Reaction products of benzenesulfonic acid, mono-C20-24 (even)-sec-alkyl derivs. para-, calcium salts

Toxicity to aquatic algae and cyanobacteria

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Justification for type of information:

REPORTING FORMAT FOR THE ANALOGUE APPROACH
In this justification, the read-across (bridging) concept is applied, based on the chemical structure of the potential analogues, their toxicokinetic behaviour and other available (eco-)toxicological data.

1. HYPOTHESIS FOR THE ANALOGUE APPROACH
C20-24 calcium sulfonate and Benzenesulfonic acid, C14-24-branched and linear alkyl derivs., calcium salts (CAS 115733-09-0) are members of a category of chemicals described as alkaryl sulfonates, which was established as part of the U.S. Environmental Protection Agency High Production Volume (HPV) Challenge Program. The substances of this category have a common functional group - the salt of aryl sulfonic acid. Furthermore, they all have a divalent alkaline earth metal, one or more linear and/or branched alkyl groups of variable chain length and branching characteristics or extended heterocyclic carbon system from the sulfonated benzene ring. Finally, they have common precursors and/or the likelihood of common breakdown products via physical and biological processes, resulting in structurally similar chemicals, and similar physicochemical properties, environmental fate, ecotoxicity and mammalian toxicity.
Concerning toxicity to aquatic algae and cyanobacteria, it is believed that both substance will be metabolised by the same mechanisms by microorganisms and by other classes of living organisms. Therefore they are expected to follow the same pattern. For the detailed procedure of the read-across principle and justifications, please refer to the analogue approach justification depicted below and the separate Read-Across Statement (Chemservice S.A., 2017).

2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)
Source chemical: Benzenesulfonic acid, C14-24-branched and linear alkyl derivs., calcium salts (CAS 115733-09-0, EC No none)
Target chemical: Reaction products of benzenesulfonic acid, mono-C20-24 (even)-sec-alkyl derivs. para-, calcium salts (C20-24 calcium sulfonate, CAS No none, EC No none)

3. ANALOGUE APPROACH JUSTIFICATION
C20-24 calcium sulfonate and Benzenesulfonic acid, C14-24-branched and linear alkyl derivs., calcium salts (CAS 115733-09-0) are UVCB substances that are produced using similar manufacturing process and raw materials and are manufactured in mineral oil. They are members of a category of chemicals described as alkaryl sulfonates, which was established as part of the U.S. Environmental Protection Agency High Production Volume (HPV) Challenge Program. These substances are similar in that they have a common functional group, the salt of aryl sulfonic acid. TOXMATCH and OECD Toolbox QSAR structure similarity assessments using Tanimoto distance fingerprint, Hellinger distance atom environment, Euclidian distance and Dice calculations indicate that these substances are very similar. Likewise, they have similar physicochemical properties, similar environmental fate characteristics, and similar ecotoxicity and mammalian toxicity profiles. For example, these substances can dissociate only in the presence of strong acids such as in the stomach but are not expected to dissociate under environmental conditions. For further details on this, please refer to the separate Read-Across Statement (Chemservice S.A., 2017). The similar toxicity profiles indicate that they have a similar MOA. C20-24 calcium sulfonate and Benzenesulfonic acid, C14-24-branched and linear alkyl derivs., calcium salts (CAS 115733-09-0) are not classified for environmental toxicity.
The similar findings (refer to data matrix outlined below and the separate Read-Across Statement) for both substances support the conclusion that similar molecules are expected to be formed from both substances, and in consequence, similar effects can be reasonably expected. Hence, the analogue may perfectly serve as a read-across substance for the C20-24 calcium sulfonate and vice versa. So, based on the WOE of these data, the available data on CAS 115733-09-0 can be used to cover the systemic endpoints currently lacking for C20-24 calcium sulfonate and read across is scientifically justified, making further testing obsolete.

