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Environmental fate & pathways

Phototransformation in air

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Endpoint:
phototransformation in air
Type of information:
calculation (if not (Q)SAR)
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Accepted, well-documented calculation method
Justification for type of information:
1. SOFTWARE
US EPA (2012). Estimation Programs Interface Suite™ (EPI Suite) for Microsoft® Windows, v 4.11. United States Environmental Protection Agency, Washington, DC, USA.

2. MODEL (incl. version number)
Program AOP, version 1.92

3. SMILES OR OTHER IDENTIFIERS USED AS INPUT FOR THE MODEL
c(c(ccc1)C(C2)(C)C)(c1)C2(c(cccc3)c3)C (ECHA"s Reference Substance SMILES notation "CC1(C)CC(C)(c2ccccc2)c3ccccc13" results in the same structure)

4. SCIENTIFIC VALIDITY OF THE (Q)SAR MODEL
- Defined endpoint: yes, overall OH-rate constant for the atmospheric, gas-phase reaction, half-life
- Unambiguous algorithm: yes
- Defined domain of applicability: see under Attached justification

5. APPLICABILITY DOMAIN
- Descriptor domain: specified by molecular fragments
- Similarity with analogues in the training set:
- Other considerations (as appropriate): for more detailed information see under Attached justification

6. ADEQUACY OF THE RESULT
Result of the prediction is used as information for the dimeric constituents of the registration substance Naphtha (petroleum), steam-cracked, C8-10 aromatic hydrocarbon fraction, alkylated and oligomerised and as weight of evidence information on the phototransformation in air of the substance.
Qualifier:
no guideline followed
Principles of method if other than guideline:
(Q)SAR calculation with calculation programme US EPA EPI Suite v4.11, component AOPWIN (v1.92); estimation of rate of phototransformation of organic substances by OH radicals in air (US EPA 2011. Estimation Programs Interface Suite™ for Microsoft® Windows, v 4.11; United States Environmental Protection Agency, Washington, DC, US)
Estimation method (if used):
PHOTOCHEMICAL REACTION WITH OH RADICALS
- Concentration of OH radicals: 1.5 × 10E6 molecules (radicals)/cm³ per 12-h of daylight.
- Computer programme: US EPA EPI Suite, version 4.1, program component AOPWIN, version 1.92
Key result
DT50:
0.985 d
Test condition:
The half-life of 0.985 days corresponds to a half-life of 11.824 hrs (estimation is based on a 12 hour day)
Key result
Reaction with:
OH radicals
Rate constant:
0 cm³ molecule-1 d-1

Half-life was estimated using an overall OH rate constant of 10.8554 E-12 cm³/molecule-sec and taking into account a 12-hr day (fast reacting chemicals) and an OH radical concentration of 1.5 E6 OH/cm³.

Validity criteria fulfilled:
not applicable
Conclusions:
Phototransformation of 1,1,3-trimethyl-3-phenylindan in air is fast.
Endpoint:
phototransformation in air
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
weight of evidence
Justification for type of information:
REPORTING FORMAT FOR THE ANALOGUE APPROACH

1. HYPOTHESIS FOR THE ANALOGUE APPROACH
The source test material 1,1,3-trimethyl-3-phenylindan [CAS no 6362-80-7] is a constituent of the target substance representing the dimeric fraction of the oligomerisation products.
The target substance ‘Naphtha (petroleum), steam-cracked, C8-10 aromatic hydrocarbon fraction, alkylated and oligomerised’ (NAF-AO) [EC no. 701-299-207] consists of a complex mixture of numerous aryl-aliphatic constituents. Its components can basically divided into groups corresponding to their level of oligomerisation (dimers, trimers, tetramers).
Being a constituent of the target substance NAF-AO, test results of the source substance represent at least in part the properties of NAF-AO with regard to phototransformation in air.

