Dioxybenzone

Toxicity to aquatic algae and cyanobacteria

Administrative data

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2017-12-18 - 2018-03-28

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: GLP study according to guideline

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2018

Report date:

2018

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Freshwater Alga and Cyanobacteria, Growth Inhibition Test)

Version / remarks:

Adopted March 2006 and updated Annex 5 July 2011

GLP compliance:

yes (incl. QA statement)

Remarks:

March 2015

Test material

Test material information

Constituent 1

Reference substance name:

Dioxybenzone

EC Number:

205-026-8

EC Name:

Dioxybenzone

Cas Number:

131-53-3

Molecular formula:

C14H12O4

IUPAC Name:

2-(2-hydroxybenzoyl)-5-methoxyphenol

Test material form:

solid: particulate/powder

Specific details on test material used for the study:

Name: 2,2’ -Dihydroxy-4-methoxybenzophenone
Batch/Lot Number: CM70314A1
Description: Yellow powder
Expiry Date: 14 March 2019
Purity: 99.8%
Storage Conditions: Room Temperature, protected from light

Sampling and analysis

Analytical monitoring:

yes

Details on sampling:

- Concentrations: 10.0, 4.55, 2.07, 0.939 and 0.427% of a filtrate at a loading rate of 100 mg test item/L
- Sampling method: Control and test solution were sampled in dupblicate at the start of exposure and at 72h.
- Sample storage conditions before analysis: All samples were stored in amber glass bottles in the dark at a temperature of ≤ -18°C after sampling and before shipment.

Test solutions

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION
The following approach was used taking into account aspects of ISO 14442 (2006), Water quality - Guidelines for algal growth inhibition tests with poorly soluble materials, volatile compounds, metals and waste water, and OECD 2000, Guidance Document on Aquatic Toxicity Testing of Difficult Substances and Mixtures. OECD Series on Testing and Assessment Number 23. ENV/JM/MONO(2000)6.

A stock solution at a nominal loading rate of 100 mg/L was prepared by adding 49.97 mg test item to 500 mL test medium. This stock solution stirred with a magnetic stirrer at 800 rpm for 46 h and 15 min at ambient temperature in the dark. After that, the stock solution was filtered, using a glass fibre filter with an average retention capacity of 0.4 µm (MN 85/220). The initial 100 mL of the filtrate were discarded. Visual inspection of the filtrate showed a clear solution without Tyndall effect.

Test organisms

Test organisms (species):

Raphidocelis subcapitata (previous names: Pseudokirchneriella subcapitata, Selenastrum capricornutum)

Details on test organisms:

TEST ORGANISM
- Strain: SAG 61.81
- Source: Sammlung von Algenkulturen, Albrecht-von-Haller-Institut, Universität Göttingen, Germany.

Study design

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Test conditions

Test temperature:

22.67 °C

pH:

7.7 - 8.7

Details on test conditions:

TEST SYSTEM
- Test vessel: Glass Erlenmeyer flasks (300 mL) covered by air-permeable lids
- Material, size, headspace, fill volume: 100±5 mL vill volume
- Initial cells density: 0.3 × 10^4
- Control end cells density: 97.24 × 10^4
- No. of vessels per concentration (replicates): 3
- No. of vessels per control (replicates): 6

GROWTH MEDIUM
- Standard medium used: yes

OTHER TEST CONDITIONS
- Sterile test conditions: yes
- Adjustment of pH: no
- Photoperiod: 24h light / 0h dark
- Light intensity and quality: Mean 83.6 µE m–2s–1

Reference substance (positive control):

yes

Remarks:

potassium dichromate

Results and discussion

Effect concentrations

Effect concentrations 1

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

1.27 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

act. ingr.

Basis for effect:

growth rate

Effect concentrations 2

Key result

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

1.04 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

act. ingr.

Basis for effect:

growth rate

Effect concentrations 3

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

0.907 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

act. ingr.