4. DATA MATRIX
There is mainly data available on the toxicological properties of the analogues CAS 61789-86-4 / its overbased version CAS 68783-96-0 and for CAS 70024-69-0 / its overbased version CAS 70024-71-4. Data on Reaction products of benzenesulfonic acid, mono-C20-24 (even)-sec-alkyl derivs. para-, calcium salts covers merely the physico chemical properties. Hence, the identification and discussion of common properties of the analogues and the C20-24 calcium sulfonate will be mainly based on this physicochemical data.
The available data for the following physico-chemical properties, which are relevant for absorption into living organisms, are very similar. The substances are rather huge molecules and have a similar molecular weight range, which triggers already similarities in their absorption/adsorption and desorption behaviour. Furthermore, the physico-chemical properties like their partition coefficient, water solubility and vapour pressure are similar. Regarding the application of these substances, the substances are usually solved in an inert mineral oil to enable handling. The C20-24 calcium sulfonate and all analogous substances are hydrolytically stable in the natural environment, as they do not contain hydrolysable groups. In addition, at least CAS 70024-69-0 and CAS 61789-86-4 are not readily biodegradable, and the available data suggests this to apply also for C20-24 calcium sulfonate. Taking into account the vast amount of data available for partition coefficient data on various calcium sulfonates it can be concluded that they do not have a significant potential for bioaccumulation in aquatic and terrestrial organisms. However, they are expected to be adsorbed to a significant extent to the sediment and soil and to be thereby not bioavailable, which was confirmed by the results of short-term toxicity tests to fish, daphnia and algae for CAS 70024-71-4; CAS 115733-09-0 and CAS 61789-64-4, in which the lowest LL50 was already > 100 mg/L WAF.
For the following toxicological endpoints there is data available derived from CAS 70024-69-0/ CAS 70024-71-4, Analogue of CAS 70024-69-0, CAS 115733-09-0, CAS 61789-86-4/ CAS 68783-96-0 and CAS 75975-85-8: Acute toxicity, Skin irritation / corrosion, Eye irritation /corrosion, Skin sensitization, Repeated dose toxicity, Genetic toxicity in vitro and in vivo and Toxicity to reproduction (fertility / developmental toxicity). Furthermore a rather extensive data package is available concerning the human sensitization potential of numerous analogous substances. For the acute oral toxicity, the values for all read across substances are very high, all LD50 values being above 2000 mg/kg (reaching in older tests up to greater than 20,000 mg/kg) and the values for the substances can be considered as similar within normal biological variations. The substances are also not toxic via the inhalation or the dermal route of exposure. Regarding Skin/Eye Irritation, the available data on CAS 70024-69-0 and CAS 61789-86-4 shows both substances to be not irritating to the skin or the eyes. The skin sensitization data in animals and humans (for CAS 75975-85-8; CAS 61789-86-4 and EC 939-141-6) evaluated in a weight-of-evidence approach indicates that low TBN calcium sulfonates (TBN < 300) are skin sensitizers with a specific concentration limit (SCL) of 10% and that high TBN calcium sulfonates (TBN ≥ 300) are not skin sensitizers. Last but not least, the available genetic toxicity data for Analogue of CAS 70024-69-0, CAS 61789-86-4 and its overbased version CAS 68783-96-0 prove all of these substances to be not mutagenic. The NOAELs derived for the endpoints Repeated dose toxicity (Analogue of CAS 70024-69-0 and CAS 61789-86-4) and Toxicity to reproduction (fertility / developmental toxicity for CAS 115733-09-0)) have been also found to be in a similar range.
For further details please refer to the seperate Read-Across Statement (Chemservice S.A., 2017) and/or the robust study summaries of the respective studies in this IUCLID file.

Reason / purpose for cross-reference:

read-across source

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

other: WAF loading rates

Basis for effect:

growth rate

Duration:

96 h

Dose descriptor:

NOEC

Effect conc.:

1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

other: WAF loading rates

Basis for effect:

biomass

Duration:

72 h

Dose descriptor:

EL50

Effect conc.:

> 1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

other: WAF loading rates

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

EL50

Effect conc.:

> 1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

other: WAF loading rates

Basis for effect:

biomass

Duration:

96 h

Dose descriptor:

EL50

Effect conc.:

> 1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

other: WAF loading rates

Basis for effect:

growth rate

Duration:

96 h

Dose descriptor:

EL50

Effect conc.:

> 1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

other: WAF loading rates

Basis for effect:

biomass

Details on results:

The control response was satisfactory.
At 72-hours, biomass measurements were 80 %, 62 % and 70 % of the control at 100, 300 and 1000 mg/L WAF, respectively. At 96-hours, biomass measurements were 70 %, 66 % and 88 % of the control at 100, 300 and 1000 mg/L WAF, respectively.