2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)
The source substance 1,1,3-trimethyl-3-phenylindan is a constituent of the target substance NAF-AO. It is a dimerisation product of aryl-olefinic components ((methyl-)2-phenylpropene, (methyl)indene) in the starting material. Its concentration in NAF-AO is ca. 3 to 15%. It is representative for the total group of dimeric constituents in NAF-AO, which amount to about 20 to 70%. A the study covers (Q)SAR calculations for the substance, information on analytical purity is not relevant.
The target substance NAF-AO is a UVCB substance obtained in an acid catalysed alkylation and oligomerisation reaction of the starting material ‘Naphtha (petroleum), steam-cracked, C8-10 aromatic hydrocarbon fraction’. This material comprises predominantly styrene and indene derivatives. In the production process, oligomerisation products of C8-10 aromatic hydrocarbons are formed consisting of dimeric, trimeric, and oligomeric (n ≥ 4) products. These products consist of two, three, or more aromatic rings connected by methyl-substituted alkenyl carbon-chains (dimers, trimers, oligomers). The aromatic substituents include besides benzene also indan. Based on the degree of oligomerisation, constituents are combined into the three different groups, the dimers, trimers, and higher oligomers. Depending on the type of technical product (Novares L 100, L 700, TL 10), composition with respect to different component groups will vary (dimers from ca. 20 to 70%, trimers from ca. 10 to 30%, higher oligomers from ca. 15 to 50%).
NAF-AO is a viscous oily material with a low water solubility (between 0.6 and 1.3 mg/L depending on its composition). Values for water solubility obtained by (Q)SAR (US EPA EPI suite) for individual model constituents are lower (between 0.082 and 0.038 mg/L for dimers and between 0.011 and 0.027 mg/L for trimers). Overall, the water solubility of NAF-AO is low to very low depending on the technical product and its composition (higher percentages of trimers and higher oligomers will reduce the water solubility).

3. ANALOGUE APPROACH JUSTIFICATION
Properties of the target substance NAF-AO relevant for phototransformation in air will be determined by the properties of its constituents. Under environmental conditions or during processing of the target substance, environmentally available or volatile components can be released. Out of the dimers, trimers, and oligomers, this will primarily be the dimers.
All constituents in combination will specify the distribution properties and fate in air of the substance NAF-AO as such. Half-live in air will be determined by the half-lives of its constituents. Therefore, it is justified to use data determined for a constituent of NAF-AO that represents the dimers fraction (1,1,3-trimethyl-3-phenylindan), in a weight of evidence approach to characterise the photochemical degradation in air of NAF-AO.
Reason / purpose:
read-across source
Principles of method if other than guideline:
Read-across to preceding entry:
Source test material: 1,1,3-trimethyl-3-phenylindan;
Reference: Wildschütte 2015
Key result
DT50:
0.985 d
Test condition:
The half-life of 0.985 days corresponds to a half-life of 11.824 hrs (estimation is based on a 12 hour day)
Remarks on result:
other: the test result of the source substance is adopted as weight of evidence for the target substance NAF-AO
Key result
Reaction with:
OH radicals
Rate constant:
0 cm³ molecule-1 d-1
Remarks on result:
other: the test result of the source substance is adopted as weight of evidence for the target substance NAF-AO

Half-life was estimated using an overall OH rate constant of 10.8554 E-12 cm³/molecule-sec and taking into account a 12-hr day (fast reacting chemicals) and an OH radical concentration of 1.5 E6 OH/cm³.

Conclusions:
The phototransformation of the source substance 1,1,3-trimethyl-3-phenylindan in air is fast. This result is adopted as weight of evidence for the target substance 'Naphtha (petroleum), steam-cracked, C8-10 aromatic hydrocarbon fraction, alkylated and oligomerised' (NAF-AO).
Endpoint:
phototransformation in air
Type of information:
calculation (if not (Q)SAR)
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Accepted, well-documented calculation method
Justification for type of information:
1. SOFTWARE
US EPA (2012). Estimation Programs Interface Suite™ (EPI Suite) for Microsoft® Windows, v 4.11. United States Environmental Protection Agency, Washington, DC, USA.

