED OR IMPORTED IN QUANTITIES OF 100 TONNES OR MORE , an adsorption study need not be conducted if: — based on the physicochemical properties the substance can be expected to have a low potential for adsorption (e.g. the substance has a low octanol water partition coefficient), or — the substance and its degradation products decompose rapidly. Octanol/Water Partition Coefficient of Talc (Mg3H2(SiO3)4) is low (log Kow = -9.40)

 

The estimated Henrys Law Constant (25 deg C) measured by calculation from EPI SuiteTM v4.1, HENRYWIN v3.20 Program was 5.539E-029 atm-m3/mole (5.613E-024 Pa-m3/mole)

This is Exposure Assessment Tools and Models made from EPA (Environmental Protection Agency).

 

Talc (Mg3H2(SiO3)4) has no affinity to be in air . The direct emissions to soil , surface water and sediment are significant, therefore Talc (Mg3H2(SiO3)4) will be almost exclusively be found in soil , sediment and surface water.

 

 

Mackay fugacity modelling (level 3) indicates that, taking into account degradation and using inflow parameters which are consistent with the known production tonnage of this substance in, fugacity coefficient indicates that environmental concentrations in water are predicted to be 2.4e-034 (atm), in air (atm) 1.46e-032 and soil 9.45e-036 (atm) and sediment to be  2.98e-034 (atm).

These are negligible low levels. This can be considered a worse case prediction as it assumes all product is emitted with no emission control systems used.