Results with reference substance (positive control):

Not applicable.

Reported statistics and error estimates:

A parametric one-way analysis of variance (ANOVA) and Dunnett's test were used to calculate the No Observed Effect Level (NOEL).

The test vessels containing 1000mg/L WAFs were slightly cloudy at the start of the test and at 24hours. The algal population grew well during the test, resulting in an average of 1711000 cells/mL in the control (doubling time: 13 hours). Cell growth data from the acute toxicity test with the WAF of 3 concentrations of substance and the freshwater alga, Selenastrum capricornutum are provided below with % growth rates compared to control are shown below at time points 0, 24, 48, 72 and 96 hours.

Table 1. Cell growth data

0 (control)		1	10	18	123	826	1,555
		2	10	21	145	1,008	1,866
		Mean	10	20	134	917	1,711
	%	Control	—	—	—	—	-—
100 mg/L WAF		1	10	15	118	680	1,250
		2	10	18	133	790	1,145
		Mean	10	17	126	735	1,198
	%	Control	100	85	94	80	70
300 mg/L WAF		1	10	<10	120	506	1,125
		2	10	<10	107	638	1,120
		Mean	10	<10	114	572	1,122
	%	Control	100	< 50	85	62	66
1000 mg/L WAF		1	10	<10	132	654	1,610
		2	10	<10	125	632	1,385
		Mean	10	<10	129	643	1,498
	%	Control	100	< 50	96	70	88

 

Based on the number of cells/mL or the average specific growth rate, the 72 and 96 hour EC50s are > 1000 mg/L.

No effects (size differences, unusual cell shapes, colors, flocculations, adherence of cells to test containers, or aggregation of cells) were noted. Based on the number of cells/mL or the average specific growth rate, the 72 and 96 hour NOEC values are 1000 mg/L.

Validity criteria fulfilled:

yes

Remarks:

Scientifically validity criteria were fulfilled.

Conclusions:

The report summarises a valid guideline study with GLP compliance. The calcium sulfonate Read-Across substance (CAS 115733-09-0) was not toxic to Selenastrum capricornutum at a loading rate up to 1000 mg/L nominal WAF, therefore the ErL50(96h) as well as the EbL50(96h) are considered to be > 1000mg/L. These results can be used to fulfill the information requirements for the chemical substance Reaction products of benzenesulfonic acid, mono-C20-24 (even)-sec-alkyl derivs. para-, calcium salts, due to the high structural similarity of these substances. For the detailed procedure of the read-across principle and justifications, please refer to the separate Read-Across Statement (Chemservice S.A., 2017).

Executive summary:

In a 96-hour acute toxicity study, the cultures of Selenastrum capricornutum (new name: Pseudokirchneriella subcapitata) were exposed to Benzenesulfonic acid, C14-24 branched/linear alkyl derivative, calcium salt (CAS 115733-09-0) at nominal concentrations of 100, 300 and 1000 mg/L as WAF loading rates under static conditions in accordance with the EPA Guideline OTS 797.1050 (Ward, 1994). Water Accommodated Fractions (WAFs) were prepared due to the intrinsic properties of the test substance (i.e. low water solubility). Daily cell counts and cell observations were made visually by means of direct microscopic examination with a hemocytometer. The algal population grew well during the test, since an average of 1,711,000 cells/mL were recorded in the control group; resulting in a doubling time of 13 h. The test vessels containing 1000 mg/L WAF were slightly cloudy at the start of the test and after 24 h exposure time. After 72 hours, biomass measurements were 80 %, 62 % and 70 % of the control at 100, 300 and 1000 mg/L WAF, respectively. At 96 hours, biomass measurements were 70 %, 66 % and 88 % of the control at 100, 300 and 1000 mg/L WAF, respectively. Based on these findings, the ErL50(72h), ErL50(96h), EbL50(72h) as well as the EbL50(96h) value is considered to be > 1000 mg/L. A parametic one-way analysis of variance (ANOVA) and Dunnett´s test were used to calculate the corresponding No Observed Effect Level (NOEL), which is reported as 1000 mg/L WAF for each sampling period.