2. MODEL (incl. version number)
Program AOP, version 1.92

3. SMILES OR OTHER IDENTIFIERS USED AS INPUT FOR THE MODEL
c(cccc1)(c1)C(CC(c(cccc2)c2)=C)(C)C (ECHA"s Reference Substance SMILES notation "CC(C)(CC(=C)c1ccccc1)c2ccccc2" results in the same structure)

4. SCIENTIFIC VALIDITY OF THE (Q)SAR MODEL
- Defined endpoint: yes, overall OH-rate constant for the atmospheric, gas-phase reaction, half-life
- Unambiguous algorithm: yes
- Defined domain of applicability: see under Attached justification

5. APPLICABILITY DOMAIN
- Descriptor domain: specified by molecular fragments
- Similarity with analogues in the training set:
- Other considerations (as appropriate): for more detailed information see under Attached justification

6. ADEQUACY OF THE RESULT
Result of the prediction is used as information for the dimeric constituents of the registration substance Naphtha (petroleum), steam-cracked, C8-10 aromatic hydrocarbon fraction, alkylated and oligomerised and as weight of evidence information on the phototransformation in air of the substance.
Qualifier:
no guideline followed
Principles of method if other than guideline:
Q)SAR calculation with calculation program US EPA EPI Suite v4.11, component AOPWIN (v1.92); estimation of rate of phototransformation of organic substances by OH radicals in air (US EPA 2011. Estimation Programs Interface Suite™ for Microsoft® Windows, v 4.11; United States Environmental Protection Agency, Washington, DC, US)
Estimation method (if used):
PHOTOCHEMICAL REACTION WITH OH RADICALS
- Concentration of OH radicals: 1.5 E6 molecules (radicals)/cm³ per 12-h of daylight.
- Overall OH rate constant: 59.0123 E-12 cm³/molecule-sec
- Temperature for which rate constant was calculated: 25 °C

REACTION WITH OZONE
- Ozone concentration: 7 E11 molecules/cm³ (30 ppb) per 24 hours (day)
- Overall Ozone rate constant: 13.650 E-17 cm³/molecule-sec
- Temperature for which rate constant was calculated: 25 °C

COMPUTER PROGRAM
- US EPA EPI Suite, version 4.1, program component AOPWIN, version 1.92
Key result
DT50:
0.181 d
Test condition:
reaction with OH radicals; the half-life of 0.181 days corresponds to a half-life of 2.175 hrs (estimation is based on a 12 hour day)
Key result
DT50:
0.084 d
Test condition:
reaction with ozone; the half-life of 0.084 days corresponds to a half-life of 2.015 hrs (estimation is based on a 24 hour day)
Key result
Reaction with:
OH radicals
Rate constant:
0 cm³ molecule-1 d-1
Key result
Reaction with:
ozone
Rate constant:
0 cm³ molecule-1 d-1

Half-life for the reaction with OH radicals was estimated using an overall OH rate constant of 59.0123 E-12 cm³/molecule-sec and taking into account a 12-hr day (fast reacting chemicals) and an OH radical concentration of 1.5 E6 OH/cm³.

Half-life for the reaction with ozone was estimated using an overall ozone rate constant of 13.650 E-17 cm³/molecule-sec and taking into account a 24-hr day and an ozone concentration of 7 E6 molecules/cm³.

