Single Wall Carbon Nanotubes (SWCNT)

PBT assessment

PBT assessment: overall result

Reference

Reference 1

Name:

Single Wall Carbon Nanotubes (SWCNT)

Type of composition:

boundary composition of the substance

State / form:

solid: nanoform

Reference substance:

Single Wall Carbon Nanotubes (SWCNT)

Type of information reported:

set of nanoforms

Reason / purpose:

justification for reporting set of similar nanoforms

Remarks:

Material purity belonging to one set of nanoforms as described in this Boundary composition

Related information:

Single Wall Carbon Nanotubes (SWCNT)

Reason / purpose:

justification for reporting set of similar nanoforms

Remarks:

Material purity belonging to one set of nanoforms as described in this Boundary composition

Related information:

Single Wall Carbon Nanotubes (SWCNT)

Shape category:

elongated

Shape:

tube

Pure shape:

yes

Shape category:

elongated

Percentile:

D90

Typical value:

ca. 2 nm

Range:

>= 1.9 - <= 2.2 nm

Percentile:

D50

Typical value:

ca. 1.69 nm

Range:

>= 1.6 - <= 1.8 nm

Percentile:

D10

Typical value:

ca. 1.35 nm

Range:

>= 1.2 - <= 1.45 nm

Typical length:

ca. 10 μm

Range of length:

>= 1 - <= 20 μm

Range of lateral dimension 1:

>= 1 - <= 2.4 nm

Range of lateral dimension 2:

>= 1 - <= 2.4 nm

Range of aspect ratio (:1):

>= 2 000 - <= 10 000

Fraction of constituent particles in the size range 1-100 nm:

>= 90 - <= 100 %

Structure:

amorphous

Pure structure:

yes

Range of specific surface area:

>= 300 - <= 1 500 m²/g

Surface treatment applied:

no

Does the set contain both treated and non-surface treated nanoforms?:

no

Reference 2

Name:

Single Wall Carbon Nanotubes (SWCNT)

Type of composition:

legal entity composition of the substance

State / form:

solid: nanoform

Related composition:

Single Wall Carbon Nanotubes (SWCNT)

Reference substance:

Single Wall Carbon Nanotubes (SWCNT)

Type of information reported:

single nanoform

Shape category:

elongated

Shape:

tube

Pure shape:

yes

Shape category:

elongated

Percentile:

D10

Typical value:

ca. 1.3 nm

Range:

>= 1.2 - <= 1.4 nm

Percentile:

D50

Typical value:

ca. 1.7 nm

Range:

>= 1.6 - <= 1.8 nm

Percentile:

D90

Typical value:

ca. 2 nm

Range:

>= 1.9 - <= 2.2 nm

Typical length:

ca. 10 μm

Range of length:

>= 1 - <= 20 μm

Range of lateral dimension 1:

>= 1 - <= 2.4 nm

Range of lateral dimension 2:

>= 1 - <= 2.4 nm

Typical aspect ratio (:1):

ca. 5 000 :1

Range of aspect ratio (:1):

>= 2 000 - <= 10 000

Fraction of constituent particles in the size range 1-100 nm:

>= 90 - <= 100 %

Structure:

amorphous

Pure structure:

yes

Typical specific surface area:

ca. 1 000 m²/g

Range of specific surface area:

>= 600 - <= 1 300 m²/g

Surface treatment applied:

no

Reference 3

Name:

Single Wall Carbon Nanotubes (SWCNT)

Type of composition:

legal entity composition of the substance

State / form:

solid: nanoform

Related composition:

Single Wall Carbon Nanotubes (SWCNT)

Reference substance:

Single Wall Carbon Nanotubes (SWCNT)

Type of information reported:

single nanoform

Shape category:

elongated

Shape:

tube

Pure shape:

yes

Shape category:

elongated

Percentile:

D90

Typical value:

2 nm

Range:

>= 1.95 - <= 2.1 nm

Percentile:

D50

Typical value:

1.68 nm

Range:

>= 1.66 - 1.7 nm

Percentile:

D10

Typical value:

ca. 1.4 nm

Range:

>= 1.38 - 1.45 nm

Typical length:

ca. 10 μm

Range of length:

>= 1 - <= 20 μm

Range of lateral dimension 1:

>= 1 - <= 2.2 nm

Range of lateral dimension 2:

>= 1 - <= 2.2 nm

Typical aspect ratio (:1):

ca. 5 000 :1

Range of aspect ratio (:1):

>= 2 000 - <= 10 000

Fraction of constituent particles in the size range 1-100 nm:

>= 90 - <= 100 %

Structure:

amorphous

Pure structure:

yes

Typical specific surface area:

ca. 650 m²/g

Range of specific surface area:

>= 300 - <= 700 m²/g

Surface treatment applied:

no

PBT status:

the substance is not PBT / vPvB

Justification:

The concept of PBT and vPvB assessment is hardly applicable to inorganic substances such as single wall carbon nanotubes.

Classical biodegradability studies according to OECD 301 or OECD 302 are not applicable to inorganic material such as single wall carbon nanotubes (SWCNT). However, as SWCNT are also investigated in medicinal applications as carrier for pharmaceutical drugs for use in oral or intravenous therapy treatment and the detoxification of this material in vivo is of utmost importance, the metabolism of these carriers, intentionally if deposited in human bodies, is intensively investigated to ensure safety of such carriers in medicinal use. In various scientific papers it has been described that there are different enzymatic peroxidase assisted mechanisms that biodegrade single wall carbon nanotubes, finally leading to CO2 by such oxidative clearance mechanism. It appears that BSA (blood serum proteins) and different oxidase enzymes such as lactoperoxidase, horseradish peroxidase, lignin peroxidase and myeloperoxidase all were confirmed degrading single wall carbon nanotubes in vivo. Such mechanisms do take place in vivo but also in the environment, and thus it can be assumed that corresponding clearance mechanisms in the environment do also take place, finally degrading such single wall carbon nanotubes to carbon dioxide.

Classical bioaccumulation studies such as determination of the n-octanol/water partitioning coefficient or bioconcentration studies in fish are not applicable to SWCNT for various reasons: a) the substance is inorganic and thus the concept is not applicable; b) the substance is fully insoluble in water and its molecular weight is comparable to a polymer, thus making a penetration through cell membranes, being a pre-requisite for accumulation, virtually impossible; and c) it is almost impossible to analyse the substance quantitatively in biota, as element wise the substance consist of carbon only, which is ubiquitous in biota. Given the complex production process in large scale, 14C marked material is almost impossible to be generated, which would be required to investigate bioaccumulation by radio-carbon methods.

However, considering the size of such “molecules” and the overwhelming scientific literature describing the availability of various oxidase enzymes to catalise oxidative degradation, bioaccumulation in biota appears unlikely.

Finally, no information on systemic toxicity is known so far and a repeated dose toxicity study, combined with a reproductive toxicity screening study, according to OECD 422, in which male and female rats were exposed to 1000 mg/kg bw/d via diet, revealed no effects by the test substance, neither to parental animals nor to pups.

In conclusion, no indication for persistence, bioaccumulation or toxicity is available.