These results can be used to fulfill the information requirements for the chemical substance Reaction products of benzenesulfonic acid, mono-C20-24 (even)-sec-alkyl derivs. para-, calcium salts, due to the high structural similarity of these substances. For the detailed procedure of the read-across principle and justifications, please refer to the separate Read-Across Statement (Chemservice S.A., 2017).

Reference 2

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Justification for type of information:

REPORTING FORMAT FOR THE ANALOGUE APPROACH
In this justification, the read-across (bridging) concept is applied, based on the chemical structure of the potential analogues, their toxicokinetic behaviour and other available (eco-)toxicological data.

1. HYPOTHESIS FOR THE ANALOGUE APPROACH
C20-24 calcium sulfonate and Sulfonic acids, petroleum, calcium salts (CAS 61789-86-4) are members of a category of chemicals described as alkaryl sulfonates, which was established as part of the U.S. Environmental Protection Agency High Production Volume (HPV) Challenge Program. The substances of this category have a common functional group - the salt of aryl sulfonic acid. Furthermore, they all have a divalent alkaline earth metal, one or more linear and/or branched alkyl groups of variable chain length and branching characteristics or extended heterocyclic carbon system from the sulfonated benzene ring. Finally, they have common precursors and/or the likelihood of common breakdown products via physical and biological processes, resulting in structurally similar chemicals, and similar physicochemical properties, environmental fate, ecotoxicity and mammalian toxicity.
Concerning toxicity to aquatic algae and cyanobacteria, it is believed that both substance will be metabolised by the same mechanisms by microorganisms and by other classes of living organisms. Therefore they are expected to follow the same pattern. For the detailed procedure of the read-across principle and justifications, please refer to the analogue approach justification depicted below and the separate Read-Across Statement (Chemservice S.A., 2017).

2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)
Source chemical: Sulfonic acids, petroleum, calcium salts (CAS 61789-86-4, EC 263-093-9)
Target chemical: Reaction products of benzenesulfonic acid, mono-C20-24 (even)-sec-alkyl derivs. para-, calcium salts (C20-24 calcium sulfonate, CAS No none, EC No none)

3. ANALOGUE APPROACH JUSTIFICATION
C20-24 calcium sulfonate and Sulfonic acids, petroleum, calcium salts (CAS 61789-86-4) are UVCB substances that are produced using similar manufacturing process and raw materials and are manufactured in mineral oil. They are members of a category of chemicals described as alkaryl sulfonates, which was established as part of the U.S. Environmental Protection Agency High Production Volume (HPV) Challenge Program. These substances are similar in that they have a common functional group, the salt of aryl sulfonic acid. TOXMATCH and OECD Toolbox QSAR structure similarity assessments using Tanimoto distance fingerprint, Hellinger distance atom environment, Euclidian distance and Dice calculations indicate that these substances are only similar to a certain extent. However, a certain difference can be expected due to the presence of additional benzene rings and a significantly increased amount of secondary alkylations. They have similar physicochemical properties, similar environmental fate characteristics, and similar ecotoxicity and mammalian toxicity profiles. For example, these substances can dissociate only in the presence of strong acids such as in the stomach but are not expected to dissociate under environmental conditions. For further details on this, please refer to the separate Read-Across Statement (Chemservice S.A., 2017). The similar toxicity profiles indicate that they have a similar MOA. C20-24 calcium sulfonate and Sulfonic acids, petroleum, calcium salts (CAS 61789-86-4) are both not classified for environmental toxicity.
The similar findings (refer to data matrix outlined below and the separate Read-Across Statement) for both substances support the conclusion that similar molecules are expected to be formed from both substances, and in consequence, similar effects can be reasonably expected. Hence, the analogue may serve in a worst case approach as a read-across substance for the C20-24 calcium sulfonate. So, based on the WOE of these data, the available data on CAS 61789-86-4 can be used to cover the systemic endpoints currently lacking for C20-24 calcium sulfonate and read across is scientifically justified, making further testing obsolete.