Validity criteria fulfilled:
not applicable
Conclusions:
Phototransformation of 1,1'-(1,1-dimethyl-3-methylene-1,3-propanediyl)bisbenzene in air is fast.
Endpoint:
phototransformation in air
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
weight of evidence
Justification for type of information:
REPORTING FORMAT FOR THE ANALOGUE APPROACH

1. HYPOTHESIS FOR THE ANALOGUE APPROACH
The source test material 1,1’-(4-methylpent-1-ene-2,4-diyl)dibenzene [CAS no 6362-80-7] is a constituent of the target substance representing the dimeric fraction of the oligomerisation products.
The target substance ‘Naphtha (petroleum), steam-cracked, C8-10 aromatic hydrocarbon fraction, alkylated and oligomerised’ (NAF-AO) [EC no. 701-299-207] consists of a complex mixture of numerous aryl-aliphatic constituents. Its components can basically divided into groups corresponding to their level of oligomerisation (dimers, trimers, tetramers).
Being a constituent of the target substance NAF-AO, test results of the source substance represent at least in part the properties of NAF-AO with regard to phototransformation in air.

2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)
The source substance 1,1’-(4-methylpent-1-ene-2,4-diyl)dibenzene is a constituent of the target substance NAF-AO. It is a dimerisation product of aryl-olefinic components ((methyl-)2-phenylpropene, (methyl)indene) in the starting material. Its concentration in NAF-AO is ca. 5 to 15%. It is representative for the total group of dimeric constituents in NAF-AO, which amount to about 20 to 70%. A the study covers (Q)SAR calculations for the substance, information on analytical purity is not relevant.
The target substance NAF-AO is a UVCB substance obtained in an acid catalysed alkylation and oligomerisation reaction of the starting material ‘Naphtha (petroleum), steam-cracked, C8-10 aromatic hydrocarbon fraction’. This material comprises predominantly styrene and indene derivatives. In the production process, oligomerisation products of C8-10 aromatic hydrocarbons are formed consisting of dimeric, trimeric, and oligomeric (n ≥ 4) products. These products consist of two, three, or more aromatic rings connected by methyl-substituted alkenyl carbon-chains (dimers, trimers, oligomers). The aromatic substituents include besides benzene also indan. Based on the degree of oligomerisation, constituents are combined into the three different groups, the dimers, trimers, and higher oligomers. Depending on the type of technical product (Novares L 100, L 700, TL 10), composition with respect to different component groups will vary (dimers from ca. 20 to 70%, trimers from ca. 10 to 30%, higher oligomers from ca. 15 to 50%).
NAF-AO is a viscous oily material with a low water solubility (between 0.6 and 1.3 mg/L depending on its composition). Values for water solubility obtained by (Q)SAR (US EPA EPI suite) for individual model constituents are lower (between 0.082 and 0.038 mg/L for dimers and between 0.011 and 0.027 mg/L for trimers). Overall, the water solubility of NAF-AO is low to very low depending on the technical product and its composition (higher percentages of trimers and higher oligomers will reduce the water solubility).

3. ANALOGUE APPROACH JUSTIFICATION
Properties of the target substance NAF-AO relevant for phototransformation in air will be determined by the properties of its constituents. Under environmental conditions or during processing of the target substance, environmentally available or volatile components can be released. Out of the dimers, trimers, and oligomers, this will primarily be the dimers.
All constituents in combination will specify the distribution properties and fate in air of the substance NAF-AO as such. Half-live in air will be determined by the half-lives of its constituents. Therefore, it is justified to use data determined for a constituent of NAF-AO that represents the dimers fraction (1,1’-(4-methylpent-1-ene-2,4-diyl)dibenzene), in a weight of evidence approach to characterise the photochemical degradation in air of NAF-AO.
Reason / purpose:
read-across source
Principles of method if other than guideline:
Read-across to preceding entry:
Source test material: 1,1'-(4-methylpent-1-ene-2,4-diyl)dibenzene;
Reference: Wildschütte 2015
Key result
DT50:
0.181 d
Test condition:
The half-life of 0.181 days corresponds to a half-life of 2.175 hrs (estimation is based on a 12 hour day)
Remarks on result:
other: the test result of the source substance is adopted as weight of evidence for the target substance NAF-AO
Key result
Reaction with:
OH radicals
Rate constant:
0 cm³ molecule-1 d-1
Remarks on result:
other: the test result of the source substance is adopted as weight of evidence for the target substance NAF-AO

Half-life was estimated using an overall OH rate constant of 59.0123 E-12 cm³/molecule-sec and taking into account a 12-hr day (fast reacting chemicals) and an OH radical concentration of 1.5 E6 OH/cm³.