Basis for effect:

biomass

Effect concentrations 4

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

0.549 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

act. ingr.

Basis for effect:

biomass

Details on results:

- Exponential growth in the control: yes
- Observation of abnormalities (for algal test):
In none of the concentration levels up to 4.55 % of a saturated solution at a loading rate of 100 mg/L were deformed and/or damaged algal cells observed during microscopic inspection. At the highest concentration level (10.0 % of a saturated solution at a loading rate of 100 mg/L) the cells were thin and small.

Validity criteria
The mean biomass increase in the control cultures was at least of 16 within the 72h test period (factor was 324.1), the mean coefficient of variation for section-by-section specific growht rates in the control cultures was less than 35% (9.5%) and the coefficient of variation of average specific growth rates during test period in replicate control cultures was less than 7% (0.8%)
The study is therefore considered to be valid.

Results with reference substance (positive control):

Growth rate ErC50 (0–72 h): 0.952 mg/L
This value is within the range of the international ring test (ISO (2004). Therefore the results of this reference test are acceptable and the test conditions are reliable.

Any other information on results incl. tables

Table 1 Summary of biological results based on measured test item concentrations given in mg/L

	Endpoints [mg test item/L]
Parameter	EC10	EC20	EC50	NOEC	LOEC
Yield (95% cI)	0.549 (0.454–0.622)	0.652 (0.564–0.718)	0.907 (0.846–0.957)	0.471	1.12
Growth Rate (95% cI)	1.04 (n.d.)	1.11 (n.d.)	1.27 (n.d.)	0.471	1.12

cl: confidence limit

n.d.: not determined due to mathematical reasons or inappropriate data

Table 2: Summary of biological results based on nominal test item concentrations given in % of a filtrate at a loading rate of 100 mg test item/L

	Endpoints [%^a)]
Parameter	EC10	EC20	EC50	NOEC	LOEC
Yield (95% cI)	2.38 (1.91-2.71)	2.78 (2.36-3.08)	3.76 (3.48-3.98)	2.07	4.55
Growth Rate (95% cI)	4.13 (0.573-4.33)	4.52 (3.87-4.56)	5.36 (4.95-152)	2.07	4.55

cl: confidence limit

^a)% of a saturated solution at a loading rate of 100 mg/L

Table 3: Summary of measured concentrations at the beginning and at the end of the test.

Conc. Level	Test period	Nominal concentration	Measured concentration	% of measured initial (time 0 hours) concentration	Geometric mean measured concentration over 72 h
	[d]	[%^a)]	[mg test item/L]	[%]	[mg test item/L]
Control	0	0	n.d.	–	–
C1	0	0.427	0.104	–	–
C2	0	0.939	0.226	–	–
C3	0	2.07	0.480	–	–
C4	0	4.55	1.132	–	–
C5	0	10.0	2.543	–	–
Control	3	0	n.d.	–	n.d.
C1	3	0.427	0.0989	95	0.101
C2	3	0.939	0.209	92	0.217
C3	3	2.07	0.463	96	0.471
C4	3	4.55	1.105	98	1.12
C5	3	10.0	2.403	94	2.47

LOQ = Limit of Quantification (0.07 mg/L)

n.d.: not determined, “Limit of Detection”(0.003 mg/L)

^a)% of a saturated solution at a loading rate of 100 mg/L

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Conclusions:

Expressed in terms of measured concentrations, the ErC50 for freshwater algae was 1.27 mg/L and ErC10 1.04 mg/L.

Executive summary:

The acute toxicity of the Dioxybenzone to algae was tested according to OECD guideline 201 and GLP conditions.

A clear concentration-response relationship was observed for both biological parameters growth rate and yield during the exposure period.

The EbC50 of Raphidocelis subcapitata was determined to be 0.907 mg/L and EbC10 0.549 mg/L.

The ErC50 of Raphidocelis subcapitata was determined to be 1.27 mg/L and ErC10 1.04 mg/L.