4. DATA MATRIX
There is mainly data available on the toxicological properties of the analogues CAS 61789-86-4 / its overbased version CAS 68783-96-0 and for CAS 70024-69-0 / its overbased version CAS 70024-71-4. Data on Reaction products of benzenesulfonic acid, mono-C20-24 (even)-sec-alkyl derivs. para-, calcium salts covers merely the physico chemical properties. Hence, the identification and discussion of common properties of the analogues and the C20-24 calcium sulfonate will be mainly based on this physicochemical data.
The available data for the following physico-chemical properties, which are relevant for absorption into living organisms, are very similar. The substances are rather huge molecules and have a similar molecular weight range, which triggers already similarities in their absorption/adsorption and desorption behaviour. Furthermore, the physico-chemical properties like their partition coefficient, water solubility and vapour pressure are similar. Regarding the application of these substances, the substances are usually solved in an inert mineral oil to enable handling. The C20-24 calcium sulfonate and all analogous substances are hydrolytically stable in the natural environment, as they do not contain hydrolysable groups. In addition, at least CAS 70024-69-0 and CAS 61789-86-4 are not readily biodegradable, and the available data suggests this to apply also for C20-24 calcium sulfonate. Taking into account the vast amount of data available for partition coefficient data on various calcium sulfonates it can be concluded that they do not have a significant potential for bioaccumulation in aquatic and terrestrial organisms. However, they are expected to be adsorbed to a significant extent to the sediment and soil and to be thereby not bioavailable, which was confirmed by the results of short-term toxicity tests to fish, daphnia and algae for CAS 70024-71-4; CAS 115733-09-0 and CAS 61789-64-4, in which the lowest LL50 was already > 100 mg/L WAF.
For the following toxicological endpoints there is data available derived from CAS 70024-69-0/ CAS 70024-71-4, Analogue of CAS 70024-69-0, CAS 115733-09-0, CAS 61789-86-4/ CAS 68783-96-0 and CAS 75975-85-8: Acute toxicity, Skin irritation / corrosion, Eye irritation /corrosion, Skin sensitization, Repeated dose toxicity, Genetic toxicity in vitro and in vivo and Toxicity to reproduction (fertility / developmental toxicity). Furthermore a rather extensive data package is available concerning the human sensitization potential of numerous analogous substances. For the acute oral toxicity, the values for all read across substances are very high, all LD50 values being above 2000 mg/kg (reaching in older tests up to greater than 20,000 mg/kg) and the values for the substances can be considered as similar within normal biological variations. The substances are also not toxic via the inhalation or the dermal route of exposure. Regarding Skin/Eye Irritation, the available data on CAS 70024-69-0 and CAS 61789-86-4 shows both substances to be not irritating to the skin or the eyes. The skin sensitization data in animals and humans (for CAS 75975-85-8; CAS 61789-86-4 and EC 939-141-6) evaluated in a weight-of-evidence approach indicates that low TBN calcium sulfonates (TBN < 300) are skin sensitizers with a specific concentration limit (SCL) of 10% and that high TBN calcium sulfonates (TBN ≥ 300) are not skin sensitizers. Last but not least, the available genetic toxicity data for Analogue of CAS 70024-69-0, CAS 61789-86-4 and its overbased version CAS 68783-96-0 prove all of these substances to be not mutagenic. The NOAELs derived for the endpoints Repeated dose toxicity (Analogue of CAS 70024-69-0 and CAS 61789-86-4) and Toxicity to reproduction (fertility / developmental toxicity for CAS 115733-09-0)) have been also found to be in a similar range.
For further details please refer to the separate Read-Across Statement (Chemservice S.A., 2017) and/or the robust study summaries of the respective studies in this IUCLID file.

Reason / purpose for cross-reference:

read-across source

Duration:

72 h

Dose descriptor:

EL50

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

other: WAF loading rate

Basis for effect:

biomass

Duration:

72 h

Dose descriptor:

NOELR

Effect conc.:

100 mg/L

Nominal / measured:

nominal

Conc. based on:

other: WAF loading rate

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

EL50

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

other: WAF loading rate

Basis for effect:

growth rate

Details on results:

- Exponential growth in the control: yes
- Observation of abnormalities: No abnormalities were detected in any of the control or test cultures at 72 hours
- Any observations (e.g. precipitation) that might cause a difference between measured and nominal values: At the start and end of the mixing period and after the 1 hour settlement period, the 100 mg/L WAF loading rate was observed to have formed a clear, colourless media column with test material floating at the media surface. Microscopic examination of the WAF showed there to be no globules/micro-dispersions of the test material. At the start of the test, all control and test cultures were observed to be clear, colourless solutions. After the 72-hour test period, all control and test cultures were observed to be green dispersions.