Conclusions:
The phototransformation of the source substance 1,1'-(1,1-dimethyl-3-methylene-1,3-propanediyl)bisbenzene in air is fast. This result is adopted as weight of evidence for the target substance 'Naphtha (petroleum), steam-cracked, C8-10 aromatic hydrocarbon fraction, alkylated and oligomerised' (NAF-AO).

Description of key information

Half-life of the substance ‘Naphtha (petroleum), steam-cracked, C8-10 aromatic hydrocarbon fraction, alkylated and oligomerised’ (NAF-AO) (see Chap. 1) [EC no. 701-299-7] in air is estimated to be short (1 day). This is based on the estimation of half-lives of major constituents for the reaction with OH radicals and ozone in air with the calculation programme US EPA EPI Suite.

Key value for chemical safety assessment

Half-life in air:
1 d
Degradation rate constant with OH radicals:
0 cm³ molecule-1 d-1

Additional information

Half-lives of constituents of the substance 'Naphtha (petroleum), steam-cracked, C8-10 aromatic hydrocarbon fraction, alkylated and oligomerised' (NAF-AO) (see Chap. 1) [EC no. 701-299-7] for the reaction with OH radicals and ozone in air have been calculated with the program US EPA EPI Suite v4.11, program component AOPWIN v1.92. Results are displayed in the following table. Results for OH radicals are based on a 12-hr day while results for ozone are based on a 24-hr day.

 

EC Name

 

Half-life
(reaction with OH radicals)

Half-life
(reaction with ozone)

1,1,3 -trimethyl-3-phenylindan
(indanderivative)
CAS No.: 3910-35-8

Dimer of  C8-10 aromatic hydrocarbon fraction (monomer)

0.985 days (11.824 hrs)

no olefin or acetylene

1,1'-(1,1-dimethyl-3-methylene-1,3-propanediyl)bisbenzene
(1-pentene derivative)
CASNo.: 6362-80-7

Dimer of C8-10 aromatic hydrocarbon fraction (monomer)

0.181 days (2.175 hrs)

0.084 days (2.015 hrs)

1,1'-(1,3,3-trimethylprop-1-ene-1,3-diyl)dibenzene
(2-pentene derivative)
CAS No.: 6258-73-7

 Dimer of C8-10 aromatic hydrocarbon fraction (monomer)

0.114 days (1.373 hrs)

0.084 days (2.015 hrs)

1,3-dimethyl-1-(2-methyl-2-phenylpropyl)-3-phenylindan

(indanderivative)

CAS No.: 41906-71-2

 Trimer of C8-10 aromatic hydrocarbon fraction (monomer)

0.639 days (7.671 hrs)

no olefin or acetylene

1,1',1''-(1,1,3-trimethyl-5-methylenepentane-1,3,5-triyl)tribenzene

(1-heptene derivative)

CASNo.: 62604-62-0

 Trimer of C8-10 aromatic hydrocarbon fraction (monomer)

0.165 days (1.978 hrs)

0.084 days (2.015 hrs)

1,1',1''-(1,3,5,5-tetramethylpent-1-ene-1,3,5-triyl)tribenzene

(2-heptene derivative)

CASNo.: 19303-34-5

 Trimer of C8-10 aromatic hydrocarbon fraction (monomer)

0.108 days (1.292 hrs)

0.084 days (2.015 hrs)

 

In general, phototransformation half-lives for all substances are short (below 1 day). Within the same molecular size (dimers or trimers), half-lives change depending on the structure of the substance (indan derivatives > 1-olefines > 2-olefines). Within the same substance class, half-lives decrease with increasing size (dimer to trimer).

For two substances (CAS No. 3910-35-8 and 6362-80-7), robust study summaries (study records) are included in this section.