Results with reference substance (positive control):

Not applicable.

Reported statistics and error estimates:

Statistical analysis of the growth rate data was conducted using a Student's t-test incorporating Bartlett's test for homogeneity of variance. There were no statistical differences (P >= 0.05) between the control and 100 mg/L WAF loading rate. Therefore, the NOEL was 100 mg/L nominal WAF loading rate.

Table 2: Effects of sulphonic acids, petroleum, calcium salts on growth of Scenedesmus subspicatus

Nominal loading rate (mg/L)	Replicate	pH		Cell density (cells/mL)				AUC at 72 hours	% Inhibition	Growth rate (0-72 hours)	% Inhibition
		0 hours	72 hours	0 hours	24 hours	48 hours	72 hours
Control	1	7.2	7.6	9.46 x10^3	5.76 x10^4	1.77 x10^5	3.76 x10^5	9.48 x10^6	-	0.051	-
	2	7.2	7.6	9.89 x10^3	5.76 x10^4	1.90 x10^5	3.92 x10^5
	3	7.2	7.6	9.49 x10^3	5.31 x10^4	1.47 x10^5	3.82 x10^5
	Mean	-	-	9.61 x10^3	5.61 x10^4	1.71 x10^5	3.83 x10^5
100	1	7.2	7.6	9.97 x10^3	5.96 x10^4	2.28 x10^5	4.14 x10^5	1.19 x10^7	[26]	0.052	[2]
	2	7.2	7.6	1.02 x10^4	6.62 x10^4	2.30 x10^5	3.97 x10^5
	3	7.2	7.6	9.80 x10^3	7.06 x10^4	2.22 x10^5	4.95 x10^5
	4	7.2	7.6	1.10 x10^4	7.55 x10^4	2.31 x10^5	4.77 x10^5
	5	7.2	7.6	1.03 x10^4	7.95 x10^4	2.33 x10^5	4.43 x10^5
	6	7.2	7.6	9.78 x10^3	7.29 x10^4	2.33 x10^5	4.38 x10^5
	Mean	-	-	1.02 x10^4	7.07 x10^4	2.29 x10^5	4.44 x10^5

AUC: Area under the curve

[Increase in growth compared to the control]

Comparison of areas under the growth curves

The area under the curve is taken to be an index of growth and was calculated using the following formula:

A=N₁- N₀x t₁+N₁+ N₂– 2N₀x (t₂- t₁) +N_n-1 + Nn – 2N₀x (t_n– t_n-1)

         2                       2                                           2

where

A = area

N₀= cell concentration at the start of the test

N₁= cell concentration at t1

N_n= cell concentration at tn

t₁= time of first measurement (hours from start)

t_n= time at nth measurement (hours from start)

Percentage inhibition of growth at each loading rate (IA) was calculated by comparing the area under the test curve (At) with that under the control curve (Ac) using the following equation:

IA =A_c- A_tx 100

         A_c

Comparison of growth rates

The average maximum growth rate (µ) for each culture was calculated from the straight section of the growth curve using the following equation:

µ =lnN_n- lnN₁

         t_n- t₁

where

µ = average maximum growth rate

N₀= cell concentration at the start of test

N_n= cell concentration at tn

t₀= time at first measurement (0 hours)

t_n= time of nth measurement (hours from the start)

Validity criteria fulfilled:

yes

Conclusions:

The study report is a valid guideline study with GLP compliance. The calcium sulfonate Read-Across substance (CAS 61789 -86 -4) was not toxic to Selenastrum capricornutum at a loading rate up to 1000 mg/L nominal WAF, therefore the ErL50(96h) as well as the EbL50(96h) are considered to be > 100 mg/L. These results can be used to fulfill the information requirements for the chemical substance Reaction products of benzenesulfonic acid, mono-C20-24 (even)-sec-alkyl derivs. para-, calcium salts, due to the high structural similarity of these substances. For the detailed procedure of the read-across principle and justifications, please refer to the separate Read-Across Statement (Chemservice S.A., 2017).

Executive summary:

In a 72 hour toxicity study, the cultures of the green algae (Scenedesmus subspicatus CCAP 276/20) were exposed to sulphonic acids, petroleum, calcium salts (CAS 61789 -86 -4) at nominal concentrations of 0 and 100 mg/L nominal WAF loading rate under static conditions in accordance with the guideline OECD Guideline 201 (Alga, Growth Inhibition Test). The EL50 based biomass was >100 mg/L and the EL50 based on growth rate was >100 mg/L. There were no compound related phytotoxic effects.

 

This toxicity study is classified as acceptable and satisfies the guideline requirements for an algal growth inhibition study.

 

Results Synopsis

 

Test Organism: Scenedesmus subspicatus CCAP 276/20

Test Type: Static

72 hr EC50 (biomass): >100 mg/L WAF loading rate

72 hr EC50 (growth rate): >100 mg/L WAF loading rate

These results can be used to fulfill the information requirements for the chemical substance Reaction products of benzenesulfonic acid, mono-C20-24 (even)-sec-alkyl derivs. para-, calcium salts, due to the high structural similarity of these substances. For the detailed procedure of the read-across principle and justifications, please refer to the separate Read-Across Statement (Chemservice S.A., 2017).

Description of key information

RA_CAS115733-09-0_EPA OTS 797.1050_Selenastrum capricornutum: NOEL: 1000 mg/L WAF, ErL50(72h) > 1000 mg/L. 
RA_CAS61789-86-4_OECD201_Scenedesmus subspicatus: NOEL: 100 mg/L WAF, ErL50(72h) > 100 mg/L. 

Key value for chemical safety assessment

EC50 for freshwater algae:

1 000 mg/L

EC10 or NOEC for freshwater algae:

1 000 mg/L

Additional information

General considerations

For the substance itself, no experimental data are available. The toxicity to aquatic algae was investigated for two different analogue structures of the calcium sulfonate target substance (Reaction products of benzenesulfonic acid, mono-C20-24 (even)-sec-alkyl derivs. para-, calcium salts). Since both substances belong to the same chemical group, aryl-alkyl sulfonates, the same behaviour and toxicity potential can be expected. Calcium sulfonate read-across substances (CAS 115733-09-0 and CAS 61789-86-4) were used to fulfil the requirements for the endpoint of toxicity to algae and cyanobacteria. Investigations concerning toxicity in marine algae were not performed. For the detailed procedure of the read-across principle and justifications, please refer to the separate Read-Across Statement attached to this Chemical Safety Report (Chemservice S.A., 2017).

Experimental results -Selenastrum capricornutum

In a key study the calcium sulfonate read-across substance (CAS 115733-09-0) was tested at nominal concentrations of 100, 300 and 1000 mg/L as WAF loading rates under static conditions (Ward, 1994). The study was performed according to US EPA Guideline OTS 797.1050. The algal population grew well during the test, since an average of 1,711,000 cells/mL was recorded in the control group; resulting in a doubling time of 13 h. The test vessels containing 1000 mg/L WAF were slightly cloudy at the start of the test and after 24 h exposure time. After 72 hours, biomass measurements were 80 %, 62 % and 70 % of the control at 100, 300 and 1000 mg/L WAF, respectively. At 96-hours, biomass measurements were 70 %, 66 % and 88 % of the control at 100, 300 and 1000 mg/L WAF, respectively. Based on these findings, the ErL50 (72h), ErL50(96h), EbL50(72h) as well as the EbL50(96h) value are considered to be > 1000 mg/L. The corresponding No Observed Effect Level (NOEL) amounts to 1000 mg/L WAF for each sampling period.

Experimental results -Scenedesmus subspicatus

In a 72 hour key study, the cultures of the green algae (Scenedesmus subspicatus) were exposed to sulphonic acids, petroleum, calcium salts (CAS 61789 -86 -4) at nominal concentrations of 0 and 100 mg/L nominal WAF loading rate under static conditions (limit test). The test was performed by Mead (2005) in accordance with the OECD Guideline 201 (Alga, Growth Inhibition Test). The EL50 based biomass was > 100 mg/L and the EL50 based on growth rate was > 100 mg/L. There were no compound related phytotoxic effects.